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ftrace: Add support for function argument to graph tracer

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Wire up the code to print function arguments in the function graph
tracer. This functionality can be enabled/disabled during runtime with
options/funcgraph-args.

Example usage:

6)              | dummy_xmit [dummy](skb = 0x8887c100, dev = 0x872ca000) {
6)              |   consume_skb(skb = 0x8887c100) {
6)              |     skb_release_head_state(skb = 0x8887c100) {
6)  0.178 us    |       sock_wfree(skb = 0x8887c100)
6)  0.627 us    |     }

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Guo Ren <guoren@kernel.org>
Cc: Donglin Peng <dolinux.peng@gmail.com>
Cc: Zheng Yejian <zhengyejian@huaweicloud.com>
Link: https://lore.kernel.org/20250227185822.810321199@goodmis.org
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Co-developed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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 2025-02-27 13:58:06 -05:00 committed by Steven Rostedt (Google)
parent 533c20b062
commit ff5c9c576e
4 changed files with 124 additions and 35 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

6
kernel/trace/Kconfig
View file

@ -268,6 +268,12 @@ config FUNCTION_TRACE_ARGS
depends on HAVE_FUNCTION_ARG_ACCESS_API
depends on DEBUG_INFO_BTF
default y
help
If supported with function argument access API and BTF, then
the function tracer and function graph tracer will support printing
of function arguments. This feature is off by default, and can be
enabled via the trace option func-args (for the function tracer) and
funcgraph-args (for the function graph tracer)
config DYNAMIC_FTRACE
bool "enable/disable function tracing dynamically"

1
kernel/trace/trace.h
View file

@ -897,6 +897,7 @@ static __always_inline bool ftrace_hash_empty(struct ftrace_hash *hash)
#define TRACE_GRAPH_PRINT_RETVAL 0x800
#define TRACE_GRAPH_PRINT_RETVAL_HEX 0x1000
#define TRACE_GRAPH_PRINT_RETADDR 0x2000
#define TRACE_GRAPH_ARGS 0x4000
#define TRACE_GRAPH_PRINT_FILL_SHIFT 28
#define TRACE_GRAPH_PRINT_FILL_MASK (0x3 << TRACE_GRAPH_PRINT_FILL_SHIFT)

7
kernel/trace/trace_entries.h
View file

@ -72,17 +72,18 @@ FTRACE_ENTRY_REG(function, ftrace_entry,
);
/* Function call entry */
FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,
FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry,
TRACE_GRAPH_ENT,
F_STRUCT(
__field_struct( struct ftrace_graph_ent, graph_ent )
__field_packed( unsigned long, graph_ent, func )
__field_packed( int, graph_ent, depth )
__field_packed( unsigned long, graph_ent, depth )
__dynamic_array(unsigned long, args )
),
F_printk("--> %ps (%d)", (void *)__entry->func, __entry->depth)
F_printk("--> %ps (%lu)", (void *)__entry->func, __entry->depth)
);
#ifdef CONFIG_FUNCTION_GRAPH_RETADDR

