blob: 7d79b5194a4a7648a7ec9ebd28cea50250ca53c6 [file] [log] [blame]
#define _GNU_SOURCE
#include "dynlink.h"
#include <ctype.h>
#include <dlfcn.h>
#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <lib/processargs/processargs.h>
#include <lib/zircon-internal/align.h>
#include <lib/zircon-internal/default_stack_size.h>
#include <limits.h>
#include <link.h>
#include <pthread.h>
#include <setjmp.h>
#include <stdalign.h>
#include <stdarg.h>
#include <stdatomic.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <unistd.h>
#include <zircon/dlfcn.h>
#include <zircon/fidl.h>
#include <zircon/process.h>
#include <zircon/sanitizer.h>
#include <zircon/status.h>
#include <zircon/syscalls/log.h>
#include <ldmsg/ldmsg.h>
#include <runtime/thread.h>
#include "asan_impl.h"
#include "libc.h"
#include "relr.h"
#include "stdio_impl.h"
#include "threads_impl.h"
#include "zircon_impl.h"
static void early_init(void);
static void error(const char*, ...);
static void debugmsg(const char*, ...);
static zx_status_t get_library_vmo(const char* name, zx_handle_t* vmo);
static void loader_svc_config(const char* config);
#define MAXP2(a, b) (-(-(a) & -(b)))
#define VMO_NAME_DL_ALLOC "ld.so.1-internal-heap"
#define VMO_NAME_UNKNOWN "<unknown ELF file>"
#define VMO_NAME_PREFIX_BSS "bssN:"
#define VMO_NAME_PREFIX_DATA "dataN:"
#define VMO_NAME_PREFIX_RELRO "relro:"
#define KEEP_DSO_VMAR __has_feature(xray_instrument)
struct dso {
// Must be first.
struct link_map l_map;
const struct gnu_note* build_id_note;
// TODO(mcgrathr): Remove build_id_log when everything uses markup.
struct iovec build_id_log;
atomic_flag logged;
// ID of this module for symbolizer markup.
unsigned int module_id;
const char* soname;
Phdr* phdr;
unsigned int phnum;
size_t phentsize;
int refcnt;
zx_handle_t vmar; // Closed after relocation.
Sym* syms;
uint32_t* hashtab;
uint32_t* ghashtab;
int16_t* versym;
char* strings;
unsigned char* map;
size_t map_len;
signed char global;
char relocated;
char constructed;
struct dso **deps, *needed_by;
struct tls_module tls;
size_t tls_id;
size_t code_start, code_end;
size_t relro_start, relro_end;
void** new_dtv;
unsigned char* new_tls;
atomic_int new_dtv_idx, new_tls_idx;
struct dso* fini_next;
struct funcdesc {
void* addr;
size_t* got;
} * funcdescs;
size_t* got;
struct dso* buf[];
};
struct symdef {
Sym* sym;
struct dso* dso;
};
union gnu_note_name {
char name[sizeof("GNU")];
uint32_t word;
};
#define GNU_NOTE_NAME ((union gnu_note_name){.name = "GNU"})
_Static_assert(sizeof(GNU_NOTE_NAME.name) == sizeof(GNU_NOTE_NAME.word), "");
struct gnu_note {
Elf64_Nhdr nhdr;
union gnu_note_name name;
alignas(4) uint8_t desc[];
};
#define MIN_TLS_ALIGN alignof(struct pthread)
#define NO_INLINE __attribute__((noinline))
#define ADDEND_LIMIT 32
static size_t *saved_addends, *apply_addends_to;
static struct dso ldso, vdso;
static struct dso *head, *tail, *fini_head;
static struct dso* detached_head;
static unsigned long long gencnt;
static int runtime __asm__("_dynlink_runtime") __USED;
static int ldso_fail;
static jmp_buf* rtld_fail;
static pthread_rwlock_t lock;
static struct r_debug debug;
static struct tls_module* tls_tail;
static size_t tls_cnt, tls_offset = 16, tls_align = MIN_TLS_ALIGN;
static size_t static_tls_cnt;
static pthread_mutex_t init_fini_lock = {
._m_attr = PTHREAD_MUTEX_MAKE_ATTR(PTHREAD_MUTEX_RECURSIVE, PTHREAD_PRIO_NONE)};
static bool log_libs = false;
static atomic_uintptr_t unlogged_tail;
static zx_handle_t loader_svc = ZX_HANDLE_INVALID;
static zx_handle_t logger = ZX_HANDLE_INVALID;
// Various tools use this value to bootstrap their knowledge of the process.
// E.g., the list of loaded shared libraries is obtained from here.
// The value is stored in the process's ZX_PROPERTY_PROCESS_DEBUG_ADDR so that
// tools can obtain the value when aslr is enabled.
struct r_debug* _dl_debug_addr = &debug;
// If true then dump load map data in a specific format for tracing.
// This is used by Intel PT (Processor Trace) support for example when
// post-processing the h/w trace.
static bool trace_maps = false;
void _dl_rdlock(void) { pthread_rwlock_rdlock(&lock); }
void _dl_unlock(void) { pthread_rwlock_unlock(&lock); }
static void _dl_wrlock(void) { pthread_rwlock_wrlock(&lock); }
NO_ASAN __NO_SAFESTACK static int dl_strcmp(const char* l, const char* r) {
for (; *l == *r && *l; l++, r++)
;
return *(unsigned char*)l - *(unsigned char*)r;
}
#define strcmp(l, r) dl_strcmp(l, r)
// Signals a debug breakpoint. It does't use __builtin_trap() because that's
// actually an "undefined instruction" rather than a debug breakpoint, and
// __builtin_trap() documented to never return. We don't want the compiler to
// optimize later code away because it assumes the trap will never be returned
// from.
//
// NOTE: The x64 reported address when reading the exception's instruction pointer
// will be offset by one byte. This is because x64 will report the address as being
// the one *after* executing the breakpoint, while ARM will report the address of
// the breakpoint instruction. Thus the reporting address will be 1 byte higher
// in the case of x64 and the caller will need to offset it back in order to get
// the correct address of the debug trap.
void debug_break(void);
#if defined(__x86_64__)
__asm__(
".pushsection .text, \"ax\", @progbits\n"
".global debug_break\n"
"debug_break:\n"
"int3\n"
"ret\n"
".popsection\n");
#elif defined(__aarch64__)
__asm__(
".pushsection .text, \"ax\", %progbits\n"
".global debug_break\n"
"debug_break:\n"
"brk 0\n"
"ret\n"
".popsection\n");
#endif
__NO_SAFESTACK static bool should_break_on_load(void) {
intptr_t dyn_break_on_load = 0;
zx_status_t status = _zx_object_get_property(__zircon_process_self, ZX_PROP_PROCESS_BREAK_ON_LOAD,
&dyn_break_on_load, sizeof(dyn_break_on_load));
if (status != ZX_OK)
return false;
return dyn_break_on_load != 0;
}
// Simple bump allocator for dynamic linker internal data structures.
// This allocator is single-threaded: it can be used only at startup or
// while holding the big lock. These allocations can never be freed
// once in use. But it does support a simple checkpoint and rollback
// mechanism to undo all allocations since the checkpoint, used for the
// abortive dlopen case.
union allocated_types {
struct dso dso;
size_t tlsdesc[2];
};
#define DL_ALLOC_ALIGN alignof(union allocated_types)
static uintptr_t alloc_base, alloc_limit, alloc_ptr;
__NO_SAFESTACK NO_ASAN __attribute__((malloc)) static void* dl_alloc(size_t size) {
// Round the size up so the allocation pointer always stays aligned.
size = (size + DL_ALLOC_ALIGN - 1) & -DL_ALLOC_ALIGN;
// Get more pages if needed. The remaining partial page, if any,
// is wasted unless the system happens to give us the adjacent page.
if (alloc_limit - alloc_ptr < size) {
size_t chunk_size = (size + PAGE_SIZE - 1) & -PAGE_SIZE;
zx_handle_t vmo;
zx_status_t status = _zx_vmo_create(chunk_size, 0, &vmo);
if (status != ZX_OK)
return NULL;
_zx_object_set_property(vmo, ZX_PROP_NAME, VMO_NAME_DL_ALLOC, sizeof(VMO_NAME_DL_ALLOC));
uintptr_t chunk;
status = _zx_vmar_map(_zx_vmar_root_self(), ZX_VM_PERM_READ | ZX_VM_PERM_WRITE, 0, vmo, 0,
chunk_size, &chunk);
_zx_handle_close(vmo);
if (status != ZX_OK)
return NULL;
if (chunk != alloc_limit)
alloc_ptr = alloc_base = chunk;
alloc_limit = chunk + chunk_size;
}
void* block = (void*)alloc_ptr;
alloc_ptr += size;
return block;
}
struct dl_alloc_checkpoint {
uintptr_t ptr, base;
};
__NO_SAFESTACK
static void dl_alloc_checkpoint(struct dl_alloc_checkpoint* state) {
state->ptr = alloc_ptr;
state->base = alloc_base;
}
__NO_SAFESTACK
static void dl_alloc_rollback(const struct dl_alloc_checkpoint* state) {
uintptr_t frontier = alloc_ptr;
// If we're still using the same contiguous chunk as the checkpoint
// state, we can just restore the old state directly and waste nothing.
// If we've allocated new chunks since then, the best we can do is
// reset to the beginning of the current chunk, since we haven't kept
// track of the past chunks.
alloc_ptr = alloc_base == state->base ? state->ptr : alloc_base;
memset((void*)alloc_ptr, 0, frontier - alloc_ptr);
}
/* Compute load address for a virtual address in a given dso. */
__NO_SAFESTACK NO_ASAN static inline size_t saddr(struct dso* p, size_t v) {
return p->l_map.l_addr + v;
}
__NO_SAFESTACK NO_ASAN static inline void* laddr(struct dso* p, size_t v) {
return (void*)saddr(p, v);
}
__NO_SAFESTACK NO_ASAN static inline void (*fpaddr(struct dso* p, size_t v))(void) {
return (void (*)(void))saddr(p, v);
}
// Accessors for dso previous and next pointers.
__NO_SAFESTACK NO_ASAN static inline struct dso* dso_next(struct dso* p) {
return (struct dso*)p->l_map.l_next;
}
__NO_SAFESTACK NO_ASAN static inline struct dso* dso_prev(struct dso* p) {
return (struct dso*)p->l_map.l_prev;
}
__NO_SAFESTACK NO_ASAN static inline void dso_set_next(struct dso* p, struct dso* next) {
p->l_map.l_next = next ? &next->l_map : NULL;
}
__NO_SAFESTACK NO_ASAN static inline void dso_set_prev(struct dso* p, struct dso* prev) {
p->l_map.l_prev = prev ? &prev->l_map : NULL;
}
// TODO(mcgrathr): Working around arcane compiler issues; find a better way.
// The compiler can decide to turn the loop below into a memset call. Since
// memset is an exported symbol, calls to that name are PLT calls. But this
// code runs before PLT calls are available. So use the .weakref trick to
// tell the assembler to rename references (the compiler generates) to memset
// to __libc_memset. That's a hidden symbol that won't cause a PLT entry to
// be generated, so it's safe to use in calls here.
//
// Under ASan, the compiler generates calls to __asan_memset instead.
// That is normally a PLT call to the ASan runtime DSO, before PLT
// resolution it might not even have been mapped in yet.
//
// A further issue is that the __asan_memset implementation may use
// ShadowCallStack, but some calls here are before stack ABI setup
// necessary for that to work. So redirecting to __libc_memset also
// ensures those calls reach libc's own memset implementation, which is
// always a leaf function that doesn't require the ShadowCallStack ABI.
//
// Note this also affects the explicit memset calls made in this source
// file. That's necessary for some of the instances: those made before PLT
// resolution and/or stack ABI setup are complete. It's superfluous for
// the instances that can only happen later (e.g. via dl* calls), but
// happens anyway since this symbol redirection is necessary to catch the
// compiler-generated calls. However, relying on this implicit redirection
// rather than explicitly using __libc_memset in the early-startup calls
// here means that the compiler gets to decide whether to inline each case
// or generate the memset call.
