6.4-stable review patch. If anyone has any objections, please let me know.
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From: Sven Schnelle svens@linux.ibm.com
[ Upstream commit 887f92e09ef34a949745ad26ce82be69e2dabcf6 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace_events_synth.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-)
diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index da0627fa91caf..a4c58a932dfa6 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. */