135
kernel/trace/trace_functions_graph.c
View file

@ -70,6 +70,10 @@ static struct tracer_opt trace_opts[] = {
#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
/* Display function return address ? */
{ TRACER_OPT(funcgraph-retaddr, TRACE_GRAPH_PRINT_RETADDR) },
#endif
#ifdef CONFIG_FUNCTION_TRACE_ARGS
/* Display function arguments ? */
{ TRACER_OPT(funcgraph-args, TRACE_GRAPH_ARGS) },
#endif
/* Include sleep time (scheduled out) between entry and return */
{ TRACER_OPT(sleep-time, TRACE_GRAPH_SLEEP_TIME) },
@ -110,25 +114,43 @@ static void
print_graph_duration(struct trace_array *tr, unsigned long long duration,
struct trace_seq *s, u32 flags);
int __trace_graph_entry(struct trace_array *tr,
struct ftrace_graph_ent *trace,
unsigned int trace_ctx)
static int __graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace,
unsigned int trace_ctx, struct ftrace_regs *fregs)
{
struct ring_buffer_event *event;
struct trace_buffer *buffer = tr->array_buffer.buffer;
struct ftrace_graph_ent_entry *entry;
int size;
event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT,
sizeof(*entry), trace_ctx);
/* If fregs is defined, add FTRACE_REGS_MAX_ARGS long size words */
size = sizeof(*entry) + (FTRACE_REGS_MAX_ARGS * !!fregs * sizeof(long));
event = trace_buffer_lock_reserve(buffer, TRACE_GRAPH_ENT, size, trace_ctx);
if (!event)
return 0;
entry = ring_buffer_event_data(event);
entry->graph_ent = *trace;
#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
if (fregs) {
for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
entry->args[i] = ftrace_regs_get_argument(fregs, i);
}
#endif
trace_buffer_unlock_commit_nostack(buffer, event);
return 1;
}
int __trace_graph_entry(struct trace_array *tr,
struct ftrace_graph_ent *trace,
unsigned int trace_ctx)
{
return __graph_entry(tr, trace, trace_ctx, NULL);
}
#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
int __trace_graph_retaddr_entry(struct trace_array *tr,
struct ftrace_graph_ent *trace,
@ -174,7 +196,7 @@ struct fgraph_times {
unsigned long long sleeptime; /* may be optional! */
};
int trace_graph_entry(struct ftrace_graph_ent *trace,
static int graph_entry(struct ftrace_graph_ent *trace,
struct fgraph_ops *gops,
struct ftrace_regs *fregs)
{
@ -246,7 +268,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
unsigned long retaddr = ftrace_graph_top_ret_addr(current);
ret = __trace_graph_retaddr_entry(tr, trace, trace_ctx, retaddr);
} else {
ret = __trace_graph_entry(tr, trace, trace_ctx);
ret = __graph_entry(tr, trace, trace_ctx, fregs);
}
}
preempt_enable_notrace();
@ -254,6 +276,20 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
return ret;
}
int trace_graph_entry(struct ftrace_graph_ent *trace,
struct fgraph_ops *gops,
struct ftrace_regs *fregs)
{
return graph_entry(trace, gops, NULL);
}
static int trace_graph_entry_args(struct ftrace_graph_ent *trace,
struct fgraph_ops *gops,
struct ftrace_regs *fregs)
{
return graph_entry(trace, gops, fregs);
}
static void
__trace_graph_function(struct trace_array *tr,
unsigned long ip, unsigned int trace_ctx)
@ -418,6 +454,9 @@ static int graph_trace_init(struct trace_array *tr)
{
int ret;
if (tracer_flags_is_set(TRACE_GRAPH_ARGS))
tr->gops->entryfunc = trace_graph_entry_args;
else
tr->gops->entryfunc = trace_graph_entry;
if (tracing_thresh)
@ -775,7 +814,7 @@ static void print_graph_retaddr(struct trace_seq *s, struct fgraph_retaddr_ent_e
static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entry *entry,
struct ftrace_graph_ret *graph_ret, void *func,
u32 opt_flags, u32 trace_flags)
u32 opt_flags, u32 trace_flags, int args_size)
{
unsigned long err_code = 0;
unsigned long retval = 0;
@ -809,7 +848,14 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
if (entry->ent.type != TRACE_GRAPH_RETADDR_ENT)
print_retaddr = false;
trace_seq_printf(s, "%ps();", func);
trace_seq_printf(s, "%ps", func);
if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
print_function_args(s, entry->args, (unsigned long)func);
trace_seq_putc(s, ';');
} else
trace_seq_puts(s, "();");
if (print_retval || print_retaddr)
trace_seq_puts(s, " /*");
else
@ -836,7 +882,8 @@ static void print_graph_retval(struct trace_seq *s, struct ftrace_graph_ent_entr
#else
#define print_graph_retval(_seq, _ent, _ret, _func, _opt_flags, _trace_flags) do {} while (0)
#define print_graph_retval(_seq, _ent, _ret, _func, _opt_flags, _trace_flags, args_size) \
do {} while (0)
#endif
@ -852,10 +899,14 @@ print_graph_entry_leaf(struct trace_iterator *iter,
