From: Steven Rostedt <rostedt@goodmis•org>
To: Jiri Kosina <jkosina@suse•cz>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi•com>,
Andrew Morton <akpm@linux-foundation•org>,
Stephen Rothwell <sfr@canb•auug.org.au>,
Josh Poimboeuf <jpoimboe@redhat•com>,
Christoph Hellwig <hch@infradead•org>,
linux-kernel@vger•kernel.org, live-patching@vger•kernel.org,
linux-next@vger•kernel.org
Subject: Re: [PATCH] ftrace: don't allow IPMODIFY without proper compiler support (was Re: Re: livepatching tree for linux-next)
Date: Tue, 13 Jan 2015 21:12:23 -0500 [thread overview]
Message-ID: <20150113211223.18908f21@grimm.local.home> (raw)
In-Reply-To: <alpine.LNX.2.00.1501132345080.4162@pobox.suse.cz>
On Tue, 13 Jan 2015 23:47:57 +0100 (CET)
Jiri Kosina <jkosina@suse•cz> wrote:
> From: Jiri Kosina <jkosina@suse•cz>
> Subject: [PATCH] ftrace: don't allow IPMODIFY without proper compiler
> support
>
> Using IPMODIFY needs to be allowed only with compilers which are
> guaranteed to generate function prologues compatible with function
> redirection through changing instruction pointer in saved regs.
>
> For example changing regs->ip on x86_64 in cases when gcc is using
> mcount (and not fentry) is not allowed, because at the time mcount
> call is issued, the original function's prologue has already been
> executed, which leads to all kinds of inconsistent havoc.
>
> There is currently no way to express dependency on gcc features in
> Kconfig, (CC_USING_FENTRY is defined only during build, so it's not
> possible for Kconfig symbol to depend on it) so this needs to be
> checked in runtime.
>
> Mark x86_64 with fentry supported for now. Other archs can be added
> gradually.
>
> Signed-off-by: Jiri Kosina <jkosina@suse•cz>
> ---
> arch/x86/include/asm/ftrace.h | 2 ++
> include/linux/ftrace.h | 4 ++++
> kernel/trace/ftrace.c | 5 +++++
> 3 files changed, 11 insertions(+)
>
> 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; })
> #endif
> #define MCOUNT_INSN_SIZE 5 /* sizeof mcount call */
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 1da6029..655ba99 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -244,6 +244,10 @@ static inline int
> ftrace_function_local_disabled(struct ftrace_ops *ops) extern void
> ftrace_stub(unsigned long a0, unsigned long a1, struct ftrace_ops
> *op, struct pt_regs *regs);
> +#ifndef arch_ftrace_ipmodify_compiler_support
> +/* let's not make any implicit assumptions about profiling call
> placement */ +# define arch_ftrace_ipmodify_compiler_support() { 0; }
Is there any reason that this is a macro function? Why not just define:
#define ftrace_ipmodify_supported 0
?
-- Steve
> +#endif
> #else /* !CONFIG_FUNCTION_TRACER */
> /*
> * (un)register_ftrace_function must be a macro since the ops
> parameter 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;
> + }
> +
> /*
> * Since the IPMODIFY is a very address sensitive action, we
> do not
> * allow ftrace_ops to set all functions to new hash.
>
next prev parent reply other threads:[~2015-01-14 2:12 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-22 19:52 livepatching tree for linux-next Jiri Kosina
2014-12-23 9:46 ` Christoph Hellwig
2014-12-23 15:10 ` Josh Poimboeuf
2014-12-26 4:56 ` Stephen Rothwell
2015-01-07 22:43 ` Andrew Morton
2015-01-07 23:01 ` Jiri Kosina
2015-01-07 23:30 ` Andrew Morton
2015-01-07 23:49 ` Jiri Kosina
2015-01-07 23:57 ` Andrew Morton
2015-01-08 0:11 ` Jiri Kosina
2015-01-08 0:33 ` Andrew Morton
2015-01-08 2:22 ` Jingoo Han
2015-01-12 12:45 ` Masami Hiramatsu
2015-01-13 22:47 ` [PATCH] ftrace: don't allow IPMODIFY without proper compiler support (was Re: Re: livepatching tree for linux-next) Jiri Kosina
2015-01-14 2:12 ` Steven Rostedt [this message]
2015-01-14 8:47 ` [PATCH 1/2 v2] ftrace: don't allow IPMODIFY without proper compiler support Jiri Kosina
2015-01-14 8:48 ` [PATCH 2/2] kprobes: compile out IPMODIFY support if ftrace doesn't support it Jiri Kosina
2015-01-15 3:04 ` Masami Hiramatsu
2015-01-15 3:34 ` [PATCH 1/2 v2] ftrace: don't allow IPMODIFY without proper compiler support Masami Hiramatsu
2015-01-15 9:34 ` Jiri Kosina
2015-01-15 9:50 ` [PATCH 1/2 v3] " Jiri Kosina
2015-01-15 9:50 ` [PATCH 2/2 v3] kprobes: compile out IPMODIFY support if ftrace doesn't support it Jiri Kosina
2015-01-16 16:35 ` [PATCH 1/2 v3] ftrace: don't allow IPMODIFY without proper compiler support Steven Rostedt
2015-01-16 16:41 ` Jiri Kosina
2015-01-16 16:53 ` Steven Rostedt
2015-01-14 2:34 ` [PATCH] ftrace: don't allow IPMODIFY without proper compiler support (was Re: Re: livepatching tree for linux-next) Masami Hiramatsu
2015-01-14 8:34 ` Jiri Kosina
2015-01-09 10:03 ` livepatching tree for linux-next Jiri Kosina
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