binutils-gdb/gdb/nat/x86-linux-tdesc.c

/* Target description related code for GNU/Linux x86 (i386 and x86-64).

   Copyright (C) 2024-2025 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
   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 "nat/x86-linux-tdesc.h"
#ifdef __x86_64__
#include "arch/amd64.h"
#include "arch/amd64-linux-tdesc.h"
#endif
#include "arch/i386.h"
#include "arch/i386-linux-tdesc.h"

#include "nat/x86-linux.h"
#include "nat/gdb_ptrace.h"
#include "nat/x86-xstate.h"
#include "gdbsupport/x86-xstate.h"

#ifndef __x86_64__
#include <sys/procfs.h>
#include "nat/i386-linux.h"
#endif

#include <sys/uio.h>
#include <elf.h>

#ifndef IN_PROCESS_AGENT

/* See nat/x86-linux-tdesc.h.  */

const target_desc *
x86_linux_tdesc_for_tid (int tid, uint64_t *xstate_bv_storage,
			 x86_xsave_layout *xsave_layout_storage)
{
#ifdef __x86_64__
  x86_linux_arch_size arch_size = x86_linux_ptrace_get_arch_size (tid);
  bool is_64bit = arch_size.is_64bit ();
  bool is_x32 = arch_size.is_x32 ();

  if (sizeof (void *) == 4 && is_64bit && !is_x32)
    {
#ifdef GDBSERVER
      error (_("Can't debug 64-bit process with 32-bit GDBserver"));
#else
      error (_("Can't debug 64-bit process with 32-bit GDB"));
#endif
    }

#elif HAVE_PTRACE_GETFPXREGS
  if (have_ptrace_getfpxregs == TRIBOOL_UNKNOWN)
    {
      elf_fpxregset_t fpxregs;

      if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
	{
	  have_ptrace_getfpxregs = TRIBOOL_FALSE;
	  have_ptrace_getregset = TRIBOOL_FALSE;
	}
      else
	have_ptrace_getfpxregs = TRIBOOL_TRUE;
    }

  if (have_ptrace_getfpxregs == TRIBOOL_FALSE)
    return i386_linux_read_description (X86_XSTATE_X87_MASK);
#endif

  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)
	{
	  /* Can't fetch the xcr0 value so pick a simple default.  This
	     default has x87 and sse bits set.  These bits are ignored for
	     amd64 and x32 targets, but are checked for on i386.  Without
	     these bits being set we generate a completely empty tdesc for
	     i386 which will be rejected by GDB.  */
	  have_ptrace_getregset = TRIBOOL_FALSE;
	  *xstate_bv_storage = X86_XSTATE_SSE_MASK;
	}
      else
	{
	  have_ptrace_getregset = TRIBOOL_TRUE;

	  /* Get XCR0 from XSAVE extended state.  */
	  uint64_t xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
				      / sizeof (uint64_t))];

	  *xsave_layout_storage
	    = x86_fetch_xsave_layout (xcr0, x86_xsave_length ());

	  *xstate_bv_storage = xcr0;
	  if (x86_check_ssp_support (tid))
	    *xstate_bv_storage |= X86_XSTATE_CET_U;
	}
    }

  /* Use cached XSTATE_BV_STORAGE value.  */
  uint64_t xstate_bv_features_bits = *xstate_bv_storage & X86_XSTATE_ALL_MASK;

#ifdef __x86_64__
  if (is_64bit)
    return amd64_linux_read_description (xstate_bv_features_bits, is_x32);
  else
#endif
    return i386_linux_read_description (xstate_bv_features_bits);
}

#endif /* !IN_PROCESS_AGENT */