* [PATCH RESEND v3 1/3] tracing/synthetic: use union instead of casts
2023-08-16 15:49 [PATCH RESEND v3 0/3] few fixes for synthetic trace events Sven Schnelle
@ 2023-08-16 15:49 ` Sven Schnelle
2023-08-25 8:26 ` kernel test robot
2023-08-16 15:49 ` [PATCH RESEND v3 2/3] tracing/synthetic: skip first entry for stack traces Sven Schnelle
` (2 subsequent siblings)
3 siblings, 1 reply; 6+ messages in thread
From: Sven Schnelle @ 2023-08-16 15:49 UTC (permalink / raw)
To: Steven Rostedt; +Cc: linux-kernel, Masami Hiramatsu, linux-trace-kernel, bpf
The current code uses a lot of casts to access the fields
member in struct synth_trace_events with different sizes.
This makes the code hard to read, and had already introduced
an endianness bug. Use a union and struct instead.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
---
include/linux/trace_events.h | 11 ++++
kernel/trace/trace.h | 8 +++
kernel/trace/trace_events_synth.c | 87 +++++++++++++------------------
3 files changed, 56 insertions(+), 50 deletions(-)
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 3930e676436c..1e8bbdb8da90 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -59,6 +59,17 @@ int trace_raw_output_prep(struct trace_iterator *iter,
extern __printf(2, 3)
void trace_event_printf(struct trace_iterator *iter, const char *fmt, ...);
+/* Used to find the offset and length of dynamic fields in trace events */
+struct trace_dynamic_info {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+ u16 offset;
+ u16 len;
+#else
+ u16 len;
+ u16 offset;
+#endif
+};
+
/*
* The trace entry - the most basic unit of tracing. This is what
* is printed in the end as a single line in the trace output, such as:
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index e1edc2197fc8..95956f75bea5 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1295,6 +1295,14 @@ static inline void trace_branch_disable(void)
/* set ring buffers to default size if not already done so */
int tracing_update_buffers(void);
+union trace_synth_field {
+ u8 as_u8;
+ u16 as_u16;
+ u32 as_u32;
+ u64 as_u64;
+ struct trace_dynamic_info as_dynamic;
+};
+
struct ftrace_event_field {
struct list_head link;
const char *name;
diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index dd398afc8e25..7fff8235075f 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -127,7 +127,7 @@ static bool synth_event_match(const char *system, const char *event,
struct synth_trace_event {
struct trace_entry ent;
- u64 fields[];
+ union trace_synth_field fields[];
};
static int synth_event_define_fields(struct trace_event_call *call)
@@ -321,19 +321,19 @@ static const char *synth_field_fmt(char *type)
static void print_synth_event_num_val(struct trace_seq *s,
char *print_fmt, char *name,
- int size, u64 val, char *space)
+ int size, union trace_synth_field *val, char *space)
{
switch (size) {
case 1:
- trace_seq_printf(s, print_fmt, name, (u8)val, space);
+ trace_seq_printf(s, print_fmt, name, val->as_u8, space);
break;
case 2:
- trace_seq_printf(s, print_fmt, name, (u16)val, space);
+ trace_seq_printf(s, print_fmt, name, val->as_u16, space);
break;
case 4:
- trace_seq_printf(s, print_fmt, name, (u32)val, space);
+ trace_seq_printf(s, print_fmt, name, val->as_u32, space);
break;
default:
@@ -374,36 +374,26 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter,
/* parameter values */
if (se->fields[i]->is_string) {
if (se->fields[i]->is_dynamic) {
- u32 offset, data_offset;
- char *str_field;
-
- offset = (u32)entry->fields[n_u64];
- data_offset = offset & 0xffff;
-
- str_field = (char *)entry + data_offset;
+ union trace_synth_field *data = &entry->fields[n_u64];
trace_seq_printf(s, print_fmt, se->fields[i]->name,
STR_VAR_LEN_MAX,
- str_field,
+ (char *)entry + data->as_dynamic.offset,
i == se->n_fields - 1 ? "" : " ");
n_u64++;
} else {
trace_seq_printf(s, print_fmt, se->fields[i]->name,
STR_VAR_LEN_MAX,
- (char *)&entry->fields[n_u64],
+ (char *)&entry->fields[n_u64].as_u64,
i == se->n_fields - 1 ? "" : " ");
n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
}
} else if (se->fields[i]->is_stack) {
- u32 offset, data_offset, len;
unsigned long *p, *end;
+ union trace_synth_field *data = &entry->fields[n_u64];
- offset = (u32)entry->fields[n_u64];
- data_offset = offset & 0xffff;
- len = offset >> 16;
-
- p = (void *)entry + data_offset;
- end = (void *)p + len - (sizeof(long) - 1);
+ p = (void *)entry + data->as_dynamic.offset;
+ end = (void *)p + data->as_dynamic.len - (sizeof(long) - 1);
trace_seq_printf(s, "%s=STACK:\n", se->fields[i]->name);
@@ -419,13 +409,13 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter,
print_synth_event_num_val(s, print_fmt,
se->fields[i]->name,
se->fields[i]->size,
- entry->fields[n_u64],
+ &entry->fields[n_u64],
space);
if (strcmp(se->fields[i]->type, "gfp_t") == 0) {
trace_seq_puts(s, " (");
trace_print_flags_seq(s, "|",
- entry->fields[n_u64],
