162306a36Sopenharmony_ci/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ 262306a36Sopenharmony_ci#ifndef _ASM_X86_UCONTEXT_H 362306a36Sopenharmony_ci#define _ASM_X86_UCONTEXT_H 462306a36Sopenharmony_ci 562306a36Sopenharmony_ci/* 662306a36Sopenharmony_ci * Indicates the presence of extended state information in the memory 762306a36Sopenharmony_ci * layout pointed by the fpstate pointer in the ucontext's sigcontext 862306a36Sopenharmony_ci * struct (uc_mcontext). 962306a36Sopenharmony_ci */ 1062306a36Sopenharmony_ci#define UC_FP_XSTATE 0x1 1162306a36Sopenharmony_ci 1262306a36Sopenharmony_ci#ifdef __x86_64__ 1362306a36Sopenharmony_ci/* 1462306a36Sopenharmony_ci * UC_SIGCONTEXT_SS will be set when delivering 64-bit or x32 signals on 1562306a36Sopenharmony_ci * kernels that save SS in the sigcontext. All kernels that set 1662306a36Sopenharmony_ci * UC_SIGCONTEXT_SS will correctly restore at least the low 32 bits of esp 1762306a36Sopenharmony_ci * regardless of SS (i.e. they implement espfix). 1862306a36Sopenharmony_ci * 1962306a36Sopenharmony_ci * Kernels that set UC_SIGCONTEXT_SS will also set UC_STRICT_RESTORE_SS 2062306a36Sopenharmony_ci * when delivering a signal that came from 64-bit code. 2162306a36Sopenharmony_ci * 2262306a36Sopenharmony_ci * Sigreturn restores SS as follows: 2362306a36Sopenharmony_ci * 2462306a36Sopenharmony_ci * if (saved SS is valid || UC_STRICT_RESTORE_SS is set || 2562306a36Sopenharmony_ci * saved CS is not 64-bit) 2662306a36Sopenharmony_ci * new SS = saved SS (will fail IRET and signal if invalid) 2762306a36Sopenharmony_ci * else 2862306a36Sopenharmony_ci * new SS = a flat 32-bit data segment 2962306a36Sopenharmony_ci * 3062306a36Sopenharmony_ci * This behavior serves three purposes: 3162306a36Sopenharmony_ci * 3262306a36Sopenharmony_ci * - Legacy programs that construct a 64-bit sigcontext from scratch 3362306a36Sopenharmony_ci * with zero or garbage in the SS slot (e.g. old CRIU) and call 3462306a36Sopenharmony_ci * sigreturn will still work. 3562306a36Sopenharmony_ci * 3662306a36Sopenharmony_ci * - Old DOSEMU versions sometimes catch a signal from a segmented 3762306a36Sopenharmony_ci * context, delete the old SS segment (with modify_ldt), and change 3862306a36Sopenharmony_ci * the saved CS to a 64-bit segment. These DOSEMU versions expect 3962306a36Sopenharmony_ci * sigreturn to send them back to 64-bit mode without killing them, 4062306a36Sopenharmony_ci * despite the fact that the SS selector when the signal was raised is 4162306a36Sopenharmony_ci * no longer valid. UC_STRICT_RESTORE_SS will be clear, so the kernel 4262306a36Sopenharmony_ci * will fix up SS for these DOSEMU versions. 4362306a36Sopenharmony_ci * 4462306a36Sopenharmony_ci * - Old and new programs that catch a signal and return without 4562306a36Sopenharmony_ci * modifying the saved context will end up in exactly the state they 4662306a36Sopenharmony_ci * started in, even if they were running in a segmented context when 4762306a36Sopenharmony_ci * the signal was raised.. Old kernels would lose track of the 4862306a36Sopenharmony_ci * previous SS value. 4962306a36Sopenharmony_ci */ 5062306a36Sopenharmony_ci#define UC_SIGCONTEXT_SS 0x2 5162306a36Sopenharmony_ci#define UC_STRICT_RESTORE_SS 0x4 5262306a36Sopenharmony_ci#endif 5362306a36Sopenharmony_ci 5462306a36Sopenharmony_ci#include <asm-generic/ucontext.h> 5562306a36Sopenharmony_ci 5662306a36Sopenharmony_ci#endif /* _ASM_X86_UCONTEXT_H */ 57