執行檔瘦身

讀取 ELF(Executable and Linkable Format) 格式的執行檔 stripex1，顯示此執行檔包含原始的 75 個符號項目。

[dywang@dyH gcc]$ readelf -s stripex1

# readelf -s stripex1

Symbol table '.dynsym' contains 4 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND printf@GLIBC_2.2.5 (2)
     2: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND __gmon_start__
     3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@GLIBC_2.2.5 (2)

Symbol table '.symtab' contains 75 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 0000000000400200     0 SECTION LOCAL  DEFAULT    1 
     2: 000000000040021c     0 SECTION LOCAL  DEFAULT    2 
     3: 000000000040023c     0 SECTION LOCAL  DEFAULT    3 
     4: 0000000000400260     0 SECTION LOCAL  DEFAULT    4 
     5: 0000000000400280     0 SECTION LOCAL  DEFAULT    5 
     6: 00000000004002e0     0 SECTION LOCAL  DEFAULT    6 
     7: 0000000000400320     0 SECTION LOCAL  DEFAULT    7 
     8: 0000000000400328     0 SECTION LOCAL  DEFAULT    8 
     9: 0000000000400348     0 SECTION LOCAL  DEFAULT    9 
    10: 0000000000400360     0 SECTION LOCAL  DEFAULT   10 
    11: 0000000000400390     0 SECTION LOCAL  DEFAULT   11 
    12: 00000000004003a8     0 SECTION LOCAL  DEFAULT   12 
    13: 00000000004003e0     0 SECTION LOCAL  DEFAULT   13 
    14: 0000000000400608     0 SECTION LOCAL  DEFAULT   14 
    15: 0000000000400618     0 SECTION LOCAL  DEFAULT   15 
    16: 0000000000400634     0 SECTION LOCAL  DEFAULT   16 
    17: 0000000000400660     0 SECTION LOCAL  DEFAULT   17 
    18: 0000000000600700     0 SECTION LOCAL  DEFAULT   18 
    19: 0000000000600710     0 SECTION LOCAL  DEFAULT   19 
    20: 0000000000600720     0 SECTION LOCAL  DEFAULT   20 
    21: 0000000000600728     0 SECTION LOCAL  DEFAULT   21 
    22: 00000000006008b8     0 SECTION LOCAL  DEFAULT   22 
    23: 00000000006008c0     0 SECTION LOCAL  DEFAULT   23 
    24: 00000000006008e8     0 SECTION LOCAL  DEFAULT   24 
    25: 00000000006008f8     0 SECTION LOCAL  DEFAULT   25 
    26: 0000000000000000     0 SECTION LOCAL  DEFAULT   26 
    27: 0000000000000000     0 SECTION LOCAL  DEFAULT   27 
    28: 0000000000000000     0 SECTION LOCAL  DEFAULT   28 
    29: 0000000000000000     0 SECTION LOCAL  DEFAULT   29 
    30: 0000000000000000     0 SECTION LOCAL  DEFAULT   30 
    31: 0000000000000000     0 SECTION LOCAL  DEFAULT   31 
    32: 0000000000000000     0 SECTION LOCAL  DEFAULT   32 
    33: 0000000000000000     0 SECTION LOCAL  DEFAULT   33 
    34: 000000000040040c     0 FUNC    LOCAL  DEFAULT   13 call_gmon_start
    35: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS crtstuff.c
    36: 0000000000600700     0 OBJECT  LOCAL  DEFAULT   18 __CTOR_LIST__
    37: 0000000000600710     0 OBJECT  LOCAL  DEFAULT   19 __DTOR_LIST__
    38: 0000000000600720     0 OBJECT  LOCAL  DEFAULT   20 __JCR_LIST__
    39: 0000000000400430     0 FUNC    LOCAL  DEFAULT   13 __do_global_dtors_aux
    40: 00000000006008f8     1 OBJECT  LOCAL  DEFAULT   25 completed.6349