//
// All the same applies to memcpy calls here as well, since __asan_memcpy
// is a PLT call that uses ShadowCallStack.
__asm__(".weakref memcpy,__libc_memcpy");
__asm__(".weakref memset,__libc_memset");
#if __has_feature(address_sanitizer)
__asm__(".weakref __asan_memcpy,__libc_memcpy");
__asm__(".weakref __asan_memset,__libc_memset");
#endif
__NO_SAFESTACK NO_ASAN static void decode_vec(ElfW(Dyn) * v, size_t* a, size_t cnt) {
size_t i;
for (i = 0; i < cnt; i++)
a[i] = 0;
for (; v->d_tag; v++)
if (v->d_tag - 1 < cnt - 1) {
a[0] |= 1UL << v->d_tag;
a[v->d_tag] = v->d_un.d_val;
}
}
__NO_SAFESTACK NO_ASAN static int search_vec(ElfW(Dyn) * v, size_t* r, size_t key) {
for (; v->d_tag != key; v++)
if (!v->d_tag)
return 0;
*r = v->d_un.d_val;
return 1;
}
__NO_SAFESTACK NO_ASAN static uint32_t sysv_hash(const char* s0) {
const unsigned char* s = (void*)s0;
uint_fast32_t h = 0;
while (*s) {
h = 16 * h + *s++;
h ^= h >> 24 & 0xf0;
}
return h & 0xfffffff;
}
__NO_SAFESTACK NO_ASAN static uint32_t gnu_hash(const char* s0) {
const unsigned char* s = (void*)s0;
uint_fast32_t h = 5381;
for (; *s; s++)
h += h * 32 + *s;
return h;
}
__NO_SAFESTACK NO_ASAN static Sym* sysv_lookup(const char* s, uint32_t h, struct dso* dso) {
size_t i;
Sym* syms = dso->syms;
uint32_t* hashtab = dso->hashtab;
char* strings = dso->strings;
for (i = hashtab[2 + h % hashtab[0]]; i; i = hashtab[2 + hashtab[0] + i]) {
if ((!dso->versym || dso->versym[i] >= 0) && (!strcmp(s, strings + syms[i].st_name)))
return syms + i;
}
return 0;
}
__NO_SAFESTACK NO_ASAN static Sym* gnu_lookup(uint32_t h1, uint32_t* hashtab, struct dso* dso,
const char* s) {
uint32_t nbuckets = hashtab[0];
uint32_t* buckets = hashtab + 4 + hashtab[2] * (sizeof(size_t) / 4);
uint32_t i = buckets[h1 % nbuckets];
if (!i)
return 0;
uint32_t* hashval = buckets + nbuckets + (i - hashtab[1]);
for (h1 |= 1;; i++) {
uint32_t h2 = *hashval++;
if ((h1 == (h2 | 1)) && (!dso->versym || dso->versym[i] >= 0) &&
!strcmp(s, dso->strings + dso->syms[i].st_name))
return dso->syms + i;
if (h2 & 1)
break;
}
return 0;
}
__NO_SAFESTACK NO_ASAN static Sym* gnu_lookup_filtered(uint32_t h1, uint32_t* hashtab,
struct dso* dso, const char* s,
uint32_t fofs, size_t fmask) {
const size_t* bloomwords = (const void*)(hashtab + 4);
size_t f = bloomwords[fofs & (hashtab[2] - 1)];
if (!(f & fmask))
return 0;
f >>= (h1 >> hashtab[3]) % (8 * sizeof f);
if (!(f & 1))
return 0;
return gnu_lookup(h1, hashtab, dso, s);
}
#define OK_TYPES \
(1 << STT_NOTYPE | 1 << STT_OBJECT | 1 << STT_FUNC | 1 << STT_COMMON | 1 << STT_TLS)
#define OK_BINDS (1 << STB_GLOBAL | 1 << STB_WEAK | 1 << STB_GNU_UNIQUE)
__NO_SAFESTACK NO_ASAN static struct symdef find_sym(struct dso* dso, const char* s, int need_def) {
uint32_t h = 0, gh = 0, gho = 0, *ght;
size_t ghm = 0;
struct symdef def = {};
for (; dso; dso = dso_next(dso)) {
Sym* sym;
if (!dso->global)
continue;
if ((ght = dso->ghashtab)) {
if (!ghm) {
gh = gnu_hash(s);
int maskbits = 8 * sizeof ghm;
gho = gh / maskbits;
ghm = 1ul << gh % maskbits;
}
sym = gnu_lookup_filtered(gh, ght, dso, s, gho, ghm);
} else {
if (!h)
h = sysv_hash(s);
sym = sysv_lookup(s, h, dso);
}
if (!sym)
continue;
if (!sym->st_shndx)
if (need_def || (sym->st_info & 0xf) == STT_TLS)
continue;
if (!sym->st_value)
if ((sym->st_info & 0xf) != STT_TLS)
continue;
if (!(1 << (sym->st_info & 0xf) & OK_TYPES))
continue;
if (!(1 << (sym->st_info >> 4) & OK_BINDS))
continue;
if (def.sym && sym->st_info >> 4 == STB_WEAK)
continue;
def.sym = sym;
def.dso = dso;
if (sym->st_info >> 4 == STB_GLOBAL)
break;
}
return def;
}
__attribute__((__visibility__("hidden"))) ptrdiff_t __tlsdesc_static(void), __tlsdesc_dynamic(void);
__NO_SAFESTACK NO_ASAN static void do_relocs(struct dso* dso, size_t* rel, size_t rel_size,
size_t stride) {
ElfW(Addr) base = dso->l_map.l_addr;
Sym* syms = dso->syms;
char* strings = dso->strings;
Sym* sym;
const char* name;
void* ctx;
int type;
int sym_index;
struct symdef def;
size_t* reloc_addr;
size_t sym_val;
size_t tls_val;
size_t addend;
int skip_relative = 0, reuse_addends = 0, save_slot = 0;
if (dso == &ldso) {
/* Only ldso's REL table needs addend saving/reuse. */
if (rel == apply_addends_to)
reuse_addends = 1;
skip_relative = 1;
}
for (; rel_size; rel += stride, rel_size -= stride * sizeof(size_t)) {
if (skip_relative && R_TYPE(rel[1]) == REL_RELATIVE)
continue;
type = R_TYPE(rel[1]);
if (type == REL_NONE)
continue;
sym_index = R_SYM(rel[1]);
reloc_addr = laddr(dso, rel[0]);
if (sym_index) {
sym = syms + sym_index;
name = strings + sym->st_name;
ctx = type == REL_COPY ? dso_next(head) : head;
def = (sym->st_info & 0xf) == STT_SECTION ? (struct symdef){.dso = dso, .sym = sym}
: find_sym(ctx, name, type == REL_PLT);
if (!def.sym && (sym->st_shndx != SHN_UNDEF || sym->st_info >> 4 != STB_WEAK)) {
error("Error relocating %s: %s: symbol not found", dso->l_map.l_name, name);
if (runtime)
longjmp(*rtld_fail, 1);
continue;
}
} else {
name = "(local)";
sym = 0;
def.sym = 0;
def.dso = dso;
}
if (stride > 2) {
addend = rel[2];
} else if (type == REL_GOT || type == REL_PLT || type == REL_COPY) {
addend = 0;
} else if (reuse_addends) {
/* Save original addend in stage 2 where the dso
* chain consists of just ldso; otherwise read back
* saved addend since the inline one was clobbered. */
if (head == &ldso)
saved_addends[save_slot] = *reloc_addr;
addend = saved_addends[save_slot++];
} else {
addend = *reloc_addr;
}
sym_val = def.sym ? saddr(def.dso, def.sym->st_value) : 0;
tls_val = def.sym ? def.sym->st_value : 0;
switch (type) {
case REL_NONE:
break;
case REL_OFFSET:
addend -= (size_t)reloc_addr;
case REL_SYMBOLIC:
case REL_GOT:
case REL_PLT:
*reloc_addr = sym_val + addend;
break;
case REL_RELATIVE:
*reloc_addr = base + addend;
break;
case REL_COPY:
memcpy(reloc_addr, (void*)sym_val, sym->st_size);
break;
case REL_OFFSET32:
*(uint32_t*)reloc_addr = sym_val + addend - (size_t)reloc_addr;
break;
case REL_FUNCDESC:
*reloc_addr = def.sym ? (size_t)(def.dso->funcdescs + (def.sym - def.dso->syms)) : 0;
break;
case REL_FUNCDESC_VAL:
if ((sym->st_info & 0xf) == STT_SECTION)
*reloc_addr += sym_val;
else
*reloc_addr = sym_val;
reloc_addr[1] = def.sym ? (size_t)def.dso->got : 0;
break;
case REL_DTPMOD:
*reloc_addr = def.dso->tls_id;
break;
case REL_DTPOFF:
*reloc_addr = tls_val + addend - DTP_OFFSET;
break;
#ifdef TLS_ABOVE_TP
case REL_TPOFF:
*reloc_addr = tls_val + def.dso->tls.offset + addend;
break;
#else
case REL_TPOFF:
*reloc_addr = tls_val - def.dso->tls.offset + addend;
break;
case REL_TPOFF_NEG:
*reloc_addr = def.dso->tls.offset - tls_val + addend;
break;
#endif
case REL_TLSDESC:
if (stride < 3)
addend = reloc_addr[1];
if (runtime && def.dso->tls_id >= static_tls_cnt) {
size_t* new = dl_alloc(2 * sizeof(size_t));
if (!new) {
error("Error relocating %s: cannot allocate TLSDESC for %s", dso->l_map.l_name, name);
longjmp(*rtld_fail, 1);
}
new[0] = def.dso->tls_id;
new[1] = tls_val + addend;
reloc_addr[0] = (size_t)__tlsdesc_dynamic;
reloc_addr[1] = (size_t) new;
} else {
reloc_addr[0] = (size_t)__tlsdesc_static;
#ifdef TLS_ABOVE_TP
reloc_addr[1] = tls_val + def.dso->tls.offset + addend;
#else
reloc_addr[1] = tls_val - def.dso->tls.offset + addend;
#endif
}
break;
default:
error("Error relocating %s: unsupported relocation type %d", dso->l_map.l_name, type);
if (runtime)
longjmp(*rtld_fail, 1);
continue;
}
}
}
__NO_SAFESTACK static void unmap_library(struct dso* dso) {
if (dso->map && dso->map_len) {
munmap(dso->map, dso->map_len);
}
if (dso->vmar != ZX_HANDLE_INVALID) {
_zx_vmar_destroy(dso->vmar);
_zx_handle_close(dso->vmar);
dso->vmar = ZX_HANDLE_INVALID;
}
}
// app.module_id is always zero, so assignments start with 1.
__NO_SAFESTACK NO_ASAN static void assign_module_id(struct dso* dso) {
static unsigned int last_module_id;
dso->module_id = ++last_module_id;
}
// Locate the build ID note just after mapping the segments in.
// This is called from dls2, so it cannot use any non-static functions.
__NO_SAFESTACK NO_ASAN static bool find_buildid_note(struct dso* dso, const Phdr* seg) {
const char* end = laddr(dso, seg->p_vaddr + seg->p_filesz);
for (const struct gnu_note* n = laddr(dso, seg->p_vaddr); (const char*)n < end;
n = (const void*)((const char*)&n->name + ((n->nhdr.n_namesz + 3) & -4) +
((n->nhdr.n_descsz + 3) & -4))) {
if (n->nhdr.n_type == NT_GNU_BUILD_ID && n->nhdr.n_namesz == sizeof(GNU_NOTE_NAME) &&
n->name.word == GNU_NOTE_NAME.word) {
dso->build_id_note = n;
return true;
}
}
return false;
}
// TODO(mcgrathr): Remove this all when everything uses markup.
// We pre-format the log line for each DSO early so that we can log it
// without running any nontrivial code. We use hand-rolled formatting
// code to avoid using large and complex code like the printf engine.
