[PATCH] perf tools: Add symfs option for off-box analysis using specified tree

[David Ahern <daahern@cisco.com>]

The symfs argument allows analysis of perf.data file using a locally
accessible filesystem tree with debug symbols - e.g., tree created
during image builds, sshfs mount, loop mounted KVM disk images,
USB keys, initrds, etc. Anything with an OS tree can be analyzed from
anywhere without the need to populate a local data store with
build-ids.

Signed-off-by: David Ahern <daahern@cisco.com>
---
 tools/perf/builtin-annotate.c  |   16 +++++--
 tools/perf/builtin-diff.c      |    2 +
 tools/perf/builtin-report.c    |    2 +
 tools/perf/builtin-timechart.c |    2 +
 tools/perf/util/hist.c         |   14 +++++-
 tools/perf/util/symbol.c       |   82 +++++++++++++++++++++++++---------------
 tools/perf/util/symbol.h       |    1 +
 7 files changed, 80 insertions(+), 39 deletions(-)

diff --git a/tools/perf/builtin-annotate.c b/tools/perf/builtin-annotate.c
index 6d5604d8d..1db38da 100644
--- a/tools/perf/builtin-annotate.c
+++ b/tools/perf/builtin-annotate.c
@@ -280,7 +280,8 @@ static int hist_entry__tty_annotate(struct hist_entry *he)
 	struct map *map = he->ms.map;
 	struct dso *dso = map->dso;
 	struct symbol *sym = he->ms.sym;
-	const char *filename = dso->long_name, *d_filename;
+	const char *filename = dso->long_name;
+	char d_filename[PATH_MAX];
 	u64 len;
 	LIST_HEAD(head);
 	struct objdump_line *pos, *n;
@@ -288,10 +289,13 @@ static int hist_entry__tty_annotate(struct hist_entry *he)
 	if (hist_entry__annotate(he, &head, 0) < 0)
 		return -1;
 
-	if (full_paths)
-		d_filename = filename;
-	else
-		d_filename = basename(filename);
+	if (full_paths) {
+		snprintf(d_filename, sizeof(d_filename), "%s%s",
+			 symbol_conf.symfs, filename);
+	} else {
+		snprintf(d_filename, sizeof(d_filename), "%s/%s",
+			 symbol_conf.symfs, basename(filename));
+	}
 
 	len = sym->end - sym->start;
 
@@ -437,6 +441,8 @@ static const struct option options[] = {
 		    "print matching source lines (may be slow)"),
 	OPT_BOOLEAN('P', "full-paths", &full_paths,
 		    "Don't shorten the displayed pathnames"),
+	OPT_STRING(0, "symfs", &symbol_conf.symfs, "directory",
+		    "Look for files with symbols relative to this directory"),
 	OPT_END()
 };
 
diff --git a/tools/perf/builtin-diff.c b/tools/perf/builtin-diff.c
index fca1d44..85a8179 100644
--- a/tools/perf/builtin-diff.c
+++ b/tools/perf/builtin-diff.c
@@ -191,6 +191,8 @@ static const struct option options[] = {
 	OPT_STRING('t', "field-separator", &symbol_conf.field_sep, "separator",
 		   "separator for columns, no spaces will be added between "
 		   "columns '.' is reserved."),
+	OPT_STRING(0, "symfs", &symbol_conf.symfs, "directory",
+		    "Look for files with symbols relative to this directory"),
 	OPT_END()
 };
 
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index b0c6995..371b184 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -480,6 +480,8 @@ static const struct option options[] = {
 		   "columns '.' is reserved."),
 	OPT_BOOLEAN('U', "hide-unresolved", &hide_unresolved,
 		    "Only display entries resolved to a symbol"),
+	OPT_STRING(0, "symfs", &symbol_conf.symfs, "directory",
+		    "Look for files with symbols relative to this directory"),
 	OPT_END()
 };
 
diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c
index 9bcc38f..fa07ece 100644
--- a/tools/perf/builtin-timechart.c
+++ b/tools/perf/builtin-timechart.c
@@ -1018,6 +1018,8 @@ static const struct option options[] = {
 	OPT_CALLBACK('p', "process", NULL, "process",
 		      "process selector. Pass a pid or process name.",
 		       parse_process),
+	OPT_STRING(0, "symfs", &symbol_conf.symfs, "directory",
+		    "Look for files with symbols relative to this directory"),
 	OPT_END()
 };
 
diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 2022e87..b24ae53 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -1092,6 +1092,12 @@ int hist_entry__annotate(struct hist_entry *self, struct list_head *head,
 	FILE *file;
 	int err = 0;
 	u64 len;
+	char symfs_filename[PATH_MAX];
+
+	if (filename) {
+		snprintf(symfs_filename, sizeof(symfs_filename), "%s%s",
+		 symbol_conf.symfs, filename);
+	}
 
 	if (filename == NULL) {
 		if (dso->has_build_id) {
@@ -1100,9 +1106,9 @@ int hist_entry__annotate(struct hist_entry *self, struct list_head *head,
 			return -ENOMEM;
 		}
 		goto fallback;
-	} else if (readlink(filename, command, sizeof(command)) < 0 ||
+	} else if (readlink(symfs_filename, command, sizeof(command)) < 0 ||
 		   strstr(command, "[kernel.kallsyms]") ||
-		   access(filename, R_OK)) {
+		   access(symfs_filename, R_OK)) {
 		free(filename);
 fallback:
 		/*
@@ -1111,6 +1117,8 @@ fallback:
 		 * DSO is the same as when 'perf record' ran.
 		 */
 		filename = dso->long_name;
+		snprintf(symfs_filename, sizeof(symfs_filename), "%s%s",
+		 symbol_conf.symfs, filename);
 		free_filename = false;
 	}
 
@@ -1137,7 +1145,7 @@ fallback:
 		 "objdump --start-address=0x%016Lx --stop-address=0x%016Lx -dS -C %s|grep -v %s|expand",
 		 map__rip_2objdump(map, sym->start),
 		 map__rip_2objdump(map, sym->end),
-		 filename, filename);
+		 symfs_filename, filename);
 
 	pr_debug("Executing: %s\n", command);
 
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index f40c076..9e2cc44 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -41,6 +41,7 @@ struct symbol_conf symbol_conf = {
 	.exclude_other	  = true,
 	.use_modules	  = true,
 	.try_vmlinux_path = true,
+	.symfs           = "",
 };
 
 int dso__name_len(const struct dso *self)
@@ -833,8 +834,11 @@ static int dso__synthesize_plt_symbols(struct  dso *self, struct map *map,
 	char sympltname[1024];
 	Elf *elf;
 	int nr = 0, symidx, fd, err = 0;
+	char name[PATH_MAX];
 
-	fd = open(self->long_name, O_RDONLY);
+	snprintf(name, sizeof(name), "%s%s",
+		 symbol_conf.symfs, self->long_name);
+	fd = open(name, O_RDONLY);
 	if (fd < 0)
 		goto out;
 
@@ -1446,16 +1450,19 @@ int dso__load(struct dso *self, struct map *map, symbol_filter_t filter)
 	     self->origin++) {
 		switch (self->origin) {
 		case DSO__ORIG_BUILD_ID_CACHE:
-			if (dso__build_id_filename(self, name, size) == NULL)
+			/* skip the locally configured cache if a symfs is given */
+			if ((strlen(symbol_conf.symfs) != 0) ||
+			    (dso__build_id_filename(self, name, size) == NULL)) {
 				continue;
+			}
 			break;
 		case DSO__ORIG_FEDORA:
-			snprintf(name, size, "/usr/lib/debug%s.debug",
-				 self->long_name);
+			snprintf(name, size, "%s/usr/lib/debug%s.debug",
+				 symbol_conf.symfs, self->long_name);
 			break;
 		case DSO__ORIG_UBUNTU:
-			snprintf(name, size, "/usr/lib/debug%s",
-				 self->long_name);
+			snprintf(name, size, "%s/usr/lib/debug%s",
+				 symbol_conf.symfs, self->long_name);
 			break;
 		case DSO__ORIG_BUILDID: {
 			char build_id_hex[BUILD_ID_SIZE * 2 + 1];
@@ -1467,12 +1474,13 @@ int dso__load(struct dso *self, struct map *map, symbol_filter_t filter)
 					  sizeof(self->build_id),
 					  build_id_hex);
 			snprintf(name, size,
-				 "/usr/lib/debug/.build-id/%.2s/%s.debug",
-				 build_id_hex, build_id_hex + 2);
+				 "%s/usr/lib/debug/.build-id/%.2s/%s.debug",
+				 symbol_conf.symfs, build_id_hex, build_id_hex + 2);
 			}
 			break;
 		case DSO__ORIG_DSO:
-			snprintf(name, size, "%s", self->long_name);
+			snprintf(name, size, "%s%s",
+			     symbol_conf.symfs, self->long_name);
 			break;
 		case DSO__ORIG_GUEST_KMODULE:
 			if (map->groups && map->groups->machine)
@@ -1778,17 +1786,20 @@ static int dso__load_vmlinux(struct dso *self, struct map *map,
 			     const char *vmlinux, symbol_filter_t filter)
 {
 	int err = -1, fd;
+	char symfs_vmlinux[PATH_MAX];
 
