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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>
52 lines
2.1 KiB
C
52 lines
2.1 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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#ifndef GDB_NAT_X86_LINUX_TDESC_H
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#define GDB_NAT_X86_LINUX_TDESC_H
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#include "gdbsupport/function-view.h"
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struct target_desc;
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struct x86_xsave_layout;
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/* Return the target description for Linux thread TID.
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The storage pointed to by XSTATE_BV_STORAGE and XSAVE_LAYOUT_STORAGE must
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exist until the program (GDB or gdbserver) terminates, this storage is
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used to cache the xstate_bv and xsave layout values. The values pointed to
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by these arguments are only updated at most once, the first time this
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function is called if the have_ptrace_getregset global is set to
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TRIBOOL_UNKNOWN.
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This function returns a target description based on the extracted xcr0
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value along with other characteristics of the thread identified by TID.
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This function can return nullptr if we encounter a machine configuration
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for which a target_desc cannot be created. Ideally this would not be
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the case, we should be able to create a target description for every
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possible machine configuration. See amd64_linux_read_description and
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i386_linux_read_description for cases when nullptr might be
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returned. */
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extern const target_desc *x86_linux_tdesc_for_tid
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(int tid, uint64_t *xstate_bv_storage,
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x86_xsave_layout *xsave_layout_storage);
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#endif /* GDB_NAT_X86_LINUX_TDESC_H */
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