// Each line looks like "dso: id=... base=0x... name=...\n".
#define BUILD_ID_LOG_1 "dso: id="
#define BUILD_ID_LOG_NONE "none"
#define BUILD_ID_LOG_2 " base=0x"
#define BUILD_ID_LOG_3 " name="
__NO_SAFESTACK static size_t build_id_log_size(struct dso* dso, size_t namelen) {
size_t id_size = (dso->build_id_note == NULL ? sizeof(BUILD_ID_LOG_NONE) - 1
: dso->build_id_note->nhdr.n_descsz * 2);
return (sizeof(BUILD_ID_LOG_1) - 1 + id_size + sizeof(BUILD_ID_LOG_2) - 1 + (sizeof(size_t) * 2) +
sizeof(BUILD_ID_LOG_3) - 1 + namelen + 1);
}
__NO_SAFESTACK static void format_build_id_log(struct dso* dso, char* buffer, const char* name,
size_t namelen) {
#define HEXDIGITS "0123456789abcdef"
const struct gnu_note* note = dso->build_id_note;
dso->build_id_log.iov_base = buffer;
memcpy(buffer, BUILD_ID_LOG_1, sizeof(BUILD_ID_LOG_1) - 1);
char* p = buffer + sizeof(BUILD_ID_LOG_1) - 1;
if (note == NULL) {
memcpy(p, BUILD_ID_LOG_NONE, sizeof(BUILD_ID_LOG_NONE) - 1);
p += sizeof(BUILD_ID_LOG_NONE) - 1;
} else {
for (Elf64_Word i = 0; i < note->nhdr.n_descsz; ++i) {
uint8_t byte = note->desc[i];
*p++ = HEXDIGITS[byte >> 4];
*p++ = HEXDIGITS[byte & 0xf];
}
}
memcpy(p, BUILD_ID_LOG_2, sizeof(BUILD_ID_LOG_2) - 1);
p += sizeof(BUILD_ID_LOG_2) - 1;
uintptr_t base = (uintptr_t)dso->l_map.l_addr;
unsigned int shift = sizeof(uintptr_t) * 8;
do {
shift -= 4;
*p++ = HEXDIGITS[(base >> shift) & 0xf];
} while (shift > 0);
memcpy(p, BUILD_ID_LOG_3, sizeof(BUILD_ID_LOG_3) - 1);
p += sizeof(BUILD_ID_LOG_3) - 1;
memcpy(p, name, namelen);
p += namelen;
*p++ = '\n';
dso->build_id_log.iov_len = p - buffer;
#undef HEXDIGITS
}
__NO_SAFESTACK static void allocate_and_format_build_id_log(struct dso* dso) {
const char* name = dso->l_map.l_name;
if (name[0] == '\0')
name = dso->soname == NULL ? "<application>" : dso->soname;
size_t namelen = strlen(name);
char* buffer = dl_alloc(build_id_log_size(dso, namelen));
format_build_id_log(dso, buffer, name, namelen);
}
// TODO(mcgrathr): Remove above when everything uses markup.
// Format the markup elements by hand to avoid using large and complex code
// like the printf engine.
__NO_SAFESTACK static char* format_string(char* p, const char* string, size_t len) {
return memcpy(p, string, len) + len;
}
#define FORMAT_HEX_VALUE_SIZE (2 + (sizeof(uint64_t) * 2))
#define HEXDIGITS "0123456789abcdef"
__NO_SAFESTACK static char* format_hex_value(char buffer[FORMAT_HEX_VALUE_SIZE], uint64_t value) {
char* p = buffer;
if (value == 0) {
// No "0x" prefix on zero.
*p++ = '0';
} else {
*p++ = '0';
*p++ = 'x';
// Skip the high nybbles that are zero.
int shift = 60;
while ((value >> shift) == 0) {
shift -= 4;
}
do {
*p++ = HEXDIGITS[(value >> shift) & 0xf];
shift -= 4;
} while (shift >= 0);
}
return p;
}
__NO_SAFESTACK static char* format_hex_string(char* p, const uint8_t* string, size_t len) {
for (size_t i = 0; i < len; ++i) {
uint8_t byte = string[i];
*p++ = HEXDIGITS[byte >> 4];
*p++ = HEXDIGITS[byte & 0xf];
}
return p;
}
// The format theoretically does not constrain the size of build ID notes,
// but there is a reasonable upper bound.
#define MAX_BUILD_ID_SIZE 64
// Likewise, there's no real limit on the length of module names.
// But they're only included in the markup output to be informative,
// so truncating them is OK.
#define MODULE_NAME_SIZE 64
#define MODULE_ELEMENT_BEGIN "{{{module:"
#define MODULE_ELEMENT_BUILD_ID_BEGIN ":elf:"
#define MODULE_ELEMENT_END "}}}\n"
#define MODULE_ELEMENT_SIZE \
(sizeof(MODULE_ELEMENT_BEGIN) - 1 + FORMAT_HEX_VALUE_SIZE + 1 + MODULE_NAME_SIZE + \
sizeof(MODULE_ELEMENT_BUILD_ID_BEGIN) - 1 + (MAX_BUILD_ID_SIZE * 2) + 1 + \
sizeof(MODULE_ELEMENT_END))
__NO_SAFESTACK static void log_module_element(struct dso* dso) {
char buffer[MODULE_ELEMENT_SIZE];
char* p = format_string(buffer, MODULE_ELEMENT_BEGIN, sizeof(MODULE_ELEMENT_BEGIN) - 1);
p = format_hex_value(p, dso->module_id);
*p++ = ':';
const char* name = dso->l_map.l_name;
if (name[0] == '\0') {
name = dso->soname == NULL ? "<application>" : dso->soname;
}
size_t namelen = strlen(name);
if (namelen > MODULE_NAME_SIZE) {
namelen = MODULE_NAME_SIZE;
}
p = format_string(p, name, namelen);
p = format_string(p, MODULE_ELEMENT_BUILD_ID_BEGIN, sizeof(MODULE_ELEMENT_BUILD_ID_BEGIN) - 1);
if (dso->build_id_note) {
p = format_hex_string(p, dso->build_id_note->desc, dso->build_id_note->nhdr.n_descsz);
}
p = format_string(p, MODULE_ELEMENT_END, sizeof(MODULE_ELEMENT_END) - 1);
_dl_log_write(buffer, p - buffer);
}
#define MMAP_ELEMENT_BEGIN "{{{mmap:"
#define MMAP_ELEMENT_LOAD_BEGIN ":load:"
#define MMAP_ELEMENT_END "}}}\n"
#define MMAP_ELEMENT_SIZE \
(sizeof(MMAP_ELEMENT_BEGIN) - 1 + FORMAT_HEX_VALUE_SIZE + 1 + FORMAT_HEX_VALUE_SIZE + 1 + \
sizeof(MMAP_ELEMENT_LOAD_BEGIN) - 1 + FORMAT_HEX_VALUE_SIZE + 1 + 3 + 1 + \
FORMAT_HEX_VALUE_SIZE)
__NO_SAFESTACK static void log_mmap_element(struct dso* dso, const Phdr* ph) {
size_t start = ph->p_vaddr & -PAGE_SIZE;
size_t end = (ph->p_vaddr + ph->p_memsz + PAGE_SIZE - 1) & -PAGE_SIZE;
char buffer[MMAP_ELEMENT_SIZE];
char* p = format_string(buffer, MMAP_ELEMENT_BEGIN, sizeof(MMAP_ELEMENT_BEGIN) - 1);
p = format_hex_value(p, saddr(dso, start));
*p++ = ':';
p = format_hex_value(p, end - start);
p = format_string(p, MMAP_ELEMENT_LOAD_BEGIN, sizeof(MMAP_ELEMENT_LOAD_BEGIN) - 1);
p = format_hex_value(p, dso->module_id);
*p++ = ':';
if (ph->p_flags & PF_R) {
*p++ = 'r';
}
if (ph->p_flags & PF_W) {
*p++ = 'w';
}
if (ph->p_flags & PF_X) {
*p++ = 'x';
}
*p++ = ':';
p = format_hex_value(p, start);
p = format_string(p, MMAP_ELEMENT_END, sizeof(MMAP_ELEMENT_END) - 1);
_dl_log_write(buffer, p - buffer);
}
// No newline because it's immediately followed by a {{{module:...}}}.
#define RESET_ELEMENT "{{{reset}}}"
__NO_SAFESTACK static void log_dso(struct dso* dso) {
if (dso == head) {
// Write the reset element before the first thing listed.
_dl_log_write(RESET_ELEMENT, sizeof(RESET_ELEMENT) - 1);
}
log_module_element(dso);
if (dso->phdr) {
for (unsigned int i = 0; i < dso->phnum; ++i) {
if (dso->phdr[i].p_type == PT_LOAD) {
log_mmap_element(dso, &dso->phdr[i]);
}
}
}
// TODO(mcgrathr): Remove this when everything uses markup.
_dl_log_write(dso->build_id_log.iov_base, dso->build_id_log.iov_len);
}
__NO_SAFESTACK void _dl_log_unlogged(void) {
// The first thread to successfully swap in 0 and get an old value
// for unlogged_tail is responsible for logging all the unlogged
// DSOs up through that pointer. If dlopen calls move the tail
// and another thread then calls into here, we can race with that
// thread. So we use a separate atomic_flag on each 'struct dso'
// to ensure only one thread prints each one.
uintptr_t last_unlogged = atomic_load_explicit(&unlogged_tail, memory_order_acquire);
do {
if (last_unlogged == 0)
return;
} while (!atomic_compare_exchange_weak_explicit(&unlogged_tail, &last_unlogged, 0,
memory_order_acq_rel, memory_order_relaxed));
for (struct dso* p = head; true; p = dso_next(p)) {
if (!atomic_flag_test_and_set_explicit(&p->logged, memory_order_relaxed)) {
log_dso(p);
}
if ((struct dso*)last_unlogged == p) {
break;
}
}
}
__NO_SAFESTACK NO_ASAN static zx_status_t map_library(zx_handle_t vmo, struct dso* dso) {
struct {
Ehdr ehdr;
// A typical ELF file has 7 or 8 phdrs, so in practice
// this is always enough. Life is simpler if there is no
// need for dynamic allocation here.
