57 lines
2.1 KiB
C
57 lines
2.1 KiB
C
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/* 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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