Re: [perfmon2] [PATCH] Limit functions visibility in the libpfm library to ones listed in header files

[William C. <wc...@re...>]

On 03/12/2016 05:50 PM, Andreas Beckmann wrote:
> On 2016-03-12 17:10, Stephane Eranian wrote:
>> Hi Will,
>>
>> I tried your patch on my Ubuntu system.
>> It is using gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.1).
>>
>> It compiles fine but I see no difference in size using size -t lib/libpfm.a.
> 
>> So do you need a specific compiler version or the patch is missing
>> something?
> 
> That patch primarily affects the (exported) content of the shared
> library, not the static library.
> 
> I gave it a short test on Debian and papi (the only user of the libpfm4
> package) continued to work after I installed the new libpfm4 package
> which exports fewer symbols. (In Debian, papi is built against the
> separately packaged libpfm4, not the bundled copy. It uses the shared
> library.)
> 
> Andreas

Hi Stephane and Andreas,

Yes, the change is only going to affect the libpfm.so file.  The libpfm.a is going to be the same.  the abidiff from libabigail (https://www.sourceware.org/libabigail/) shows that a lot of the internal symbols are no longer exported.  Attached is the output of:


 abidiff libpfm-4.7.0.orig/lib/libpfm.so.4.7.0 libpfm-4.7.0.hidden/lib/libpfm.so.4.7.0 > abidiff.log


eu-size shows the reduction in size:

$ eu-size libpfm-4.7.0.orig/lib/libpfm.so.4.7.0 libpfm-4.7.0.hidden/lib/libpfm.so.4.7.0 
              text               data                bss                dec            hex filename
           1120871             673600               6208            1800679         1b79e7 libpfm-4.7.0.orig/lib/libpfm.so.4.7.0
           1106646             673368               6208            1786222         1b416e libpfm-4.7.0.hidden/lib/libpfm.so.4.7.0

"eu-readelf -l" also shows the reductions:

$ eu-readelf -l libpfm-4.7.0.orig/lib/libpfm.so.4.7.0 libpfm-4.7.0.hidden/lib/libpfm.so.4.7.0 

libpfm-4.7.0.orig/lib/libpfm.so.4.7.0:

Program Headers:
  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
  LOAD           0x000000 0x0000000000000000 0x0000000000000000 0x111c4c 0x111c4c R E 0x200000
  LOAD           0x112570 0x0000000000312570 0x0000000000312570 0x0a4768 0x0a5fb0 RW  0x200000
  DYNAMIC        0x1a5da0 0x00000000003a5da0 0x00000000003a5da0 0x0001d0 0x0001d0 RW  0x8
  NOTE           0x0001c8 0x00000000000001c8 0x00000000000001c8 0x000024 0x000024 R   0x4
  GNU_EH_FRAME   0x10f614 0x000000000010f614 0x000000000010f614 0x00078c 0x00078c R   0x4
  GNU_STACK      0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW  0x10
  GNU_RELRO      0x112570 0x0000000000312570 0x0000000000312570 0x093a90 0x093a90 R   0x1

 Section to Segment mapping:
  Segment Sections...
   00      [RO: .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .text .fini .rodata .eh_frame_hdr .eh_frame]
   01      [RELRO: .init_array .fini_array .jcr .data.rel.ro .dynamic .got] .got.plt .data .bss
   02      [RELRO: .dynamic]
   03      [RO: .note.gnu.build-id]
   04      [RO: .eh_frame_hdr]
   05     
   06      [RELRO: .init_array .fini_array .jcr .data.rel.ro .dynamic .got]

libpfm-4.7.0.hidden/lib/libpfm.so.4.7.0:

Program Headers:
  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
  LOAD           0x000000 0x0000000000000000 0x0000000000000000 0x10e4cc 0x10e4cc R E 0x200000
  LOAD           0x10e5c8 0x000000000030e5c8 0x000000000030e5c8 0x0a4670 0x0a5eb8 RW  0x200000
  DYNAMIC        0x1a1de0 0x00000000003a1de0 0x00000000003a1de0 0x0001d0 0x0001d0 RW  0x8
  NOTE           0x0001c8 0x00000000000001c8 0x00000000000001c8 0x000024 0x000024 R   0x4
  GNU_EH_FRAME   0x10be94 0x000000000010be94 0x000000000010be94 0x00078c 0x00078c R   0x4
  GNU_STACK      0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW  0x10
  GNU_RELRO      0x10e5c8 0x000000000030e5c8 0x000000000030e5c8 0x093a38 0x093a38 R   0x1

 Section to Segment mapping:
  Segment Sections...
   00      [RO: .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .text .fini .rodata .eh_frame_hdr .eh_frame]
   01      [RELRO: .init_array .fini_array .jcr .data.rel.ro .dynamic .got] .got.plt .data .bss
   02      [RELRO: .dynamic]
   03      [RO: .note.gnu.build-id]
   04      [RO: .eh_frame_hdr]
   05     
   06      [RELRO: .init_array .fini_array .jcr .data.rel.ro .dynamic .got]


-Will