golden hour

/usr/include/asm

File/Folder	Size	Actions
a.out.h	756 B
amd_hsmp.h	11.28 KB
auxvec.h	546 B
bitsperlong.h	321 B
boot.h	323 B
bootparam.h	8.31 KB
bpf_perf_event.h	40 B
byteorder.h	200 B
debugreg.h	3.25 KB
e820.h	2.52 KB
errno.h	31 B
fcntl.h	31 B
hw_breakpoint.h	69 B
hwcap2.h	324 B
ioctl.h	31 B
ioctls.h	32 B
ipcbuf.h	32 B
ist.h	854 B
kvm.h	20.4 KB
kvm_para.h	4.22 KB
kvm_perf.h	388 B
ldt.h	1.28 KB
mce.h	1.69 KB
mman.h	413 B
msgbuf.h	1.05 KB
msr.h	346 B
mtrr.h	3.9 KB
param.h	31 B
perf_regs.h	1.37 KB
poll.h	30 B
posix_types.h	224 B
posix_types_32.h	765 B
posix_types_64.h	609 B
posix_types_x32.h	581 B
prctl.h	1.08 KB
processor-flags.h	6.97 KB
ptrace-abi.h	1.99 KB
ptrace.h	1.46 KB
resource.h	34 B
sembuf.h	1.04 KB
setup.h	6 B
sgx.h	8.15 KB
shmbuf.h	1.29 KB
sigcontext.h	9.5 KB
sigcontext32.h	271 B
siginfo.h	422 B
signal.h	2.02 KB
socket.h	32 B
sockios.h	33 B
stat.h	3.06 KB
statfs.h	416 B
svm.h	9.59 KB
swab.h	724 B
termbits.h	34 B
termios.h	33 B
types.h	31 B
ucontext.h	2.07 KB
unistd.h	623 B
unistd_32.h	11.8 KB
unistd_64.h	9.7 KB
unistd_x32.h	17.01 KB
vm86.h	3.11 KB
vmx.h	7.29 KB
vsyscall.h	263 B

Edit: ucontext.h

/* 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 */