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Message-ID: <dcac0917-0cb8-c0d1-e5bb-0144c38a65f3@huaweicloud.com>
Date: Fri, 6 Sep 2024 11:49:10 +0800
From: Zheng Yejian <zhengyejian@...weicloud.com>
To: Sven Schnelle <svens@...ux.ibm.com>, Steven Rostedt
<rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] tracing: add arguments to function tracer
On 2024/9/4 14:59, Sven Schnelle wrote:
> Wire up the code to print function arguments in the function tracer.
> This functionality can be enabled/disabled during compile time by
> setting CONFIG_FUNCTION_TRACE_ARGS and during runtime with
> options/func-args.
>
> ping-689 [004] b.... 77.170220: dummy_xmit(skb = 0x82904800, dev = 0x882d0000) <-dev_hard_start_xmit
>
> Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
> ---
> kernel/trace/trace.c | 8 +++++-
> kernel/trace/trace.h | 4 ++-
> kernel/trace/trace_entries.h | 7 +++--
> kernel/trace/trace_functions.c | 46 +++++++++++++++++++++++++++----
> kernel/trace/trace_irqsoff.c | 4 +--
> kernel/trace/trace_output.c | 14 ++++++++--
> kernel/trace/trace_sched_wakeup.c | 4 +--
> 7 files changed, 71 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index ebe7ce2f5f4a..8118e4c8c649 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2864,7 +2864,7 @@ trace_buffer_unlock_commit_nostack(struct trace_buffer *buffer,
>
> void
> trace_function(struct trace_array *tr, unsigned long ip, unsigned long
> - parent_ip, unsigned int trace_ctx)
> + parent_ip, unsigned int trace_ctx, struct ftrace_regs *regs)
> {
> struct trace_event_call *call = &event_function;
> struct trace_buffer *buffer = tr->array_buffer.buffer;
> @@ -2878,6 +2878,12 @@ trace_function(struct trace_array *tr, unsigned long ip, unsigned long
> entry = ring_buffer_event_data(event);
> entry->ip = ip;
> entry->parent_ip = parent_ip;
> +#ifdef CONFIG_FUNCTION_TRACE_ARGS
> + if (regs)
> + entry->regs = *regs;
> + else
> + memset(&entry->regs, 0, sizeof(struct ftrace_regs));
> +#endif
>
> if (!call_filter_check_discard(call, entry, buffer, event)) {
> if (static_branch_unlikely(&trace_function_exports_enabled))
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index bd3e3069300e..13cf6f97f7e0 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -673,7 +673,8 @@ unsigned long trace_total_entries(struct trace_array *tr);
> void trace_function(struct trace_array *tr,
> unsigned long ip,
> unsigned long parent_ip,
> - unsigned int trace_ctx);
> + unsigned int trace_ctx,
> + struct ftrace_regs *regs);
> void trace_graph_function(struct trace_array *tr,
> unsigned long ip,
> unsigned long parent_ip,
> @@ -870,6 +871,7 @@ static __always_inline bool ftrace_hash_empty(struct ftrace_hash *hash)
> #define TRACE_GRAPH_GRAPH_TIME 0x400
> #define TRACE_GRAPH_PRINT_RETVAL 0x800
> #define TRACE_GRAPH_PRINT_RETVAL_HEX 0x1000
> +#define TRACE_GRAPH_ARGS 0x2000
> #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 c47422b20908..f2021ab52da2 100644
> --- a/kernel/trace/trace_entries.h
> +++ b/kernel/trace/trace_entries.h
> @@ -61,8 +61,11 @@ FTRACE_ENTRY_REG(function, ftrace_entry,
> TRACE_FN,
>
> F_STRUCT(
> - __field_fn( unsigned long, ip )
> - __field_fn( unsigned long, parent_ip )
> + __field_fn( unsigned long, ip )
> + __field_fn( unsigned long, parent_ip )
> +#ifdef CONFIG_FUNCTION_TRACE_ARGS
> + __field_struct( struct ftrace_regs, regs )
Only function arguments are printed, they are several registers in ftrace_regs,
would it be better to store what are needed?
