blob: 95856eb839b516085e119f6b368907ebe1f5b886 [file] [log] [blame]
/*
* Post-process a vdso elf image for inclusion into qemu.
* Elf size specialization.
*
* Copyright 2023 Linaro, Ltd.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
static void elfN(bswap_ehdr)(ElfN(Ehdr) *ehdr)
{
bswaps(&ehdr->e_type); /* Object file type */
bswaps(&ehdr->e_machine); /* Architecture */
bswaps(&ehdr->e_version); /* Object file version */
bswaps(&ehdr->e_entry); /* Entry point virtual address */
bswaps(&ehdr->e_phoff); /* Program header table file offset */
bswaps(&ehdr->e_shoff); /* Section header table file offset */
bswaps(&ehdr->e_flags); /* Processor-specific flags */
bswaps(&ehdr->e_ehsize); /* ELF header size in bytes */
bswaps(&ehdr->e_phentsize); /* Program header table entry size */
bswaps(&ehdr->e_phnum); /* Program header table entry count */
bswaps(&ehdr->e_shentsize); /* Section header table entry size */
bswaps(&ehdr->e_shnum); /* Section header table entry count */
bswaps(&ehdr->e_shstrndx); /* Section header string table index */
}
static void elfN(bswap_phdr)(ElfN(Phdr) *phdr)
{
bswaps(&phdr->p_type); /* Segment type */
bswaps(&phdr->p_flags); /* Segment flags */
bswaps(&phdr->p_offset); /* Segment file offset */
bswaps(&phdr->p_vaddr); /* Segment virtual address */
bswaps(&phdr->p_paddr); /* Segment physical address */
bswaps(&phdr->p_filesz); /* Segment size in file */
bswaps(&phdr->p_memsz); /* Segment size in memory */
bswaps(&phdr->p_align); /* Segment alignment */
}
static void elfN(bswap_shdr)(ElfN(Shdr) *shdr)
{
bswaps(&shdr->sh_name);
bswaps(&shdr->sh_type);
bswaps(&shdr->sh_flags);
bswaps(&shdr->sh_addr);
bswaps(&shdr->sh_offset);
bswaps(&shdr->sh_size);
bswaps(&shdr->sh_link);
bswaps(&shdr->sh_info);
bswaps(&shdr->sh_addralign);
bswaps(&shdr->sh_entsize);
}
static void elfN(bswap_sym)(ElfN(Sym) *sym)
{
bswaps(&sym->st_name);
bswaps(&sym->st_value);
bswaps(&sym->st_size);
bswaps(&sym->st_shndx);
}
static void elfN(bswap_dyn)(ElfN(Dyn) *dyn)
{
bswaps(&dyn->d_tag); /* Dynamic type tag */
bswaps(&dyn->d_un.d_ptr); /* Dynamic ptr or val, in union */
}
static void elfN(search_symtab)(ElfN(Shdr) *shdr, unsigned sym_idx,
void *buf, bool need_bswap)
{
unsigned str_idx = shdr[sym_idx].sh_link;
ElfN(Sym) *sym = buf + shdr[sym_idx].sh_offset;
unsigned sym_n = shdr[sym_idx].sh_size / sizeof(*sym);
const char *str = buf + shdr[str_idx].sh_offset;
for (unsigned i = 0; i < sym_n; ++i) {
const char *name;
if (need_bswap) {
elfN(bswap_sym)(sym + i);
}
name = str + sym[i].st_name;
if (sigreturn_sym && strcmp(sigreturn_sym, name) == 0) {
sigreturn_addr = sym[i].st_value;
}
if (rt_sigreturn_sym && strcmp(rt_sigreturn_sym, name) == 0) {
rt_sigreturn_addr = sym[i].st_value;
}
}
}
static void elfN(process)(FILE *outf, void *buf, bool need_bswap)
{
ElfN(Ehdr) *ehdr = buf;
ElfN(Phdr) *phdr;
ElfN(Shdr) *shdr;
unsigned phnum, shnum;
unsigned dynamic_ofs = 0;
unsigned dynamic_addr = 0;
unsigned symtab_idx = 0;
unsigned dynsym_idx = 0;
unsigned first_segsz = 0;
int errors = 0;
if (need_bswap) {
elfN(bswap_ehdr)(ehdr);
}
phnum = ehdr->e_phnum;
phdr = buf + ehdr->e_phoff;
if (need_bswap) {
for (unsigned i = 0; i < phnum; ++i) {
elfN(bswap_phdr)(phdr + i);
}
}
shnum = ehdr->e_shnum;
shdr = buf + ehdr->e_shoff;
if (need_bswap) {
for (unsigned i = 0; i < shnum; ++i) {
elfN(bswap_shdr)(shdr + i);
}
}
for (unsigned i = 0; i < shnum; ++i) {
switch (shdr[i].sh_type) {
case SHT_SYMTAB:
symtab_idx = i;
break;
case SHT_DYNSYM:
dynsym_idx = i;
break;
}
}
/*
* Validate the VDSO is created as we expect: that PT_PHDR,
* PT_DYNAMIC, and PT_NOTE located in a writable data segment.
