This is the mail archive of the libc-alpha@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: RFC: Automatically test IFUNC implementations


On Fri, Sep 28, 2012 at 7:25 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Thu, Sep 27, 2012 at 5:16 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Thu, Sep 27, 2012 at 3:31 PM, Roland McGrath <roland@hack.frob.com> wrote:
>>>> I thought we'd discussed returning a count from __libc_func,
>>>> and the (static) array provided by the test program.
>>>>
>>>> Certainly that's going to be less dead bss space in libc.so.
>>>
>>> IMHO this feature must be done in a way that adds zero data space
>>> (including zero relro const data), zero bss space, and zero relocs
>>> to the library.
>>
>> I updated hjl/ifunc/test branch.  __libc_func is now specified as:
>>
>> /* Fill ARRAY of MAX elements with IFUNC implementations for function
>>    NAME supported on target machine and return the number of valid
>>    entries.  */
>> extern int __libc_func (const char *name, struct libc_func_test *array,
>>                         int max);
>>
>> arch-specific __libc_func can issue a run-time error if array is too
>> small.   There are no .bss nor .data spaces:
>>

Here are comparisons of master branch vs. hjl/ifunc/test branch:

x86-64 master branch:

[hjl@gnu-tools-1 build-x86_64-linux]$ readelf -r libc.so|wc -l
1291
[hjl@gnu-tools-1 build-x86_64-linux]$ readelf -SW libc.so | egrep "data|bss"
  [15] .rodata           PROGBITS        000000000014da60 14da60
021ad0 00   A  0   0 32
  [21] .tdata            PROGBITS        000000000039f748 19f748
000010 00 WAT  0   0  8
  [22] .tbss             NOBITS          000000000039f758 19f758
000058 00 WAT  0   0  8
  [27] .data.rel.ro      PROGBITS        000000000039f880 19f880
003320 00  WA  0   0 32
  [31] .data             PROGBITS        00000000003a3080 1a3080
0016d8 00  WA  0   0 32
  [32] .bss              NOBITS          00000000003a4760 1a4758
004520 00  WA  0   0 32
[hjl@gnu-tools-1 build-x86_64-linux]$

x86-64 hjl/ifunc/test branch:

[hjl@gnu-tools-1 build-x86_64-linux]$ readelf -r libc.so|wc -l1291
[hjl@gnu-tools-1 build-x86_64-linux]$ readelf -SW libc.so | egrep "data|bss"
  [15] .rodata           PROGBITS        000000000014eb20 14eb20
022270 00   A  0   0 32
  [21] .tdata            PROGBITS        00000000003a1758 1a1758
000010 00 WAT  0   0  8
  [22] .tbss             NOBITS          00000000003a1768 1a1768
000058 00 WAT  0   0  8
  [27] .data.rel.ro      PROGBITS        00000000003a1880 1a1880
003320 00  WA  0   0 32
  [31] .data             PROGBITS        00000000003a5080 1a5080
0016d8 00  WA  0   0 32
  [32] .bss              NOBITS          00000000003a6760 1a6758
004520 00  WA  0   0 32
[hjl@gnu-tools-1 build-x86_64-linux]$

i686 master branch:

[hjl@gnu-tools-1 build-i686-linux]$ readelf -r libc.so|wc -l
1360
[hjl@gnu-tools-1 build-i686-linux]$ readelf -SW libc.so | egrep "data|bss"
  [15] .rodata           PROGBITS        0014d140 14d140 01eed8 00   A  0   0 32
  [21] .tdata            PROGBITS        001a51fc 1a51fc 000008 00 WAT  0   0  4
  [22] .tbss             NOBITS          001a5204 1a5204 000038 00 WAT  0   0  4
  [27] .data.rel.ro      PROGBITS        001a52a0 1a52a0 001b1c 00  WA  0   0 32
  [31] .data             PROGBITS        001a7040 1a7040 000e9c 00  WA  0   0 32
  [32] .bss              NOBITS          001a7ee0 1a7edc 002c1c 00  WA  0   0 32
[hjl@gnu-tools-1 build-i686-linux]$

i686 hjl/ifunc/test branch:

[hjl@gnu-tools-1 build-i686-linux]$ readelf -r libc.so|wc -l
1360
[hjl@gnu-tools-1 build-i686-linux]$ readelf -SW libc.so | egrep "data|bss"
  [15] .rodata           PROGBITS        0014e2a0 14e2a0 01f708 00   A  0   0 32
  [21] .tdata            PROGBITS        001a6204 1a6204 000008 00 WAT  0   0  4
  [22] .tbss             NOBITS          001a620c 1a620c 000038 00 WAT  0   0  4
  [27] .data.rel.ro      PROGBITS        001a62a0 1a62a0 001b1c 00  WA  0   0 32
  [31] .data             PROGBITS        001a8040 1a8040 000e9c 00  WA  0   0 32
  [32] .bss              NOBITS          001a8ee0 1a8edc 002c1c 00  WA  0   0 32
[hjl@gnu-tools-1 build-i686-linux]$

There are no changes in run-time relocations and .data/.bss section sizes.
There are about 2K increases in .rodata section for IFUNC function name
strings.  OK to install?

Thanks.


-- 
H.J.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]