perf symbols: Add support for 'variable' symtabs

Example:

{
	u64 addr = strtoull(sym_filter, NULL, 16);
	struct map *map = map_groups__find(kmaps, MAP__VARIABLE, addr);

	if (map == NULL)
		pr_err("couldn't find map!\n");
	else {
		struct symbol *sym = map__find_symbol(map, addr, NULL);
		if (sym == NULL)
			pr_err("couldn't find addr!\n");
		else
			pr_info("addr %#Lx is in %s global var\n", addr, sym->name);
	}
	exit(0);
}

Added just after symbol__init() call in 'perf top', then:

{
        u64 addr = strtoull(sym_filter, NULL, 16);
        struct map *map = map_groups__find(kmaps, MAP__VARIABLE, addr);

        if (map == NULL)
                pr_err("couldn't find map!\n");
        else {
                struct symbol *sym = map__find_symbol(map, addr, NULL);
                if (sym == NULL)
                        pr_err("couldn't find addr!\n");
                else
                        pr_info("addr %#Lx is in %s global var\n", addr, sym->name);
        }
        exit(0);
}

[root@doppio linux-2.6-tip]# grep ' [dD] ' /proc/kallsyms | grep ' sched'
ffffffff817827d8 d sched_nr_latency
ffffffff81782ce0 d sched_domains_mutex
ffffffff8178c070 d schedstr.22423
ffffffff817909a0 d sched_register_mutex
ffffffff81823490 d sched_feat_names
ffffffff81823558 d scheduler_running
ffffffff818235b8 d sched_clock_running
ffffffff818235bc D sched_clock_stable
ffffffff81824f00 d sched_switch_trace
[root@doppio linux-2.6-tip]# perf top -s 0xffffffff817827d9
addr 0xffffffff817827d9 is in sched_nr_latency global var
[root@doppio linux-2.6-tip]# perf top -s ffffffff81782ce0
addr 0xffffffff81782ce0 is in sched_domains_mutex global var
[root@doppio linux-2.6-tip]#
[root@doppio linux-2.6-tip]# perf top -s ffffffff81782ce0 --vmlinux OFF
The file OFF cannot be used, trying to use /proc/kallsyms...addr 0xffffffff81782ce0 is in sched_domains_mutex global var
[root@doppio linux-2.6-tip]# perf top -s ffffffff818235bc --vmlinux OFF
The file OFF cannot be used, trying to use /proc/kallsyms...addr 0xffffffff818235bc is in sched_clock_stable global var
[root@doppio linux-2.6-tip]#

So it works with both /proc/kallsyms and with ELF symtabs, either
the one on the vmlinux explicitely passed via --vmlinux or in one
in the vmlinux_path that matches the buildid for the running kernel
or the one found in the buildid header section in a perf.data file.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1260550239-5372-4-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 51 insertions, 15 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index db8dc97b548b..e63ddb469de7 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -61,6 +61,8 @@ static bool symbol_type__is_a(char symbol_type, enum map_type map_type)
         switch (map_type) {
         case MAP__FUNCTION:
                 return symbol_type == 'T' || symbol_type == 'W';
+        case MAP__VARIABLE:
+                return symbol_type == 'D' || symbol_type == 'd';
         default:
                 return false;
         }
@@ -551,6 +553,13 @@ static inline int elf_sym__is_function(const GElf_Sym *sym)
                sym->st_shndx != SHN_UNDEF;
 }
 
+static inline bool elf_sym__is_object(const GElf_Sym *sym)
+{
+        return elf_sym__type(sym) == STT_OBJECT &&
+                sym->st_name != 0 &&
+                sym->st_shndx != SHN_UNDEF;
+}
+
 static inline int elf_sym__is_label(const GElf_Sym *sym)
 {
         return elf_sym__type(sym) == STT_NOTYPE &&
@@ -571,6 +580,12 @@ static inline int elf_sec__is_text(const GElf_Shdr *shdr,
         return strstr(elf_sec__name(shdr, secstrs), "text") != NULL;
 }
 