Although different archs save function arguments in different registers, store
the entire ftrace_regs are much more simple..
> +#endif
> ),
>
> F_printk(" %ps <-- %ps",
F_printk should also match F_STRUCT, otherwise 'format' info may be incorrect,
it may confuse data parsing in user tools.
> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> index 3b0cea37e029..7ff651a0b45a 100644
> --- a/kernel/trace/trace_functions.c
> +++ b/kernel/trace/trace_functions.c
> @@ -25,6 +25,9 @@ static void
> function_trace_call(unsigned long ip, unsigned long parent_ip,
> struct ftrace_ops *op, struct ftrace_regs *fregs);
> static void
> +function_args_trace_call(unsigned long ip, unsigned long parent_ip,
> + struct ftrace_ops *op, struct ftrace_regs *fregs);
> +static void
> function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
> struct ftrace_ops *op, struct ftrace_regs *fregs);
> static void
> @@ -42,9 +45,10 @@ enum {
> TRACE_FUNC_NO_OPTS = 0x0, /* No flags set. */
> TRACE_FUNC_OPT_STACK = 0x1,
> TRACE_FUNC_OPT_NO_REPEATS = 0x2,
> + TRACE_FUNC_OPT_ARGS = 0x4,
>
> /* Update this to next highest bit. */
> - TRACE_FUNC_OPT_HIGHEST_BIT = 0x4
> + TRACE_FUNC_OPT_HIGHEST_BIT = 0x8
> };
>
> #define TRACE_FUNC_OPT_MASK (TRACE_FUNC_OPT_HIGHEST_BIT - 1)
> @@ -114,6 +118,8 @@ static ftrace_func_t select_trace_function(u32 flags_val)
> switch (flags_val & TRACE_FUNC_OPT_MASK) {
> case TRACE_FUNC_NO_OPTS:
> return function_trace_call;
> + case TRACE_FUNC_OPT_ARGS:
> + return function_args_trace_call;
> case TRACE_FUNC_OPT_STACK:
> return function_stack_trace_call;
> case TRACE_FUNC_OPT_NO_REPEATS:
> @@ -198,7 +204,34 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
> cpu = smp_processor_id();
> data = per_cpu_ptr(tr->array_buffer.data, cpu);
> if (!atomic_read(&data->disabled))
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, NULL);
> +
> + ftrace_test_recursion_unlock(bit);
> +}
> +
> +static void
> +function_args_trace_call(unsigned long ip, unsigned long parent_ip,
> + struct ftrace_ops *op, struct ftrace_regs *fregs)
> +{
> + struct trace_array *tr = op->private;
> + struct trace_array_cpu *data;
> + unsigned int trace_ctx;
> + int bit;
> + int cpu;
> +
> + if (unlikely(!tr->function_enabled))
> + return;
> +
> + bit = ftrace_test_recursion_trylock(ip, parent_ip);
> + if (bit < 0)
> + return;
> +
> + trace_ctx = tracing_gen_ctx();
> +
> + cpu = smp_processor_id();
> + data = per_cpu_ptr(tr->array_buffer.data, cpu);
> + if (!atomic_read(&data->disabled))
> + trace_function(tr, ip, parent_ip, trace_ctx, fregs);
>
> ftrace_test_recursion_unlock(bit);
> }
> @@ -247,7 +280,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
>
> if (likely(disabled == 1)) {
> trace_ctx = tracing_gen_ctx_flags(flags);
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, NULL);
> #ifdef CONFIG_UNWINDER_FRAME_POINTER
> if (ftrace_pids_enabled(op))
> skip++;
> @@ -329,7 +362,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
> trace_ctx = tracing_gen_ctx_flags(flags);
> process_repeats(tr, ip, parent_ip, last_info, trace_ctx);
>
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, NULL);
>
> out:
> ftrace_test_recursion_unlock(bit);
> @@ -368,7 +401,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
> trace_ctx = tracing_gen_ctx_flags(flags);
> process_repeats(tr, ip, parent_ip, last_info, trace_ctx);
>
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, NULL);
