/* 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 0x1 #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them back to 64-bit mode without killing them, * despite the fact that the SS selector when the signal was raised is * no longer valid.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 0x2 #define UC_STRICT_RESTORE_SS 0x4 #endif #include <asm-generic/ucontext.h> #endif /* _ASM_X86_UCONTEXT_H */