Re: [PATCH 2/5] perf annotate: use run-command.h to fork objdump

From: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
To: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Jin Yao <yao.jin@linux.intel.com>,
	Song Liu <songliubraving@fb.com>,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 2/5] perf annotate: use run-command.h to fork objdump
Date: Mon, 14 Oct 2019 11:18:28 -0300	[thread overview]
Message-ID: <20191014141828.GG19627@kernel.org> (raw)
In-Reply-To: <20191010183649.23768-3-irogers@google.com>

Em Thu, Oct 10, 2019 at 11:36:46AM -0700, Ian Rogers escreveu:
> Reduce duplicated logic by using the subcmd library. Ensure when errors
> occur they are reported to the caller. Before this patch, if no lines are
> read the error status is 0.

Thanks, applied and tested.

- Arnaldo

> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/annotate.c | 71 +++++++++++++++++++-------------------
>  1 file changed, 36 insertions(+), 35 deletions(-)
> 
> diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> index 1487849a191a..fc12c5cfe112 100644
> --- a/tools/perf/util/annotate.c
> +++ b/tools/perf/util/annotate.c
> @@ -43,6 +43,7 @@
>  #include <linux/string.h>
>  #include <bpf/libbpf.h>
>  #include <subcmd/parse-options.h>
> +#include <subcmd/run-command.h>
>  
>  /* FIXME: For the HE_COLORSET */
>  #include "ui/browser.h"
> @@ -1843,12 +1844,18 @@ static int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
>  	struct kcore_extract kce;
>  	bool delete_extract = false;
>  	bool decomp = false;
> -	int stdout_fd[2];
>  	int lineno = 0;
>  	int nline;
> -	pid_t pid;
>  	char *line;
>  	size_t line_len;
> +	const char *objdump_argv[] = {
> +		"/bin/sh",
> +		"-c",
> +		NULL, /* Will be the objdump command to run. */
> +		"--",
> +		NULL, /* Will be the symfs path. */
> +	};
> +	struct child_process objdump_process;
>  	int err = dso__disassemble_filename(dso, symfs_filename, sizeof(symfs_filename));
>  
>  	if (err)
> @@ -1878,7 +1885,7 @@ static int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
>  
>  		if (dso__decompress_kmodule_path(dso, symfs_filename,
>  						 tmp, sizeof(tmp)) < 0)
> -			goto out;
> +			return -1;
>  
>  		decomp = true;
>  		strcpy(symfs_filename, tmp);
> @@ -1903,38 +1910,28 @@ static int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
>  
>  	pr_debug("Executing: %s\n", command);
>  
> -	err = -1;
> -	if (pipe(stdout_fd) < 0) {
> -		pr_err("Failure creating the pipe to run %s\n", command);
> -		goto out_free_command;
> -	}
> -
> -	pid = fork();
> -	if (pid < 0) {
> -		pr_err("Failure forking to run %s\n", command);
> -		goto out_close_stdout;
> -	}
> +	objdump_argv[2] = command;
> +	objdump_argv[4] = symfs_filename;
>  
> -	if (pid == 0) {
> -		close(stdout_fd[0]);
> -		dup2(stdout_fd[1], 1);
> -		close(stdout_fd[1]);
> -		execl("/bin/sh", "sh", "-c", command, "--", symfs_filename,
> -		      NULL);
> -		perror(command);
> -		exit(-1);
> +	/* Create a pipe to read from for stdout */
> +	memset(&objdump_process, 0, sizeof(objdump_process));
> +	objdump_process.argv = objdump_argv;
> +	objdump_process.out = -1;
> +	if (start_command(&objdump_process)) {
> +		pr_err("Failure starting to run %s\n", command);
> +		err = -1;
> +		goto out_free_command;
>  	}
>  
> -	close(stdout_fd[1]);
> -
> -	file = fdopen(stdout_fd[0], "r");
> +	file = fdopen(objdump_process.out, "r");
>  	if (!file) {
>  		pr_err("Failure creating FILE stream for %s\n", command);
>  		/*
>  		 * If we were using debug info should retry with
>  		 * original binary.
>  		 */
> -		goto out_free_command;
> +		err = -1;
> +		goto out_close_stdout;
>  	}
>  
>  	/* Storage for getline. */
> @@ -1958,8 +1955,14 @@ static int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
>  	}
>  	free(line);
>  
> -	if (nline == 0)
> +	err = finish_command(&objdump_process);
> +	if (err)
> +		pr_err("Error running %s\n", command);
> +
> +	if (nline == 0) {
> +		err = -1;
>  		pr_err("No output from %s\n", command);
> +	}
>  
>  	/*
>  	 * kallsyms does not have symbol sizes so there may a nop at the end.
> @@ -1969,23 +1972,21 @@ static int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
>  		delete_last_nop(sym);
>  
>  	fclose(file);
> -	err = 0;
> +
> +out_close_stdout:
> +	close(objdump_process.out);
> +
>  out_free_command:
>  	free(command);
> -out_remove_tmp:
> -	close(stdout_fd[0]);
>  
> +out_remove_tmp:
>  	if (decomp)
>  		unlink(symfs_filename);
>  
>  	if (delete_extract)
>  		kcore_extract__delete(&kce);
> -out:
> -	return err;
>  
> -out_close_stdout:
> -	close(stdout_fd[1]);
> -	goto out_free_command;
> +	return err;
>  }
>  
>  static void calc_percent(struct sym_hist *sym_hist,
> -- 
> 2.23.0.581.g78d2f28ef7-goog

-- 

- Arnaldo