[PATCH V5 1/3] tools/perf: Add text_end to "struct dso" to save .text section size

[Namhyung Kim]

On Mon, Oct 2, 2023 at 11:47 PM Athira Rajeev
<atrajeev at linux.vnet.ibm.com> wrote:
>
>
>
> > On 03-Oct-2023, at 9:58 AM, Namhyung Kim <namhyung at kernel.org> wrote:
> >
> > Hello,
> >
> > On Thu, Sep 28, 2023 at 12:52 AM Athira Rajeev
> > <atrajeev at linux.vnet.ibm.com> wrote:
> >>
> >> Update "struct dso" to include new member "text_end".
> >> This new field will represent the offset for end of text
> >> section for a dso. For elf, this value is derived as:
> >> sh_size (Size of section in byes) + sh_offset (Section file
> >> offst) of the elf header for text.
> >>
> >> For bfd, this value is derived as:
> >> 1. For PE file,
> >> section->size + ( section->vma - dso->text_offset)
> >> 2. Other cases:
> >> section->filepos (file position) + section->size (size of
> >> section)
> >>
> >> To resolve the address from a sample, perf looks at the
> >> DSO maps. In case of address from a kernel module, there
> >> were some address found to be not resolved. This was
> >> observed while running perf test for "Object code reading".
> >> Though the ip falls beteen the start address of the loaded
> >> module (perf map->start ) and end address ( perf map->end),
> >> it was unresolved.
> >>
> >> Example:
> >>
> >>    Reading object code for memory address: 0xc008000007f0142c
> >>    File is: /lib/modules/6.5.0-rc3+/kernel/fs/xfs/xfs.ko
> >>    On file address is: 0x1114cc
> >>    Objdump command is: objdump -z -d --start-address=0x11142c --stop-address=0x1114ac /lib/modules/6.5.0-rc3+/kernel/fs/xfs/xfs.ko
> >>    objdump read too few bytes: 128
> >>    test child finished with -1
> >>
> >> Here, module is loaded at:
> >>    # cat /proc/modules | grep xfs
> >>    xfs 2228224 3 - Live 0xc008000007d00000
> >>
> >> From objdump for xfs module, text section is:
> >>    text 0010f7bc  0000000000000000 0000000000000000 000000a0 2**4
> >>
> >> Here the offset for 0xc008000007f0142c ie  0x112074 falls out
> >> .text section which is up to 0x10f7bc.
> >>
> >> In this case for module, the address 0xc008000007e11fd4 is pointing
> >> to stub instructions. This address range represents the module stubs
> >> which is allocated on module load and hence is not part of DSO offset.
> >>
> >> To identify such  address, which falls out of text
> >> section and within module end, added the new field "text_end" to
> >> "struct dso".
> >>
> >> Reported-by: Disha Goel <disgoel at linux.ibm.com>
> >> Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
> >> Reviewed-by: Adrian Hunter <adrian.hunter at intel.com>
> >> Reviewed-by: Kajol Jain <kjain at linux.ibm.com>
> >
> > For the series,
> > Acked-by: Namhyung Kim <namhyung at kernel.org>
> >
> > Thanks,
> > Namhyung
>
> Thanks for checking Namhyung,

Applied to perf-tools-next, thanks!