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Re: Help with getting CFA for split debuginfo files
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Wed, 07 May 2014 11:48:43 +0200
- Subject: Re: Help with getting CFA for split debuginfo files
Hi Sukadev,
On Tue, 2014-05-06 at 16:32 -0700, Sukadev Bhattiprolu wrote:
> But I am not sure how to extend the code to work with PC value that points
> to, say __random(), in glibc.
>
> I have these installed:
>
> glibc-common-2.18-11.fc20.ppc64p7
> glibc-2.18-11.fc20.ppc64p7
> glibc-headers-2.18-11.fc20.ppc64p7
> glibc-debuginfo-common-2.18-11.fc20.ppc64p7
> glibc-devel-2.18-11.fc20.ppc64p7
> glibc-debuginfo-2.18-11.fc20.ppc64p7
>
> $ objdump -D /usr/lib64/libc-2.18.so
>
> ....
> 00000080a7be3bf0 <.__random>:
> 80a7be3bf0: 7c 08 02 a6 mflr r0
> 80a7be3bf4: fb e1 ff f8 std r31,-8(r1)
> 80a7be3bf8: 60 00 00 00 nop
> 80a7be3bfc: 39 00 00 01 li r8,1
> 80a7be3c00: 3b e2 9a f0 addi r31,r2,-25872
> 80a7be3c04: 39 40 00 00 li r10,0
> 80a7be3c08: f8 01 00 10 std r0,16(r1)
> 80a7be3c0c: f8 21 ff 71 stdu r1,-144(r1)
> 80a7be3c10: 7d 20 f8 29 lwarx r9,0,r31,1
> 80a7be3c14: 7c 09 50 00 cmpw r9,r10
> 80a7be3c18: 40 82 00 0c bne 80a7be3c24 <.__random+0x34>
> 80a7be3c1c: 7d 00 f9 2d stwcx. r8,0,r31
> >>>> 80a7be3c20: 40 c2 ff f0 bne- 80a7be3c10 <.__random+0x20>
> ....
>
> $ ./crc5 80a7be3c20 80a7be3c20 /usr/lib64/libc-2.18.so
> Error dwarf_cfi_addrframe(): : no matching address range
> Error with addr 0x80a7be3c20
>
> $ ./crc5 80a7be3c20 80a7be3c20 /usr/lib/debug/lib64/libc.so.6.debug
> Error dwfl_addrmodule: no error
> Error with addr 0x80a7be3c20
>
> Pls find the code attached. Appreciate any comments on how to extend it
> to work with split debug info files.
The first invocation should work (it will find the separate debug info
file that matches itself through dwfl_standard_find_debuginfo).
You find the .debug_frame CFI through dwfl_module_dwarf_cfi and then
lookup the address using dwarf_cfi_addrframe. The .debug_frame
apparently exists but doesn't contain the requested address. You should
then try to find it through the .eh_frame CFI using dwfl_module_eh_cfi
(or just swap the dwfl_module_dwarf_cfi and dwfl_module_eh_cfi calls
since on fedora the .eh_frame should always be complete because GCC uses
-fasynchronous-unwind-tables by default).
Cheers,
Mark