cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ucontext.h (2117B)

      1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
      2#ifndef _ASM_X86_UCONTEXT_H
      3#define _ASM_X86_UCONTEXT_H
      4
      5/*
      6 * Indicates the presence of extended state information in the memory
      7 * layout pointed by the fpstate pointer in the ucontext's sigcontext
      8 * struct (uc_mcontext).
      9 */
     10#define UC_FP_XSTATE	0x1
     11
     12#ifdef __x86_64__
     13/*
     14 * UC_SIGCONTEXT_SS will be set when delivering 64-bit or x32 signals on
     15 * kernels that save SS in the sigcontext.  All kernels that set
     16 * UC_SIGCONTEXT_SS will correctly restore at least the low 32 bits of esp
     17 * regardless of SS (i.e. they implement espfix).
     18 *
     19 * Kernels that set UC_SIGCONTEXT_SS will also set UC_STRICT_RESTORE_SS
     20 * when delivering a signal that came from 64-bit code.
     21 *
     22 * Sigreturn restores SS as follows:
     23 *
     24 * if (saved SS is valid || UC_STRICT_RESTORE_SS is set ||
     25 *     saved CS is not 64-bit)
     26 *         new SS = saved SS  (will fail IRET and signal if invalid)
     27 * else
     28 *         new SS = a flat 32-bit data segment
     29 *
     30 * This behavior serves three purposes:
     31 *
     32 * - Legacy programs that construct a 64-bit sigcontext from scratch
     33 *   with zero or garbage in the SS slot (e.g. old CRIU) and call
     34 *   sigreturn will still work.
     35 *
     36 * - Old DOSEMU versions sometimes catch a signal from a segmented
     37 *   context, delete the old SS segment (with modify_ldt), and change
     38 *   the saved CS to a 64-bit segment.  These DOSEMU versions expect
     39 *   sigreturn to send them back to 64-bit mode without killing them,
     40 *   despite the fact that the SS selector when the signal was raised is
     41 *   no longer valid.  UC_STRICT_RESTORE_SS will be clear, so the kernel
     42 *   will fix up SS for these DOSEMU versions.
     43 *
     44 * - Old and new programs that catch a signal and return without
     45 *   modifying the saved context will end up in exactly the state they
     46 *   started in, even if they were running in a segmented context when
     47 *   the signal was raised..  Old kernels would lose track of the
     48 *   previous SS value.
     49 */
     50#define UC_SIGCONTEXT_SS	0x2
     51#define UC_STRICT_RESTORE_SS	0x4
     52#endif
     53
     54#include <asm-generic/ucontext.h>
     55
     56#endif /* _ASM_X86_UCONTEXT_H */