* PHDR and DYNAMIC require relocation, and NOTE will get the
* linux version number.
*/
for (unsigned i = 0; i < phnum; ++i) {
if (phdr[i].p_type != PT_LOAD) {
continue;
}
if (first_segsz != 0) {
fprintf(stderr, "Multiple LOAD segments\n");
errors++;
}
if (phdr[i].p_offset != 0) {
fprintf(stderr, "LOAD segment does not cover EHDR\n");
errors++;
}
if (phdr[i].p_vaddr != 0) {
fprintf(stderr, "LOAD segment not loaded at address 0\n");
errors++;
}
first_segsz = phdr[i].p_filesz;
if (first_segsz < ehdr->e_phoff + phnum * sizeof(*phdr)) {
fprintf(stderr, "LOAD segment does not cover PHDRs\n");
errors++;
}
if ((phdr[i].p_flags & (PF_R | PF_W)) != (PF_R | PF_W)) {
fprintf(stderr, "LOAD segment is not read-write\n");
errors++;
}
}
for (unsigned i = 0; i < phnum; ++i) {
const char *which;
switch (phdr[i].p_type) {
case PT_PHDR:
which = "PT_PHDR";
break;
case PT_NOTE:
which = "PT_NOTE";
break;
case PT_DYNAMIC:
dynamic_ofs = phdr[i].p_offset;
dynamic_addr = phdr[i].p_vaddr;
which = "PT_DYNAMIC";
break;
default:
continue;
}
if (first_segsz < phdr[i].p_vaddr + phdr[i].p_filesz) {
fprintf(stderr, "LOAD segment does not cover %s\n", which);
errors++;
}
}
if (errors) {
exit(EXIT_FAILURE);
}
/* Relocate the program headers. */
for (unsigned i = 0; i < phnum; ++i) {
output_reloc(outf, buf, &phdr[i].p_vaddr);
output_reloc(outf, buf, &phdr[i].p_paddr);
}
/* Relocate the DYNAMIC entries. */
if (dynamic_addr) {
ElfN(Dyn) *dyn = buf + dynamic_ofs;
__typeof(dyn->d_tag) tag;
do {
if (need_bswap) {
elfN(bswap_dyn)(dyn);
}
tag = dyn->d_tag;
switch (tag) {
case DT_HASH:
case DT_SYMTAB:
case DT_STRTAB:
case DT_VERDEF:
case DT_VERSYM:
case DT_PLTGOT:
case DT_ADDRRNGLO ... DT_ADDRRNGHI:
/* These entries store an address in the entry. */
output_reloc(outf, buf, &dyn->d_un.d_val);
break;
case DT_NULL:
case DT_STRSZ:
case DT_SONAME:
case DT_DEBUG:
case DT_FLAGS:
case DT_FLAGS_1:
case DT_SYMBOLIC:
case DT_BIND_NOW:
case DT_VERDEFNUM:
case DT_VALRNGLO ... DT_VALRNGHI:
/* These entries store an integer in the entry. */
break;
case DT_SYMENT:
if (dyn->d_un.d_val != sizeof(ElfN(Sym))) {
fprintf(stderr, "VDSO has incorrect dynamic symbol size\n");
errors++;
}
break;
case DT_REL:
case DT_RELSZ:
case DT_RELA:
case DT_RELASZ:
/*
* These entries indicate that the VDSO was built incorrectly.
* It should not have any real relocations.
* ??? The RISC-V toolchain will emit these even when there
* are no relocations. Validate zeros.
*/
if (dyn->d_un.d_val != 0) {
fprintf(stderr, "VDSO has dynamic relocations\n");
errors++;
}
break;
case DT_RELENT:
case DT_RELAENT:
case DT_TEXTREL:
/* These entries store an integer in the entry. */
/* Should not be required; see above. */
break;
case DT_NEEDED:
case DT_VERNEED:
case DT_PLTREL:
case DT_JMPREL:
case DT_RPATH:
case DT_RUNPATH:
fprintf(stderr, "VDSO has external dependencies\n");
errors++;
break;
case PT_LOPROC + 3:
if (ehdr->e_machine == EM_PPC64) {
break; /* DT_PPC64_OPT: integer bitmask */
}
goto do_default;
default:
do_default:
/* This is probably something target specific. */
fprintf(stderr, "VDSO has unknown DYNAMIC entry (%lx)\n",
(unsigned long)tag);
errors++;
break;
}
dyn++;
} while (tag != DT_NULL);
if (errors) {
exit(EXIT_FAILURE);
}
}
/* Relocate the dynamic symbol table. */
if (dynsym_idx) {
ElfN(Sym) *sym = buf + shdr[dynsym_idx].sh_offset;
unsigned sym_n = shdr[dynsym_idx].sh_size / sizeof(*sym);
for (unsigned i = 0; i < sym_n; ++i) {
output_reloc(outf, buf, &sym[i].st_value);
}
}
/* Search both dynsym and symtab for the signal return symbols. */
if (dynsym_idx) {
elfN(search_symtab)(shdr, dynsym_idx, buf, need_bswap);
}
if (symtab_idx) {
elfN(search_symtab)(shdr, symtab_idx, buf, need_bswap);
}
}