ELF文件格式详解

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# 查看所有信息
readelf -a file_name

# 查看ELF Header
readelf -h file_name

# 查看程序段（segment） 等价于 readelf -l
readelf --segments file_name

# 查看符号表 --wide 选项用于避免输出被截断 也可以-W
readelf -s --wide file_name

# 查看节（section） 等价于 readelf -S  ,可以显示 ELF 文件的 节区头信息，查看 file_name 是否是 debug 模式编译文件
readelf --sections file_name

# 查看动态段信息,比如共享库依赖、动态符号、重定位信息、程序入口点等
readelf -d file_name

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ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x2a7d00
  Start of program headers:          64 (bytes into file)
  Start of section headers:          721384 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         11
  Size of section headers:           64 (bytes)
  Number of section headers:         41
  Section header string table index: 39

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readelf -s --wide file_name

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// step 1: 读取ELF Header
memcpy(&hdr, data, sizeof(hdr));

// step 2: 读取节名字符串表的位置
spot = hdr.e_shoff;  // section header偏移
strndx = hdr.e_shstrndx;  // 字符串表索引
stroff = spot + strndx * hdr.e_shentsize;  // 字符串表实际偏移
memcpy(&shdr, (char*)data + stroff, hdr.e_shentsize);

// step 3: 读取字符串表
strtable = (char*)malloc(shdr.sh_size);
memcpy(strtable, (char*)data + shdr.sh_offset, shdr.sh_size);

// step 4: 遍历所有section header
for (i = 0; i < hdr.e_shnum; ++i) {
    memcpy(&shdr, (char*)data + spot, hdr.e_shentsize);
    spot += hdr.e_shentsize;
    sh_name = &strtable[shdr.sh_name];
    printf("[%d] %s\n", i, sh_name);
}

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[0]
[1] .interp
[2] .note.gnu.property
[3] .note.gnu.build-id
[4] .note.ABI-tag
...
[21] .init_array
[22] .fini_array
[23] .dynamic
[24] .got
[25] .data
[26] .bss
[27] .comment
[28] .symtab
[29] .strtab
[30] .shstrtab

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Magic String
Number of Bundle Entries
Bundle Struct 1
Bundle Struct 2
...
Bundle Struct N
Code Object 1
Code Object 2
...
Code Object N

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93: 0000000000208d78     8 OBJECT    GLOBAL DEFAULT   21 _Z15matrixTransposePfS_i
95: 00000000000010e0   122 FUNC    GLOBAL DEFAULT   13 _Z30__device_stub__matrixTransposePfS_i

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Num:    Value          Size Type    Bind   Vis      Ndx Name
1: 0000000000001000   148 FUNC    GLOBAL PROTECTED    7 _Z15matrixTransposePfS_i
2: 0000000000000540    64 OBJECT    GLOBAL PROTECTED    6 _Z15matrixTransposePfS_i.kd

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.amdhsa_kernel _Z15matrixTransposePfS_i
    .amdhsa_group_segment_fixed_size 0
    .amdhsa_private_segment_fixed_size 0
    .amdhsa_kernarg_size 20          // 内核参数大小
    .amdhsa_user_sgpr_count 6        // 用户SGPR数量
    .amdhsa_user_sgpr_dispatch_ptr 1
    .amdhsa_user_sgpr_kernarg_segment_ptr 1
    .amdhsa_user_sgpr_flat_scratch_init 1
    .amdhsa_system_sgpr_workgroup_id_x 1
    .amdhsa_system_sgpr_workgroup_id_y 1
    ...
.end_amdhsa_kernel

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llvm-amdgpu-objdump --inputs=MatrixTranspose