Phdr phdrs[16];
} buf;
size_t phsize;
size_t addr_min = SIZE_MAX, addr_max = 0, map_len;
size_t this_min, this_max;
size_t nsegs = 0;
const Ehdr* const eh = &buf.ehdr;
Phdr *ph, *ph0;
unsigned char *map = MAP_FAILED, *base;
size_t dyn = 0;
size_t tls_image = 0;
size_t i;
size_t l;
zx_status_t status = _zx_vmo_get_size(vmo, &l);
if (status != ZX_OK)
return status;
status = _zx_vmo_read(vmo, &buf, 0, sizeof(buf) < l ? sizeof(buf) : l);
if (status != ZX_OK)
return status;
// We cannot support ET_EXEC in the general case, because its fixed
// addresses might conflict with where the dynamic linker has already
// been loaded. It's also policy in Fuchsia that all executables are
// PIEs to maximize ASLR security benefits. So don't even try to
// handle loading ET_EXEC.
if (l < sizeof *eh || eh->e_type != ET_DYN)
goto noexec;
phsize = eh->e_phentsize * eh->e_phnum;
if (phsize > sizeof(buf.phdrs))
goto noexec;
if (eh->e_phoff + phsize > l) {
status = _zx_vmo_read(vmo, buf.phdrs, eh->e_phoff, phsize);
if (status != ZX_OK)
goto error;
ph = ph0 = buf.phdrs;
} else {
ph = ph0 = (void*)((char*)&buf + eh->e_phoff);
}
const Phdr* first_note = NULL;
const Phdr* last_note = NULL;
for (i = eh->e_phnum; i; i--, ph = (void*)((char*)ph + eh->e_phentsize)) {
switch (ph->p_type) {
case PT_LOAD:
nsegs++;
if (ph->p_vaddr < addr_min) {
addr_min = ph->p_vaddr;
}
if (ph->p_vaddr + ph->p_memsz > addr_max) {
addr_max = ph->p_vaddr + ph->p_memsz;
}
if (ph->p_flags & PF_X) {
dso->code_start = addr_min;
dso->code_end = addr_max;
}
break;
case PT_DYNAMIC:
dyn = ph->p_vaddr;
break;
case PT_TLS:
tls_image = ph->p_vaddr;
dso->tls.align = ph->p_align;
dso->tls.len = ph->p_filesz;
dso->tls.size = ph->p_memsz;
break;
case PT_GNU_RELRO:
dso->relro_start = ph->p_vaddr;
dso->relro_end = ph->p_vaddr + ph->p_memsz;
break;
case PT_NOTE:
if (first_note == NULL)
first_note = ph;
last_note = ph;
break;
case PT_GNU_STACK:
if (ph->p_flags & PF_X) {
error(
"%s requires executable stack"
" (built with -z execstack?),"
" which Fuchsia will never support",
dso->soname == NULL ? dso->l_map.l_name : dso->soname);
goto noexec;
}
break;
}
}
if (!dyn)
goto noexec;
addr_max += PAGE_SIZE - 1;
addr_max &= -PAGE_SIZE;
addr_min &= -PAGE_SIZE;
map_len = addr_max - addr_min;
// Allocate a VMAR to reserve the whole address range. Stash
// the new VMAR's handle until relocation has finished, because
// we need it to adjust page protections for RELRO.
uintptr_t vmar_base;
status = _zx_vmar_allocate(
__zircon_vmar_root_self,
ZX_VM_CAN_MAP_READ | ZX_VM_CAN_MAP_WRITE | ZX_VM_CAN_MAP_EXECUTE | ZX_VM_CAN_MAP_SPECIFIC, 0,
map_len, &dso->vmar, &vmar_base);
if (status != ZX_OK) {
error("failed to reserve %zu bytes of address space: %d\n", map_len, status);
goto error;
}
char vmo_name[ZX_MAX_NAME_LEN];
if (_zx_object_get_property(vmo, ZX_PROP_NAME, vmo_name, sizeof(vmo_name)) != ZX_OK ||
vmo_name[0] == '\0')
memcpy(vmo_name, VMO_NAME_UNKNOWN, sizeof(VMO_NAME_UNKNOWN));
dso->map = map = (void*)vmar_base;
dso->map_len = map_len;
base = map - addr_min;
dso->phdr = 0;
dso->phnum = 0;
uint_fast16_t nbss = 0, ndata = 0;
for (ph = ph0, i = eh->e_phnum; i; i--, ph = (void*)((char*)ph + eh->e_phentsize)) {
if (ph->p_type != PT_LOAD)
continue;
/* Check if the programs headers are in this load segment, and
* if so, record the address for use by dl_iterate_phdr. */
if (!dso->phdr && eh->e_phoff >= ph->p_offset &&
eh->e_phoff + phsize <= ph->p_offset + ph->p_filesz) {
dso->phdr = (void*)(base + ph->p_vaddr + (eh->e_phoff - ph->p_offset));
dso->phnum = eh->e_phnum;
dso->phentsize = eh->e_phentsize;
}
this_min = ph->p_vaddr & -PAGE_SIZE;
this_max = (ph->p_vaddr + ph->p_memsz + PAGE_SIZE - 1) & -PAGE_SIZE;
size_t off_start = ph->p_offset & -PAGE_SIZE;
zx_vm_option_t zx_options = ZX_VM_SPECIFIC | ZX_VM_ALLOW_FAULTS;
zx_options |= (ph->p_flags & PF_R) ? ZX_VM_PERM_READ : 0;
zx_options |= (ph->p_flags & PF_W) ? ZX_VM_PERM_WRITE : 0;
zx_options |= (ph->p_flags & PF_X) ? ZX_VM_PERM_EXECUTE : 0;
uintptr_t mapaddr = (uintptr_t)base + this_min;
zx_handle_t map_vmo = vmo;
size_t map_size = this_max - this_min;
if (map_size == 0)
continue;
if (ph->p_flags & PF_W) {
size_t data_size = ((ph->p_vaddr + ph->p_filesz + PAGE_SIZE - 1) & -PAGE_SIZE) - this_min;
if (data_size == 0) {
// This segment is purely zero-fill.
status = _zx_vmo_create(map_size, 0, &map_vmo);
if (status == ZX_OK) {
char name[ZX_MAX_NAME_LEN] = VMO_NAME_PREFIX_BSS;
memcpy(&name[sizeof(VMO_NAME_PREFIX_BSS) - 1], vmo_name,
ZX_MAX_NAME_LEN - sizeof(VMO_NAME_PREFIX_BSS));
// Replace the N with a digit for how many bssN's there have been.
name[sizeof(VMO_NAME_PREFIX_BSS) - 3] = "0123456789abcdef"[nbss++];
_zx_object_set_property(map_vmo, ZX_PROP_NAME, name, strlen(name));
}
} else {
// Get a writable (lazy) copy of the portion of the file VMO.
status = _zx_vmo_create_child(vmo, ZX_VMO_CHILD_COPY_ON_WRITE | ZX_VMO_CHILD_RESIZABLE,
off_start, data_size, &map_vmo);
if (status == ZX_OK && map_size > data_size) {
// Extend the writable VMO to cover the .bss pages too.
// These pages will be zero-filled, not copied from the
// file VMO.
status = _zx_vmo_set_size(map_vmo, map_size);
if (status != ZX_OK) {
_zx_handle_close(map_vmo);
goto error;
}
}
if (status == ZX_OK) {
char name[ZX_MAX_NAME_LEN] = VMO_NAME_PREFIX_DATA;
memcpy(&name[sizeof(VMO_NAME_PREFIX_DATA) - 1], vmo_name,
ZX_MAX_NAME_LEN - sizeof(VMO_NAME_PREFIX_DATA));
if (ph->p_vaddr >= dso->relro_start && ph->p_vaddr + ph->p_memsz <= dso->relro_end) {
// Make "data1" be "relro" instead when the RELRO region covers
// the entire segment.
static_assert(sizeof(VMO_NAME_PREFIX_DATA) == sizeof(VMO_NAME_PREFIX_RELRO), "");
memcpy(name, VMO_NAME_PREFIX_RELRO, sizeof(VMO_NAME_PREFIX_RELRO) - 1);
} else {
// Replace the N with a digit for how many dataN's.
name[sizeof(VMO_NAME_PREFIX_DATA) - 3] = "0123456789abcdef"[ndata++];
}
_zx_object_set_property(map_vmo, ZX_PROP_NAME, name, strlen(name));
}
}
if (status != ZX_OK)
goto error;
off_start = 0;
} else if (ph->p_memsz > ph->p_filesz) {
// Read-only .bss is not a thing.
goto noexec;
}
status = _zx_vmar_map(dso->vmar, zx_options, mapaddr - vmar_base, map_vmo, off_start, map_size,
&mapaddr);
if (map_vmo != vmo)
_zx_handle_close(map_vmo);
if (status != ZX_OK)
goto error;
if (ph->p_memsz > ph->p_filesz) {
// The final partial page of data from the file is followed by
// whatever the file's contents there are, but in the memory
// image that partial page should be all zero.
uintptr_t file_end = (uintptr_t)base + ph->p_vaddr + ph->p_filesz;
uintptr_t map_end = mapaddr + map_size;
if (map_end > file_end)
memset((void*)file_end, 0, map_end - file_end);
}
}
dso->l_map.l_addr = (uintptr_t)base;
dso->l_map.l_ld = laddr(dso, dyn);
if (dso->tls.size)
dso->tls.image = laddr(dso, tls_image);
if (first_note != NULL) {
for (const Phdr* seg = first_note; seg <= last_note; ++seg) {
if (seg->p_type == PT_NOTE && find_buildid_note(dso, seg))
break;
}
}
return ZX_OK;
noexec:
// We overload this to translate into ENOEXEC later.
status = ZX_ERR_WRONG_TYPE;
error:
if (map != MAP_FAILED)
unmap_library(dso);
if (dso->vmar != ZX_HANDLE_INVALID && !KEEP_DSO_VMAR)
_zx_handle_close(dso->vmar);
dso->vmar = ZX_HANDLE_INVALID;
return status;
}
__NO_SAFESTACK NO_ASAN static void decode_dyn(struct dso* p) {
size_t dyn[DT_NUM];
decode_vec(p->l_map.l_ld, dyn, DT_NUM);
p->syms = laddr(p, dyn[DT_SYMTAB]);
p->strings = laddr(p, dyn[DT_STRTAB]);
if (dyn[0] & (1 << DT_SONAME))
p->soname = p->strings + dyn[DT_SONAME];
if (dyn[0] & (1 << DT_HASH))
p->hashtab = laddr(p, dyn[DT_HASH]);
if (dyn[0] & (1 << DT_PLTGOT))
p->got = laddr(p, dyn[DT_PLTGOT]);
if (search_vec(p->l_map.l_ld, dyn, DT_GNU_HASH))
p->ghashtab = laddr(p, *dyn);
if (search_vec(p->l_map.l_ld, dyn, DT_VERSYM))
p->versym = laddr(p, *dyn);
}
__NO_SAFESTACK static size_t count_syms(struct dso* p) {
if (p->hashtab)
return p->hashtab[1];
size_t nsym, i;
uint32_t* buckets = p->ghashtab + 4 + (p->ghashtab[2] * sizeof(size_t) / 4);
uint32_t* hashval;
for (i = nsym = 0; i < p->ghashtab[0]; i++) {
if (buckets[i] > nsym)
nsym = buckets[i];
}
if (nsym) {
hashval = buckets + p->ghashtab[0] + (nsym - p->ghashtab[1]);
do
nsym++;
while (!(*hashval++ & 1));
}
return nsym;
}
__NO_SAFESTACK static struct dso* find_library_in(struct dso* p, const char* name) {
while (p != NULL) {
if (!strcmp(p->l_map.l_name, name) || (p->soname != NULL && !strcmp(p->soname, name))) {
++p->refcnt;
break;
}
p = dso_next(p);
}
return p;
}
__NO_SAFESTACK static struct dso* find_library(const char* name) {
// First see if it's in the general list.
struct dso* p = find_library_in(head, name);
if (p == NULL && detached_head != NULL) {
// ldso is not in the list yet, so the first search didn't notice
// anything that is only a dependency of ldso, i.e. the vDSO.
// See if the lookup by name matches ldso or its dependencies.
p = find_library_in(detached_head, name);
if (p == &ldso) {
// If something depends on libc (&ldso), we actually want
// to pull in the entire detached list in its existing
// order (&ldso is always last), so that libc stays after
// its own dependencies.
dso_set_prev(detached_head, tail);
dso_set_next(tail, detached_head);
tail = p;
detached_head = NULL;
} else if (p != NULL) {
// Take it out of its place in the list rooted at detached_head.
if (dso_prev(p) != NULL)
dso_set_next(dso_prev(p), dso_next(p));
else
detached_head = dso_next(p);
if (dso_next(p) != NULL) {
dso_set_prev(dso_next(p), dso_prev(p));
dso_set_next(p, NULL);
}
// Stick it on the main list.
dso_set_next(tail, p);
dso_set_prev(p, tail);
tail = p;
}
}
return p;
}
#define MAX_BUILDID_SIZE 64
__NO_SAFESTACK static void trace_load(struct dso* p) {
static zx_koid_t pid = ZX_KOID_INVALID;
if (pid == ZX_KOID_INVALID) {
zx_info_handle_basic_t process_info;
if (_zx_object_get_info(__zircon_process_self, ZX_INFO_HANDLE_BASIC, &process_info,
sizeof(process_info), NULL, NULL) == ZX_OK) {
pid = process_info.koid;
} else {
// No point in continually calling zx_object_get_info.
// The first 100 are reserved.
pid = 1;
}
}
// Compute extra values useful to tools.
