[dtrace-discuss] What are .dynstr dtrace strings and why they change?

[Alexander Kolbasov]

Ali Bahrami <Ali.Bahrami at Sun.COM> wrote:

    Ali>  I'm betting that these are local symbols referenced by the .SUNW_ldynsym
    Ali> section, which is an allocable section, and therefore uses the
    Ali> dynstr:

Are these randomly generated during each build or they are
deterministic? Does it mean that wsdiff will always pick these up as a
change in libc?

- Akolb

    Ali> 	ali at rtld% elfdump -sN.SUNW_ldynsym /lib/libc.so | grep dtrace
    Ali> 	      [12]  0x000a7202 0x0000038f  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	      [66]  0x000a6360 0x00000260  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [134]  0x000a7a30 0x0000024d  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [349]  0x000a6a50 0x00000139  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [368]  0x000a6b90 0x00000111  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [473]  0x000a5e40 0x000001ed  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [601]  0x000a6ff0 0x00000073  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [655]  0x000a6646 0x0000026a  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [684]  0x000a76d0 0x00000172  FUNC LOCL  H    0 .text          $dtrace9391.
    Ali> 	     [762]  0x00000000 0x00000000  FILE LOCL  D    0 ABS            dtrace_data.

    Ali> .SUNW_ldynsym lets us report names for static functions instead of hex addresses
    Ali> when looking at stripped objects. For example, 'pstack' uses this, via libproc.
    Ali> For more about this:

    Ali>     PSARC 2006/526 SHT_SUNW_LDYNSYM - default local symbol addition
    Ali>     4934427 runtime linker should load up static symbol names visible to dladdr()



    >> 
    >> Once the following bug is putback, it will be possible for DTrace to mark
    >> these temporary symbols so that they don't show up in the final binary at
    >> all:
    >> 
    >> 6602451 new symbol visibilities required: EXPORTED, SINGLETON and ELIMINATE
    >> 

    Ali> I believe Rod filed the RTI for this today, so we're getting close.

    Ali> - Ali