+ entry->fields[n_u64].as_u64,
__flags);
trace_seq_putc(s, ')');
}
@@ -454,21 +444,16 @@ static unsigned int trace_string(struct synth_trace_event *entry,
int ret;
if (is_dynamic) {
- u32 data_offset;
+ union trace_synth_field *data = &entry->fields[*n_u64];
- data_offset = struct_size(entry, fields, event->n_u64);
- data_offset += data_size;
-
- len = fetch_store_strlen((unsigned long)str_val);
-
- data_offset |= len << 16;
- *(u32 *)&entry->fields[*n_u64] = data_offset;
+ data->as_dynamic.offset = struct_size(entry, fields, event->n_u64) + data_size;
+ data->as_dynamic.len = fetch_store_strlen((unsigned long)str_val);
ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
(*n_u64)++;
} else {
- str_field = (char *)&entry->fields[*n_u64];
+ str_field = (char *)&entry->fields[*n_u64].as_u64;
#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
if ((unsigned long)str_val < TASK_SIZE)
@@ -492,6 +477,7 @@ static unsigned int trace_stack(struct synth_trace_event *entry,
unsigned int data_size,
unsigned int *n_u64)
{
+ union trace_synth_field *data = &entry->fields[*n_u64];
unsigned int len;
u32 data_offset;
void *data_loc;
@@ -515,8 +501,9 @@ static unsigned int trace_stack(struct synth_trace_event *entry,
memcpy(data_loc, stack, len);
/* Fill in the field that holds the offset/len combo */
- data_offset |= len << 16;
- *(u32 *)&entry->fields[*n_u64] = data_offset;
+
+ data->as_dynamic.offset = data_offset;
+ data->as_dynamic.len = len;
(*n_u64)++;
@@ -592,19 +579,19 @@ static notrace void trace_event_raw_event_synth(void *__data,
switch (field->size) {
case 1:
- *(u8 *)&entry->fields[n_u64] = (u8)val;
+ entry->fields[n_u64].as_u8 = (u8)val;
break;
case 2:
- *(u16 *)&entry->fields[n_u64] = (u16)val;
+ entry->fields[n_u64].as_u16 = (u16)val;
break;
case 4:
- *(u32 *)&entry->fields[n_u64] = (u32)val;
+ entry->fields[n_u64].as_u32 = (u32)val;
break;
default:
- entry->fields[n_u64] = val;
+ entry->fields[n_u64].as_u64 = val;
break;
}
n_u64++;
@@ -1791,19 +1778,19 @@ int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
switch (field->size) {
case 1:
- *(u8 *)&state.entry->fields[n_u64] = (u8)val;
+ state.entry->fields[n_u64].as_u8 = (u8)val;
break;
case 2:
- *(u16 *)&state.entry->fields[n_u64] = (u16)val;
+ state.entry->fields[n_u64].as_u16 = (u16)val;
break;
case 4:
- *(u32 *)&state.entry->fields[n_u64] = (u32)val;
+ state.entry->fields[n_u64].as_u32 = (u32)val;
break;
default:
- state.entry->fields[n_u64] = val;
+ state.entry->fields[n_u64].as_u64 = val;
break;
}
n_u64++;
@@ -1884,19 +1871,19 @@ int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
switch (field->size) {
case 1:
- *(u8 *)&state.entry->fields[n_u64] = (u8)val;
+ state.entry->fields[n_u64].as_u8 = (u8)val;
break;
case 2:
- *(u16 *)&state.entry->fields[n_u64] = (u16)val;
+ state.entry->fields[n_u64].as_u16 = (u16)val;
break;
case 4:
- *(u32 *)&state.entry->fields[n_u64] = (u32)val;
+ state.entry->fields[n_u64].as_u32 = (u32)val;
break;
default:
- state.entry->fields[n_u64] = val;
+ state.entry->fields[n_u64].as_u64 = val;
break;
}
n_u64++;
@@ -2031,19 +2018,19 @@ static int __synth_event_add_val(const char *field_name, u64 val,
} else {
switch (field->size) {
case 1:
- *(u8 *)&trace_state->entry->fields[field->offset] = (u8)val;
+ trace_state->entry->fields[field->offset].as_u8 = (u8)val;
break;
case 2:
- *(u16 *)&trace_state->entry->fields[field->offset] = (u16)val;
+ trace_state->entry->fields[field->offset].as_u16 = (u16)val;
break;
case 4:
- *(u32 *)&trace_state->entry->fields[field->offset] = (u32)val;
+ trace_state->entry->fields[field->offset].as_u32 = (u32)val;
break;
default:
- trace_state->entry->fields[field->offset] = val;
+ trace_state->entry->fields[field->offset].as_u64 = val;
break;
}
}
--
2.39.2
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH RESEND v3 2/3] tracing/synthetic: skip first entry for stack traces
2023-08-16 15:49 [PATCH RESEND v3 0/3] few fixes for synthetic trace events Sven Schnelle
2023-08-16 15:49 ` [PATCH RESEND v3 1/3] tracing/synthetic: use union instead of casts Sven Schnelle
@ 2023-08-16 15:49 ` Sven Schnelle
2023-08-16 15:49 ` [PATCH RESEND v3 3/3] tracing/synthetic: allocate one additional element for size Sven Schnelle
2023-08-17 15:05 ` [PATCH RESEND v3 0/3] few fixes for synthetic trace events Steven Rostedt
3 siblings, 0 replies; 6+ messages in thread
From: Sven Schnelle @ 2023-08-16 15:49 UTC (permalink / raw)
To: Steven Rostedt; +Cc: linux-kernel, Masami Hiramatsu, linux-trace-kernel, bpf
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.
Fixes: 00cf3d672a9d ("tracing: Allow synthetic events to pass around stacktraces")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
---
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 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. */
--
2.39.2
^ permalink raw reply related [flat|nested] 6+ messages in thread