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6f52b16c | 1 | /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ |
1965aae3 PA |
2 | #ifndef _ASM_X86_UCONTEXT_H |
3 | #define _ASM_X86_UCONTEXT_H | |
003a46cf | 4 | |
6c25da5a AL |
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41 | * no longer valid.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 | |
c37b5efe | 53 | |
73a2d096 | 54 | #include <asm-generic/ucontext.h> |
003a46cf | 55 | |
1965aae3 | 56 | #endif /* _ASM_X86_UCONTEXT_H */ |