On Tue, 25 Feb 2025 17:26:03 -0500
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> From: Sven Schnelle <svens@xxxxxxxxxxxxx>
>
> 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: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
> Cc: Guo Ren <guoren@xxxxxxxxxx>
> Cc: Donglin Peng <dolinux.peng@xxxxxxxxx>
> Cc: Zheng Yejian <zhengyejian@xxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/20241223201542.067076254@xxxxxxxxxxx
> Co-developed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
> Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxxx>
> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
> ---
> kernel/trace/Kconfig | 6 ++
> kernel/trace/trace.h | 1 +
> kernel/trace/trace_entries.h | 7 +-
> kernel/trace/trace_functions_graph.c | 143 +++++++++++++++++++++------
> 4 files changed, 122 insertions(+), 35 deletions(-)
>
> diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> index 60412c1012ef..033fba0633cf 100644
> --- a/kernel/trace/Kconfig
> +++ b/kernel/trace/Kconfig
> @@ -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"
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 9c21ba45b7af..6963cd83b6da 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -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)
>
> diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> index fbfb396905a6..77a8ba3bc1e3 100644
> --- a/kernel/trace/trace_entries.h
> +++ b/kernel/trace/trace_entries.h
> @@ -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
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index 136c750b0b4d..406b21472bde 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -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 +114,41 @@ 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));
Is `!!fregs` always 1 if fregs != NULL? (seems to depend on compiler)
Others looks good to me.
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Thank you,
> +
> + 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;
> +
> + entry = ring_buffer_event_data(event);
> + entry->graph_ent = *trace;
> +
> + if (fregs) {
> + for (int i = 0; i < FTRACE_REGS_MAX_ARGS; i++)
> + entry->args[i] = ftrace_regs_get_argument(fregs, i);
> + }
> +
> 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,
> @@ -174,9 +194,9 @@ struct fgraph_times {
> unsigned long long sleeptime; /* may be optional! */
> };
>
> -int trace_graph_entry(struct ftrace_graph_ent *trace,
> - struct fgraph_ops *gops,
> - struct ftrace_regs *fregs)
> +static int graph_entry(struct ftrace_graph_ent *trace,
> + struct fgraph_ops *gops,
> + struct ftrace_regs *fregs)
> {
> unsigned long *task_var = fgraph_get_task_var(gops);
> struct trace_array *tr = gops->private;
> @@ -246,7 +266,7 @@ 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 +274,20 @@ 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)
> @@ -418,7 +452,10 @@ static int graph_trace_init(struct trace_array *tr)
> {
> int ret;
>
> - tr->gops->entryfunc = trace_graph_entry;
> + 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)
> tr->gops->retfunc = trace_graph_thresh_return;
> @@ -775,7 +812,7 @@ 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 +846,14 @@ 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 +880,8 @@ 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 +897,14 @@ 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 +936,25 @@ 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 +971,7 @@ 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 +996,17 @@ 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 +1176,38 @@ 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 +1281,8 @@ 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 +1410,8 @@ 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: {
> --
> 2.47.2
>
>
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
