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40 * no longer valid.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