可执行页面中加载的.rodata节

gcc -m32 1.c ):

int main(void)
{
    // EB is the opcode for jmp rel/8
    // FE is hex for -2
    // So this is essentially an infinite loop

    ((void(*)(void))"\xEB\xFE")();
}

objdump -d a.out ),您可以看到呼叫…地址中的任何内容 0x8048480 :

080483d6 <main>:
 ....
 80483e7:   b8 80 84 04 08          mov    $0x8048480,%eax
 80483ec:   ff d0                   call   *%eax
 ....

objdump -s -j .rodata a.out 给予:

Contents of section .rodata:
 8048478 03000000 01000200 ebfe00             ...........
                           ~~~~  

.rodata 部分所以我跑了 readelf --sections a.out

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .interp           PROGBITS        08048154 000154 000013 00   A  0   0  1
  [ 2] .note.ABI-tag     NOTE            08048168 000168 000020 00   A  0   0  4
  [ 3] .note.gnu.build-i NOTE            08048188 000188 000024 00   A  0   0  4
  [ 4] .gnu.hash         GNU_HASH        080481ac 0001ac 000020 04   A  5   0  4
  [ 5] .dynsym           DYNSYM          080481cc 0001cc 000040 10   A  6   1  4
  [ 6] .dynstr           STRTAB          0804820c 00020c 000045 00   A  0   0  1
  [ 7] .gnu.version      VERSYM          08048252 000252 000008 02   A  5   0  2
  [ 8] .gnu.version_r    VERNEED         0804825c 00025c 000020 00   A  6   1  4
  [ 9] .rel.dyn          REL             0804827c 00027c 000008 08   A  5   0  4
  [10] .rel.plt          REL             08048284 000284 000008 08  AI  5  23  4
  [11] .init             PROGBITS        0804828c 00028c 000023 00  AX  0   0  4
  [12] .plt              PROGBITS        080482b0 0002b0 000020 04  AX  0   0 16
  [13] .plt.got          PROGBITS        080482d0 0002d0 000008 00  AX  0   0  8
  [14] .text             PROGBITS        080482e0 0002e0 000182 00  AX  0   0 16
  [15] .fini             PROGBITS        08048464 000464 000014 00  AX  0   0  4
  [16] .rodata           PROGBITS        08048478 000478 00000b 00   A  0   0  4
  [17] .eh_frame_hdr     PROGBITS        08048484 000484 000034 00   A  0   0  4
  [18] .eh_frame         PROGBITS        080484b8 0004b8 0000e0 00   A  0   0  4
  [19] .init_array       INIT_ARRAY      08049f0c 000f0c 000004 04  WA  0   0  4
  [20] .fini_array       FINI_ARRAY      08049f10 000f10 000004 04  WA  0   0  4
  [21] .dynamic          DYNAMIC         08049f14 000f14 0000e8 08  WA  6   0  4
  [22] .got              PROGBITS        08049ffc 000ffc 000004 04  WA  0   0  4
  [23] .got.plt          PROGBITS        0804a000 001000 000010 04  WA  0   0  4
  [24] .data             PROGBITS        0804a010 001010 000008 00  WA  0   0  4
  [25] .bss              NOBITS          0804a018 001018 000004 00  WA  0   0  1
  [26] .comment          PROGBITS        00000000 001018 00001a 01  MS  0   0  1
  [27] .symtab           SYMTAB          00000000 001034 0003f0 10     28  45  4
  [28] .strtab           STRTAB          00000000 001424 0001bd 00      0   0  1
  [29] .shstrtab         STRTAB          00000000 0015e1 000105 00      0   0  1

因此,在ELF二进制文件中,该部分被标记为不可执行。但在内存中,页面是可执行的( cat /proc/xxx/maps

08048000-08049000 r-xp 00000000 08:01 663551 /home/andrew/Desktop/a.out
08049000-0804a000 r--p 00000000 08:01 663551 /home/andrew/Desktop/a.out
0804a000-0804b000 rw-p 00001000 08:01 663551 /home/andrew/Desktop/a.out

我最初的猜测是这些部分的间距太近(两者都有) AX 和 A 中的部分 08048000-08049000 范围),因此Linux被迫为页面提供ELF权限位的并集( AX | A == AX .罗达 节(通过添加许多长字符串),包含 节仍然是可执行的。为什么会这样?