On Fri, Jan 19, 2024 at 04:08:24PM +0800, Huang Yiwei wrote: > Currently ftrace only dumps the global trace buffer on an OOPs. For > debugging a production usecase, instance trace will be helpful to > check specific problems since global trace buffer may be used for > other purposes. > > This patch extend the ftrace_dump_on_oops parameter to dump a specific > trace instance: > > - ftrace_dump_on_oops=0: as before -- don't dump > - ftrace_dump_on_oops[=1]: as before -- dump the global trace buffer > on all CPUs > - ftrace_dump_on_oops=2 or =orig_cpu: as before -- dump the global > trace buffer on CPU that triggered the oops > - ftrace_dump_on_oops=<instance_name>: new behavior -- dump the > tracing instance matching <instance_name> > > Also, the sysctl node can handle the input accordingly. > > Cc: Ross Zwisler <zwis...@google.com> > Signed-off-by: Joel Fernandes (Google) <j...@joelfernandes.org> > Signed-off-by: Huang Yiwei <quic_hyi...@quicinc.com> > --- > Link: > https://lore.kernel.org/linux-trace-kernel/20221209125310.450ae...@gandalf.local.home/ > > .../admin-guide/kernel-parameters.txt | 9 +-- > Documentation/admin-guide/sysctl/kernel.rst | 11 ++-- > include/linux/ftrace.h | 4 +- > include/linux/kernel.h | 1 + > kernel/sysctl.c | 4 +- > kernel/trace/trace.c | 64 ++++++++++++++----- > kernel/trace/trace_selftest.c | 2 +- > 7 files changed, 65 insertions(+), 30 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > b/Documentation/admin-guide/kernel-parameters.txt > index a36cf8cc582c..b3aa533253f1 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1559,12 +1559,13 @@ > The above will cause the "foo" tracing instance to > trigger > a snapshot at the end of boot up. > > - ftrace_dump_on_oops[=orig_cpu] > + ftrace_dump_on_oops[=orig_cpu | =<instance>] > [FTRACE] will dump the trace buffers on oops. > - If no parameter is passed, ftrace will dump > - buffers of all CPUs, but if you pass orig_cpu, it will > + If no parameter is passed, ftrace will dump global > + buffers of all CPUs, if you pass orig_cpu, it will > dump only the buffer of the CPU that triggered the > - oops. > + oops, or specific instance will be dumped if instance > + name is passed. > > ftrace_filter=[function-list] > [FTRACE] Limit the functions traced by the function > diff --git a/Documentation/admin-guide/sysctl/kernel.rst > b/Documentation/admin-guide/sysctl/kernel.rst > index 6584a1f9bfe3..ecf036b63c48 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -296,11 +296,12 @@ kernel panic). This will output the contents of the > ftrace buffers to > the console. This is very useful for capturing traces that lead to > crashes and outputting them to a serial console. > > -= =================================================== > -0 Disabled (default). > -1 Dump buffers of all CPUs. > -2 Dump the buffer of the CPU that triggered the oops. > -= =================================================== > +=========== =================================================== > +0 Disabled (default). > +1 Dump buffers of all CPUs. > +2(orig_cpu) Dump the buffer of the CPU that triggered the oops. > +<instance> Dump the specific instance buffer. > +=========== =================================================== > > > ftrace_enabled, stack_tracer_enabled > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index e8921871ef9a..f20de4621ec1 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -1151,7 +1151,9 @@ static inline void unpause_graph_tracing(void) { } > #ifdef CONFIG_TRACING > enum ftrace_dump_mode; > > -extern enum ftrace_dump_mode ftrace_dump_on_oops; > +#define MAX_TRACER_SIZE 100 > +extern char ftrace_dump_on_oops[]; > +extern enum ftrace_dump_mode get_ftrace_dump_mode(void); > extern int tracepoint_printk; > > extern void disable_trace_on_warning(void); > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index d9ad21058eed..de4a76036372 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -255,6 +255,7 @@ enum ftrace_dump_mode { > DUMP_NONE, > DUMP_ALL, > DUMP_ORIG, > + DUMP_INSTANCE, > }; > > #ifdef CONFIG_TRACING > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 157f7ce2942d..81cc974913bb 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1710,9 +1710,9 @@ static struct ctl_table kern_table[] = { > { > .procname = "ftrace_dump_on_oops", > .data = &ftrace_dump_on_oops, > - .maxlen = sizeof(int), > + .maxlen = MAX_TRACER_SIZE, > .mode = 0644, > - .proc_handler = proc_dointvec, > + .proc_handler = proc_dostring, > }, > { > .procname = "traceoff_on_warning", > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index a0defe156b57..9a76a278e5c3 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -130,9 +130,10 @@ cpumask_var_t __read_mostly tracing_buffer_mask; > * /proc/sys/kernel/ftrace_dump_on_oops > * Set 1 if you want to dump buffers of all CPUs > * Set 2 if you want to dump the buffer of the CPU that triggered oops > + * Set instance name if you want to dump the specific trace instance > */ > - > -enum ftrace_dump_mode ftrace_dump_on_oops; > +/* Set to string format zero to disable by default */ > +char ftrace_dump_on_oops[MAX_TRACER_SIZE] = "0"; > > /* When set, tracing will stop when a WARN*() is hit */ > int __disable_trace_on_warning; > @@ -178,7 +179,6 @@ static void ftrace_trace_userstack(struct trace_array *tr, > struct trace_buffer *buffer, > unsigned int trace_ctx); > > -#define MAX_TRACER_SIZE 100 > static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata; > static char *default_bootup_tracer; > > @@ -201,19 +201,32 @@ static int __init set_cmdline_ftrace(char *str) > } > __setup("ftrace=", set_cmdline_ftrace); > > +enum ftrace_dump_mode get_ftrace_dump_mode(void) > +{ > + if (!strcmp("0", ftrace_dump_on_oops)) Would using a strncmp be better in this case? And this question goes for all the strcmp in the patch. Something like strncmp("0", ftrace_dump_on_oops, 1); when they are equal, it would avoid 2 assignments and two comparisons. Also might avoid runaway comparisons if the first string constant changes in the future.
Or maybe strncmp("0", ftrace_dump_on_oops, 2); if you want to check if
they are both null terminated.
> + return DUMP_NONE;
> + else if (!strcmp("1", ftrace_dump_on_oops))
> + return DUMP_ALL;
> + else if (!strcmp("orig_cpu", ftrace_dump_on_oops) ||
> + !strcmp("2", ftrace_dump_on_oops))
> + return DUMP_ORIG;
> + else
> + return DUMP_INSTANCE;
> +}
> +
> static int __init set_ftrace_dump_on_oops(char *str)
> {
> - if (*str++ != '=' || !*str || !strcmp("1", str)) {
> - ftrace_dump_on_oops = DUMP_ALL;
> + if (!*str) {
> + strscpy(ftrace_dump_on_oops, "1", MAX_TRACER_SIZE);
> return 1;
> }
>
> - if (!strcmp("orig_cpu", str) || !strcmp("2", str)) {
> - ftrace_dump_on_oops = DUMP_ORIG;
> - return 1;
> - }
> + if (*str++ == '=') {