> __trace_stack(tr, trace_ctx, STACK_SKIP);
> }
>
> @@ -382,6 +415,9 @@ static struct tracer_opt func_opts[] = {
> { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
> #endif
> { TRACER_OPT(func-no-repeats, TRACE_FUNC_OPT_NO_REPEATS) },
> +#ifdef CONFIG_FUNCTION_TRACE_ARGS
> + { TRACER_OPT(func-args, TRACE_FUNC_OPT_ARGS) },
> +#endif
> { } /* Always set a last empty entry */
> };
>
> diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
> index fce064e20570..096002c99d70 100644
> --- a/kernel/trace/trace_irqsoff.c
> +++ b/kernel/trace/trace_irqsoff.c
> @@ -150,7 +150,7 @@ irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
>
> trace_ctx = tracing_gen_ctx_flags(flags);
>
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, fregs);
>
> atomic_dec(&data->disabled);
> }
> @@ -278,7 +278,7 @@ __trace_function(struct trace_array *tr,
> if (is_graph(tr))
> trace_graph_function(tr, ip, parent_ip, trace_ctx);
> else
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, NULL);
> }
>
> #else
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index 70405c4cceb6..8fdee7b9cdba 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -1058,9 +1058,13 @@ enum print_line_t trace_nop_print(struct trace_iterator *iter, int flags,
> }
>
> static void print_fn_trace(struct trace_seq *s, unsigned long ip,
> - unsigned long parent_ip, int flags)
> + unsigned long parent_ip,
> + struct ftrace_regs *fregs,
> + int flags)
> {
> seq_print_ip_sym(s, ip, flags);
> + if (fregs)
> + print_function_args(s, fregs, ip);
>
> if ((flags & TRACE_ITER_PRINT_PARENT) && parent_ip) {
> trace_seq_puts(s, " <-");
> @@ -1074,10 +1078,14 @@ static enum print_line_t trace_fn_trace(struct trace_iterator *iter, int flags,
> {
> struct ftrace_entry *field;
> struct trace_seq *s = &iter->seq;
> + struct ftrace_regs *fregs = NULL;
>
> trace_assign_type(field, iter->ent);
>
> - print_fn_trace(s, field->ip, field->parent_ip, flags);
> +#if IS_ENABLED(CONFIG_FUNCTION_TRACE_ARGS)
> + fregs = &field->regs;
> +#endif
> + print_fn_trace(s, field->ip, field->parent_ip, fregs, flags);
> trace_seq_putc(s, '\n');
>
> return trace_handle_return(s);
> @@ -1742,7 +1750,7 @@ trace_func_repeats_print(struct trace_iterator *iter, int flags,
>
> trace_assign_type(field, iter->ent);
>
> - print_fn_trace(s, field->ip, field->parent_ip, flags);
> + print_fn_trace(s, field->ip, field->parent_ip, NULL, flags);
> trace_seq_printf(s, " (repeats: %u, last_ts:", field->count);
> trace_print_time(s, iter,
> iter->ts - FUNC_REPEATS_GET_DELTA_TS(field));
> diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
> index 130ca7e7787e..39043c955761 100644
> --- a/kernel/trace/trace_sched_wakeup.c
> +++ b/kernel/trace/trace_sched_wakeup.c
> @@ -224,7 +224,7 @@ wakeup_tracer_call(unsigned long ip, unsigned long parent_ip,
> return;
>
> local_irq_save(flags);
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, fregs);
> local_irq_restore(flags);
>
> atomic_dec(&data->disabled);
> @@ -309,7 +309,7 @@ __trace_function(struct trace_array *tr,
> if (is_graph(tr))
> trace_graph_function(tr, ip, parent_ip, trace_ctx);
> else
> - trace_function(tr, ip, parent_ip, trace_ctx);
> + trace_function(tr, ip, parent_ip, trace_ctx, NULL);
> }
>
> static int wakeup_flag_changed(struct trace_array *tr, u32 mask, int set)
--
Thanks,
Zheng Yejian
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