-	fd = open(vmlinux, O_RDONLY);
+	snprintf(symfs_vmlinux, sizeof(symfs_vmlinux), "%s/%s",
+		 symbol_conf.symfs, vmlinux);
+	fd = open(symfs_vmlinux, O_RDONLY);
 	if (fd < 0)
 		return -1;
 
 	dso__set_loaded(self, map->type);
-	err = dso__load_sym(self, map, vmlinux, fd, filter, 0, 0);
+	err = dso__load_sym(self, map, symfs_vmlinux, fd, filter, 0, 0);
 	close(fd);
 
 	if (err > 0)
-		pr_debug("Using %s for symbols\n", vmlinux);
+		pr_debug("Using %s for symbols\n", symfs_vmlinux);
 
 	return err;
 }
@@ -1866,6 +1877,10 @@ static int dso__load_kernel_sym(struct dso *self, struct map *map,
 			goto out_fixup;
 	}
 
+	/* do not try local files if a symfs was given */
+	if (strlen(symbol_conf.symfs) != 0)
+		return -1;
+
 	/*
 	 * Say the kernel DSO was created when processing the build-id header table,
 	 * we have a build-id, so check if it is the same as the running kernel,
@@ -2215,9 +2230,6 @@ static int vmlinux_path__init(void)
 	struct utsname uts;
 	char bf[PATH_MAX];
 
-	if (uname(&uts) < 0)
-		return -1;
-
 	vmlinux_path = malloc(sizeof(char *) * 5);
 	if (vmlinux_path == NULL)
 		return -1;
@@ -2230,22 +2242,30 @@ static int vmlinux_path__init(void)
 	if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
 		goto out_fail;
 	++vmlinux_path__nr_entries;
-	snprintf(bf, sizeof(bf), "/boot/vmlinux-%s", uts.release);
-	vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
-	if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
-		goto out_fail;
-	++vmlinux_path__nr_entries;
-	snprintf(bf, sizeof(bf), "/lib/modules/%s/build/vmlinux", uts.release);
-	vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
-	if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
-		goto out_fail;
-	++vmlinux_path__nr_entries;
-	snprintf(bf, sizeof(bf), "/usr/lib/debug/lib/modules/%s/vmlinux",
-		 uts.release);
-	vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
-	if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
-		goto out_fail;
-	++vmlinux_path__nr_entries;
+
+	/* if no symfs has been given try running kernel version too */
+	if (strlen(symbol_conf.symfs) == 0) {
+		if (uname(&uts) < 0)
+			return -1;
+
+		snprintf(bf, sizeof(bf), "/boot/vmlinux-%s", uts.release);
+		vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
+		if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
+			goto out_fail;
+		++vmlinux_path__nr_entries;
+		snprintf(bf, sizeof(bf), "/lib/modules/%s/build/vmlinux",
+			 uts.release);
+		vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
+		if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
+			goto out_fail;
+		++vmlinux_path__nr_entries;
+		snprintf(bf, sizeof(bf), "/usr/lib/debug/lib/modules/%s/vmlinux",
+			 uts.release);
+		vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
+		if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
+			goto out_fail;
+		++vmlinux_path__nr_entries;
+	}
 
 	return 0;
 
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 12defbe..bcd2f98 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -86,6 +86,7 @@ struct symbol_conf {
        struct strlist	*dso_list,
 			*comm_list,
 			*sym_list;
+	const char	*symfs;
 };
 
 extern struct symbol_conf symbol_conf;
-- 
1.7.2.3