• Ajay Kaher's avatar
    perf symbol: correction while adjusting symbol · 6f520ce1
    Ajay Kaher authored
    perf doesn't provide proper symbol information for specially crafted
    .debug files.
    
    Sometimes .debug file may not have similar program header as runtime
    ELF file. For example if we generate .debug file using objcopy
    --only-keep-debug resulting file will not contain .text, .data and
    other runtime sections. That means corresponding program headers will
    have zero FileSiz and modified Offset.
    
    Example: program header of text section of libxxx.so:
    
    Type           Offset             VirtAddr           PhysAddr
                   FileSiz            MemSiz              Flags  Align
    LOAD        0x00000000003d3000 0x00000000003d3000 0x00000000003d3000
                0x000000000055ae80 0x000000000055ae80  R E    0x1000
    
    Same program header after executing:
    objcopy --only-keep-debug libxxx.so libxxx.so.debug
    
    LOAD        0x0000000000001000 0x00000000003d3000 0x00000000003d3000
                0x0000000000000000 0x000000000055ae80  R E    0x1000
    
    Offset and FileSiz have been changed.
    
    Following formula will not provide correct value, if program header
    taken from .debug file (syms_ss):
    
        sym.st_value -= phdr.p_vaddr - phdr.p_offset;
    
    Correct program header information is located inside runtime ELF
    file (runtime_ss).
    
    Fixes: 2d86612a ("perf symbol: Correct address for bss symbols")
    Signed-off-by: default avatarAjay Kaher <akaher@vmware.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Alexey Makhalov <amakhalov@vmware.com>
    Cc: Jiri Olsa <jolsa@kernel.org>
    Cc: Leo Yan <leo.yan@linaro.org>
    Cc: Mark Rutland <mark.rutland@arm.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Srivatsa S. Bhat <srivatsab@vmware.com>
    Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Cc: Vasavi Sirnapalli <vsirnapalli@vmware.com>
    Link: http://lore.kernel.org/lkml/1669198696-50547-1-git-send-email-akaher@vmware.comSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    6f520ce1
symbol-elf.c 57 KB