// This is done here so that it's only done when necessary.
char buildid[MAX_BUILDID_SIZE * 2 + 1];
if (p->build_id_note) {
if (p->build_id_note->nhdr.n_descsz > MAX_BUILD_ID_SIZE) {
snprintf(buildid, sizeof(buildid), "build_id_too_large_%u", p->build_id_note->nhdr.n_descsz);
} else {
char* end =
format_hex_string(buildid, p->build_id_note->desc, p->build_id_note->nhdr.n_descsz);
*end = '\0';
}
} else {
strcpy(buildid, "<none>");
}
const char* name = p->soname == NULL ? "<application>" : p->l_map.l_name;
const char* soname = p->soname == NULL ? "<application>" : p->soname;
// The output is in multiple lines to cope with damn line wrapping.
// N.B. Programs like the Intel Processor Trace decoder parse this output.
// Do not change without coordination with consumers.
// TODO(fxbug.dev/30479): Switch to official tracing mechanism when ready.
static int seqno;
debugmsg("@trace_load: %" PRIu64 ":%da %p %p %p", pid, seqno, p->l_map.l_addr, p->map,
p->map + p->map_len);
debugmsg("@trace_load: %" PRIu64 ":%db %s", pid, seqno, buildid);
debugmsg("@trace_load: %" PRIu64 ":%dc %s %s", pid, seqno, soname, name);
++seqno;
}
__NO_SAFESTACK static void do_tls_layout(struct dso* p, char* tls_buffer, int n_th) {
if (p->tls.size == 0)
return;
p->tls_id = ++tls_cnt;
tls_align = MAXP2(tls_align, p->tls.align);
#ifdef TLS_ABOVE_TP
p->tls.offset = (tls_offset + p->tls.align - 1) & -p->tls.align;
tls_offset = p->tls.offset + p->tls.size;
#else
tls_offset += p->tls.size + p->tls.align - 1;
tls_offset -= (tls_offset + (uintptr_t)p->tls.image) & (p->tls.align - 1);
p->tls.offset = tls_offset;
#endif
if (tls_buffer != NULL) {
p->new_dtv = (void*)(-sizeof(size_t) & (uintptr_t)(tls_buffer + sizeof(size_t)));
p->new_tls = (void*)(p->new_dtv + n_th * (tls_cnt + 1));
}
if (tls_tail)
tls_tail->next = &p->tls;
else
libc.tls_head = &p->tls;
tls_tail = &p->tls;
}
__NO_SAFESTACK static zx_status_t load_library_vmo(zx_handle_t vmo, const char* name, int rtld_mode,
struct dso* needed_by, struct dso** loaded) {
struct dso *p, temp_dso = {};
size_t alloc_size;
int n_th = 0;
if (rtld_mode & RTLD_NOLOAD) {
*loaded = NULL;
return ZX_OK;
}
zx_status_t status = map_library(vmo, &temp_dso);
if (status != ZX_OK)
return status;
decode_dyn(&temp_dso);
if (temp_dso.soname != NULL) {
// Now check again if we opened the same file a second time.
// That is, a file with the same DT_SONAME string.
p = find_library(temp_dso.soname);
if (p != NULL) {
unmap_library(&temp_dso);
*loaded = p;
return ZX_OK;
}
}
// If this was loaded by VMO rather than by name, we have to synthesize
// one. If the SONAME if present. Otherwise synthesize something
// informative from the VMO (that won't look like any sensible SONAME).
char synthetic_name[ZX_MAX_NAME_LEN + 32];
if (name == NULL)
name = temp_dso.soname;
if (name == NULL) {
char vmo_name[ZX_MAX_NAME_LEN];
if (_zx_object_get_property(vmo, ZX_PROP_NAME, vmo_name, sizeof(vmo_name)) != ZX_OK)
vmo_name[0] = '\0';
zx_info_handle_basic_t info;
if (_zx_object_get_info(vmo, ZX_INFO_HANDLE_BASIC, &info, sizeof(info), NULL, NULL) != ZX_OK) {
name = "<dlopen_vmo>";
} else {
if (vmo_name[0] == '\0') {
snprintf(synthetic_name, sizeof(synthetic_name), "<VMO#%" PRIu64 ">", info.koid);
} else {
snprintf(synthetic_name, sizeof(synthetic_name), "<VMO#%" PRIu64 "=%s>", info.koid,
vmo_name);
}
name = synthetic_name;
}
}
// Calculate how many slots are needed for dependencies.
size_t ndeps = 1; // Account for a NULL terminator.
for (size_t i = 0; temp_dso.l_map.l_ld[i].d_tag; i++) {
if (temp_dso.l_map.l_ld[i].d_tag == DT_NEEDED)
++ndeps;
}
/* Allocate storage for the new DSO. When there is TLS, this
* storage must include a reservation for all pre-existing
* threads to obtain copies of both the new TLS, and an
* extended DTV capable of storing an additional slot for
* the newly-loaded DSO. */
size_t namelen = strlen(name);
size_t build_id_log_len = build_id_log_size(&temp_dso, namelen);
alloc_size = (sizeof *p + ndeps * sizeof(p->deps[0]) + namelen + 1 + build_id_log_len);
if (runtime && temp_dso.tls.image) {
size_t per_th = temp_dso.tls.size + temp_dso.tls.align + sizeof(void*) * (tls_cnt + 3);
n_th = atomic_load(&libc.thread_count);
if (n_th > SSIZE_MAX / per_th)
alloc_size = SIZE_MAX;
else
alloc_size += n_th * per_th;
}
p = dl_alloc(alloc_size);
if (!p) {
unmap_library(&temp_dso);
return ZX_ERR_NO_MEMORY;
}
*p = temp_dso;
p->refcnt = 1;
p->needed_by = needed_by;
p->l_map.l_name = (void*)&p->buf[ndeps];
memcpy(p->l_map.l_name, name, namelen);
p->l_map.l_name[namelen] = '\0';
assign_module_id(p);
format_build_id_log(p, p->l_map.l_name + namelen + 1, p->l_map.l_name, namelen);
if (runtime)
do_tls_layout(p, p->l_map.l_name + namelen + 1 + build_id_log_len, n_th);
dso_set_next(tail, p);
dso_set_prev(p, tail);
tail = p;
*loaded = p;
return ZX_OK;
}
__NO_SAFESTACK static zx_status_t load_library(const char* name, int rtld_mode,
struct dso* needed_by, struct dso** loaded) {
if (!*name)
return ZX_ERR_INVALID_ARGS;
*loaded = find_library(name);
if (*loaded != NULL)
return ZX_OK;
zx_handle_t vmo;
zx_status_t status = get_library_vmo(name, &vmo);
if (status == ZX_OK) {
status = load_library_vmo(vmo, name, rtld_mode, needed_by, loaded);
_zx_handle_close(vmo);
}
return status;
}
__NO_SAFESTACK static void load_deps(struct dso* p) {
for (; p; p = dso_next(p)) {
struct dso** deps = NULL;
// The two preallocated DSOs don't get space allocated for ->deps.
if (runtime && p->deps == NULL && p != &ldso && p != &vdso)
deps = p->deps = p->buf;
for (size_t i = 0; p->l_map.l_ld[i].d_tag; i++) {
if (p->l_map.l_ld[i].d_tag != DT_NEEDED)
continue;
const char* name = p->strings + p->l_map.l_ld[i].d_un.d_val;
struct dso* dep;
zx_status_t status = load_library(name, 0, p, &dep);
if (status != ZX_OK) {
error("Error loading shared library %s: %s (needed by %s)", name,
_zx_status_get_string(status), p->l_map.l_name);
if (runtime)
longjmp(*rtld_fail, 1);
} else if (deps != NULL) {
*deps++ = dep;
}
}
}
}
__NO_SAFESTACK NO_ASAN static void reloc_all(struct dso* p) {
size_t dyn[DT_NUM];
for (; p; p = dso_next(p)) {
if (p->relocated)
continue;
decode_vec(p->l_map.l_ld, dyn, DT_NUM);
// _dl_start did apply_relr already.
if (p != &ldso) {
apply_relr(p->l_map.l_addr, laddr(p, dyn[DT_RELR]), dyn[DT_RELRSZ]);
}
do_relocs(p, laddr(p, dyn[DT_JMPREL]), dyn[DT_PLTRELSZ], 2 + (dyn[DT_PLTREL] == DT_RELA));
do_relocs(p, laddr(p, dyn[DT_REL]), dyn[DT_RELSZ], 2);
do_relocs(p, laddr(p, dyn[DT_RELA]), dyn[DT_RELASZ], 3);
// _dl_locked_report_globals needs the precise relro bounds so those are
// what get stored. But actually applying them requires page truncation.
const size_t relro_start = p->relro_start & -PAGE_SIZE;
const size_t relro_end = p->relro_end & -PAGE_SIZE;
if (head != &ldso && relro_start != relro_end) {
zx_status_t status = _zx_vmar_protect(p->vmar, ZX_VM_PERM_READ, saddr(p, relro_start),
relro_end - relro_start);
if (status == ZX_ERR_BAD_HANDLE && p == &ldso && p->vmar == ZX_HANDLE_INVALID) {
debugmsg(
"No VMAR_LOADED handle received;"
" cannot protect RELRO for %s\n",
p->l_map.l_name);
} else if (status != ZX_OK) {
error(
"Error relocating %s: RELRO protection"
" %p+%#zx failed: %s",
p->l_map.l_name, laddr(p, relro_start), relro_end - relro_start,
_zx_status_get_string(status));
if (runtime)
longjmp(*rtld_fail, 1);
}
}
// Hold the VMAR handle only long enough to apply RELRO.
// Now it's no longer needed and the mappings cannot be
// changed any more (only unmapped).
if (p->vmar != ZX_HANDLE_INVALID && !KEEP_DSO_VMAR) {
_zx_handle_close(p->vmar);
p->vmar = ZX_HANDLE_INVALID;
}
p->relocated = 1;
}
}
__NO_SAFESTACK NO_ASAN static void kernel_mapped_dso(struct dso* p) {
size_t min_addr = -1, max_addr = 0, cnt;
const Phdr* ph = p->phdr;
for (cnt = p->phnum; cnt--; ph = (void*)((char*)ph + p->phentsize)) {
switch (ph->p_type) {
case PT_LOAD:
if (ph->p_vaddr < min_addr)
min_addr = ph->p_vaddr;
if (ph->p_vaddr + ph->p_memsz > max_addr)
max_addr = ph->p_vaddr + ph->p_memsz;
break;
case PT_DYNAMIC:
p->l_map.l_ld = laddr(p, ph->p_vaddr);
break;
case PT_GNU_RELRO:
p->relro_start = ph->p_vaddr;
p->relro_end = ph->p_vaddr + ph->p_memsz;
break;
case PT_NOTE:
if (p->build_id_note == NULL)
find_buildid_note(p, ph);
break;
}
}
min_addr &= -PAGE_SIZE;
max_addr = (max_addr + PAGE_SIZE - 1) & -PAGE_SIZE;
p->map = laddr(p, min_addr);
p->map_len = max_addr - min_addr;
assign_module_id(p);
}
void __libc_exit_fini(void) {
struct dso* p;
size_t dyn[DT_NUM];
for (p = fini_head; p; p = p->fini_next) {
if (!p->constructed)
continue;
decode_vec(p->l_map.l_ld, dyn, DT_NUM);
if (dyn[0] & (1 << DT_FINI_ARRAY)) {
size_t n = dyn[DT_FINI_ARRAYSZ] / sizeof(size_t);
size_t* fn = (size_t*)laddr(p, dyn[DT_FINI_ARRAY]) + n;
while (n--)
((void (*)(void)) * --fn)();
}
#ifndef NO_LEGACY_INITFINI
if ((dyn[0] & (1 << DT_FINI)) && dyn[DT_FINI])
fpaddr(p, dyn[DT_FINI])();
#endif
}
}
static void do_init_fini(struct dso* p) {
size_t dyn[DT_NUM];
/* Allow recursive calls that arise when a library calls
* dlopen from one of its constructors, but block any
* other threads until all ctors have finished. */
pthread_mutex_lock(&init_fini_lock);
for (; p; p = dso_prev(p)) {
if (p->constructed)
continue;
p->constructed = 1;
decode_vec(p->l_map.l_ld, dyn, DT_NUM);
if (dyn[0] & ((1 << DT_FINI) | (1 << DT_FINI_ARRAY))) {
p->fini_next = fini_head;
fini_head = p;
}
#ifndef NO_LEGACY_INITFINI
if ((dyn[0] & (1 << DT_INIT)) && dyn[DT_INIT])
fpaddr(p, dyn[DT_INIT])();
#endif
if (dyn[0] & (1 << DT_INIT_ARRAY)) {
size_t n = dyn[DT_INIT_ARRAYSZ] / sizeof(size_t);
size_t* fn = laddr(p, dyn[DT_INIT_ARRAY]);
while (n--)
((void (*)(void)) * fn++)();
}
}
pthread_mutex_unlock(&init_fini_lock);
}
void __libc_start_init(void) {
// If a preinit hook spawns a thread that calls dlopen, that thread will
// get to do_init_fini and block on the lock. Now the main thread finishes
// preinit hooks and releases the lock. Then it's a race for which thread
// gets the lock and actually runs all the normal constructors. This is
// expected, but to avoid such races preinit hooks should be very careful
// about what they do and rely on.
