perf symbols: Use both runtime and debug images

We keep both a 'runtime' elf image as well as a 'debug' elf image around
and generate symbols by looking at both of these.

This eliminates the need for the want_symtab/goto restart mechanism
combined with iterating over and reopening the elf images a second time.

Also give dso__synthsize_plt_symbols() the runtime image (which has
dynsyms) instead of the symbol image (which may only have a symtab and
no dynsyms).

Previously if a debug image was found all runtime images were ignored.

This fixes 2 issues:

 - Symbol resolution to failure on PowerPC systems with debug symbols
   installed, as the debug images lack a '.opd' section which contains
   function descriptors.

 - On all archs, plt synthesis failed when a debug image was loaded and
   that debug image lacks a dynsym section while a runtime image has a
   dynsym section.

Assumptions:

 - If a .opd section exists, it is contained in the highest priority
   image with a dynsym section.

 - This generally implies that the debug image lacks a dynsym section
   (ie: it is marked as NO_BITS).

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-17-git-send-email-cody@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 56 insertions, 33 deletions

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 36e4a458e7a1..5b37e13f08fb 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -525,6 +525,11 @@ static int dso__swap_init(struct dso *dso, unsigned char eidata)
         return 0;
 }
 
+bool symsrc__possibly_runtime(struct symsrc *ss)
+{
+        return ss->dynsym || ss->opdsec;
+}
+
 bool symsrc__has_symtab(struct symsrc *ss)
 {
         return ss->symtab != NULL;
diff --git a/tools/perf/util/symbol-minimal.c b/tools/perf/util/symbol-minimal.c
index 7747ea6d7e97..6738ea128c90 100644
--- a/tools/perf/util/symbol-minimal.c
+++ b/tools/perf/util/symbol-minimal.c
@@ -260,6 +260,12 @@ out_close:
         return -1;
 }
 
+bool symsrc__possibly_runtime(struct symsrc *ss __used)
+{
+        /* Assume all sym sources could be a runtime image. */
+        return true;
+}
+
 bool symsrc__has_symtab(struct symsrc *ss __used)
 {
         return false;
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 739e5a32366a..2293a4a5af96 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1026,11 +1026,12 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
 {
         char *name;
         int ret = -1;
-        struct symsrc ss;
         u_int i;
         struct machine *machine;
         char *root_dir = (char *) "";
-        int want_symtab;
+        int ss_pos = 0;
+        struct symsrc ss_[2];
+        struct symsrc *syms_ss = NULL, *runtime_ss = NULL;
 
         dso__set_loaded(dso, map->type);
 
@@ -1072,12 +1073,12 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
                 root_dir = machine->root_dir;
 
         /* Iterate over candidate debug images.
-         * On the first pass, only load images if they have a full symtab.
-         * Failing that, do a second pass where we accept .dynsym also
+         * Keep track of "interesting" ones (those which have a symtab, dynsym,
+         * and/or opd section) for processing.
          */
-        want_symtab = 1;
-restart:
         for (i = 0; i < DSO_BINARY_TYPE__SYMTAB_CNT; i++) {
+                struct symsrc *ss = &ss_[ss_pos];
+                bool next_slot = false;
 
                 enum dso_binary_type symtab_type = binary_type_symtab[i];
 
@@ -1086,45 +1087,55 @@ restart:
                         continue;
 
                 /* Name is now the name of the next image to try */
-                if (symsrc__init(&ss, dso, name, symtab_type) < 0)
+                if (symsrc__init(ss, dso, name, symtab_type) < 0)
                         continue;
 
-                if (want_symtab && !symsrc__has_symtab(&ss)) {
-                        symsrc__destroy(&ss);
-                        continue;
+                if (!syms_ss && symsrc__has_symtab(ss)) {
+                        syms_ss = ss;
+                        next_slot = true;
                 }
 
-                ret = dso__load_sym(dso, map, &ss, &ss, filter, 0);
-
-                /*
-                 * Some people seem to have debuginfo files _WITHOUT_ debug
-                 * info!?!?
-                 */
-                if (!ret) {
-                        symsrc__destroy(&ss);
-                        continue;
+                if (!runtime_ss && symsrc__possibly_runtime(ss)) {
+                        runtime_ss = ss;
+                        next_slot = true;
                 }
 
-                if (ret > 0) {
-                        int nr_plt;
+                if (next_slot) {
+                        ss_pos++;
 
-                        nr_plt = dso__synthesize_plt_symbols(dso, &ss, map, filter);
-                        if (nr_plt > 0)
-                                ret += nr_plt;
-                        symsrc__destroy(&ss);
-                        break;
+                        if (syms_ss && runtime_ss)
+                                break;
                 }
+
         }
 
-        /*
-         * If we wanted a full symtab but no image had one,
-         * relax our requirements and repeat the search.
-         */
-        if (ret <= 0 && want_symtab) {
-                want_symtab = 0;
-                goto restart;
+        if (!runtime_ss && !syms_ss)
+                goto out_free;
+
+        if (runtime_ss && !syms_ss) {
+                syms_ss = runtime_ss;
+        }
+
+        /* We'll have to hope for the best */
+        if (!runtime_ss && syms_ss)
+                runtime_ss = syms_ss;
+
+        if (syms_ss)
+                ret = dso__load_sym(dso, map, syms_ss, runtime_ss, filter, 0);
+        else
+                ret = -1;
+
+        if (ret > 0 && runtime_ss->dynsym) {
+                int nr_plt;
+
+                nr_plt = dso__synthesize_plt_symbols(dso, runtime_ss, map, filter);
+                if (nr_plt > 0)
+                        ret += nr_plt;
         }
 
+        for (; ss_pos > 0; ss_pos--)
+                symsrc__destroy(&ss_[ss_pos - 1]);
+out_free:
         free(name);
         if (ret < 0 && strstr(dso->name, " (deleted)") != NULL)
                 return 0;
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 1f3eed21f35d..fc4b1e630fd9 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -253,6 +253,7 @@ void symsrc__destroy(struct symsrc *ss);
 int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
                  enum dso_binary_type type);
 bool symsrc__has_symtab(struct symsrc *ss);
+bool symsrc__possibly_runtime(struct symsrc *ss);
 
 #define DSO__SWAP(dso, type, val)                       \
 ({                                                      \