+static inline bool elf_sec__is_data(const GElf_Shdr *shdr,
+                                    const Elf_Data *secstrs)
+{
+        return strstr(elf_sec__name(shdr, secstrs), "data") != NULL;
+}
+
 static inline const char *elf_sym__name(const GElf_Sym *sym,
                                         const Elf_Data *symstrs)
 {
@@ -756,6 +771,8 @@ static bool elf_sym__is_a(GElf_Sym *self, enum map_type type)
         switch (type) {
         case MAP__FUNCTION:
                 return elf_sym__is_function(self);
+        case MAP__VARIABLE:
+                return elf_sym__is_object(self);
         default:
                 return false;
         }
@@ -766,6 +783,8 @@ static bool elf_sec__is_a(GElf_Shdr *self, Elf_Data *secstrs, enum map_type type
         switch (type) {
         case MAP__FUNCTION:
                 return elf_sec__is_text(self, secstrs);
+        case MAP__VARIABLE:
+                return elf_sec__is_data(self, secstrs);
         default:
                 return false;
         }
@@ -1536,42 +1555,59 @@ size_t dsos__fprintf_buildid(FILE *fp)
                 __dsos__fprintf_buildid(&dsos__user, fp));
 }
 
-static int map_groups__create_kernel_map(struct map_groups *self, const char *vmlinux)
+static struct dso *dsos__create_kernel( const char *vmlinux)
 {
-        struct map *kmap;
         struct dso *kernel = dso__new(vmlinux ?: "[kernel.kallsyms]");
 
         if (kernel == NULL)
-                return -1;
-
-        kmap = map__new2(0, kernel, MAP__FUNCTION);
-        if (kmap == NULL)
-                goto out_delete_kernel_dso;
+                return NULL;
 
-        kmap->map_ip       = kmap->unmap_ip = identity__map_ip;
         kernel->short_name = "[kernel]";
         kernel->kernel     = 1;
 
         vdso = dso__new("[vdso]");
         if (vdso == NULL)
-                goto out_delete_kernel_map;
+                goto out_delete_kernel_dso;
         dso__set_loaded(vdso, MAP__FUNCTION);
 
         if (sysfs__read_build_id("/sys/kernel/notes", kernel->build_id,
                                  sizeof(kernel->build_id)) == 0)
                 kernel->has_build_id = true;
 
-        map_groups__insert(self, kmap);
         dsos__add(&dsos__kernel, kernel);
         dsos__add(&dsos__user, vdso);
 
-        return 0;
+        return kernel;
 
-out_delete_kernel_map:
-        map__delete(kmap);
 out_delete_kernel_dso:
         dso__delete(kernel);
-        return -1;
+        return NULL;
+}
+
+static int map_groups__create_kernel_maps(struct map_groups *self, const char *vmlinux)
+{
+        struct map *functions, *variables;
+        struct dso *kernel = dsos__create_kernel(vmlinux);
+
+        if (kernel == NULL)
+                return -1;
+
+        functions = map__new2(0, kernel, MAP__FUNCTION);
+        if (functions == NULL)
+                return -1;
+
+        variables = map__new2(0, kernel, MAP__VARIABLE);
+        if (variables == NULL) {
+                map__delete(functions);
+                return -1;
+        }
+
+        functions->map_ip = functions->unmap_ip =
+                variables->map_ip = variables->unmap_ip = identity__map_ip;
+        map_groups__insert(self, functions);
+        map_groups__insert(self, variables);
+
+        return 0;
 }
 
 static void vmlinux_path__exit(void)
@@ -1640,7 +1676,7 @@ int symbol__init(struct symbol_conf *conf)
         if (pconf->try_vmlinux_path && vmlinux_path__init() < 0)
                 return -1;
 
-        if (map_groups__create_kernel_map(kmaps, pconf->vmlinux_name) < 0) {
+        if (map_groups__create_kernel_maps(kmaps, pconf->vmlinux_name) < 0) {
                 vmlinux_path__exit();
                 return -1;
         }