path: root/gdb/amd64-linux-tdep.c

/* Target-dependent code for GNU/Linux x86-64.

   Copyright (C) 2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009
   Free Software Foundation, Inc.
   Contributed by Jiri Smid, SuSE Labs.

   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
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   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 <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "frame.h"
#include "gdbcore.h"
#include "regcache.h"
#include "osabi.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "reggroups.h"
#include "amd64-linux-tdep.h"

#include "gdb_string.h"

#include "amd64-tdep.h"
#include "solib-svr4.h"

/* Mapping between the general-purpose registers in `struct user'
   format and GDB's register cache layout.  */

/* From <sys/reg.h>.  */
static int amd64_linux_gregset_reg_offset[] =
{
  10 * 8,			/* %rax */
  5 * 8,			/* %rbx */
  11 * 8,			/* %rcx */
  12 * 8,			/* %rdx */
  13 * 8,			/* %rsi */
  14 * 8,			/* %rdi */
  4 * 8,			/* %rbp */
  19 * 8,			/* %rsp */
  9 * 8,			/* %r8 ... */
  8 * 8,
  7 * 8,
  6 * 8,
  3 * 8,
  2 * 8,
  1 * 8,
  0 * 8,			/* ... %r15 */
  16 * 8,			/* %rip */
  18 * 8,			/* %eflags */
  17 * 8,			/* %cs */
  20 * 8,			/* %ss */
  23 * 8,			/* %ds */
  24 * 8,			/* %es */
  25 * 8,			/* %fs */
  26 * 8			/* %gs */
};


/* Support for signal handlers.  */

#define LINUX_SIGTRAMP_INSN0	0x48	/* mov $NNNNNNNN, %rax */
#define LINUX_SIGTRAMP_OFFSET0	0
#define LINUX_SIGTRAMP_INSN1	0x0f	/* syscall */
#define LINUX_SIGTRAMP_OFFSET1	7

static const gdb_byte linux_sigtramp_code[] =
{
  /* mov $__NR_rt_sigreturn, %rax */
  LINUX_SIGTRAMP_INSN0, 0xc7, 0xc0, 0x0f, 0x00, 0x00, 0x00,
  /* syscall */
  LINUX_SIGTRAMP_INSN1, 0x05
};

#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code)

/* If PC is in a sigtramp routine, return the address of the start of
   the routine.  Otherwise, return 0.  */

static CORE_ADDR
amd64_linux_sigtramp_start (struct frame_info *this_frame)
{
  CORE_ADDR pc = get_frame_pc (this_frame);
  gdb_byte buf[LINUX_SIGTRAMP_LEN];

  /* We only recognize a signal trampoline if PC is at the start of
     one of the two instructions.  We optimize for finding the PC at
     the start, as will be the case when the trampoline is not the
     first frame on the stack.  We assume that in the case where the
     PC is not at the start of the instruction sequence, there will be
     a few trailing readable bytes on the stack.  */

  if (!safe_frame_unwind_memory (this_frame, pc, buf, sizeof buf))
    return 0;

  if (buf[0] != LINUX_SIGTRAMP_INSN0)
    {
      if (buf[0] != LINUX_SIGTRAMP_INSN1)
	return 0;

      pc -= LINUX_SIGTRAMP_OFFSET1;
      if (!safe_frame_unwind_memory (this_frame, pc, buf, sizeof buf))
	return 0;
    }

  if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0)
    return 0;

  return pc;
}

/* Return whether THIS_FRAME corresponds to a GNU/Linux sigtramp
   routine.  */

static int
amd64_linux_sigtramp_p (struct frame_info *this_frame)
{
  CORE_ADDR pc = get_frame_pc (this_frame);
  char *name;

  find_pc_partial_function (pc, &name, NULL, NULL);

  /* If we have NAME, we can optimize the search.  The trampoline is
     named __restore_rt.  However, it isn't dynamically exported from
     the shared C library, so the trampoline may appear to be part of
     the preceding function.  This should always be sigaction,
     __sigaction, or __libc_sigaction (all aliases to the same
     function).  */
  if (name == NULL || strstr (name, "sigaction") != NULL)
    return (amd64_linux_sigtramp_start (this_frame) != 0);

  return (strcmp ("__restore_rt", name) == 0);
}

/* Offset to struct sigcontext in ucontext, from <asm/ucontext.h>.  */
#define AMD64_LINUX_UCONTEXT_SIGCONTEXT_OFFSET 40

/* Assuming THIS_FRAME is a GNU/Linux sigtramp routine, return the
   address of the associated sigcontext structure.  */

static CORE_ADDR
amd64_linux_sigcontext_addr (struct frame_info *this_frame)
{
  CORE_ADDR sp;
  gdb_byte buf[8];

  get_frame_register (this_frame, AMD64_RSP_REGNUM, buf);
  sp = extract_unsigned_integer (buf, 8);

  /* The sigcontext structure is part of the user context.  A pointer
     to the user context is passed as the third argument to the signal
     handler, i.e. in %rdx.  Unfortunately %rdx isn't preserved across
     function calls so we can't use it.  Fortunately the user context
     is part of the signal frame and the unwound %rsp directly points
     at it.  */
  return sp + AMD64_LINUX_UCONTEXT_SIGCONTEXT_OFFSET;
}


