• Athira Rajeev's avatar
    tools/perf/tests: Fix object code reading to skip address that falls out of text section · 8f5b62a1
    Athira Rajeev authored
    The testcase "Object code reading" fails in somecases
    for "fs_something" sub test as below:
    
        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
    
    This can alo be reproduced when running perf record with
    workload that exercises fs_something() code. In the test
    setup, this is exercising xfs code since root is xfs.
    
        # perf record ./a.out
        # perf report -v |grep "xfs.ko"
          0.76% a.out /lib/modules/6.5.0-rc3+/kernel/fs/xfs/xfs.ko  0xc008000007de5efc B [k] xlog_cil_commit
          0.74% a.out  /lib/modules/6.5.0-rc3+/kernel/fs/xfs/xfs.ko  0xc008000007d5ae18 B [k] xfs_btree_key_offset
          0.74% a.out  /lib/modules/6.5.0-rc3+/kernel/fs/xfs/xfs.ko  0xc008000007e11fd4 B [k] 0x0000000000112074
    
    Here addr "0xc008000007e11fd4" is not resolved. since this is a
    kernel module, its offset is from the DSO. Xfs module is loaded
    at 0xc008000007d00000
    
       # cat /proc/modules | grep xfs
        xfs 2228224 3 - Live 0xc008000007d00000
    
    And size is 0x220000. So its loaded between  0xc008000007d00000
    and 0xc008000007f20000. From objdump, text section is:
        text 0010f7bc  0000000000000000 0000000000000000 000000a0 2**4
    
    Hence perf captured ip maps to 0x112074 which is:
    ( ip - start of module ) + a0
    
    This offset 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 address this issue in "object code reading", skip the sample if
    address falls out of text section and is within the module end.
    Use the "text_end" member of "struct dso" to do this check.
    
    To address this issue in "perf report", exploring an option of
    having stubs range as part of the /proc/kallsyms, so that perf
    report can resolve addresses in stubs range
    
    However this patch uses text_end to skip the stub range for
    Object code reading testcase.
    Reported-by: default avatarDisha Goel <disgoel@linux.ibm.com>
    Signed-off-by: default avatarAthira Rajeev <atrajeev@linux.vnet.ibm.com>
    Tested-by: Disha Goel<disgoel@linux.ibm.com>
    Reviewed-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
    Reviewed-by: default avatarKajol Jain <kjain@linux.ibm.com>
    Cc: maddy@linux.ibm.com
    Cc: disgoel@linux.vnet.ibm.com
    Cc: linuxppc-dev@lists.ozlabs.org
    Link: https://lore.kernel.org/r/20230928075213.84392-3-atrajeev@linux.vnet.ibm.comSigned-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
    8f5b62a1
code-reading.c 16.2 KB