diff options
| author | David Woodhouse <dwmw@amazon.co.uk> | 2026-04-28 21:59:52 +0100 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2026-05-08 17:00:12 +0200 |
| commit | 786a45757dcdf8f2beb9d4a6db605db16c18b2b4 (patch) | |
| tree | f5d57a7b53e9093012536318dac63a3a698de544 | |
| parent | 5772f6535227ebd104065d80afa8ed3478d34c5c (diff) | |
x86/kexec: Push kjump return address even for non-kjump kexec
The version of purgatory code shipped by kexec-tools attempts to look above
the top of its stack to find a return address for a kjump, even in a non-kjump
kexec.
After the commit in Fixes: the word above the stack might not be there,
leading to a fault (which is at least now caught by my exception-handling code
in kexec).
That commit fixed things for the actual kjump path, but no longer
"gratuitously" pushes the unused return address to the stack in the non-kjump
path. Put that *back* in the non-kjump path, to prevent purgatory from
crashing when trying to access it.
Fixes: 2cacf7f23a02 ("x86/kexec: Fix stack and handling of re-entry point for ::preserve_context")
Reported-by: Rohan Kakulawaram <rohanka@google.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Rohan Kakulawaram <rohanka@google.com>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/32d627134143ffd957891cb697138e839c623211.camel@infradead.org
| -rw-r--r-- | arch/x86/kernel/relocate_kernel_64.S | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 4ffba68dc57b..eaeb77464c06 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -136,6 +136,14 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) * %r13 original CR4 when relocate_kernel() was invoked */ + /* + * Set return address to 0 if not preserving context. The purgatory + * shipped in kexec-tools will unconditionally look for the return + * address on the stack and set a kexec_jump_back_entry= command + * line option if it's non-zero. There's no other way that it can + * tell a preserve-context (kjump) kexec from a normal one. + */ + pushq $0 /* store the start address on the stack */ pushq %rdx |