/* From <asm/sigcontext.h>.  */
static int amd64_linux_sc_reg_offset[] =
{
  13 * 8,			/* %rax */
  11 * 8,			/* %rbx */
  14 * 8,			/* %rcx */
  12 * 8,			/* %rdx */
  9 * 8,			/* %rsi */
  8 * 8,			/* %rdi */
  10 * 8,			/* %rbp */
  15 * 8,			/* %rsp */
  0 * 8,			/* %r8 */
  1 * 8,			/* %r9 */
  2 * 8,			/* %r10 */
  3 * 8,			/* %r11 */
  4 * 8,			/* %r12 */
  5 * 8,			/* %r13 */
  6 * 8,			/* %r14 */
  7 * 8,			/* %r15 */
  16 * 8,			/* %rip */
  17 * 8,			/* %eflags */

  /* FIXME: kettenis/2002030531: The registers %cs, %fs and %gs are
     available in `struct sigcontext'.  However, they only occupy two
     bytes instead of four, which makes using them here rather
     difficult.  Leave them out for now.  */
  -1,				/* %cs */
  -1,				/* %ss */
  -1,				/* %ds */
  -1,				/* %es */
  -1,				/* %fs */
  -1				/* %gs */
};

/* Replacement register functions which know about %orig_rax.  */

static const char *
amd64_linux_register_name (struct gdbarch *gdbarch, int reg)
{
  if (reg == AMD64_LINUX_ORIG_RAX_REGNUM)
    return "orig_rax";

  return amd64_register_name (gdbarch, reg);
}

static struct type *
amd64_linux_register_type (struct gdbarch *gdbarch, int reg)
{
  if (reg == AMD64_LINUX_ORIG_RAX_REGNUM)
    return builtin_type_int64;

  return amd64_register_type (gdbarch, reg);
}

static int
amd64_linux_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
				 struct reggroup *group)
{ 
  if (regnum == AMD64_LINUX_ORIG_RAX_REGNUM)
    return (group == system_reggroup
            || group == save_reggroup
            || group == restore_reggroup);
  return default_register_reggroup_p (gdbarch, regnum, group);
}

/* Set the program counter for process PTID to PC.  */

static void
amd64_linux_write_pc (struct regcache *regcache, CORE_ADDR pc)
{
  regcache_cooked_write_unsigned (regcache, AMD64_RIP_REGNUM, pc);

  /* We must be careful with modifying the program counter.  If we
     just interrupted a system call, the kernel might try to restart
     it when we resume the inferior.  On restarting the system call,
     the kernel will try backing up the program counter even though it
     no longer points at the system call.  This typically results in a
     SIGSEGV or SIGILL.  We can prevent this by writing `-1' in the
     "orig_rax" pseudo-register.

     Note that "orig_rax" is saved when setting up a dummy call frame.
     This means that it is properly restored when that frame is
     popped, and that the interrupted system call will be restarted
     when we resume the inferior on return from a function call from
     within GDB.  In all other cases the system call will not be
     restarted.  */
  regcache_cooked_write_unsigned (regcache, AMD64_LINUX_ORIG_RAX_REGNUM, -1);
}

static void
amd64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  tdep->gregset_reg_offset = amd64_linux_gregset_reg_offset;
  tdep->gregset_num_regs = ARRAY_SIZE (amd64_linux_gregset_reg_offset);
  tdep->sizeof_gregset = 27 * 8;

  amd64_init_abi (info, gdbarch);

  tdep->sigtramp_p = amd64_linux_sigtramp_p;
  tdep->sigcontext_addr = amd64_linux_sigcontext_addr;
  tdep->sc_reg_offset = amd64_linux_sc_reg_offset;
  tdep->sc_num_regs = ARRAY_SIZE (amd64_linux_sc_reg_offset);

  /* GNU/Linux uses SVR4-style shared libraries.  */
  set_solib_svr4_fetch_link_map_offsets
    (gdbarch, svr4_lp64_fetch_link_map_offsets);

  /* Add the %orig_rax register used for syscall restarting.  */
  set_gdbarch_write_pc (gdbarch, amd64_linux_write_pc);
  set_gdbarch_num_regs (gdbarch, AMD64_LINUX_NUM_REGS);
  set_gdbarch_register_name (gdbarch, amd64_linux_register_name);
  set_gdbarch_register_type (gdbarch, amd64_linux_register_type);
  set_gdbarch_register_reggroup_p (gdbarch, amd64_linux_register_reggroup_p);

  /* Enable TLS support.  */
  set_gdbarch_fetch_tls_load_module_address (gdbarch,
                                             svr4_fetch_objfile_link_map);
}


/* Provide a prototype to silence -Wmissing-prototypes.  */
extern void _initialize_amd64_linux_tdep (void);

void
_initialize_amd64_linux_tdep (void)
{
  gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
			  GDB_OSABI_LINUX, amd64_linux_init_abi);
}