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/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _ASM_X86_UCONTEXT_H
#define _ASM_X86_UCONTEXT_H
/*
* Indicates the presence of extended state information in the memory
* layout pointed by the fpstate pointer in the ucontext's sigcontext
* struct (uc_mcontext).
*/
#define UC_FP_XSTATE 0x1
#ifdef __x86_64__
/*
* UC_SIGCONTEXT_SS will be set when delivering 64-bit or x32 signals on
* kernels that save SS in the sigcontext. All kernels that set
* UC_SIGCONTEXT_SS will correctly restore at least the low 32 bits of esp
* regardless of SS (i.e. they implement espfix).
*
* Kernels that set UC_SIGCONTEXT_SS will also set UC_STRICT_RESTORE_SS
* when delivering a signal that came from 64-bit code.
*
* Sigreturn restores SS as follows:
*
* if (saved SS is valid || UC_STRICT_RESTORE_SS is set ||
* saved CS is not 64-bit)
* new SS = saved SS (will fail IRET and signal if invalid)
* else
* new SS = a flat 32-bit data segment
*
* This behavior serves three purposes:
*
* - Legacy programs that construct a 64-bit sigcontext from scratch
* with zero or garbage in the SS slot (e.g. old CRIU) and call
* sigreturn will still work.
*
* - Old DOSEMU versions sometimes catch a signal from a segmented
* context, delete the old SS segment (with modify_ldt), and change
* the saved CS to a 64-bit segment. These DOSEMU versions expect
* sigreturn to send them back to 64-bit mode without killing them,
* despite the fact that the SS selector when the signal was raised is
* no longer valid. UC_STRICT_RESTORE_SS will be clear, so the kernel
* will fix up SS for these DOSEMU versions.
*
* - Old and new programs that catch a signal and return without
* modifying the saved context will end up in exactly the state they
* started in, even if they were running in a segmented context when
* the signal was raised.. Old kernels would lose track of the
* previous SS value.
*/
#define UC_SIGCONTEXT_SS 0x2
#define UC_STRICT_RESTORE_SS 0x4
#endif
#include <asm-generic/ucontext.h>
#endif /* _ASM_X86_UCONTEXT_H */
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