diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 0974f957b8fa2634409ff46e8de915b1380e87a8..2ca107f3efdf3c8434fff20349908f7cc3531e74 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -823,6 +823,19 @@ int cmd_record(int argc, const char **argv, const char *prefix __used)
symbol__init();
+ if (symbol_conf.kptr_restrict)
+ pr_warning("WARNING: Kernel address maps "
+ "(/proc/{kallsyms,modules}) are restricted, "
+ "check /proc/sys/kernel/kptr_restrict.\n\n"
+ "Samples in kernel functions may not be resolved "
+ "if a suitable vmlinux file is not found in the "
+ "buildid cache or in the vmlinux path.\n\n"
+ "Samples in kernel modules won't be resolved "
+ "at all.\n\n"
+ "If some relocation was applied (e.g. kexec) "
+ "symbols may be misresolved even with a suitable "
+ "vmlinux or kallsyms file.\n\n");
+
if (no_buildid_cache || no_buildid)
disable_buildid_cache();
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 498c6f70a74784ecd249ccd0c9cc495651f1047d..99156c35bc6284b5fc42cc2731979bd5a6b3ba9b 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -116,6 +116,9 @@ static int process_sample_event(union perf_event *event,
if (al.filtered || (hide_unresolved && al.sym == NULL))
return 0;
+ if (al.map != NULL)
+ al.map->dso->hit = 1;
+
if (perf_session__add_hist_entry(session, &al, sample, evsel)) {
pr_debug("problem incrementing symbol period, skipping event\n");
return -1;
@@ -249,6 +252,8 @@ static int __cmd_report(void)
u64 nr_samples;
struct perf_session *session;
struct perf_evsel *pos;
+ struct map *kernel_map;
+ struct kmap *kernel_kmap;
const char *help = "For a higher level overview, try: perf report --sort comm,dso";
signal(SIGINT, sig_handler);
@@ -268,6 +273,27 @@ static int __cmd_report(void)
if (ret)
goto out_delete;
+ kernel_map = session->host_machine.vmlinux_maps[MAP__FUNCTION];
+ kernel_kmap = map__kmap(kernel_map);
+ if (kernel_map == NULL ||
+ (kernel_map->dso->hit &&
+ (kernel_kmap->ref_reloc_sym == NULL ||
+ kernel_kmap->ref_reloc_sym->addr == 0))) {
+ const struct dso *kdso = kernel_map->dso;
+
+ ui__warning("Kernel address maps "
+ "(/proc/{kallsyms,modules}) were restricted, "
+ "check /proc/sys/kernel/kptr_restrict before "
+ "running 'perf record'.\n\n%s\n\n"
+ "Samples in kernel modules can't be resolved "
+ "as well.\n\n",
+ RB_EMPTY_ROOT(&kdso->symbols[MAP__FUNCTION]) ?
+ "As no suitable kallsyms nor vmlinux was found, "
+ "kernel samples can't be resolved." :
+ "If some relocation was applied (e.g. kexec) "
+ "symbols may be misresolved.");
+ }
+
if (dump_trace) {
perf_session__fprintf_nr_events(session, stdout);
goto out_delete;
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 6635fcd11ca558e1831d331a500474c8908a58d1..0fe9adf76379ecc02895cfbb46f35dcc8666dcbd 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -553,9 +553,18 @@ static int perf_event__process_kernel_mmap(union perf_event *event,
goto out_problem;
perf_event__set_kernel_mmap_len(event, machine->vmlinux_maps);
- perf_session__set_kallsyms_ref_reloc_sym(machine->vmlinux_maps,
- symbol_name,
- event->mmap.pgoff);
+
+ /*
+ * Avoid using a zero address (kptr_restrict) for the ref reloc
+ * symbol. Effectively having zero here means that at record
+ * time /proc/sys/kernel/kptr_restrict was non zero.
+ */
+ if (event->mmap.pgoff != 0) {
+ perf_session__set_kallsyms_ref_reloc_sym(machine->vmlinux_maps,
+ symbol_name,
+ event->mmap.pgoff);
+ }
+
if (machine__is_default_guest(machine)) {
/*
* preload dso of guest kernel and modules
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 0717bebc76494d24cfc68bec984aba404058438c..afb0849fe530e5f4a06937457bb98644acf681df 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -193,9 +193,13 @@ int build_id_cache__add_s(const char *sbuild_id, const char *debugdir,
*linkname = malloc(size), *targetname;
int len, err = -1;
- if (is_kallsyms)
+ if (is_kallsyms) {
+ if (symbol_conf.kptr_restrict) {
+ pr_debug("Not caching a kptr_restrict'ed /proc/kallsyms\n");
+ return 0;
+ }
realname = (char *)name;
- else
+ } else
realname = realpath(name, NULL);
if (realname == NULL || filename == NULL || linkname == NULL)
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 516876dfbe5280af9bd52179c07d99b16ed43233..eec196329fd92c2e0567c8af5535ae1a99fcc4b1 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -676,9 +676,30 @@ discard_symbol: rb_erase(&pos->rb_node, root);
return count + moved;
}
+static bool symbol__restricted_filename(const char *filename,
+ const char *restricted_filename)
+{
+ bool restricted = false;
+
+ if (symbol_conf.kptr_restrict) {
+ char *r = realpath(filename, NULL);
+
+ if (r != NULL) {
+ restricted = strcmp(r, restricted_filename) == 0;
+ free(r);
+ return restricted;
+ }
+ }
+
+ return restricted;
+}
+
int dso__load_kallsyms(struct dso *dso, const char *filename,
struct map *map, symbol_filter_t filter)
{
+ if (symbol__restricted_filename(filename, "/proc/kallsyms"))
+ return -1;
+
if (dso__load_all_kallsyms(dso, filename, map) < 0)
return -1;
@@ -1790,6 +1811,9 @@ static int machine__create_modules(struct machine *machine)
modules = path;
}
+ if (symbol__restricted_filename(path, "/proc/modules"))
+ return -1;
+
file = fopen(modules, "r");
if (file == NULL)
return -1;
@@ -2239,6 +2263,9 @@ static u64 machine__get_kernel_start_addr(struct machine *machine)
}
}
+ if (symbol__restricted_filename(filename, "/proc/kallsyms"))
+ return 0;
+
if (kallsyms__parse(filename, &args, symbol__in_kernel) <= 0)
return 0;
@@ -2410,6 +2437,25 @@ static int setup_list(struct strlist **list, const char *list_str,
return 0;
}
+static bool symbol__read_kptr_restrict(void)
+{
+ bool value = false;
+
+ if (geteuid() != 0) {
+ FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
+ if (fp != NULL) {
+ char line[8];
+
+ if (fgets(line, sizeof(line), fp) != NULL)
+ value = atoi(line) != 0;
+
+ fclose(fp);
+ }
+ }
+
+ return value;
+}
+
int symbol__init(void)
{
const char *symfs;
@@ -2456,6 +2502,8 @@ int symbol__init(void)
if (symfs != symbol_conf.symfs)
free((void *)symfs);
+ symbol_conf.kptr_restrict = symbol__read_kptr_restrict();
+
symbol_conf.initialized = true;
return 0;
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 242de0101a868f99d38c0fbf7348590556f8187f..325ee36a9d29d63d82973d262816f91a064813f2 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -75,7 +75,8 @@ struct symbol_conf {
use_callchain,
exclude_other,
show_cpu_utilization,
- initialized;
+ initialized,
+ kptr_restrict;
const char *vmlinux_name,
*kallsyms_name,
*source_prefix,