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6ef3896cfe
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>
128 lines
3.6 KiB
C
128 lines
3.6 KiB
C
/* Target description related code for GNU/Linux x86 (i386 and x86-64).
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Copyright (C) 2024-2025 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "nat/x86-linux-tdesc.h"
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#ifdef __x86_64__
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#include "arch/amd64.h"
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#include "arch/amd64-linux-tdesc.h"
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#endif
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#include "arch/i386.h"
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#include "arch/i386-linux-tdesc.h"
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#include "nat/x86-linux.h"
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#include "nat/gdb_ptrace.h"
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#include "nat/x86-xstate.h"
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#include "gdbsupport/x86-xstate.h"
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#ifndef __x86_64__
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#include <sys/procfs.h>
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#include "nat/i386-linux.h"
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#endif
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#include <sys/uio.h>
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#include <elf.h>
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#ifndef IN_PROCESS_AGENT
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/* See nat/x86-linux-tdesc.h. */
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const target_desc *
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x86_linux_tdesc_for_tid (int tid, uint64_t *xstate_bv_storage,
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x86_xsave_layout *xsave_layout_storage)
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{
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#ifdef __x86_64__
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x86_linux_arch_size arch_size = x86_linux_ptrace_get_arch_size (tid);
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bool is_64bit = arch_size.is_64bit ();
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bool is_x32 = arch_size.is_x32 ();
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if (sizeof (void *) == 4 && is_64bit && !is_x32)
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{
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#ifdef GDBSERVER
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error (_("Can't debug 64-bit process with 32-bit GDBserver"));
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#else
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error (_("Can't debug 64-bit process with 32-bit GDB"));
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#endif
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}
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#elif HAVE_PTRACE_GETFPXREGS
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if (have_ptrace_getfpxregs == TRIBOOL_UNKNOWN)
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{
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elf_fpxregset_t fpxregs;
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if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
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{
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have_ptrace_getfpxregs = TRIBOOL_FALSE;
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have_ptrace_getregset = TRIBOOL_FALSE;
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}
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else
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have_ptrace_getfpxregs = TRIBOOL_TRUE;
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}
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if (have_ptrace_getfpxregs == TRIBOOL_FALSE)
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return i386_linux_read_description (X86_XSTATE_X87_MASK);
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#endif
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if (have_ptrace_getregset == TRIBOOL_UNKNOWN)
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{
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uint64_t xstateregs[(X86_XSTATE_SSE_SIZE / sizeof (uint64_t))];
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struct iovec iov;
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iov.iov_base = xstateregs;
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iov.iov_len = sizeof (xstateregs);
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/* Check if PTRACE_GETREGSET works. */
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if (ptrace (PTRACE_GETREGSET, tid,
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(unsigned int) NT_X86_XSTATE, &iov) < 0)
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{
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/* Can't fetch the xcr0 value so pick a simple default. This
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default has x87 and sse bits set. These bits are ignored for
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amd64 and x32 targets, but are checked for on i386. Without
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these bits being set we generate a completely empty tdesc for
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i386 which will be rejected by GDB. */
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have_ptrace_getregset = TRIBOOL_FALSE;
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*xstate_bv_storage = X86_XSTATE_SSE_MASK;
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}
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else
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{
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have_ptrace_getregset = TRIBOOL_TRUE;
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/* Get XCR0 from XSAVE extended state. */
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uint64_t xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
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/ sizeof (uint64_t))];
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*xsave_layout_storage
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= x86_fetch_xsave_layout (xcr0, x86_xsave_length ());
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*xstate_bv_storage = xcr0;
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}
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}
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/* Use cached XSTATE_BV_STORAGE value. */
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uint64_t xstate_bv_features_bits = *xstate_bv_storage & X86_XSTATE_ALL_MASK;
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#ifdef __x86_64__
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if (is_64bit)
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return amd64_linux_read_description (xstate_bv_features_bits, is_x32);
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else
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#endif
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return i386_linux_read_description (xstate_bv_features_bits);
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}
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#endif /* !IN_PROCESS_AGENT */
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