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/* Native-dependent code for GNU/Linux x86 (i386 and x86-64).
Copyright (C) 1999-2016 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>. */
#include "defs.h"
#include "inferior.h"
#include "elf/common.h"
#include "gdb_proc_service.h"
#include "nat/gdb_ptrace.h"
#include <sys/user.h>
#include <sys/procfs.h>
#include <sys/uio.h>
#include "x86-nat.h"
#include "linux-nat.h"
#ifndef __x86_64__
#include "i386-linux-nat.h"
#include "x86-linux-nat.h"
#include "i386-linux-tdep.h"
#ifdef __x86_64__
#include "amd64-linux-tdep.h"
#include "x86-xstate.h"
#include "nat/linux-btrace.h"
#include "nat/linux-nat.h"
#include "nat/x86-linux.h"
#include "nat/x86-linux-dregs.h"
#include "nat/linux-ptrace.h"
/* Per-thread arch-specific data we want to keep. */
struct arch_lwp_info
/* Non-zero if our copy differs from what's recorded in the thread. */
int debug_registers_changed;
/* linux_nat_new_fork hook. */
static void
x86_linux_new_fork (struct lwp_info *parent, pid_t child_pid)
pid_t parent_pid;
struct x86_debug_reg_state *parent_state;
struct x86_debug_reg_state *child_state;
/* NULL means no watchpoint has ever been set in the parent. In
that case, there's nothing to do. */
if (parent->arch_private == NULL)
/* Linux kernel before 2.6.33 commit
will inherit hardware debug registers from parent
on fork/vfork/clone. Newer Linux kernels create such tasks with
zeroed debug registers.
GDB core assumes the child inherits the watchpoints/hw
breakpoints of the parent, and will remove them all from the
forked off process. Copy the debug registers mirrors into the
new process so that all breakpoints and watchpoints can be
removed together. The debug registers mirror will become zeroed
in the end before detaching the forked off process, thus making
this compatible with older Linux kernels too. */
parent_pid = ptid_get_pid (parent->ptid);
parent_state = x86_debug_reg_state (parent_pid);
child_state = x86_debug_reg_state (child_pid);
*child_state = *parent_state;
static void (*super_post_startup_inferior) (struct target_ops *self,
ptid_t ptid);
static void
x86_linux_child_post_startup_inferior (struct target_ops *self, ptid_t ptid)
x86_cleanup_dregs ();
super_post_startup_inferior (self, ptid);
#ifdef __x86_64__
/* Value of CS segment register:
64bit process: 0x33
32bit process: 0x23 */
#define AMD64_LINUX_USER64_CS 0x33
/* Value of DS segment register:
LP64 process: 0x0
X32 process: 0x2b */
#define AMD64_LINUX_X32_DS 0x2b
/* Get Linux/x86 target description from running target. */
static const struct target_desc *
x86_linux_read_description (struct target_ops *ops)
int tid;
int is_64bit = 0;
#ifdef __x86_64__
int is_x32;
static uint64_t xcr0;
uint64_t xcr0_features_bits;
/* GNU/Linux LWP ID's are process ID's. */
tid = ptid_get_lwp (inferior_ptid);
if (tid == 0)
tid = ptid_get_pid (inferior_ptid); /* Not a threaded program. */
#ifdef __x86_64__
unsigned long cs;
unsigned long ds;
/* Get CS register. */
errno = 0;
cs = ptrace (PTRACE_PEEKUSER, tid,
offsetof (struct user_regs_struct, cs), 0);
if (errno != 0)
perror_with_name (_("Couldn't get CS register"));
is_64bit = cs == AMD64_LINUX_USER64_CS;
/* Get DS register. */
errno = 0;
ds = ptrace (PTRACE_PEEKUSER, tid,
offsetof (struct user_regs_struct, ds), 0);
if (errno != 0)
perror_with_name (_("Couldn't get DS register"));
is_x32 = ds == AMD64_LINUX_X32_DS;
if (sizeof (void *) == 4 && is_64bit && !is_x32)
error (_("Can't debug 64-bit process with 32-bit GDB"));
if (have_ptrace_getfpxregs == -1)
elf_fpxregset_t fpxregs;
if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
have_ptrace_getfpxregs = 0;
have_ptrace_getregset = TRIBOOL_FALSE;
return tdesc_i386_mmx_linux;
if (have_ptrace_getregset == TRIBOOL_UNKNOWN)
uint64_t xstateregs[(X86_XSTATE_SSE_SIZE / sizeof (uint64_t))];
struct iovec iov;
iov.iov_base = xstateregs;
iov.iov_len = sizeof (xstateregs);
/* Check if PTRACE_GETREGSET works. */
if (ptrace (PTRACE_GETREGSET, tid,
(unsigned int) NT_X86_XSTATE, &iov) < 0)
have_ptrace_getregset = TRIBOOL_FALSE;
have_ptrace_getregset = TRIBOOL_TRUE;
/* Get XCR0 from XSAVE extended state. */
xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
/ sizeof (uint64_t))];
/* Check the native XCR0 only if PTRACE_GETREGSET is available. If
PTRACE_GETREGSET is not available then set xcr0_features_bits to
zero so that the "no-features" descriptions are returned by the
switches below. */
if (have_ptrace_getregset == TRIBOOL_TRUE)
xcr0_features_bits = xcr0 & X86_XSTATE_ALL_MASK;
xcr0_features_bits = 0;
if (is_64bit)
#ifdef __x86_64__
switch (xcr0_features_bits)
case X86_XSTATE_AVX512_MASK:
if (is_x32)
return tdesc_x32_avx512_linux;
