livepatch: handle ancient compilers with more grace
We are aborting a build in case when gcc doesn't support fentry on x86_64
(regs->ip modification can't really reliably work with mcount).
This however breaks allmodconfig for people with older gccs that don't
support -mfentry.
Turn the build-time failure into runtime failure, resulting in the whole
infrastructure not being initialized if CC_USING_FENTRY is unset.
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h
index b5608d7..26e5813 100644
--- a/arch/x86/include/asm/livepatch.h
+++ b/arch/x86/include/asm/livepatch.h
@@ -25,9 +25,13 @@
#include <linux/ftrace.h>
#ifdef CONFIG_LIVE_PATCHING
+static inline int klp_check_compiler_support(void)
+{
#ifndef CC_USING_FENTRY
-#error Your compiler must support -mfentry for live patching to work
+ return 1;
#endif
+ return 0;
+}
extern int klp_write_module_reloc(struct module *mod, unsigned long type,
unsigned long loc, unsigned long value);
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 6f63879..ce42d3b 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -911,6 +911,12 @@
{
int ret;
+ ret = klp_check_compiler_support();
+ if (ret) {
+ pr_info("Your compiler is too old; turning off.\n");
+ return -EINVAL;
+ }
+
ret = register_module_notifier(&klp_module_nb);
if (ret)
return ret;