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Date: Wed, 14 Jan 2015 09:34:30 +0100 (CET) From: Jiri Kosina <jkosina@...e.cz> To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> cc: Andrew Morton <akpm@...ux-foundation.org>, Stephen Rothwell <sfr@...b.auug.org.au>, Josh Poimboeuf <jpoimboe@...hat.com>, Christoph Hellwig <hch@...radead.org>, linux-kernel@...r.kernel.org, live-patching@...r.kernel.org, linux-next@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org> Subject: Re: [PATCH] ftrace: don't allow IPMODIFY without proper compiler support (was Re: Re: livepatching tree for linux-next) On Wed, 14 Jan 2015, Masami Hiramatsu wrote: > > diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h > > index f45acad..29fa417 100644 > > --- a/arch/x86/include/asm/ftrace.h > > +++ b/arch/x86/include/asm/ftrace.h > > @@ -4,8 +4,10 @@ > > #ifdef CONFIG_FUNCTION_TRACER > > #ifdef CC_USING_FENTRY > > # define MCOUNT_ADDR ((long)(__fentry__)) > > +# define arch_ftrace_ipmodify_compiler_support(void) ({ 1; }) > > #else > > # define MCOUNT_ADDR ((long)(mcount)) > > +#define arch_ftrace_ipmodify_compiler_support(void) ({ 0; }) > > Hmm, can we just define ARCH_FTRACE_SUPPORT_IPMODIFY here? Yup, that's more or less what Steven suggested as well. I'll send v2. > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > index 929a733..11370fd 100644 > > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -1809,6 +1809,11 @@ static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops, > > if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY)) > > return 0; > > > > + if (!arch_ftrace_ipmodify_compiler_support()) { > > + WARN(1, "Your compiler doesn't support features necessary for IPMODIFY"); > > + return 0; > > + } > > Actually, if ftrace doesn't support IPMODIFY, I would like to just drop > the entire code for CONFIG_KPROBES_ON_FTRACE(this is a hidden config), > instead of checking at runtime. > > So, there are 2 ifdefs of code in kernel/kprobes.c for > CONFIG_KPROBES_ON_FTRACE, those should also check > ARCH_FTRACE_SUPPORT_IPMODIFY too. Makes sense. Will send that as a followup patch once the way how to do this in ftrace is settled. Thanks, -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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