Files
binutils-gdb/gdb/arch/amd64.c
Christina Schimpe 6ef3896cfe gdb, gdbserver: Use xstate_bv for target description creation on x86.
The XSAVE function set is organized in state components, which are a set of
registers or parts of registers.  So-called XSAVE-supported features are
organized using state-component bitmaps, each bit corresponding to a
single state component.

The Intel Software Developer's Manual uses the term xstate_bv for a
state-component bitmap, which is defined as XCR0 | IA32_XSS.  The control
register XCR0 only contains a state-component bitmap that specifies user state
components, while IA32_XSS contains a state-component bitmap that specifies
supervisor state components.

Until now, XCR0 is used as input for target description creation in GDB.
However, a following patch will add userspace support for the CET shadow
stack feature by Intel.  The CET state is configured in IA32_XSS and consists
of 2 state components:
- State component 11 used for the 2 MSRs controlling user-mode
  functionality for CET (CET_U state)
- State component 12 used for the 3 MSRs containing shadow-stack pointers
  for privilege levels 0-2 (CET_S state).

Reading the CET shadow stack pointer register on linux requires a separate
ptrace call using NT_X86_SHSTK.  To pass the CET shadow stack enablement
state we would like to pass the xstate_bv value instead of xcr0 for target
description creation.  To prepare for that, we rename the xcr0 mask
values for target description creation to xstate_bv.  However, this
patch doesn't add any functional changes in GDB.

Future states specified in IA32_XSS such as CET will create a combined
xstate_bv_mask including xcr0 register value and its corresponding bit in
the state component bitmap.  This combined mask will then be used to create
the target descriptions.

Reviewed-By: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Approved-By: Luis Machado <luis.machado@arm.com>
2025-08-29 17:02:09 +00:00

73 lines
2.3 KiB
C

/* Copyright (C) 2017-2025 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 "amd64.h"
#include "gdbsupport/x86-xstate.h"
#include "gdbsupport/osabi.h"
#include <stdlib.h>
#include "../features/i386/64bit-avx.c"
#include "../features/i386/64bit-avx512.c"
#include "../features/i386/64bit-core.c"
#include "../features/i386/64bit-linux.c"
#include "../features/i386/64bit-segments.c"
#include "../features/i386/64bit-sse.c"
#include "../features/i386/pkeys.c"
#include "../features/i386/x32-core.c"
/* See arch/amd64.h. */
target_desc *
amd64_create_target_description (uint64_t xstate_bv, bool is_x32,
bool is_linux, bool segments)
{
target_desc_up tdesc = allocate_target_description ();
#ifndef IN_PROCESS_AGENT
set_tdesc_architecture (tdesc.get (),
is_x32 ? "i386:x64-32" : "i386:x86-64");
if (is_linux)
set_tdesc_osabi (tdesc.get (), GDB_OSABI_LINUX);
#endif
long regnum = 0;
if (is_x32)
regnum = create_feature_i386_x32_core (tdesc.get (), regnum);
else
regnum = create_feature_i386_64bit_core (tdesc.get (), regnum);
regnum = create_feature_i386_64bit_sse (tdesc.get (), regnum);
if (is_linux)
regnum = create_feature_i386_64bit_linux (tdesc.get (), regnum);
if (segments)
regnum = create_feature_i386_64bit_segments (tdesc.get (), regnum);
if (xstate_bv & X86_XSTATE_AVX)
regnum = create_feature_i386_64bit_avx (tdesc.get (), regnum);
if (xstate_bv & X86_XSTATE_AVX512)
regnum = create_feature_i386_64bit_avx512 (tdesc.get (), regnum);
if (xstate_bv & X86_XSTATE_PKRU)
regnum = create_feature_i386_pkeys (tdesc.get (), regnum);
return tdesc.release ();
}