pthread_mutex_lock(&init_fini_lock);
size_t dyn[DT_NUM];
decode_vec(head->l_map.l_ld, dyn, DT_NUM);
if (dyn[0] & (1ul << DT_PREINIT_ARRAY)) {
size_t n = dyn[DT_PREINIT_ARRAYSZ] / sizeof(size_t);
size_t* fn = laddr(head, dyn[DT_PREINIT_ARRAY]);
while (n--)
((void (*)(void)) * fn++)();
}
pthread_mutex_unlock(&init_fini_lock);
do_init_fini(tail);
}
// This function exists just to have a breakpoint set on its entry point.
// Define it in assembly as a single return instruction to avoid any ABI
// interactions.
void _dl_debug_state(void);
__asm__(
".pushsection .text._dl_debug_state,\"ax\",%progbits\n"
".type _dl_debug_state,%function\n"
"_dl_debug_state: ret\n"
".size _dl_debug_state, . - _dl_debug_state\n"
".popsection");
__attribute__((__visibility__("hidden"))) void* __tls_get_new(size_t* v) {
pthread_t self = __pthread_self();
if (v[0] <= (size_t)self->head.dtv[0]) {
return (char*)self->head.dtv[v[0]] + v[1] + DTP_OFFSET;
}
/* This is safe without any locks held because, if the caller
* is able to request the Nth entry of the DTV, the DSO list
* must be valid at least that far out and it was synchronized
* at program startup or by an already-completed call to dlopen. */
struct dso* p;
for (p = head; p->tls_id != v[0]; p = dso_next(p))
;
/* Get new DTV space from new DSO if needed */
if (v[0] > (size_t)self->head.dtv[0]) {
void** newdtv = p->new_dtv + (v[0] + 1) * atomic_fetch_add(&p->new_dtv_idx, 1);
memcpy(newdtv, self->head.dtv, ((size_t)self->head.dtv[0] + 1) * sizeof(void*));
newdtv[0] = (void*)v[0];
self->head.dtv = newdtv;
}
/* Get new TLS memory from all new DSOs up to the requested one */
unsigned char* mem;
for (p = head;; p = dso_next(p)) {
if (!p->tls_id || self->head.dtv[p->tls_id])
continue;
mem = p->new_tls + (p->tls.size + p->tls.align) * atomic_fetch_add(&p->new_tls_idx, 1);
mem += ((uintptr_t)p->tls.image - (uintptr_t)mem) & (p->tls.align - 1);
self->head.dtv[p->tls_id] = mem;
memcpy(mem, p->tls.image, p->tls.len);
if (p->tls_id == v[0])
break;
}
return mem + v[1] + DTP_OFFSET;
}
__NO_SAFESTACK struct pthread* __init_main_thread(zx_handle_t thread_self) {
pthread_attr_t attr = DEFAULT_PTHREAD_ATTR;
char thread_self_name[ZX_MAX_NAME_LEN];
if (_zx_object_get_property(thread_self, ZX_PROP_NAME, thread_self_name,
sizeof(thread_self_name)) != ZX_OK)
strcpy(thread_self_name, "(initial-thread)");
thrd_t td = __allocate_thread(attr._a_guardsize, attr._a_stacksize, thread_self_name, NULL);
if (td == NULL) {
debugmsg("No memory for %zu bytes thread-local storage.\n", libc.tls_size);
_exit(127);
}
zx_status_t status = zxr_thread_adopt(thread_self, &td->zxr_thread);
if (status != ZX_OK)
__builtin_trap();
zxr_tp_set(thread_self, pthread_to_tp(td));
// Now that the thread descriptor is set up, it's safe to use the
// dlerror machinery.
runtime = 1;
return td;
}
__NO_SAFESTACK static void update_tls_size(void) {
libc.tls_cnt = tls_cnt;
libc.tls_align = tls_align;
libc.tls_size =
ZX_ALIGN((1 + tls_cnt) * sizeof(void*) + tls_offset + sizeof(struct pthread) + tls_align * 2,
tls_align);
// TODO(mcgrathr): The TLS block is always allocated in whole pages.
// We should keep track of the available slop to the end of the page
// and make dlopen use that for new dtv/TLS space when it fits.
}
/* Stage 1 of the dynamic linker is defined in dlstart.c. It calls the
* following stage 2 and stage 3 functions via primitive symbolic lookup
* since it does not have access to their addresses to begin with. */
/* Stage 2 of the dynamic linker is called after relative relocations
* have been processed. It can make function calls to static functions
* and access string literals and static data, but cannot use extern
* symbols. Its job is to perform symbolic relocations on the dynamic
* linker itself, but some of the relocations performed may need to be
* replaced later due to copy relocations in the main program. */
static dl_start_return_t __dls3(void* start_arg);
__NO_SAFESTACK NO_ASAN __attribute__((__visibility__("hidden"))) dl_start_return_t __dls2(
void* start_arg, void* vdso_map) {
ldso.l_map.l_addr = (uintptr_t)__ehdr_start;
Ehdr* ehdr = (void*)ldso.l_map.l_addr;
ldso.l_map.l_name = (char*)"libc.so";
ldso.global = -1;
ldso.phnum = ehdr->e_phnum;
ldso.phdr = laddr(&ldso, ehdr->e_phoff);
ldso.phentsize = ehdr->e_phentsize;
kernel_mapped_dso(&ldso);
decode_dyn(&ldso);
if (vdso_map != NULL) {
// The vDSO was mapped in by our creator. Stitch it in as
// a preloaded shared object right away, so ld.so itself
// can depend on it and require its symbols.
vdso.l_map.l_addr = (uintptr_t)vdso_map;
vdso.l_map.l_name = (char*)"<vDSO>";
vdso.global = -1;
Ehdr* ehdr = vdso_map;
vdso.phnum = ehdr->e_phnum;
vdso.phdr = laddr(&vdso, ehdr->e_phoff);
vdso.phentsize = ehdr->e_phentsize;
kernel_mapped_dso(&vdso);
decode_dyn(&vdso);
dso_set_prev(&vdso, &ldso);
dso_set_next(&ldso, &vdso);
tail = &vdso;
}
/* Prepare storage for to save clobbered REL addends so they
* can be reused in stage 3. There should be very few. If
* something goes wrong and there are a huge number, abort
* instead of risking stack overflow. */
size_t dyn[DT_NUM];
decode_vec(ldso.l_map.l_ld, dyn, DT_NUM);
size_t* rel = laddr(&ldso, dyn[DT_REL]);
size_t rel_size = dyn[DT_RELSZ];
size_t addend_rel_cnt = 0;
apply_addends_to = rel;
for (; rel_size; rel += 2, rel_size -= 2 * sizeof(size_t)) {
switch (R_TYPE(rel[1])) {
// These types do not need a saved addend. Only REL_RELATIVE uses an
// addend at all, and all REL_RELATIVE relocs in ldso were already
// processed in phase 1 and are just skipped now. Note this must
// match the logic in do_relocs so that the indices always match up.
case REL_RELATIVE:
case REL_GOT:
case REL_PLT:
case REL_COPY:
break;
default:
addend_rel_cnt++;
}
}
if (addend_rel_cnt >= ADDEND_LIMIT)
__builtin_trap();
size_t addends[addend_rel_cnt];
saved_addends = addends;
head = &ldso;
reloc_all(&ldso);
ldso.relocated = 0;
// Make sure all the relocations have landed before calling __dls3,
// which relies on them.
atomic_signal_fence(memory_order_seq_cst);
return __dls3(start_arg);
}
#define LIBS_VAR "LD_DEBUG="
#define TRACE_VAR "LD_TRACE="
__NO_SAFESTACK static void scan_env_strings(const char* strings, const char* limit,
uint32_t count) {
while (count-- > 0) {
char* end = memchr(strings, '\0', limit - strings);
if (end == NULL) {
break;
}
if (end - strings >= sizeof(LIBS_VAR) - 1 && !memcmp(strings, LIBS_VAR, sizeof(LIBS_VAR) - 1)) {
if (strings[sizeof(LIBS_VAR) - 1] != '\0') {
log_libs = true;
}
} else if (end - strings >= sizeof(TRACE_VAR) - 1 &&
!memcmp(strings, TRACE_VAR, sizeof(TRACE_VAR) - 1)) {
// Features like Intel Processor Trace require specific output in a
// specific format. Thus this output has its own env var.
if (strings[sizeof(TRACE_VAR) - 1] != '\0') {
trace_maps = true;
}
}
strings = end + 1;
}
}
/* Stage 3 of the dynamic linker is called with the dynamic linker/libc
* fully functional. Its job is to load (if not already loaded) and
* process dependencies and relocations for the main application and
* transfer control to its entry point. */
__NO_SAFESTACK static void* dls3(zx_handle_t exec_vmo, const char* argv0, const char* env_strings,
const char* env_strings_limit, uint32_t env_strings_count) {
// First load our own dependencies. Usually this will be just the
// vDSO, which is already loaded, so there will be nothing to do.
// In a sanitized build, we'll depend on the sanitizer runtime DSO
// and load that now (and its dependencies, such as the unwinder).
load_deps(&ldso);
// Now reorder the list so that we appear last, after all our
// dependencies. This ensures that e.g. the sanitizer runtime's
// malloc will be chosen over ours, even if the application
// doesn't itself depend on the sanitizer runtime SONAME.
dso_set_prev(dso_next(&ldso), NULL);
detached_head = dso_next(&ldso);
dso_set_prev(&ldso, tail);
dso_set_next(&ldso, NULL);
dso_set_next(tail, &ldso);
static struct dso app;
libc.page_size = PAGE_SIZE;
scan_env_strings(env_strings, env_strings_limit, env_strings_count);
zx_status_t status = map_library(exec_vmo, &app);
_zx_handle_close(exec_vmo);
if (status != ZX_OK) {
debugmsg("%s: %s: Not a valid dynamic program (%s)\n", ldso.l_map.l_name, argv0,
_zx_status_get_string(status));
_exit(1);
}
app.l_map.l_name = (char*)argv0;
if (app.tls.size) {
libc.tls_head = tls_tail = &app.tls;
app.tls_id = tls_cnt = 1;
#ifdef TLS_ABOVE_TP
app.tls.offset = (tls_offset + app.tls.align - 1) & -app.tls.align;
tls_offset = app.tls.offset + app.tls.size;
#else
tls_offset = app.tls.offset =
app.tls.size + (-((uintptr_t)app.tls.image + app.tls.size) & (app.tls.align - 1));
#endif
tls_align = MAXP2(tls_align, app.tls.align);
}
app.global = 1;
decode_dyn(&app);
// Format the build ID log lines for the three special cases.
allocate_and_format_build_id_log(&ldso);
allocate_and_format_build_id_log(&vdso);
allocate_and_format_build_id_log(&app);
/* Initial dso chain consists only of the app. */
head = tail = &app;
// Load preload/needed libraries, add their symbols to the global
// namespace, and perform all remaining relocations.
