The code in _apply_alternatives() will unconditionally attempt to read
__initdata_cf_clobber_{start,end} when called as part of applying alternatives
to a livepatch payload. That leads to a page-fault as
__initdata_cf_clobber_{start,end} living in .init section will have been
unmapped by the time a livepatch gets loaded.
Fix by adding a check that limits the clobbering of endbr64 instructions to
boot time only.
Fixes: 37ed5da851b8 ('x86/altcall: Optimise away endbr64 instruction where
possible')
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
xen/arch/x86/alternative.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
index 21af0e825822..2e7ba6e0b833 100644
--- a/xen/arch/x86/alternative.c
+++ b/xen/arch/x86/alternative.c
@@ -326,7 +326,7 @@ static void init_or_livepatch _apply_alternatives(struct
alt_instr *start,
* Clobber endbr64 instructions now that altcall has finished optimising
* all indirect branches to direct ones.
*/
- if ( force && cpu_has_xen_ibt )
+ if ( force && cpu_has_xen_ibt && system_state < SYS_STATE_active )
{
void *const *val;
unsigned int clobbered = 0;
--
2.44.0
