From b9dfe0bed999d23ee8838d389637dd8aef83fafa Mon Sep 17 00:00:00 2001 From: Jiri Kosina Date: Fri, 9 Jan 2015 10:53:21 +0100 Subject: [PATCH] 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 Signed-off-by: Jiri Kosina Signed-off-by: Andrew Morton Acked-by: Josh Poimboeuf --- arch/x86/include/asm/livepatch.h | 6 +++++- kernel/livepatch/core.c | 6 ++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h index b5608d7757fd..26e58134c8cb 100644 --- a/arch/x86/include/asm/livepatch.h +++ b/arch/x86/include/asm/livepatch.h @@ -25,9 +25,13 @@ #include #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 6f6387912da7..ce42d3b930dc 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -911,6 +911,12 @@ static int klp_init(void) { 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;