> + strscpy(ftrace_dump_on_oops, str, MAX_TRACER_SIZE);
> + return 1;
> + }
>
> - return 0;
> + return 0;
> }
> __setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
>
> @@ -10085,14 +10098,16 @@ static struct notifier_block trace_die_notifier = {
> static int trace_die_panic_handler(struct notifier_block *self,
> unsigned long ev, void *unused)
> {
> - if (!ftrace_dump_on_oops)
> + enum ftrace_dump_mode dump_mode = get_ftrace_dump_mode();
> +
> + if (!dump_mode)
> return NOTIFY_DONE;
>
> /* The die notifier requires DIE_OOPS to trigger */
> if (self == &trace_die_notifier && ev != DIE_OOPS)
> return NOTIFY_DONE;
>
> - ftrace_dump(ftrace_dump_on_oops);
> + ftrace_dump(dump_mode);
>
> return NOTIFY_DONE;
> }
> @@ -10133,12 +10148,12 @@ trace_printk_seq(struct trace_seq *s)
> trace_seq_init(s);
> }
>
> -void trace_init_global_iter(struct trace_iterator *iter)
> +static void trace_init_iter(struct trace_iterator *iter, struct trace_array
> *tr)
> {
> - iter->tr = &global_trace;
> + iter->tr = tr;
> iter->trace = iter->tr->current_trace;
> iter->cpu_file = RING_BUFFER_ALL_CPUS;
> - iter->array_buffer = &global_trace.array_buffer;
> + iter->array_buffer = &tr->array_buffer;
>
> if (iter->trace && iter->trace->open)
> iter->trace->open(iter);
> @@ -10158,6 +10173,11 @@ void trace_init_global_iter(struct trace_iterator
> *iter)
> iter->fmt_size = STATIC_FMT_BUF_SIZE;
> }
>
> +void trace_init_global_iter(struct trace_iterator *iter)
> +{
> + trace_init_iter(iter, &global_trace);
> +}
> +
> void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
> {
> /* use static because iter can be a bit big for the stack */
> @@ -10168,6 +10188,15 @@ void ftrace_dump(enum ftrace_dump_mode
> oops_dump_mode)
> unsigned long flags;
> int cnt = 0, cpu;
>
> + if (oops_dump_mode == DUMP_INSTANCE) {
> + tr = trace_array_find(ftrace_dump_on_oops);
> + if (!tr) {
> + printk(KERN_TRACE "Instance %s not found\n",
> + ftrace_dump_on_oops);
> + return;
> + }
> + }
> +
> /* Only allow one dump user at a time. */
> if (atomic_inc_return(&dump_running) != 1) {
> atomic_dec(&dump_running);
> @@ -10182,12 +10211,12 @@ void ftrace_dump(enum ftrace_dump_mode
> oops_dump_mode)
> * If the user does a sysrq-z, then they can re-enable
> * tracing with echo 1 > tracing_on.
> */
> - tracing_off();
> + tracer_tracing_off(tr);
>
> local_irq_save(flags);
>
> /* Simulate the iterator */
> - trace_init_global_iter(&iter);
> + trace_init_iter(&iter, tr);
>
> for_each_tracing_cpu(cpu) {
> atomic_inc(&per_cpu_ptr(iter.array_buffer->data,
> cpu)->disabled);
> @@ -10200,6 +10229,7 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
>
> switch (oops_dump_mode) {
> case DUMP_ALL:
> + case DUMP_INSTANCE:
> iter.cpu_file = RING_BUFFER_ALL_CPUS;
> break;
> case DUMP_ORIG:
> diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
> index 529590499b1f..a9750a680324 100644
> --- a/kernel/trace/trace_selftest.c
> +++ b/kernel/trace/trace_selftest.c
> @@ -768,7 +768,7 @@ static int trace_graph_entry_watchdog(struct
> ftrace_graph_ent *trace)
> if (unlikely(++graph_hang_thresh > GRAPH_MAX_FUNC_TEST)) {
> ftrace_graph_stop();
> printk(KERN_WARNING "BUG: Function graph tracer hang!\n");
> - if (ftrace_dump_on_oops) {
> + if (get_ftrace_dump_mode()) {
> ftrace_dump(DUMP_ALL);
> /* ftrace_dump() disables tracing */
> tracing_on();
> --
> 2.25.1
>
--
Joel Granados
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