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authorDavid Woodhouse <dwmw@amazon.co.uk>2024-12-05 15:05:07 +0000
committerIngo Molnar <mingo@kernel.org>2024-12-06 10:35:49 +0100
commit07fa619f2a40c221ea27747a3323cabc59ab25eb (patch)
tree99ddd8bff52042babb33db5a4c5123295293d993 /lib/ctype.c
parent73da582a476ea6e3512f89f8ed57dfed945829a2 (diff)
x86/kexec: Restore GDT on return from ::preserve_context kexec
The restore_processor_state() function explicitly states that "the asm code that gets us here will have restored a usable GDT". That wasn't true in the case of returning from a ::preserve_context kexec. Make it so. Without this, the kernel was depending on the called function to reload a GDT which is appropriate for the kernel before returning. Test program: #include <unistd.h> #include <errno.h> #include <stdio.h> #include <stdlib.h> #include <linux/kexec.h> #include <linux/reboot.h> #include <sys/reboot.h> #include <sys/syscall.h> int main (void) { struct kexec_segment segment = {}; unsigned char purgatory[] = { 0x66, 0xba, 0xf8, 0x03, // mov $0x3f8, %dx 0xb0, 0x42, // mov $0x42, %al 0xee, // outb %al, (%dx) 0xc3, // ret }; int ret; segment.buf = &purgatory; segment.bufsz = sizeof(purgatory); segment.mem = (void *)0x400000; segment.memsz = 0x1000; ret = syscall(__NR_kexec_load, 0x400000, 1, &segment, KEXEC_PRESERVE_CONTEXT); if (ret) { perror("kexec_load"); exit(1); } ret = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, LINUX_REBOOT_CMD_KEXEC); if (ret) { perror("kexec reboot"); exit(1); } printf("Success\n"); return 0; } Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20241205153343.3275139-2-dwmw2@infradead.org
Diffstat (limited to 'lib/ctype.c')
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