[PATCH v2 1/1] perf annotate: check that objdump correctly works

[Alexis Berlemont <alexis.berlemont@gmail.com>]

Before disassembling, the tool objdump is called just to be sure:
* objdump is available in the path;
* objdump is an executable binary;
* objdump has no dependency issue or anything else.

This objdump "pre-"command is only necessary because the real objdump
command is followed by some " | grep ..."; this prevents the shell
from returning the exit code of objdump execution.

Signed-off-by: Alexis Berlemont <alexis.berlemont@gmail.com>
---
 tools/perf/util/annotate.c | 69 +++++++++++++++++++++++++++++++++++++++++++---
 tools/perf/util/annotate.h |  3 ++
 2 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index ea7e0de4b9c1..6fbaabbc9d2a 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -20,9 +20,12 @@
 #include "block-range.h"
 #include "arch/common.h"
 #include <regex.h>
+#include <unistd.h>
 #include <pthread.h>
 #include <linux/bitops.h>
 #include <sys/utsname.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 
 const char 	*disassembler_style;
 const char	*objdump_path;
@@ -1286,6 +1289,21 @@ int symbol__strerror_disassemble(struct symbol *sym __maybe_unused, struct map *
 			  "  --vmlinux vmlinux\n", build_id_msg ?: "");
 	}
 		break;
+
+	case SYMBOL_ANNOTATE_ERRNO__NO_OBJDUMP:
+		scnprintf(buf, buflen, "No objdump tool available in $PATH\n");
+		break;
+
+	case SYMBOL_ANNOTATE_ERRNO__NO_EXEC_OBJDUMP:
+		scnprintf(buf, buflen,
+			"The objdump tool found in $PATH cannot be executed\n");
+		break;
+
+	case SYMBOL_ANNOTATE_ERRNO__NO_OUTPUT:
+		scnprintf(buf, buflen,
+			"The objdump tool returned no disassembled code\n");
+		break;
+
 	default:
 		scnprintf(buf, buflen, "Internal error: Invalid %d error code\n", errnum);
 		break;
@@ -1329,6 +1347,44 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
 	return 0;
 }
 
+static int annotate__check_exec(int pid, const char *command)
+{
+	int wstatus, err;
+
+	err = waitpid(pid, &wstatus, 0);
+	if (err < 0) {
+		pr_err("Failure calling waitpid: %s: (%s)\n",
+			strerror(errno), command);
+		return -1;
+	}
+
+	pr_debug("%s: %d %d\n", command, pid, WEXITSTATUS(wstatus));
+
+	switch (WEXITSTATUS(wstatus)) {
+	case 0:
+		/* Success */
+		err = 0;
+		break;
+	case 127:
+		/* The shell did not find objdump in the path */
+		err = SYMBOL_ANNOTATE_ERRNO__NO_OBJDUMP;
+		break;
+	default:
+		/*
+		 * In the default case, we consider that objdump
+		 * cannot be executed; so it gathers many fault
+		 * scenarii:
+		 * - objdump is not an executable (126);
+		 * - objdump has some dependency issue;
+		 * - ...
+		 */
+		err = SYMBOL_ANNOTATE_ERRNO__NO_EXEC_OBJDUMP;
+		break;
+	}
+
+	return err;
+}
+
 static const char *annotate__norm_arch(const char *arch_name)
 {
 	struct utsname uts;
@@ -1426,7 +1482,8 @@ int symbol__disassemble(struct symbol *sym, struct map *map, const char *arch_na
 	snprintf(command, sizeof(command),
 		 "%s %s%s --start-address=0x%016" PRIx64
 		 " --stop-address=0x%016" PRIx64
-		 " -l -d %s %s -C %s 2>/dev/null|grep -v %s|expand",
+		 " -l -d %s %s -C %s 2>/dev/null | "
+		 "{ grep -v %s || true; } | expand",
 		 objdump_path ? objdump_path : "objdump",
 		 disassembler_style ? "-M " : "",
 		 disassembler_style ? disassembler_style : "",
@@ -1454,7 +1511,7 @@ int symbol__disassemble(struct symbol *sym, struct map *map, const char *arch_na
 		close(stdout_fd[0]);
 		dup2(stdout_fd[1], 1);
 		close(stdout_fd[1]);
-		execl("/bin/sh", "sh", "-c", command, NULL);
+		execl("/bin/sh", "sh", "-o", "pipefail", "-c", command, NULL);
 		perror(command);
 		exit(-1);
 	}
@@ -1479,8 +1536,12 @@ int symbol__disassemble(struct symbol *sym, struct map *map, const char *arch_na
 		nline++;
 	}
 
-	if (nline == 0)
+	err = annotate__check_exec(pid, command);
+
+	if (err == 0 && nline == 0) {
 		pr_err("No output from %s\n", command);
+		err = SYMBOL_ANNOTATE_ERRNO__NO_OUTPUT;
+	}
 
 	/*
 	 * kallsyms does not have symbol sizes so there may a nop at the end.
@@ -1490,7 +1551,7 @@ int symbol__disassemble(struct symbol *sym, struct map *map, const char *arch_na
 		delete_last_nop(sym);
 
 	fclose(file);
-	err = 0;
+
 out_remove_tmp:
 	close(stdout_fd[0]);
 
diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
index 87e4cadc5d27..123f60c509a9 100644
--- a/tools/perf/util/annotate.h
+++ b/tools/perf/util/annotate.h
@@ -172,6 +172,9 @@ enum symbol_disassemble_errno {
 	__SYMBOL_ANNOTATE_ERRNO__START		= -10000,
 
 	SYMBOL_ANNOTATE_ERRNO__NO_VMLINUX	= __SYMBOL_ANNOTATE_ERRNO__START,
+	SYMBOL_ANNOTATE_ERRNO__NO_EXEC_OBJDUMP,
+	SYMBOL_ANNOTATE_ERRNO__NO_OBJDUMP,
+	SYMBOL_ANNOTATE_ERRNO__NO_OUTPUT,
 
 	__SYMBOL_ANNOTATE_ERRNO__END,
 };
-- 
2.11.0