//
// Do TLS layout for DSOs after loading, but before relocation.
// This needs to be after the main program's TLS setup (just
// above), which has to be the first since it can use static TLS
// offsets (local-exec TLS model) that are presumed to start at
// the beginning of the static TLS block. But we may have loaded
// some libraries (sanitizer runtime) before that, so we don't do
// each library's TLS setup directly in load_library_vmo.
load_deps(&app);
app.global = 1;
for (struct dso* p = dso_next(&app); p != NULL; p = dso_next(p)) {
p->global = 1;
do_tls_layout(p, NULL, 0);
}
for (size_t i = 0; app.l_map.l_ld[i].d_tag; i++) {
if (!DT_DEBUG_INDIRECT && app.l_map.l_ld[i].d_tag == DT_DEBUG)
app.l_map.l_ld[i].d_un.d_ptr = (size_t)&debug;
if (DT_DEBUG_INDIRECT && app.l_map.l_ld[i].d_tag == DT_DEBUG_INDIRECT) {
size_t* ptr = (size_t*)app.l_map.l_ld[i].d_un.d_ptr;
*ptr = (size_t)&debug;
}
}
/* The main program must be relocated LAST since it may contin
* copy relocations which depend on libraries' relocations. */
reloc_all(dso_next(&app));
reloc_all(&app);
update_tls_size();
static_tls_cnt = tls_cnt;
if (ldso_fail)
_exit(127);
// Logically we could now switch to "runtime mode", because
// startup-time dynamic linking work per se is done now. However,
// the real concrete meaning of "runtime mode" is that the dlerror
// machinery is usable. It's not usable until the thread descriptor
// has been set up. So the switch to "runtime mode" happens in
// __init_main_thread instead.
atomic_init(&unlogged_tail, (uintptr_t)tail);
debug.r_version = 1;
debug.r_brk = (uintptr_t)&_dl_debug_state;
debug.r_brk_on_load = (uintptr_t)&debug_break;
debug.r_map = &head->l_map;
debug.r_ldbase = ldso.l_map.l_addr;
debug.r_state = 0;
// Check if the process has to issue a debug trap after this load.
// If setting ZX_PROP_PROCESS_DEBUG_ADDR fails, crashlogger backtraces, debugger
// sessions, etc. will be problematic, but this isn't fatal.
//
// TODO(dje): Is there a way to detect we're here because of being
// an injected process (launchpad_start_injected)? IWBN to print a
// warning here but launchpad_start_injected can trigger this.
// Fallback to the previous magic number approach.
//
// The ZX_PROP_PROCESS_DEBUG_ADDR being set to 1 on startup is a signal
// to issue a debug breakpoint after setting the property to signal to a
// debugger that the property is now valid.
intptr_t existing_debug_addr = 0;
status = _zx_object_get_property(__zircon_process_self, ZX_PROP_PROCESS_DEBUG_ADDR,
&existing_debug_addr, sizeof(existing_debug_addr));
bool break_after_set =
(status == ZX_OK) && (existing_debug_addr == ZX_PROCESS_DEBUG_ADDR_BREAK_ON_SET);
// Once we already checked for the magic number, we set the correct value for the property.
_zx_object_set_property(__zircon_process_self, ZX_PROP_PROCESS_DEBUG_ADDR, &_dl_debug_addr,
sizeof(_dl_debug_addr));
// First check if the user is using ZX_PROP_PROCESS_BREAK_ON_LOAD.
if (should_break_on_load() || break_after_set) {
debug_break();
}
_dl_debug_state();
if (log_libs)
_dl_log_unlogged();
if (trace_maps) {
for (struct dso* p = &app; p != NULL; p = dso_next(p)) {
trace_load(p);
}
}
// Reset from the argv0 value so we don't save a dangling pointer
// into the caller's stack frame.
app.l_map.l_name = (char*)"";
// Check for a PT_GNU_STACK header requesting a main thread stack size.
libc.stack_size = ZIRCON_DEFAULT_STACK_SIZE;
for (size_t i = 0; i < app.phnum; i++) {
if (app.phdr[i].p_type == PT_GNU_STACK) {
size_t size = app.phdr[i].p_memsz;
if (size > 0)
libc.stack_size = size;
break;
}
}
const Ehdr* ehdr = (void*)app.map;
return laddr(&app, ehdr->e_entry);
}
__NO_SAFESTACK NO_ASAN static dl_start_return_t __dls3(void* start_arg) {
zx_handle_t bootstrap = (uintptr_t)start_arg;
uint32_t nbytes, nhandles;
zx_status_t status = processargs_message_size(bootstrap, &nbytes, &nhandles);
if (status != ZX_OK) {
error("processargs_message_size bootstrap handle %#x failed: %d (%s)", bootstrap, status,
_zx_status_get_string(status));
nbytes = nhandles = 0;
}
// Do not allow any zero length VLAs allocated on the stack.
//
// TODO(44088) : See this bug for options which might allow us to avoid the
// need for variable length arrays of any form at this stage.
if ((nbytes == 0) || (nhandles == 0)) {
__builtin_trap();
_exit(1);
}
PROCESSARGS_BUFFER(buffer, nbytes);
zx_handle_t handles[nhandles];
zx_proc_args_t* procargs;
uint32_t* handle_info;
if (status == ZX_OK)
status =
processargs_read(bootstrap, buffer, nbytes, handles, nhandles, &procargs, &handle_info);
if (status != ZX_OK) {
error(
"bad message of %u bytes, %u handles"
" from bootstrap handle %#x: %d (%s)",
nbytes, nhandles, bootstrap, status, _zx_status_get_string(status));
nbytes = nhandles = 0;
}
zx_handle_t exec_vmo = ZX_HANDLE_INVALID;
for (int i = 0; i < nhandles; ++i) {
switch (PA_HND_TYPE(handle_info[i])) {
case PA_LDSVC_LOADER:
if (loader_svc != ZX_HANDLE_INVALID || handles[i] == ZX_HANDLE_INVALID) {
error("bootstrap message bad LOADER_SVC %#x vs %#x", handles[i], loader_svc);
}
loader_svc = handles[i];
break;
case PA_VMO_EXECUTABLE:
if (exec_vmo != ZX_HANDLE_INVALID || handles[i] == ZX_HANDLE_INVALID) {
error("bootstrap message bad EXEC_VMO %#x vs %#x", handles[i], exec_vmo);
}
exec_vmo = handles[i];
break;
case PA_FD:
if (logger != ZX_HANDLE_INVALID || handles[i] == ZX_HANDLE_INVALID) {
error("bootstrap message bad FD %#x vs %#x", handles[i], logger);
}
logger = handles[i];
break;
case PA_VMAR_LOADED:
if (ldso.vmar != ZX_HANDLE_INVALID || handles[i] == ZX_HANDLE_INVALID) {
error("bootstrap message bad VMAR_LOADED %#x vs %#x", handles[i], ldso.vmar);
}
ldso.vmar = handles[i];
break;
case PA_PROC_SELF:
__zircon_process_self = handles[i];
break;
case PA_VMAR_ROOT:
__zircon_vmar_root_self = handles[i];
break;
default:
_zx_handle_close(handles[i]);
break;
}
}
// TODO(mcgrathr): For now, always use a kernel log channel.
// This needs to be replaced by a proper unprivileged logging scheme ASAP.
if (logger == ZX_HANDLE_INVALID) {
_zx_debuglog_create(ZX_HANDLE_INVALID, 0, &logger);
}
if (__zircon_process_self == ZX_HANDLE_INVALID)
error("bootstrap message bad no proc self");
if (__zircon_vmar_root_self == ZX_HANDLE_INVALID)
error("bootstrap message bad no root vmar");
// At this point we can make system calls and have our essential
// handles, so things are somewhat normal.
early_init();
// The initial processargs message may not pass the application
// name or any other arguments, so we check that condition.
void* entry =
dls3(exec_vmo, procargs->args_num == 0 ? "" : (const char*)&buffer[procargs->args_off],
(const char*)&buffer[procargs->environ_off], (const char*)&buffer[nbytes],
procargs->environ_num);
if (vdso.global <= 0) {
// Nothing linked against the vDSO. Ideally we would unmap the
// vDSO, but there is no way to do it because the unmap system call
// would try to return to the vDSO code and crash.
if (ldso.global < 0) {
// TODO(mcgrathr): We could free all heap data structures, and
// with some vDSO assistance unmap ourselves and unwind back to
// the user entry point. Thus a program could link against the
// vDSO alone and not use this libc/ldso at all after startup.
// We'd need to be sure there are no TLSDESC entries pointing
// back to our code, but other than that there should no longer
// be a way to enter our code.
} else {
debugmsg("Dynamic linker %s doesn't link in vDSO %s???\n", ldso.l_map.l_name,
vdso.l_map.l_name);
_exit(127);
}
} else if (ldso.global <= 0) {
// This should be impossible.
__builtin_trap();
}
#ifdef __aarch64__
// The official psABI document at
// https://developer.arm.com/docs/ihi0057/c/dwarf-for-the-arm-64-bit-architecture-aarch64-abi-2018q4
// does not assign a DWARF register number for TPIDR_mode. For now use 128, which
// is above the range reserved in the ABI.
// TODO(mcgrathr): I've pinged ARM about assigning more numbers; hopefully we'll
// get a tentative assignment from them soon and update this to match.
#define DWARG_REGNO_TP 128 // TPIDR_EL0
#elif defined(__x86_64__)
#define DWARG_REGNO_TP 58 // %fs.base
#endif
// This has to be inside some function so that it can use extended asm to
// inject constants from C. It has to be somewhere that definitely doesn't
// get optimized away as unreachable by the compiler so that it's actually
// assembled into the final shared library.
//
// This establishes a new protocol with the debugger: there will be a
// debugging section called .zxdb_debug_api; this is allocated for the
// convenience of zxdb's current implementation, but in principle should be
// non-allocated like other such sections. ELF symbols in this section
// provide named API "calls". Each "call" is a DWARF expression whose
// offset into the section and size in bytes are indicated by the st_value
// and st_size fields of the symbol. The protocol for what values each call
// expects on the stack and/or delivers on the stack on return is described
// for each call below. Every call may need access to process memory via
// DW_OP_deref et al. Some calls need access to thread registers via
// DW_OP_breg*; these calls document that need in their "Input:" section.
// Any DW_OP_addr operations encode an address relative to the load address
// of the module containing this section.
uintptr_t bogon;
__asm__ volatile(
// Since libc is linked with --gc-sections, the .zxdb_debug_api section
// will be dropped as unreferenced since it's an allocated section. By
// rights, it should be a non-allocated section, but making it allocated
// simplifies things for zxdb right now and is harmless enough. But, it
// means something must prevent the section from being GC'd. So this
// useless instruction serves that purpose.
#ifdef __aarch64__
"adrp %0, zxdb.thrd_t\n"
#elif defined(__x86_64__)
"lea zxdb.thrd_t(%%rip), %0\n"
#endif
".pushsection .zxdb_debug_api,\"a\",%%progbits\n"
#define DEBUG_API(name) #name ":\n"
#define DEBUG_API_END(name) ".size " #name ", . - " #name "\n"
// zxdb.thrd_t: Yield the thrd_current() value from thread registers.
// zxdb.pthread_t: Yield the pthread_self() value from thread registers.
// Input: Consumes no stack entries; uses thread registers.
// Output: Pushes one word, to be displayed as a thrd_t value.
// This is the value thrd_current() returns in this thread; as per the
// C standard, this value never changes for the lifetime of the thread.
// In Fuchsia's implementation thrd_t and pthread_t happen to be the
// same thing and thrd_current() and pthread_self() always return the
// same thing. That is why these two debugging APIs are just aliases
// for the same code, but it is not something a debugger should assume
// generically as it might differ in future implementations.