struct ftrace_graph_ret *graph_ret;
struct ftrace_graph_ent *call;
unsigned long long duration;
unsigned long ret_func;
unsigned long func;
int args_size;
int cpu = iter->cpu;
int i;
args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
graph_ret = &ret_entry->ret;
call = &entry->graph_ent;
duration = ret_entry->rettime - ret_entry->calltime;
@ -887,16 +938,25 @@ print_graph_entry_leaf(struct trace_iterator *iter,
for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
trace_seq_putc(s, ' ');
ret_func = graph_ret->func + iter->tr->text_delta;
/*
* Write out the function return value or return address
*/
if (flags & (__TRACE_GRAPH_PRINT_RETVAL | __TRACE_GRAPH_PRINT_RETADDR)) {
print_graph_retval(s, entry, graph_ret,
(void *)graph_ret->func + iter->tr->text_delta,
flags, tr->trace_flags);
flags, tr->trace_flags, args_size);
} else {
trace_seq_printf(s, "%ps();\n", (void *)func);
trace_seq_printf(s, "%ps", (void *)ret_func);
if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
print_function_args(s, entry->args, ret_func);
trace_seq_putc(s, ';');
} else
trace_seq_puts(s, "();");
}
trace_seq_printf(s, "\n");
print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET,
cpu, iter->ent->pid, flags);
@ -913,6 +973,7 @@ print_graph_entry_nested(struct trace_iterator *iter,
struct fgraph_data *data = iter->private;
struct trace_array *tr = iter->tr;
unsigned long func;
int args_size;
int i;
if (data) {
@ -937,7 +998,17 @@ print_graph_entry_nested(struct trace_iterator *iter,
func = call->func + iter->tr->text_delta;
trace_seq_printf(s, "%ps() {", (void *)func);
trace_seq_printf(s, "%ps", (void *)func);
args_size = iter->ent_size - offsetof(struct ftrace_graph_ent_entry, args);
if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long))
print_function_args(s, entry->args, func);
else
trace_seq_puts(s, "()");
trace_seq_puts(s, " {");
if (flags & __TRACE_GRAPH_PRINT_RETADDR &&
entry->ent.type == TRACE_GRAPH_RETADDR_ENT)
print_graph_retaddr(s, (struct fgraph_retaddr_ent_entry *)entry,
@ -1107,21 +1178,38 @@ print_graph_entry(struct ftrace_graph_ent_entry *field, struct trace_seq *s,
struct trace_iterator *iter, u32 flags)
{
struct fgraph_data *data = iter->private;
struct ftrace_graph_ent *call = &field->graph_ent;
struct ftrace_graph_ent *call;
struct ftrace_graph_ret_entry *leaf_ret;
static enum print_line_t ret;
int cpu = iter->cpu;
/*
* print_graph_entry() may consume the current event,
* thus @field may become invalid, so we need to save it.
* sizeof(struct ftrace_graph_ent_entry) is very small,
* it can be safely saved at the stack.
*/
struct ftrace_graph_ent_entry *entry;
u8 save_buf[sizeof(*entry) + FTRACE_REGS_MAX_ARGS * sizeof(long)];
/* The ent_size is expected to be as big as the entry */
if (iter->ent_size > sizeof(save_buf))
iter->ent_size = sizeof(save_buf);
entry = (void *)save_buf;
memcpy(entry, field, iter->ent_size);
call = &entry->graph_ent;
if (check_irq_entry(iter, flags, call->func, call->depth))
return TRACE_TYPE_HANDLED;
print_graph_prologue(iter, s, TRACE_GRAPH_ENT, call->func, flags);
leaf_ret = get_return_for_leaf(iter, field);
leaf_ret = get_return_for_leaf(iter, entry);
if (leaf_ret)
ret = print_graph_entry_leaf(iter, field, leaf_ret, s, flags);
ret = print_graph_entry_leaf(iter, entry, leaf_ret, s, flags);
else
ret = print_graph_entry_nested(iter, field, s, cpu, flags);
ret = print_graph_entry_nested(iter, entry, s, cpu, flags);
if (data) {
/*
@ -1195,7 +1283,8 @@ print_graph_return(struct ftrace_graph_ret_entry *retentry, struct trace_seq *s,
* funcgraph-retval option is enabled.
*/
if (flags & __TRACE_GRAPH_PRINT_RETVAL) {
print_graph_retval(s, NULL, trace, (void *)func, flags, tr->trace_flags);
print_graph_retval(s, NULL, trace, (void *)func, flags,
tr->trace_flags, 0);
} else {
/*
* If the return function does not have a matching entry,
@ -1323,16 +1412,8 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
switch (entry->type) {
case TRACE_GRAPH_ENT: {
/*
* print_graph_entry() may consume the current event,
* thus @field may become invalid, so we need to save it.
* sizeof(struct ftrace_graph_ent_entry) is very small,
* it can be safely saved at the stack.
*/
struct ftrace_graph_ent_entry saved;
trace_assign_type(field, entry);
saved = *field;
return print_graph_entry(&saved, s, iter, flags);
return print_graph_entry(field, s, iter, flags);
}
#ifdef CONFIG_FUNCTION_GRAPH_RETADDR
case TRACE_GRAPH_RETADDR_ENT: {