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我尝试通过选项减小二进制objcopy大小--remove-section。删除节后,在删除节的原始位置会保留一些空白空间。有没有办法调整部分的偏移量以避免这些空白?

对于 emxaple,我删除了.eh_frame_hdr部分,并且在剥离的二进制文件中从 0x0764 开始有 0x03c 空白空间。

There are 35 section headers, starting at offset 0x1c78:

Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
  [ 1] .interp           PROGBITS        0000000000400238 000238 00001c 00   A  0   0  1
  [ 2] .note.ABI-tag     NOTE            0000000000400254 000254 000020 00   A  0   0  4
  [ 3] .note.gnu.build-id NOTE            0000000000400274 000274 000024 00   A  0   0  4
  [ 4] .gnu.hash         GNU_HASH        0000000000400298 000298 00001c 00   A  5   0  8
  [ 5] .dynsym           DYNSYM          00000000004002b8 0002b8 000078 18   A  6   1  8
  [ 6] .dynstr           STRTAB          0000000000400330 000330 000060 00   A  0   0  1
  [ 7] .gnu.version      VERSYM          0000000000400390 000390 00000a 02   A  5   0  2
  [ 8] .gnu.version_r    VERNEED         00000000004003a0 0003a0 000040 00   A  6   2  8
  [ 9] .rela.dyn         RELA            00000000004003e0 0003e0 000030 18   A  5   0  8
  [10] .rela.plt         RELA            0000000000400410 000410 000030 18  AI  5  27  8
  [11] .init             PROGBITS        0000000000400440 000440 000017 00  AX  0   0  4
  [12] .rela.init        RELA            0000000000000000 0018c0 000018 18   I 32  11  8
  [13] .plt              PROGBITS        0000000000400460 000460 000030 10  AX  0   0 16
  [14] .text             PROGBITS        0000000000400490 000490 0002c2 00  AX  0   0 16
  [15] .rela.text        RELA            0000000000000000 0018d8 0001c8 18   I 32  14  8
  [16] .fini             PROGBITS        0000000000400754 000754 000009 00  AX  0   0  4
  [17] .rodata           PROGBITS        0000000000400760 000760 000004 04  AM  0   0  4
  [18] .eh_frame_hdr     PROGBITS        0000000000400764 000764 00003c 00   A  0   0  4
  [19] .eh_frame         PROGBITS        00000000004007a0 0007a0 000100 00   A  0   0  8
  [20] .rela.eh_frame    RELA            0000000000000000 001aa0 000078 18   I 32  19  8
  [21] .init_array       INIT_ARRAY      0000000000600e00 000e00 000008 08  WA  0   0  8
  [22] .rela.init_array  RELA            0000000000000000 001b18 000018 18   I 32  21  8
  [23] .fini_array       FINI_ARRAY      0000000000600e08 000e08 000008 08  WA  0   0  8
  [24] .rela.fini_array  RELA            0000000000000000 001b30 000018 18   I 32  23  8
  [25] .dynamic          DYNAMIC         0000000000600e10 000e10 0001e0 10  WA  6   0  8
  [26] .got              PROGBITS        0000000000600ff0 000ff0 000010 08  WA  0   0  8
  [27] .got.plt          PROGBITS        0000000000601000 001000 000028 08  WA  0   0  8
  [28] .data             PROGBITS        0000000000601028 001028 000010 00  WA  0   0  8
  [29] .tm_clone_table   PROGBITS        0000000000601038 001038 000000 00  WA  0   0  8
  [30] .bss              NOBITS          0000000000601038 001038 000008 00  WA  0   0  1
  [31] .comment          PROGBITS        0000000000000000 001038 000029 01  MS  0   0  1
  [32] .symtab           SYMTAB          0000000000000000 001068 000630 18     33  45  8
  [33] .strtab           STRTAB          0000000000000000 001698 000227 00      0   0  1
  [34] .shstrtab         STRTAB          0000000000000000 001b48 00012c 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  l (large), p (processor specific)