DEBUG_API(zxdb.thrd_t)
DEBUG_API(zxdb.pthread_t)
".byte %c[bregx]\n"
" .uleb128 %c[tp_regno]\n"
" .sleb128 %c[pthread_tp_offset]\n"
DEBUG_API_END(zxdb.thrd_t)
DEBUG_API_END(zxdb.pthread_t)
// zxdb.link_map_tls_modid: Yield TLS module ID from `struct link_map`.
// Input: Pops a `struct link_map *` value; uses no thread registers.
// The valid `struct link_map *` pointer values can be obtained by walking
// the list from the `struct r_debug` structure accessed via the ELF
// DT_DEBUG protocol or the Zircon ZX_PROP_PROCESS_DEBUG_ADDR protocol.
// Output: Pushes one word, the TLS module ID or 0 if no PT_TLS segment.
// This value is fixed at load time, so it can be computed just once per
// module and cached. The TLS module ID is a positive integer that
// appears in GOT slots with DTPMOD relocations and can be used with
// zxdb.tlsbase (below) to refer to the given module's PT_TLS segment.
DEBUG_API(zxdb.link_map_tls_modid)
".byte %c[plus_uconst]\n"
" .uleb128 %c[tls_id_offset]\n"
".byte %c[deref]\n"
DEBUG_API_END(zxdb.link_map_tls_modid)
// zxdb.tlsbase: Yield the address of a given module's TLS block.
// Input: Pops one word, the TLS module ID; uses thread registers.
// Output: Pushes one word, the address of the thread's TLS block for
// that module or 0 if the thread hasn't allocated one. Each module
// with a PT_TLS segment has a TLS block in each thread that corresponds
// to the SHT_TLS symbols that appear in that module, which their
// st_value offsets being the offsets into that TLS block (i.e. `p_vaddr
// + st_value` is where the initial contents for that symbol appear).
// When a particular thread has not yet allocated a particular module's
// TLS block the debugger can show the initial values from the PT_TLS
// segment's p_vaddr, but cannot modify the values until the thread does
// an actual TLS access to get the block allocated. A later attempt on
// the same thread and module ID might yield a nonzero value. Once a
// nonzero value has been delivered for a given thread and module, it
// will never change but becomes an invalid pointer when the thread dies
// and when the module is unloaded.
DEBUG_API(zxdb.tlsbase)
// This matches the logic in the __tls_get_addr implementation.
".byte %c[bregx]\n" // Compute &pthread_self()->head.dtv.
" .uleb128 %c[tp_regno]\n"
" .sleb128 %c[dtv_offset]\n"
".byte %c[deref]\n" // tos is now the DTV address itself.
".byte %c[over]\n" // Push a copy of the module ID.
".byte %c[over]\n" // Save a copy of the DTV address for later.
".byte %c[deref]\n" // tos is now the thread's DTV generation.
".byte %c[le]\n" // modid <= generation?
".byte %c[bra]\n" // If yes, goto 1.
" .short 1f-0f\n"
"0:\n"
".byte %c[drop], %c[drop]\n" // Clear the stack.
".byte %c[lit0]\n" // Push return value of zero.
".byte %c[skip]\n" // Branch to the end, i.e. return.
" .short 2f-1f\n"
"1:\n"
".byte %c[swap]\n" // Get the module ID back to the top of the stack.
// The module ID is an index into the DTV; scale that to the byte offset.
".byte %c[const1u], %c[dtvscale], %c[mul]\n" // tos *= dtvscale
".byte %c[plus], %c[deref]\n" // Return dtv[id].
"2:\n"
DEBUG_API_END(zxdb.tlsbase)
#undef DEBUG_API
#undef DEBUG_API_END
".popsection"
: "=r"(bogon)
:
// DW_OP_* constants per DWARF spec.
[ bra ] "i"(0x28), [ bregx ] "i"(0x92), [ const1u ] "i"(0x08), [ deref ] "i"(0x06),
[ drop ] "i"(0x13), [ dup ] "i"(0x12), [ le ] "i"(0x2c), [ lit0 ] "i"(0x30),
[ mul ] "i"(0x1e), [ over ] "i"(0x14), [ plus ] "i"(0x22), [ plus_uconst ] "i"(0x23),
[ skip ] "i"(0x2f), [ swap ] "i"(0x16),
// Used in thrd_t.
[ tp_regno ] "i"(DWARG_REGNO_TP), [ pthread_tp_offset ] "i"(-PTHREAD_TP_OFFSET),
// Used in link_map_tls_modid.
[ tls_id_offset ] "i"(offsetof(struct dso, tls_id)),
// Used in tlsbase.
[ dtv_offset ] "i"(TP_OFFSETOF(head.dtv)), [ dtvscale ] "i"(sizeof((tcbhead_t){}.dtv[0])));
#undef OP
return DL_START_RETURN(entry, start_arg);
}
// Do sanitizer setup and whatever else must be done before dls3.
__NO_SAFESTACK NO_ASAN static void early_init(void) {
#if __has_feature(address_sanitizer)
__asan_early_init();
#endif
#ifdef DYNLINK_LDSVC_CONFIG
// Inform the loader service to look for libraries of the right variant.
loader_svc_config(DYNLINK_LDSVC_CONFIG);
#elif __has_feature(address_sanitizer)
// Inform the loader service that we prefer ASan-supporting libraries.
loader_svc_config("asan");
#endif
}
static void set_global(struct dso* p, int global) {
if (p->global > 0) {
// Short-circuit if it's already fully global. Its deps will be too.
return;
} else if (p->global == global) {
// This catches circular references as well as other redundant walks.
return;
}
p->global = global;
if (p->deps != NULL) {
for (struct dso** dep = p->deps; *dep != NULL; ++dep) {
set_global(*dep, global);
}
}
}
static void* dlopen_internal(zx_handle_t vmo, const char* file, int mode) {
// N.B. This lock order must be consistent with other uses such as
// ThreadSuspender in the __sanitizer_memory_snapshot implementation.
_dl_wrlock();
__thread_allocation_inhibit();
struct dso* orig_tail = tail;
struct dso* p;
zx_status_t status = (vmo != ZX_HANDLE_INVALID ? load_library_vmo(vmo, file, mode, head, &p)
: load_library(file, mode, head, &p));
if (status != ZX_OK) {
error("Error loading shared library %s: %s", file, _zx_status_get_string(status));
fail:
__thread_allocation_release();
_dl_unlock();
return NULL;
}
if (p == NULL) {
if (!(mode & RTLD_NOLOAD))
__builtin_trap();
error("Library %s is not already loaded", file);
goto fail;
}
struct tls_module* orig_tls_tail = tls_tail;
size_t orig_tls_cnt = tls_cnt;
size_t orig_tls_offset = tls_offset;
size_t orig_tls_align = tls_align;
struct dl_alloc_checkpoint checkpoint;
dl_alloc_checkpoint(&checkpoint);
jmp_buf jb;
rtld_fail = &jb;
if (setjmp(*rtld_fail)) {
/* Clean up anything new that was (partially) loaded */
if (p && p->deps)
set_global(p, 0);
for (p = dso_next(orig_tail); p; p = dso_next(p))
unmap_library(p);
if (!orig_tls_tail)
libc.tls_head = 0;
tls_tail = orig_tls_tail;
tls_cnt = orig_tls_cnt;
tls_offset = orig_tls_offset;
tls_align = orig_tls_align;
tail = orig_tail;
dso_set_next(tail, NULL);
dl_alloc_rollback(&checkpoint);
goto fail;
}
/* First load handling */
if (!p->deps) {
load_deps(p);
set_global(p, -1);
reloc_all(p);
set_global(p, 0);
}
if (mode & RTLD_GLOBAL) {
set_global(p, 1);
}
update_tls_size();
// Check if the process has set the state to break on this load.
if (should_break_on_load()) {
debug_break();
}
_dl_debug_state();
if (trace_maps) {
trace_load(p);
}
// Allow thread creation, now that the TLS bookkeeping is consistent.
__thread_allocation_release();
// Bump the dl_iterate_phdr dlpi_adds counter.
gencnt++;
// Collect the current new tail before we release the lock.
// Another dlopen can come in and advance the tail, but we
// alone are responsible for making sure that do_init_fini
// starts with the first object we just added.
struct dso* new_tail = tail;
// The next _dl_log_unlogged can safely read the 'struct dso' list from
// head up through new_tail. Most fields will never change again.
atomic_store_explicit(&unlogged_tail, (uintptr_t)new_tail, memory_order_release);
_dl_unlock();
if (log_libs)
_dl_log_unlogged();
do_init_fini(new_tail);
return p;
}
void* dlopen(const char* file, int mode) {
if (!file)
return head;
return dlopen_internal(ZX_HANDLE_INVALID, file, mode);
}
void* dlopen_vmo(zx_handle_t vmo, int mode) {
if (vmo == ZX_HANDLE_INVALID) {
errno = EINVAL;
return NULL;
}
return dlopen_internal(vmo, NULL, mode);
}
zx_handle_t dl_set_loader_service(zx_handle_t new_svc) {
zx_handle_t old_svc;
_dl_wrlock();
old_svc = loader_svc;
loader_svc = new_svc;
_dl_unlock();
return old_svc;
}
__attribute__((__visibility__("hidden"))) int __dl_invalid_handle(void* h) {
struct dso* p;
for (p = head; p; p = dso_next(p))
if (h == p)
return 0;
error("Invalid library handle %p", (void*)h);
return 1;
}
static void* addr2dso(size_t a) {
struct dso* p;
for (p = head; p; p = dso_next(p)) {
if (a - (size_t)p->map < p->map_len)
return p;
}
return 0;
}
void* __tls_get_addr(size_t*);
static bool find_sym_for_dlsym(struct dso* p, const char* name, uint32_t* name_gnu_hash,
uint32_t* name_sysv_hash, void** result) {
const Sym* sym;
if (p->ghashtab != NULL) {
if (*name_gnu_hash == 0)
*name_gnu_hash = gnu_hash(name);
sym = gnu_lookup(*name_gnu_hash, p->ghashtab, p, name);
} else {
if (*name_sysv_hash == 0)
*name_sysv_hash = sysv_hash(name);
sym = sysv_lookup(name, *name_sysv_hash, p);
}
if (sym && (sym->st_info & 0xf) == STT_TLS) {
*result = __tls_get_addr((size_t[]){p->tls_id, sym->st_value});
return true;
}
if (sym && sym->st_value && (1 << (sym->st_info & 0xf) & OK_TYPES)) {
*result = laddr(p, sym->st_value);
return true;
}
if (p->deps) {
for (struct dso** dep = p->deps; *dep != NULL; ++dep) {
if (find_sym_for_dlsym(*dep, name, name_gnu_hash, name_sysv_hash, result))
return true;
}
}
return false;
}
static void* do_dlsym(struct dso* p, const char* s, void* ra) {
if (p == head || p == RTLD_DEFAULT || p == RTLD_NEXT) {
if (p == RTLD_DEFAULT) {
p = head;
} else if (p == RTLD_NEXT) {
p = addr2dso((size_t)ra);
if (!p)
p = head;
p = dso_next(p);
}
struct symdef def = find_sym(p, s, 0);
if (!def.sym)
goto failed;
if ((def.sym->st_info & 0xf) == STT_TLS)
return __tls_get_addr((size_t[]){def.dso->tls_id, def.sym->st_value});
return laddr(def.dso, def.sym->st_value);
}
if (__dl_invalid_handle(p))
return 0;
uint32_t gnu_hash = 0, sysv_hash = 0;
void* result;
if (find_sym_for_dlsym(p, s, &gnu_hash, &sysv_hash, &result))
return result;
failed:
error("Symbol not found: %s", s);
return 0;
}
int dladdr(const void* addr, Dl_info* info) {
struct dso* p;
_dl_rdlock();
p = addr2dso((size_t)addr);
_dl_unlock();
if (!p)
return 0;
Sym* bestsym = NULL;
void* best = 0;
Sym* sym = p->syms;
uint32_t nsym = count_syms(p);
for (; nsym; nsym--, sym++) {