I try to reduce the binary size by objcopy with --remove-section option. After the section is removed, it remains some empty space at the original position of deleted section. Is there any way to adjust the section's offset to avoid these empty space?
For emxaple, I removed .eh_frame_hdr section, and there are 0x03c empty space starting from 0x0764 in the stripped binary.
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)
After strip:
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)
Linking is a lossy process. A relocation in .o may be resolved in the linked image. objcopy does not know whether the hidden references. Therefore, it just tries to be extremely conservative: not alter addresses after --remove-section.
If you want to avoid .eh_frame_hdr and .eh_frame, the best is to use -fno-exceptions -fno-asynchronous-unwind-tables.