/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

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#ifndef _ASM_X86_UCONTEXT_H

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#define _ASM_X86_UCONTEXT_H

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/*

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* Indicates the presence of extended state information in the memory

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* layout pointed by the fpstate pointer in the ucontext's sigcontext

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* struct (uc_mcontext).

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*/

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#define UC_FP_XSTATE 0x1

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#ifdef __x86_64__

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/*

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* UC_SIGCONTEXT_SS will be set when delivering 64-bit or x32 signals on

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* kernels that save SS in the sigcontext. All kernels that set

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* UC_SIGCONTEXT_SS will correctly restore at least the low 32 bits of esp

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* regardless of SS (i.e. they implement espfix).

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*

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* Kernels that set UC_SIGCONTEXT_SS will also set UC_STRICT_RESTORE_SS

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* when delivering a signal that came from 64-bit code.

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*

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* Sigreturn restores SS as follows:

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*

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* if (saved SS is valid || UC_STRICT_RESTORE_SS is set ||

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* saved CS is not 64-bit)

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* new SS = saved SS (will fail IRET and signal if invalid)

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* else

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* new SS = a flat 32-bit data segment

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*

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* This behavior serves three purposes:

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*

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* - Legacy programs that construct a 64-bit sigcontext from scratch

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* with zero or garbage in the SS slot (e.g. old CRIU) and call

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* sigreturn will still work.

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*

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* - Old DOSEMU versions sometimes catch a signal from a segmented

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* context, delete the old SS segment (with modify_ldt), and change

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* the saved CS to a 64-bit segment. These DOSEMU versions expect

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* sigreturn to send them back to 64-bit mode without killing them,

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* despite the fact that the SS selector when the signal was raised is

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* no longer valid. UC_STRICT_RESTORE_SS will be clear, so the kernel

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* will fix up SS for these DOSEMU versions.

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*

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* - Old and new programs that catch a signal and return without

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* modifying the saved context will end up in exactly the state they

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* started in, even if they were running in a segmented context when

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* the signal was raised.. Old kernels would lose track of the

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* previous SS value.

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*/

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#define UC_SIGCONTEXT_SS 0x2

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#define UC_STRICT_RESTORE_SS 0x4

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#endif

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#include <asm-generic/ucontext.h>

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#endif /* _ASM_X86_UCONTEXT_H */

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