Re: [PATCH 3/3] perf: parse the .debug_frame section in case.eh_frame is not present

From: Jean Pihet
Date: Thu Sep 05 2013 - 12:49:18 EST

Hi Jiri,

On 5 September 2013 18:30, Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> On Wed, Sep 04, 2013 at 08:04:14PM +0200, Jean Pihet wrote:
>> On ARM the debug info is not present in the .eh_frame sections but
>> instead in .debug_frame.
>> Use libunwind to load and parse the debug info.
>
> hum, cannot make final link:
>
> $ make LIBUNWIND_DIR=/opt/libunwind/
> CHK -fstack-protector-all
> CHK -Wstack-protector
> CHK -Wvolatile-register-var
> CHK -D_FORTIFY_SOURCE=2
> CHK bionic
> CHK libelf
> CHK libdw
> CHK -DLIBELF_MMAP
> CHK -DLIBELF_MMAP
> CHK libunwind
> CHK libaudit
>
> ...
>
> make[1]: `liblk.a' is up to date.
> SUBDIR /home/jolsa/linux-perf/tools/lib/traceevent/
> LINK perf
> libperf.a(unwind.o): In function `find_proc_info':
> /home/jolsa/linux-perf/tools/perf/util/unwind.c:339: undefined reference to `_Ux86_64_dwarf_find_debug_frame'
> collect2: ld returned 1 exit status
> make: *** [perf] Error 1
>
>
> I'm using the latest code from git://git.sv.gnu.org/libunwind.git
>
> Looks like dwarf_find_debug_frame is not exported, although
> it looks like it is based on what I see in libunwind sources ;-)
>
> What did I miss?
Weird, I do not have the error on x86_64. I am investigating this and
will come back to you asap.

>
> Also few typo comments below..
>
> thanks,
> jirka
>
>>
>> Signed-off-by: Jean Pihet <jean.pihet@xxxxxxxxxx>
>> ---
>> tools/perf/util/unwind.c | 70 +++++++++++++++++++++++++++++++++++++-----------
>> 1 file changed, 54 insertions(+), 16 deletions(-)
>>
>> diff --git a/tools/perf/util/unwind.c b/tools/perf/util/unwind.c
>> index 958723b..5353b32 100644
>> --- a/tools/perf/util/unwind.c
>> +++ b/tools/perf/util/unwind.c
>> @@ -39,6 +39,14 @@ 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 +253,9 @@ 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 +264,7 @@ 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 +273,27 @@ 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;
>> }
>>
>> +static int read_unwind_spec_debug_frame(struct dso *dso,
>> + struct machine *machine, u64 *offset)
>> +{
>
> some strange formatting issue ^^^ ;-)
I am using 4-spaces tabs. scripts/checkpatch.pl reported it to me in
the form of too long lines.
Should I change the code to 8-spaces tabs?

Thx!
Jean

>
>
>> + 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;
>> +}
>> +
>> static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
>> {
>> struct addr_location al;
>> @@ -291,20 +318,31 @@ 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)) {
>
> ditto ^^^
>
>> + 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);
>
> ditto ^^^
>
>> + }
>> +
>> + /* 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);
>
> ditto ^^^
>
>> + }
>>
>> - 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,
>> --
>> 1.7.11.7
>>
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