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

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Date:   Thu, 10 Oct 2019 11:36:46 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Song Liu <songliubraving@...com>, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 2/5] perf annotate: use run-command.h to fork objdump

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.

Signed-off-by: Ian Rogers <irogers@...gle.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