6 files changed, 133 insertions, 5 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 265425322734..8f88420e066b 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -551,6 +551,13 @@ static int __cmd_record(int argc, const char **argv)
                         return err;
         }
 
+        err = event__synthesize_kernel_mmap(process_synthesized_event,
+                                            session, "_text");
+        if (err < 0) {
+                pr_err("Couldn't record kernel reference relocation symbol.\n");
+                return err;
+        }
+
         if (!system_wide && profile_cpu == -1)
                 event__synthesize_thread(pid, process_synthesized_event,
                                          session);
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index bb0fd6da2d56..1a31feb9999f 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -189,6 +189,50 @@ void event__synthesize_threads(int (*process)(event_t *event,
         closedir(proc);
 }
 
+struct process_symbol_args {
+        const char *name;
+        u64        start;
+};
+
+static int find_symbol_cb(void *arg, const char *name, char type, u64 start)
+{
+        struct process_symbol_args *args = arg;
+
+        if (!symbol_type__is_a(type, MAP__FUNCTION) || strcmp(name, args->name))
+                return 0;
+
+        args->start = start;
+        return 1;
+}
+
+int event__synthesize_kernel_mmap(int (*process)(event_t *event,
+                                                 struct perf_session *session),
+                                  struct perf_session *session,
+                                  const char *symbol_name)
+{
+        size_t size;
+        event_t ev = {
+                .header = { .type = PERF_RECORD_MMAP },
+        };
+        /*
+         * We should get this from /sys/kernel/sections/.text, but till that is
+         * available use this, and after it is use this as a fallback for older
+         * kernels.
+         */
+        struct process_symbol_args args = { .name = symbol_name, };
+
+        if (kallsyms__parse(&args, find_symbol_cb) <= 0)
+                return -ENOENT;
+
+        size = snprintf(ev.mmap.filename, sizeof(ev.mmap.filename),
+                        "[kernel.kallsyms.%s]", symbol_name) + 1;
+        size = ALIGN(size, sizeof(u64));
+        ev.mmap.header.size = (sizeof(ev.mmap) - (sizeof(ev.mmap.filename) - size));
+        ev.mmap.start = args.start;
+
+        return process(&ev, session);
+}
+
 static void thread__comm_adjust(struct thread *self)
 {
         char *comm = self->comm;
@@ -240,9 +284,9 @@ int event__process_lost(event_t *self, struct perf_session *session)
 
 int event__process_mmap(event_t *self, struct perf_session *session)
 {
-        struct thread *thread = perf_session__findnew(session, self->mmap.pid);
-        struct map *map = map__new(&self->mmap, MAP__FUNCTION,
-                                   session->cwd, session->cwdlen);
+        struct thread *thread;
+        struct map *map;
+        static const char kmmap_prefix[] = "[kernel.kallsyms.";
 
         dump_printf(" %d/%d: [%p(%p) @ %p]: %s\n",
                     self->mmap.pid, self->mmap.tid,
@@ -251,6 +295,20 @@ int event__process_mmap(event_t *self, struct perf_session *session)
                     (void *)(long)self->mmap.pgoff,
                     self->mmap.filename);
 
+        if (self->mmap.pid == 0 &&
+            memcmp(self->mmap.filename, kmmap_prefix,
+                   sizeof(kmmap_prefix) - 1) == 0) {
+                const char *symbol_name = (self->mmap.filename +
+                                           sizeof(kmmap_prefix) - 1);
+                perf_session__set_kallsyms_ref_reloc_sym(session, symbol_name,
+                                                         self->mmap.start);
+                return 0;
+        }
+
+        thread = perf_session__findnew(session, self->mmap.pid);
+        map = map__new(&self->mmap, MAP__FUNCTION,
+                       session->cwd, session->cwdlen);
+
         if (thread == NULL || map == NULL)
                 dump_printf("problem processing PERF_RECORD_MMAP, skipping event.\n");
         else
diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
index 80fb3653c809..61fc0dc658c2 100644
--- a/tools/perf/util/event.h
+++ b/tools/perf/util/event.h
@@ -110,6 +110,10 @@ int event__synthesize_thread(pid_t pid,
 void event__synthesize_threads(int (*process)(event_t *event,
                                               struct perf_session *session),
                                struct perf_session *session);
+int event__synthesize_kernel_mmap(int (*process)(event_t *event,
+                                                 struct perf_session *session),
+                                  struct perf_session *session,
+                                  const char *symbol_name);
 
