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Code Issues Releases Wiki Activity

tracing/synthetic: Use union instead of casts 

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.

Link: https://lkml.kernel.org/r/20230816154928.4171614-2-svens@linux.ibm.com

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 00cf3d672a ("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>
This commit is contained in:
Sven Schnelle 2023-08-16 17:49:26 +02:00 committed by Steven Rostedt (Google)
parent 5450be6bef
commit ddeea494a1
3 changed files with 56 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/trace_events.h
View File

@ -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:

8
kernel/trace/trace.h
View File

@ -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;

87
kernel/trace/trace_events_synth.c
View File

@ -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;
}
}