perf: parse the .debug_frame section in case .eh_frame is not present

On ARM the debug info is not present in the .eh_frame sections but
in .debug_frame instead, in dwarf format.
Use libunwind to load and parse the debug info.

Dependencies:
 . if present, libunwind >= 1.1 is needed to prevent a segfault when
   parsing the dwarf info,
 . libunwind needs to be configured with --enable-debug-frame. Note:
   --enable-debug-frame is automatically selected on ARM.

Acked-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Jean Pihet <jean.pihet@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/tools/perf/util/unwind.c b/tools/perf/util/unwind.c
index 2f891f7e70bf9251c849780ec008ded14a2776c9..5390d0b8862a680e147cf52dd8bed22cfbba333f 100644 (file)
--- a/tools/perf/util/unwind.c
+++ b/tools/perf/util/unwind.c
@@ -39,6 +39,15 @@ UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
 
 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
 
+extern int
+UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
+                                unw_word_t ip,
+                                unw_word_t segbase,
+                                const char *obj_name, unw_word_t start,
+                                unw_word_t end);
+
+#define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
+
 #define DW_EH_PE_FORMAT_MASK   0x0f    /* format of the encoded value */
 #define DW_EH_PE_APPL_MASK     0x70    /* how the value is to be applied */
 
@@ -245,8 +254,9 @@ static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
        return 0;
 }
 
-static int read_unwind_spec(struct dso *dso, struct machine *machine,
-                           u64 *table_data, u64 *segbase, u64 *fde_count)
+static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
+                                    u64 *table_data, u64 *segbase,
+                                    u64 *fde_count)
 {
        int ret = -EINVAL, fd;
        u64 offset;
@@ -255,6 +265,7 @@ static int read_unwind_spec(struct dso *dso, struct machine *machine,
        if (fd < 0)
                return -EINVAL;
 
+       /* Check the .eh_frame section for unwinding info */
        offset = elf_section_offset(fd, ".eh_frame_hdr");
        close(fd);
 
@@ -263,10 +274,29 @@ static int read_unwind_spec(struct dso *dso, struct machine *machine,
                                          table_data, segbase,
                                          fde_count);
 
-       /* TODO .debug_frame check if eh_frame_hdr fails */
        return ret;
 }
 
+#ifndef NO_LIBUNWIND_DEBUG_FRAME
+static int read_unwind_spec_debug_frame(struct dso *dso,
+                                       struct machine *machine, u64 *offset)
+{
+       int fd = dso__data_fd(dso, machine);
+
+       if (fd < 0)
+               return -EINVAL;
+
+       /* Check the .debug_frame section for unwinding info */
+       *offset = elf_section_offset(fd, ".debug_frame");
+       close(fd);
+
+       if (*offset)
+               return 0;
+
+       return -EINVAL;
+}
+#endif
+
 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
 {
        struct addr_location al;
@@ -291,20 +321,33 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 
        pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
 
-       if (read_unwind_spec(map->dso, ui->machine,
-                            &table_data, &segbase, &fde_count))
-               return -EINVAL;
+       /* Check the .eh_frame section for unwinding info */
+       if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
+                                      &table_data, &segbase, &fde_count)) {
+               memset(&di, 0, sizeof(di));
+               di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
+               di.start_ip = map->start;
+               di.end_ip   = map->end;
+               di.u.rti.segbase    = map->start + segbase;
+               di.u.rti.table_data = map->start + table_data;
+               di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
+                                     / sizeof(unw_word_t);
+               return dwarf_search_unwind_table(as, ip, &di, pi,
+                                                need_unwind_info, arg);
+       }
+
+#ifndef NO_LIBUNWIND_DEBUG_FRAME
+       /* Check the .debug_frame section for unwinding info */
+       if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
+               memset(&di, 0, sizeof(di));
+               dwarf_find_debug_frame(0, &di, ip, 0, map->dso->name,
+                                      map->start, map->end);
+               return dwarf_search_unwind_table(as, ip, &di, pi,
+                                                need_unwind_info, arg);
+       }
+#endif
 
-       memset(&di, 0, sizeof(di));
-       di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
-       di.start_ip = map->start;
-       di.end_ip   = map->end;
-       di.u.rti.segbase    = map->start + segbase;
-       di.u.rti.table_data = map->start + table_data;
-       di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
-                             / sizeof(unw_word_t);
-       return dwarf_search_unwind_table(as, ip, &di, pi,
-                                        need_unwind_info, arg);
+       return -EINVAL;
 }
 
 static int access_fpreg(unw_addr_space_t __maybe_unused as,