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

[Jiri Olsa]

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?

Also few typo comments below..

thanks,
jirka

> 
> Signed-off-by: Jean Pihet <jean.pihet at linaro.org>
> ---
>  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 ^^^ ;-)


> +	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
>