[Bug translator/10208] Support probing glibc synthesized syscall wrappers

[Bug translator/10208] Support probing glibc synthesized syscall wrappers

[lberk at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=10208

Lukas Berk <lberk at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |lberk at redhat dot com
           Assignee|systemtap at sourceware dot org    |lberk at redhat dot com

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[Bug translator/10208] Support probing glibc synthesized syscall wrappers

[fche at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=10208

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fche at redhat dot com

--- Comment #3 from Frank Ch. Eigler <fche at redhat dot com> 2010-11-26 21:58:56 UTC ---
A related sighting:
http://sourceware.org/ml/systemtap/2010-q4/msg00250.html

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[Bug translator/10208] Support probing glibc synthesized syscall wrappers

[mjw at redhat dot com]

------- Additional Comments From mjw at redhat dot com  2009-05-28 09:32 -------
Isn't this two separate things/bug reports?
- Supporting probing on weak symbols, and
- Having debuginfo for synthesized syscall wrappers?

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[Bug translator/10208] Support probing glibc synthesized syscall wrappers

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2009-05-27 15:06 -------
It turns out there is no dwarf data for chown in glibc.
That's because many of the syscall wrappers are not written
in ordinary C code, but instead generated (assembly) code:

make[2]: Entering directory `/home/fche/Private/DEVEL/DEVEL-sourceware/glibc/io'
(echo '#include <sysdep.h>'; \
         echo 'PSEUDO (__libc_chown, chown, 3)'; \
         echo ' ret'; \
         echo 'PSEUDO_END(__libc_chown)'; \
         echo 'libc_hidden_def (__libc_chown)'; \
         echo 'weak_alias (__libc_chown, __chown)'; \
         echo 'libc_hidden_weak (__chown)'; \
         echo 'weak_alias (__libc_chown, chown)'; \
         echo 'libc_hidden_weak (chown)'; \
        ) | gcc -c -I../include -I[...] -I.. -I../libio -I. -I
/lib/modules/2.6.27.12-78.2.8.fc9.x86_64.debug/build/include -D_LIBC_REENTRANT
-include ../include/libc-symbols.h -DASSEMBLER -Wa,--noexecstack -x
assembler-with-cpp -o
/home/fche/Private/DEVEL/DEVEL-sourceware/glibc/BUILD/io/chown.o - 


objdump -dr chown.o

chown.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <__libc_chown>:
   0:   b8 5c 00 00 00          mov    $0x5c,%eax
   5:   0f 05                   syscall 
   7:   48 3d 01 f0 ff ff       cmp    $0xfffffffffffff001,%rax
   d:   0f 83 00 00 00 00       jae    13 <__libc_chown+0x13>
                        f: R_X86_64_PC32        __syscall_error-0x4
  13:   c3                      retq   


So we may have to synthesize debuginfo for these functions.
Or go debuginfo-less, and search symbol tables for plain addresses.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Support probing weak symbol |Support probing glibc
                   |functions                   |synthesized syscall wrappers


http://sourceware.org/bugzilla/show_bug.cgi?id=10208

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