[PATCH 2/2] powerpc/kexec: Disable KASAN for VMX helpers used in MMU-off path

[Sourabh Jain]

The kexec sequence invokes enter_vmx_ops() and exit_vmx_ops() with the
MMU disabled. In this context, code must not rely on normal virtual
address translations or trigger page faults.

With KASAN enabled, these functions get instrumented and may access
shadow memory using regular address translation. When executed with
the MMU off, this can lead to page faults (bad_page_fault) from which
the kernel cannot recover in the kexec path, resulting in a hang.

Mark enter_vmx_ops() and exit_vmx_ops() with __no_sanitize_address to
avoid KASAN instrumentation and ensure kexec boots fine with KASAN
enabled.

Cc: Aditya Gupta <adityag at linux.ibm.com>
Cc: Daniel Axtens <dja at axtens.net>
Cc: Hari Bathini <hbathini at linux.ibm.com>
Cc: Madhavan Srinivasan <maddy at linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Ritesh Harjani (IBM) <ritesh.list at gmail.com>
Cc: Shivang Upadhyay <shivangu at linux.ibm.com>
Cc: Venkat Rao Bagalkote <venkat88 at linux.ibm.com>
Reported-by: Aboorva Devarajan <aboorvad at linux.ibm.com>
Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
---
 arch/powerpc/lib/vmx-helper.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c
index 554b248002b4..c01b2d856650 100644
--- a/arch/powerpc/lib/vmx-helper.c
+++ b/arch/powerpc/lib/vmx-helper.c
@@ -52,7 +52,7 @@ int exit_vmx_usercopy(void)
 }
 EXPORT_SYMBOL(exit_vmx_usercopy);
 
-int enter_vmx_ops(void)
+int __no_sanitize_address enter_vmx_ops(void)
 {
 	if (in_interrupt())
 		return 0;
@@ -69,7 +69,7 @@ int enter_vmx_ops(void)
  * passed a pointer to the destination which we return as required by a
  * memcpy implementation.
  */
-void *exit_vmx_ops(void *dest)
+void __no_sanitize_address *exit_vmx_ops(void *dest)
 {
 	disable_kernel_altivec();
 	preempt_enable();
-- 
2.52.0