将ELF文件加载到内存中

我正在尝试将 elf 文件放入内存然后执行它，步骤如下：

1-要放入内存的文件

int main()
{
   printf("Hello world! \n");
   return 0;
}

2-编译它gcc -o hello hello.c -static

ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           ARM
  Version:                           0x1
  Entry point address:               0x8120
  Start of program headers:          52 (bytes into file)
  Start of section headers:          119864 (bytes into file)
  Flags:                             0x5000000, Version5 EABI
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         4
  Size of section headers:           40 (bytes)
  Number of section headers:         18
  Section header string table index: 17

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x000000 0x00008000 0x00008000 0x16828 0x16828 R E 0x1000
  LOAD           0x016840 0x0001f840 0x0001f840 0x00250 0x02660 RW  0x1000
  GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RWE 0
  EXIDX          0x015f40 0x0001df40 0x0001df40 0x008e8 0x008e8 R   0x4

3-我写了一个Loader（为ARM编译）

mmap2(0x8000, 92200, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x8000
mmap2(0x1f000, 65536, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x1f000

3.1-然后我将所有 elf 字节复制到分配中

3.2- 跳转到主函数

ldr r0, =0x008160
blx r0

.text:00008160 ; int __cdecl main(int argc, const char **argv, const char **envp)
.text:00008160                 EXPORT main
.text:00008160 main                                    ; DATA XREF: _start+8o
.text:00008160                                         ; .text:off_8150o
.text:00008160                 STMFD           SP!, {R11,LR}
.text:00008164                 ADD             R11, SP, #4
.text:00008168                 LDR             R3, =(aHelloWorld - 0x8174)
.text:0000816C                 ADD             R3, PC, R3 ; "Hello world! "
.text:00008170                 MOV             R0, R3
.text:00008174                 BLX             puts
.text:00008178                 MOV             R3, #0
.text:0000817C                 MOV             R0, R3
.text:00008180                 LDMFD           SP!, {R11,PC}
.text:00008180 ; End of function main

问题是，每次我到达 0x8174 行，然后跳入，在一些指令之后，我总是在随机位置有一个 SIGSEGV，更多时候崩溃指令是 =>0x9cc0: ldr r0, [r0, #4] with r0=0x70a34

00008000-0002f000 rwxp 00000000 00:00 0 
80000000-80001000 r-xp 00000000 b3:18 129754     /data/local/tmp/main
80001000-8001a000 rwxp 00001000 b3:18 129754     /data/local/tmp/main
becdf000-bed00000 rwxp 00000000 00:00 0 
ffff0000-ffff1000 r-xp 00000000 00:00 0          [vectors]

这些是崩溃后的更多说明：

.text:00009CB4 loc_9CB4                                ; CODE XREF: pthread_mutex_lock_impl+18j
.text:00009CB4                 MOV             R3, #0xFFFF0FE0
.text:00009CBC                 BLX             R3
.text:00009CC0                 LDR             R0, [R0,#4]

在这个位置0x9CB4， 的价值r0 is 0x1f96c（没关系），在 blx 之后的值r0 is 0x70a34

(gdb) x/10x 0xffff0fe0
0xffff0fe0: 0xee1d0f70  0xe12fff1e  0xee1d0f70  0x00000000
0xffff0ff0: 0x00000000  0x00000000  0x00000000  0x00000005
0xffff1000: Cannot access memory at address 0xffff1000

Thanks!

我正在尝试将 elf 文件放入内存然后执行它，

对于完全静态链接的可执行文件，您的步骤将有效（除非您需要跳转到_start== 入口点0x8120, not main).

然后我将所有 elf 字节复制到分配中

另一个可能的问题是没有注意.p_offset. Your memcpyies 应该看起来像这样：

unsigned char buf1[0x16828];  // read 0x16828 bytes from start of file
memcpy(0x8000, buf1, 0x16828);

unsigned char buf2[0x250];  // read 0x250 bytes from offset 0x016840 into the file
memcpy(0x0001f840, buf2, 0x250);