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Date: Thu, 30 Oct 2014 13:02:39 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
"H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Jiri Kosina <jkosina@...e.cz>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Vojtech Pavlik <vojtech@...e.cz>,
Seth Jennings <sjenning@...hat.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [for-next][PATCH 4/4] ftrace: Add more information to
ftrace_bug() output
Ben and H. Peter,
Can you give me your acked-bys for this?
Thanks!
-- Steve
On Mon, 27 Oct 2014 14:27:06 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
>
> With the introduction of the dynamic trampolines, it is useful that if
> things go wrong that ftrace_bug() produces more information about what
> the current state is. This can help debug issues that may arise.
>
> Ftrace has lots of checks to make sure that the state of the system it
> touchs is exactly what it expects it to be. When it detects an abnormality
> it calls ftrace_bug() and disables itself to prevent any further damage.
> It is crucial that ftrace_bug() produces sufficient information that
> can be used to debug the situation.
>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
> arch/powerpc/kernel/ftrace.c | 2 +-
> arch/x86/kernel/ftrace.c | 2 +-
> include/linux/ftrace.h | 4 +++-
> kernel/trace/ftrace.c | 38 +++++++++++++++++++++++++++++---------
> 4 files changed, 34 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
> index 390311c0f03d..e66af6d265e8 100644
> --- a/arch/powerpc/kernel/ftrace.c
> +++ b/arch/powerpc/kernel/ftrace.c
> @@ -449,7 +449,7 @@ void ftrace_replace_code(int enable)
> rec = ftrace_rec_iter_record(iter);
> ret = __ftrace_replace_code(rec, enable);
> if (ret) {
> - ftrace_bug(ret, rec->ip);
> + ftrace_bug(ret, rec);
> return;
> }
> }
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 4cfeca6ffe11..1aea94d336c7 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -583,7 +583,7 @@ void ftrace_replace_code(int enable)
>
> remove_breakpoints:
> pr_warn("Failed on %s (%d):\n", report, count);
> - ftrace_bug(ret, rec ? rec->ip : 0);
> + ftrace_bug(ret, rec);
> for_ftrace_rec_iter(iter) {
> rec = ftrace_rec_iter_record(iter);
> /*
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 06e3ca5a5083..619e37cc17fd 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -263,7 +263,9 @@ struct ftrace_func_command {
> int ftrace_arch_code_modify_prepare(void);
> int ftrace_arch_code_modify_post_process(void);
>
> -void ftrace_bug(int err, unsigned long ip);
> +struct dyn_ftrace;
> +
> +void ftrace_bug(int err, struct dyn_ftrace *rec);
>
> struct seq_file;
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index eab3123a1fbe..4043332f6720 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1738,10 +1738,13 @@ static void print_ip_ins(const char *fmt, unsigned char *p)
> printk(KERN_CONT "%s%02x", i ? ":" : "", p[i]);
> }
>
> +static struct ftrace_ops *
> +ftrace_find_tramp_ops_any(struct dyn_ftrace *rec);
> +
> /**
> * ftrace_bug - report and shutdown function tracer
> * @failed: The failed type (EFAULT, EINVAL, EPERM)
> - * @ip: The address that failed
> + * @rec: The record that failed
> *
> * The arch code that enables or disables the function tracing
> * can call ftrace_bug() when it has detected a problem in
> @@ -1750,8 +1753,10 @@ static void print_ip_ins(const char *fmt, unsigned char *p)
> * EINVAL - if what is read at @ip is not what was expected
> * EPERM - if the problem happens on writting to the @ip address
> */
> -void ftrace_bug(int failed, unsigned long ip)
> +void ftrace_bug(int failed, struct dyn_ftrace *rec)
> {
> + unsigned long ip = rec ? rec->ip : 0;
> +
> switch (failed) {
> case -EFAULT:
> FTRACE_WARN_ON_ONCE(1);
> @@ -1763,7 +1768,7 @@ void ftrace_bug(int failed, unsigned long ip)
> pr_info("ftrace failed to modify ");
> print_ip_sym(ip);
> print_ip_ins(" actual: ", (unsigned char *)ip);
> - printk(KERN_CONT "\n");
> + pr_cont("\n");
> break;
> case -EPERM:
> FTRACE_WARN_ON_ONCE(1);
> @@ -1775,6 +1780,24 @@ void ftrace_bug(int failed, unsigned long ip)
> pr_info("ftrace faulted on unknown error ");
> print_ip_sym(ip);
> }
> + if (rec) {
> + struct ftrace_ops *ops = NULL;
> +
> + pr_info("ftrace record flags: %lx\n", rec->flags);
> + pr_cont(" (%ld)%s", ftrace_rec_count(rec),
> + rec->flags & FTRACE_FL_REGS ? " R" : " ");
> + if (rec->flags & FTRACE_FL_TRAMP_EN) {
> + ops = ftrace_find_tramp_ops_any(rec);
> + if (ops)
> + pr_cont("\ttramp: %pS",
> + (void *)ops->trampoline);
> + else
> + pr_cont("\ttramp: ERROR!");
> +
> + }
> + ip = ftrace_get_addr_curr(rec);
> + pr_cont(" expected tramp: %lx\n", ip);
> + }
> }
>
> static int ftrace_check_record(struct dyn_ftrace *rec, int enable, int update)
> @@ -2097,7 +2120,7 @@ void __weak ftrace_replace_code(int enable)
> do_for_each_ftrace_rec(pg, rec) {
> failed = __ftrace_replace_code(rec, enable);
> if (failed) {
> - ftrace_bug(failed, rec->ip);
> + ftrace_bug(failed, rec);
> /* Stop processing */
> return;
> }
> @@ -2179,17 +2202,14 @@ struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter)
> static int
> ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec)
> {
> - unsigned long ip;
> int ret;
>
> - ip = rec->ip;
> -
> if (unlikely(ftrace_disabled))
> return 0;
>
> ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
> if (ret) {
> - ftrace_bug(ret, ip);
> + ftrace_bug(ret, rec);
> return 0;
> }
> return 1;
> @@ -2633,7 +2653,7 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
> if (ftrace_start_up && cnt) {
> int failed = __ftrace_replace_code(p, 1);
> if (failed)
> - ftrace_bug(failed, p->ip);
> + ftrace_bug(failed, p);
> }
> }
> }
--
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