• Jiri Olsa's avatar
    tools/resolve_btfids: Fix sections with wrong alignment · 51f6463a
    Jiri Olsa authored
    The data of compressed section should be aligned to 4
    (for 32bit) or 8 (for 64 bit) bytes.
    
    The binutils ld sets sh_addralign to 1, which makes libelf
    fail with misaligned section error during the update as
    reported by Jesper:
    
       FAILED elf_update(WRITE): invalid section alignment
    
    While waiting for ld fix, we can fix compressed sections
    sh_addralign value manually.
    
    Adding warning in -vv mode when the fix is triggered:
    
      $ ./tools/bpf/resolve_btfids/resolve_btfids -vv vmlinux
      ...
      section(36) .comment, size 44, link 0, flags 30, type=1
      section(37) .debug_aranges, size 45684, link 0, flags 800, type=1
       - fixing wrong alignment sh_addralign 16, expected 8
      section(38) .debug_info, size 129104957, link 0, flags 800, type=1
       - fixing wrong alignment sh_addralign 1, expected 8
      section(39) .debug_abbrev, size 1152583, link 0, flags 800, type=1
       - fixing wrong alignment sh_addralign 1, expected 8
      section(40) .debug_line, size 7374522, link 0, flags 800, type=1
       - fixing wrong alignment sh_addralign 1, expected 8
      section(41) .debug_frame, size 702463, link 0, flags 800, type=1
      section(42) .debug_str, size 1017571, link 0, flags 830, type=1
       - fixing wrong alignment sh_addralign 1, expected 8
      section(43) .debug_loc, size 3019453, link 0, flags 800, type=1
       - fixing wrong alignment sh_addralign 1, expected 8
      section(44) .debug_ranges, size 1744583, link 0, flags 800, type=1
       - fixing wrong alignment sh_addralign 16, expected 8
      section(45) .symtab, size 2955888, link 46, flags 0, type=2
      section(46) .strtab, size 2613072, link 0, flags 0, type=3
      ...
      update ok for vmlinux
    
    Another workaround is to disable compressed debug info data
    CONFIG_DEBUG_INFO_COMPRESSED kernel option.
    
    Fixes: fbbb68de ("bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object")
    Reported-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
    Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
    Acked-by: default avatarYonghong Song <yhs@fb.com>
    Cc: Mark Wielaard <mjw@redhat.com>
    Cc: Nick Clifton <nickc@redhat.com>
    Link: https://lore.kernel.org/bpf/20200819092342.259004-1-jolsa@kernel.org
    51f6463a
main.c 14.6 KB