The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 887f92e09ef34a949745ad26ce82be69e2dabcf6 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023082759-esquire-online-0814@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

887f92e09ef3 ("tracing/synthetic: Skip first entry for stack traces") ddeea494a16f ("tracing/synthetic: Use union instead of casts") 116b41162f8b ("Merge tag 'probes-v6.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 887f92e09ef34a949745ad26ce82be69e2dabcf6 Mon Sep 17 00:00:00 2001 From: Sven Schnelle svens@linux.ibm.com Date: Wed, 16 Aug 2023 17:49:27 +0200 Subject: [PATCH] tracing/synthetic: Skip first entry for stack traces

While debugging another issue I noticed that the stack trace output contains the number of entries on top:

<idle>-0 [000] d..4. 203.322502: wake_lat: pid=0 delta=2268270616 stack=STACK: => 0x10 => __schedule+0xac6/0x1a98 => schedule+0x126/0x2c0 => schedule_timeout+0x242/0x2c0 => __wait_for_common+0x434/0x680 => __wait_rcu_gp+0x198/0x3e0 => synchronize_rcu+0x112/0x138 => ring_buffer_reset_online_cpus+0x140/0x2e0 => tracing_reset_online_cpus+0x15c/0x1d0 => tracing_set_clock+0x180/0x1d8 => hist_register_trigger+0x486/0x670 => event_hist_trigger_parse+0x494/0x1318 => trigger_process_regex+0x1d4/0x258 => event_trigger_write+0xb4/0x170 => vfs_write+0x210/0xad0 => ksys_write+0x122/0x208

Fix this by skipping the first element. Also replace the pointer logic with an index variable which is easier to read.

Link: https://lkml.kernel.org/r/20230816154928.4171614-3-svens@linux.ibm.com

Cc: Masami Hiramatsu mhiramat@kernel.org Fixes: 00cf3d672a9d ("tracing: Allow synthetic events to pass around stacktraces") Signed-off-by: Sven Schnelle svens@linux.ibm.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index 7fff8235075f..80a2a832f857 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -350,7 +350,7 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter, struct trace_seq *s = &iter->seq; struct synth_trace_event *entry; struct synth_event *se; - unsigned int i, n_u64; + unsigned int i, j, n_u64; char print_fmt[32]; const char *fmt;

@@ -389,18 +389,13 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter, n_u64 += STR_VAR_LEN_MAX / sizeof(u64); } } else if (se->fields[i]->is_stack) { - unsigned long *p, *end; union trace_synth_field *data = &entry->fields[n_u64]; - - p = (void *)entry + data->as_dynamic.offset; - end = (void *)p + data->as_dynamic.len - (sizeof(long) - 1); + unsigned long *p = (void *)entry + data->as_dynamic.offset;

trace_seq_printf(s, "%s=STACK:\n", se->fields[i]->name); - - for (; *p && p < end; p++) - trace_seq_printf(s, "=> %pS\n", (void *)*p); + for (j = 1; j < data->as_dynamic.len / sizeof(long); j++) + trace_seq_printf(s, "=> %pS\n", (void *)p[j]); n_u64++; - } else { struct trace_print_flags __flags[] = { __def_gfpflag_names, {-1, NULL} }; @@ -490,10 +485,6 @@ static unsigned int trace_stack(struct synth_trace_event *entry, break; }

- /* Include the zero'd element if it fits */ - if (len < HIST_STACKTRACE_DEPTH) - len++; - len *= sizeof(long);

/* Find the dynamic section to copy the stack into. */