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Commit b9dfe0be authored Jan 09, 2015 by Jiri Kosina

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>

parent 83ac237a

arch/x86/include/asm/livepatch.h

+5 −1

Original line number	Original line	Diff line number	Diff line
	@@ -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);

kernel/livepatch/core.c

+6 −0

Original line number	Original line	Diff line number	Diff line
	@@ -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;