Since the dynamic preemption has been enabled for PREEMPT_RT we have now
CONFIG_PREEMPT and CONFIG_PREEMPT_RT set simultaneously. This affects
the vermagic strings which comes now PREEMPT with PREEMPT_RT enabled.
The PREEMPT_RT module usually can not be loaded on a PREEMPT kernel
because some symbols are missing.
However if the symbols are fine then it continues and it crashes later.
The problem is that the struct module has a different layout and the
num_exentries or init members are at a different position leading to a
crash later on. This is not necessary caught by the size check in
elf_validity_cache_index_mod() because the mem member has an alignment
requirement of __module_memory_align which is big enough keep the total
size unchanged. Therefore we should keep the string accurate instead of
removing it.
Move the PREEMPT_RT check before the PREEMPT so that it takes precedence
if both symbols are enabled.
Fixes: 35772d627b55c ("sched: Enable PREEMPT_DYNAMIC for PREEMPT_RT")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
include/linux/vermagic.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h
index a54046bf37e55..939ceabcaf06f 100644
--- a/include/linux/vermagic.h
+++ b/include/linux/vermagic.h
@@ -15,10 +15,10 @@
#else
#define MODULE_VERMAGIC_SMP ""
#endif
-#ifdef CONFIG_PREEMPT_BUILD
-#define MODULE_VERMAGIC_PREEMPT "preempt "
-#elif defined(CONFIG_PREEMPT_RT)
+#ifdef CONFIG_PREEMPT_RT
#define MODULE_VERMAGIC_PREEMPT "preempt_rt "
+#elif defined(CONFIG_PREEMPT_BUILD)
+#define MODULE_VERMAGIC_PREEMPT "preempt "
#else
#define MODULE_VERMAGIC_PREEMPT ""
#endif
--
2.45.2
