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| author | David Woodhouse <dwmw@amazon.co.uk> | 2024-12-05 15:05:07 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-12-14 19:59:56 +0100 |
| commit | 94666abe816328301e1e8885a46c99bc37b14f87 (patch) | |
| tree | 4d7e46d56fed2f812c1844a3b77c77ae064f259c /arch | |
| parent | 70d6c1badec32e6209b4c8dec80986c150999c40 (diff) | |
| download | linux-94666abe816328301e1e8885a46c99bc37b14f87.tar.gz linux-94666abe816328301e1e8885a46c99bc37b14f87.tar.bz2 linux-94666abe816328301e1e8885a46c99bc37b14f87.zip | |
x86/kexec: Restore GDT on return from ::preserve_context kexec
commit 07fa619f2a40c221ea27747a3323cabc59ab25eb upstream.
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/relocate_kernel_64.S | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 56cab1bb25f5..569d5577059d 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -240,6 +240,13 @@ SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped) movq CR0(%r8), %r8 movq %rax, %cr3 movq %r8, %cr0 + +#ifdef CONFIG_KEXEC_JUMP + /* Saved in save_processor_state. */ + movq $saved_context, %rax + lgdt saved_context_gdt_desc(%rax) +#endif + movq %rbp, %rax popf |