• Athira Rajeev's avatar
    tools/perf: Add text_end to "struct dso" to save .text section size · 26a5262d
    Athira Rajeev authored
    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: default avatarDisha Goel <disgoel@linux.ibm.com>
    Signed-off-by: default avatarAthira Rajeev <atrajeev@linux.vnet.ibm.com>
    Reviewed-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
    Reviewed-by: default avatarKajol Jain <kjain@linux.ibm.com>
    Acked-by: default avatarNamhyung Kim <namhyung@kernel.org>
    Cc: maddy@linux.ibm.com
    Cc: disgoel@linux.vnet.ibm.com
    Cc: linuxppc-dev@lists.ozlabs.org
    Link: https://lore.kernel.org/r/20230928075213.84392-1-atrajeev@linux.vnet.ibm.comSigned-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
    26a5262d
symbol-elf.c 66.1 KB