The following commit has been merged into the x86/boot branch of tip:
Commit-ID: 2114796ca041f0d3e79e5dd165219b940b23c540
Gitweb: https://git.kernel.org/tip/2114796ca041f0d3e79e5dd165219b940b23c540
Author: David Woodhouse <dwmw@xxxxxxxxxxxx>
AuthorDate: Thu, 09 Jan 2025 14:04:18
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 14 Jan 2025 13:02:40 +01:00
x86/kexec: Mark machine_kexec() with __nocfi
A recent commit caused the relocate_kernel() function to be invoked through
a function pointer, but it does not have CFI information. The resulting trap
occurs after the IDT and GDT have been invalidated, leading to a triple-fault
if CONFIG_CFI_CLANG is enabled.
Using SYM_TYPED_FUNC_START() to provide the CFI information looks like it will
require a prolonged battle with objtool. And is fairly pointless anyway, as
the actual signature comes from a __kcfi_typeid_… symbol emitted from the
C code based on the function prototype it thinks that relocate_kernel has,
rendering the check somewhat tautological.
The simple fix is just to mark machine_kexec() with __nocfi.
Fixes: eeebbde57113 ("x86/kexec: Invoke copy of relocate_kernel() instead of the original")
Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Suggested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/20250109140757.2841269-7-dwmw2@xxxxxxxxxxxxx
---
arch/x86/kernel/machine_kexec_64.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 9232ad1..1440f79 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -342,7 +342,7 @@ void machine_kexec_cleanup(struct kimage *image)
* Do not allocate memory (or fail in any way) in machine_kexec().
* We are past the point of no return, committed to rebooting now.
*/
-void machine_kexec(struct kimage *image)
+void __nocfi machine_kexec(struct kimage *image)
{
unsigned long (*relocate_kernel_ptr)(unsigned long indirection_page,
unsigned long pa_control_page,
|