linux-kernel - Re: [PATCH 04/23] perf dwarf-aux: Add die_find_func

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Message-ID: <ZfmZobDmVFxEQ6hU@x1>
Date: Tue, 19 Mar 2024 10:56:49 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Ian Rogers <irogers@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stephane Eranian <eranian@...gle.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-toolchains@...r.kernel.org, linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH 04/23] perf dwarf-aux: Add die_find_func_rettype()

On Mon, Mar 18, 2024 at 10:50:56PM -0700, Namhyung Kim wrote:
> The die_find_func_rettype() is to find a debug entry for the given
> function name and sets the type information of the return value.  By
> convention, it'd return the pointer to the type die (should be the
> same as the given mem_die argument) if found, or NULL otherwise.
> 
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/util/dwarf-aux.c | 43 +++++++++++++++++++++++++++++++++++++
>  tools/perf/util/dwarf-aux.h |  4 ++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index cd9364d296b6..9080119a258c 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -696,6 +696,49 @@ Dwarf_Die *die_find_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
>  	return die_mem;
>  }
>  
> +static int __die_find_func_rettype_cb(Dwarf_Die *die_mem, void *data)
> +{
> +	const char *func_name;
> +
> +	if (dwarf_tag(die_mem) != DW_TAG_subprogram)
> +		return DIE_FIND_CB_SIBLING;
> +
> +	func_name = dwarf_diename(die_mem);
> +	if (func_name && !strcmp(func_name, data))
> +		return DIE_FIND_CB_END;
> +
> +	return DIE_FIND_CB_SIBLING;
> +}
> +
> +/**
> + * die_find_func_rettype - Search a return type of function
> + * @cu_die: a CU DIE
> + * @name: target function name
> + * @die_mem: a buffer for result DIE
> + *
> + * Search a non-inlined function which matches to @name and stores the
> + * return type of the function to @die_mem and returns it if found.
> + * Returns NULL if failed.  Note that it doesn't needs to find a
> + * definition of the function, so it doesn't match with address.
> + * Most likely, it can find a declaration at the top level.  Thus the
> + * callback function continues to sibling entries only.
> + */
> +Dwarf_Die *die_find_func_rettype(Dwarf_Die *cu_die, const char *name,
> +				 Dwarf_Die *die_mem)
> +{
> +	Dwarf_Die tmp_die;
> +
> +	cu_die = die_find_child(cu_die, __die_find_func_rettype_cb,
> +				(void *)name, &tmp_die);
> +	if (!cu_die)
> +		return NULL;
> +
> +	if (die_get_real_type(&tmp_die, die_mem) == NULL)
> +		return NULL;


Here you check die_get_real_type() return, may I go and do the same for
the previous patch to address my review comment?

- Arnaldo

> +
> +	return die_mem;
> +}
> +
>  struct __instance_walk_param {
>  	void    *addr;
>  	int	(*callback)(Dwarf_Die *, void *);
> diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
> index 16c916311bc0..b0f25fbf9668 100644
> --- a/tools/perf/util/dwarf-aux.h
> +++ b/tools/perf/util/dwarf-aux.h
> @@ -94,6 +94,10 @@ Dwarf_Die *die_find_top_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
>  Dwarf_Die *die_find_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
>  			       Dwarf_Die *die_mem);
>  
> +/* Search a non-inlined function by name and returns its return type */
> +Dwarf_Die *die_find_func_rettype(Dwarf_Die *sp_die, const char *name,
> +				 Dwarf_Die *die_mem);
> +
>  /* Walk on the instances of given DIE */
>  int die_walk_instances(Dwarf_Die *in_die,
>  		       int (*callback)(Dwarf_Die *, void *), void *data);
> -- 
> 2.44.0.291.gc1ea87d7ee-goog