return tdesc_amd64_avx512_linux;
if (is_x32)
return tdesc_x32_avx_linux; /* No MPX on x32 using AVX. */
return tdesc_amd64_mpx_linux;
if (is_x32)
return tdesc_x32_avx_linux; /* No MPX on x32 using AVX. */
return tdesc_amd64_avx_mpx_linux;
if (is_x32)
return tdesc_x32_avx_linux;
return tdesc_amd64_avx_linux;
if (is_x32)
return tdesc_x32_linux;
return tdesc_amd64_linux;
switch (xcr0_features_bits)
case X86_XSTATE_AVX512_MASK:
return tdesc_i386_avx512_linux;
return tdesc_i386_mpx_linux;
return tdesc_i386_avx_mpx_linux;
return tdesc_i386_avx_linux;
return tdesc_i386_linux;
gdb_assert_not_reached ("failed to return tdesc");
/* Enable branch tracing. */
static struct btrace_target_info *
x86_linux_enable_btrace (struct target_ops *self, ptid_t ptid,
const struct btrace_config *conf)
struct btrace_target_info *tinfo;
errno = 0;
tinfo = linux_enable_btrace (ptid, conf);
if (tinfo == NULL)
error (_("Could not enable branch tracing for %s: %s."),
target_pid_to_str (ptid), safe_strerror (errno));
return tinfo;
/* Disable branch tracing. */
static void
x86_linux_disable_btrace (struct target_ops *self,
struct btrace_target_info *tinfo)
enum btrace_error errcode = linux_disable_btrace (tinfo);
if (errcode != BTRACE_ERR_NONE)
error (_("Could not disable branch tracing."));
/* Teardown branch tracing. */
static void
x86_linux_teardown_btrace (struct target_ops *self,
struct btrace_target_info *tinfo)
/* Ignore errors. */
linux_disable_btrace (tinfo);
static enum btrace_error
x86_linux_read_btrace (struct target_ops *self,
struct btrace_data *data,
struct btrace_target_info *btinfo,
enum btrace_read_type type)
return linux_read_btrace (data, btinfo, type);
/* See to_btrace_conf in target.h. */
static const struct btrace_config *
x86_linux_btrace_conf (struct target_ops *self,
const struct btrace_target_info *btinfo)
return linux_btrace_conf (btinfo);
/* Helper for ps_get_thread_area. Sets BASE_ADDR to a pointer to
the thread local storage (or its descriptor) and returns PS_OK
on success. Returns PS_ERR on failure. */
x86_linux_get_thread_area (pid_t pid, void *addr, unsigned int *base_addr)
/* NOTE: cagney/2003-08-26: The definition of this buffer is found
in the kernel header <asm-i386/ldt.h>. It, after padding, is 4 x
4 byte integers in size: `entry_number', `base_addr', `limit',
and a bunch of status bits.
The values returned by this ptrace call should be part of the
regcache buffer, and ps_get_thread_area should channel its
request through the regcache. That way remote targets could
provide the value using the remote protocol and not this direct
Is this function needed? I'm guessing that the `base' is the
address of a descriptor that libthread_db uses to find the
thread local address base that GDB needs. Perhaps that
descriptor is defined by the ABI. Anyway, given that
libthread_db calls this function without prompting (gdb
requesting tls base) I guess it needs info in there anyway. */
unsigned int desc[4];
/* This code assumes that "int" is 32 bits and that
GET_THREAD_AREA returns no more than 4 int values. */
gdb_assert (sizeof (int) == 4);
if (ptrace (PTRACE_GET_THREAD_AREA, pid, addr, &desc) < 0)
return PS_ERR;
*base_addr = desc[1];
return PS_OK;
/* Create an x86 GNU/Linux target. */
struct target_ops *
x86_linux_create_target (void)
/* Fill in the generic GNU/Linux methods. */
struct target_ops *t = linux_target ();
/* Initialize the debug register function vectors. */
x86_use_watchpoints (t);
x86_dr_low.set_control = x86_linux_dr_set_control;
x86_dr_low.set_addr = x86_linux_dr_set_addr;
x86_dr_low.get_addr = x86_linux_dr_get_addr;
x86_dr_low.get_status = x86_linux_dr_get_status;
x86_dr_low.get_control = x86_linux_dr_get_control;
x86_set_debug_register_length (sizeof (void *));
/* Override the GNU/Linux inferior startup hook. */
super_post_startup_inferior = t->to_post_startup_inferior;
t->to_post_startup_inferior = x86_linux_child_post_startup_inferior;
/* Add the description reader. */
t->to_read_description = x86_linux_read_description;
/* Add btrace methods. */
t->to_supports_btrace = linux_supports_btrace;
t->to_enable_btrace = x86_linux_enable_btrace;
t->to_disable_btrace = x86_linux_disable_btrace;
t->to_teardown_btrace = x86_linux_teardown_btrace;
t->to_read_btrace = x86_linux_read_btrace;
t->to_btrace_conf = x86_linux_btrace_conf;
return t;
/* Add an x86 GNU/Linux target. */
x86_linux_add_target (struct target_ops *t)
linux_nat_add_target (t);
linux_nat_set_new_thread (t, x86_linux_new_thread);
linux_nat_set_new_fork (t, x86_linux_new_fork);
linux_nat_set_forget_process (t, x86_forget_process);
linux_nat_set_prepare_to_resume (t, x86_linux_prepare_to_resume);