剥离后:

There are 34 section headers, starting at offset 0x1c28:

Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
  [ 1] .interp           PROGBITS        0000000000400238 000238 00001c 00   A  0   0  1
  [ 2] .note.ABI-tag     NOTE            0000000000400254 000254 000020 00   A  0   0  4
  [ 3] .note.gnu.build-id NOTE            0000000000400274 000274 000024 00   A  0   0  4
  [ 4] .gnu.hash         GNU_HASH        0000000000400298 000298 00001c 00   A  5   0  8
  [ 5] .dynsym           DYNSYM          00000000004002b8 0002b8 000078 18   A  6   1  8
  [ 6] .dynstr           STRTAB          0000000000400330 000330 000060 00   A  0   0  1
  [ 7] .gnu.version      VERSYM          0000000000400390 000390 00000a 02   A  5   0  2
  [ 8] .gnu.version_r    VERNEED         00000000004003a0 0003a0 000040 00   A  6   2  8
  [ 9] .rela.dyn         RELA            00000000004003e0 0003e0 000030 18   A  5   0  8
  [10] .rela.plt         RELA            0000000000400410 000410 000030 18  AI  5  26  8
  [11] .init             PROGBITS        0000000000400440 000440 000017 00  AX  0   0  4
  [12] .rela.init        RELA            0000000000000000 001880 000018 18   I 31  11  8
  [13] .plt              PROGBITS        0000000000400460 000460 000030 10  AX  0   0 16
  [14] .text             PROGBITS        0000000000400490 000490 0002c2 00  AX  0   0 16
  [15] .rela.text        RELA            0000000000000000 001898 0001c8 18   I 31  14  8
  [16] .fini             PROGBITS        0000000000400754 000754 000009 00  AX  0   0  4
  [17] .rodata           PROGBITS        0000000000400760 000760 000004 04  AM  0   0  4
  [18] .eh_frame         PROGBITS        00000000004007a0 0007a0 000100 00   A  0   0  8
  [19] .rela.eh_frame    RELA            0000000000000000 001a60 000078 18   I 31  18  8
  [20] .init_array       INIT_ARRAY      0000000000600e00 000e00 000008 08  WA  0   0  8
  [21] .rela.init_array  RELA            0000000000000000 001ad8 000018 18   I 31  20  8
  [22] .fini_array       FINI_ARRAY      0000000000600e08 000e08 000008 08  WA  0   0  8
  [23] .rela.fini_array  RELA            0000000000000000 001af0 000018 18   I 31  22  8
  [24] .dynamic          DYNAMIC         0000000000600e10 000e10 0001e0 10  WA  6   0  8
  [25] .got              PROGBITS        0000000000600ff0 000ff0 000010 08  WA  0   0  8
  [26] .got.plt          PROGBITS        0000000000601000 001000 000028 08  WA  0   0  8
  [27] .data             PROGBITS        0000000000601028 001028 000010 00  WA  0   0  8
  [28] .tm_clone_table   PROGBITS        0000000000601038 001038 000000 00  WA  0   0  8
  [29] .bss              NOBITS          0000000000601038 001038 000008 00  WA  0   0  1
  [30] .comment          PROGBITS        0000000000000000 001038 000029 01  MS  0   0  1
  [31] .symtab           SYMTAB          0000000000000000 001068 000600 18     32  43  8
  [32] .strtab           STRTAB          0000000000000000 001668 000214 00      0   0  1
  [33] .shstrtab         STRTAB          0000000000000000 001b08 00011e 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  l (large), p (processor specific)

4

1 回答 1

1

链接是一个有损的过程。.o 中的重定位可以在链接图像中解决。objcopy 不知道是否隐藏了引用。因此,它只是尽量保守:不要在 --remove-section 之后更改地址。

如果要避免 .eh_frame_hdr 和 .eh_frame,最好使用 -fno-exceptions -fno-asynchronous-unwind-tables。

于 2021-11-08T02:42:05.173 回答