 int event__process_comm(event_t *self, struct perf_session *session);
 int event__process_lost(event_t *self, struct perf_session *session);
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 7f0537d1add8..e0e6a075489e 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -401,3 +401,49 @@ bool perf_session__has_traces(struct perf_session *self, const char *msg)
 
         return true;
 }
+
+int perf_session__set_kallsyms_ref_reloc_sym(struct perf_session *self,
+                                             const char *symbol_name,
+                                             u64 addr)
+{
+        char *bracket;
+
+        self->ref_reloc_sym.name = strdup(symbol_name);
+        if (self->ref_reloc_sym.name == NULL)
+                return -ENOMEM;
+
+        bracket = strchr(self->ref_reloc_sym.name, ']');
+        if (bracket)
+                *bracket = '\0';
+
+        self->ref_reloc_sym.addr = addr;
+        return 0;
+}
+
+static u64 map__reloc_map_ip(struct map *map, u64 ip)
+{
+        return ip + (s64)map->pgoff;
+}
+
+static u64 map__reloc_unmap_ip(struct map *map, u64 ip)
+{
+        return ip - (s64)map->pgoff;
+}
+
+void perf_session__reloc_vmlinux_maps(struct perf_session *self,
+                                      u64 unrelocated_addr)
+{
+        enum map_type type;
+        s64 reloc = unrelocated_addr - self->ref_reloc_sym.addr;
+
+        if (!reloc)
+                return;
+
+        for (type = 0; type < MAP__NR_TYPES; ++type) {
+                struct map *map = self->vmlinux_maps[type];
+
+                map->map_ip = map__reloc_map_ip;
+                map->unmap_ip = map__reloc_unmap_ip;
+                map->pgoff = reloc;
+        }
+}
diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
index 8db37bbf0e62..d4a9d20f8d44 100644
--- a/tools/perf/util/session.h
+++ b/tools/perf/util/session.h
@@ -24,6 +24,10 @@ struct perf_session {
         unsigned long           unknown_events;
         struct rb_root          hists;
         u64                     sample_type;
+        struct {
+                const char      *name;
+                u64             addr;
+        }                       ref_reloc_sym;
         int                     fd;
         int                     cwdlen;
         char                    *cwd;
@@ -59,4 +63,10 @@ bool perf_session__has_traces(struct perf_session *self, const char *msg);
 
 int perf_header__read_build_ids(int input, u64 offset, u64 file_size);
 
+int perf_session__set_kallsyms_ref_reloc_sym(struct perf_session *self,
+                                             const char *symbol_name,
+                                             u64 addr);
+void perf_session__reloc_vmlinux_maps(struct perf_session *self,
+                                      u64 unrelocated_addr);
+
 #endif /* __PERF_SESSION_H */
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index e290429e9c00..da2f07f1af8f 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -956,11 +956,15 @@ static int dso__load_sym(struct dso *self, struct map *map,
 
         elf_symtab__for_each_symbol(syms, nr_syms, idx, sym) {
                 struct symbol *f;
-                const char *elf_name;
+                const char *elf_name = elf_sym__name(&sym, symstrs);
                 char *demangled = NULL;
                 int is_label = elf_sym__is_label(&sym);
                 const char *section_name;
 
+                if (kernel && session->ref_reloc_sym.name != NULL &&
+                    strcmp(elf_name, session->ref_reloc_sym.name) == 0)
+                        perf_session__reloc_vmlinux_maps(session, sym.st_value);
+
                 if (!is_label && !elf_sym__is_a(&sym, map->type))
                         continue;
 
@@ -973,7 +977,6 @@ static int dso__load_sym(struct dso *self, struct map *map,
                 if (is_label && !elf_sec__is_a(&shdr, secstrs, map->type))
                         continue;
 
-                elf_name = elf_sym__name(&sym, symstrs);
                 section_name = elf_sec__name(&shdr, secstrs);
 
                 if (kernel || kmodule) {