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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>
This commit is contained in:
Jiri Kosina 2015-01-09 10:53:21 +01:00
parent 83ac237a95
commit b9dfe0bed9
2 changed files with 11 additions and 1 deletions
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6
arch/x86/include/asm/livepatch.h
View File

@ -25,9 +25,13 @@
#include <linux/ftrace.h> #include <linux/ftrace.h>
#ifdef CONFIG_LIVE_PATCHING #ifdef CONFIG_LIVE_PATCHING
static inline int klp_check_compiler_support(void)
{
#ifndef CC_USING_FENTRY #ifndef CC_USING_FENTRY
#error Your compiler must support -mfentry for live patching to work return 1;
#endif #endif
return 0;
}
extern int klp_write_module_reloc(struct module *mod, unsigned long type, extern int klp_write_module_reloc(struct module *mod, unsigned long type,
unsigned long loc, unsigned long value); unsigned long loc, unsigned long value);

6
kernel/livepatch/core.c
View File

@ -911,6 +911,12 @@ static int klp_init(void)
{ {
int ret; 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); ret = register_module_notifier(&klp_module_nb);
if (ret) if (ret)
return ret; return ret;