    41: 0000000000600900     8 OBJECT  LOCAL  DEFAULT   25 dtor_idx.6351
    42: 00000000004004a0     0 FUNC    LOCAL  DEFAULT   13 frame_dummy
    43: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS crtstuff.c
    44: 0000000000600708     0 OBJECT  LOCAL  DEFAULT   18 __CTOR_END__
    45: 00000000004006f8     0 OBJECT  LOCAL  DEFAULT   17 __FRAME_END__
    46: 0000000000600720     0 OBJECT  LOCAL  DEFAULT   20 __JCR_END__
    47: 00000000004005d0     0 FUNC    LOCAL  DEFAULT   13 __do_global_ctors_aux
    48: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS stripex1.c
    49: 00000000006008ec     4 OBJECT  LOCAL  DEFAULT   24 i
    50: 0000000000600908     4 OBJECT  LOCAL  DEFAULT   25 local.2052
    51: 00000000006008c0     0 OBJECT  LOCAL  DEFAULT   23 _GLOBAL_OFFSET_TABLE_
    52: 00000000006006fc     0 NOTYPE  LOCAL  DEFAULT   18 __init_array_end
    53: 00000000006006fc     0 NOTYPE  LOCAL  DEFAULT   18 __init_array_start
    54: 0000000000600728     0 OBJECT  LOCAL  DEFAULT   21 _DYNAMIC
    55: 00000000006008e8     0 NOTYPE  WEAK   DEFAULT   24 data_start
    56: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND printf@@GLIBC_2.2.5
    57: 0000000000400530     2 FUNC    GLOBAL DEFAULT   13 __libc_csu_fini
    58: 00000000004003e0     0 FUNC    GLOBAL DEFAULT   13 _start
    59: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND __gmon_start__
    60: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _Jv_RegisterClasses
    61: 0000000000400608     0 FUNC    GLOBAL DEFAULT   14 _fini
    62: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@@GLIBC_
    63: 00000000006008f0     4 OBJECT  GLOBAL DEFAULT   24 global
    64: 0000000000400618     4 OBJECT  GLOBAL DEFAULT   15 _IO_stdin_used
    65: 00000000006008e8     0 NOTYPE  GLOBAL DEFAULT   24 __data_start
    66: 0000000000400620     0 OBJECT  GLOBAL HIDDEN    15 __dso_handle
    67: 0000000000600718     0 OBJECT  GLOBAL HIDDEN    19 __DTOR_END__
    68: 0000000000400540   137 FUNC    GLOBAL DEFAULT   13 __libc_csu_init
    69: 00000000006008f4     0 NOTYPE  GLOBAL DEFAULT  ABS __bss_start
    70: 0000000000600910     0 NOTYPE  GLOBAL DEFAULT  ABS _end
    71: 00000000006008f4     0 NOTYPE  GLOBAL DEFAULT  ABS _edata
    72: 00000000004004c4    27 FUNC    GLOBAL DEFAULT   13 inc_func
    73: 00000000004004df    67 FUNC    GLOBAL DEFAULT   13 main
    74: 0000000000400390     0 FUNC    GLOBAL DEFAULT   11 _init

以 strip 工具修整執行檔
```
ng@dyH gcc]$ strip -s stripex1
```

修整後的執行檔，原始的符號項目已刪除。

[dywang@dyH gcc]$ readelf -s stripex1

Symbol table '.dynsym' contains 4 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND printf@GLIBC_2.2.5 (2)
     2: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND __gmon_start__
     3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@GLIBC_2.2.5 (2)

再看檔案大小，已從 8195 bytes 降至 4368 bytes。

[dywang@dyH gcc]$ ll stripex1*
-rwxrwxr-x. 1 dywang dywang 4368 Sep  1 06:41 stripex1
-rw-rw-r--. 1 dywang dywang  323 Aug 31 22:19 stripex1.c