/* 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 0 x1
#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* no longer valid .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 0 x2
#define UC_STRICT_RESTORE_SS 0 x4
#endif
#include <asm -generic/ucontext.h>
#endif /* _ASM_X86_UCONTEXT_H */
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