ELF program/section segment解析

在linux remoteproc驱动中elf解析函数实现分析文章中介绍了在linux remoteproc驱动中对elf文件各个不同类型header parse的函数以及对应的定义。
在该文中则重点解释program segment的含义以及对应数据处理。

1 elf program segment

1.1 elf program header

/* These constants define the permissions on sections in the programheader, p_flags. */
#define PF_R            0x4
#define PF_W            0x2
#define PF_X            0x1typedef struct elf32_phdr{Elf32_Word    p_type;Elf32_Off     p_offset;Elf32_Addr    p_vaddr;Elf32_Addr    p_paddr;Elf32_Word    p_filesz;Elf32_Word    p_memsz;Elf32_Word    p_flags;Elf32_Word    p_align;
} Elf32_Phdr;typedef struct elf64_phdr {Elf64_Word p_type;Elf64_Word p_flags;Elf64_Off p_offset;           /* Segment file offset */Elf64_Addr p_vaddr;           /* Segment virtual address */Elf64_Addr p_paddr;           /* Segment physical address */Elf64_Xword p_filesz;         /* Segment size in file */Elf64_Xword p_memsz;          /* Segment size in memory */Elf64_Xword p_align;          /* Segment alignment, file & memory */
} Elf64_Phdr;

1.2 ELF32和ELF64示例

1.2.1 ELF32 program segment

以test.elf为例来分析

• Offset表示对应program segment数据在elf文件中的偏移地址
• PhysAddr表示要将该program segment的数据拷贝到的物理地址
• FileSiz表示当前program segment在elf文件中占的大小
• MemSiz表示当前program segment在对应bin文件中占的大小
• Flg表示当前program segment的属性
• Align表示当前program segment的对齐大小

$ readelf -lW test.elf Elf file type is EXEC (Executable file)Entry point 0x0There are 6 program headers, starting at offset 52Program Headers:Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg AlignEXIDX          0x09262c 0x1016262c 0x1016262c 0x00008 0x00008 R   0x4LOAD           0x010000 0x00000000 0x00000000 0x00440 0x00440 RW  0x10000LOAD           0x020000 0x10000000 0x10000000 0x00800 0x00800 R E 0x10000LOAD           0x030000 0x10100000 0x10100000 0x62638 0x62638 R E 0x10000LOAD           0x092740 0x10172740 0x10172740 0x0900c 0x5d158a0 RW  0x10000LOAD           0x000000 0xa0000000 0xa0000000 0x00000 0x04100 RW  0x10000Section to Segment mapping:Segment Sections...00     .ARM.exidx 01     .reset .rom 02     .cpu_vectors 03     .init .text .fini .rodata .ARM.exidx .eh_frame 04     shell_cmd .data .init_array .fini_array .init_array.00000 .datasafe .bss .stack .heap 05     .ram_mpu $

1.2.2 ELF64 program segment

以linux编译生成的vmlinux为例：其一共包含5个program segments；

• Offset表示对应program segment数据在elf文件中的偏移地址
• PhysAddr表示要将该program segment的数据拷贝到的物理地址
• FileSiz表示当前program segment在elf文件中占的大小
• MemSiz表示当前program segment在对应bin文件中占的大小
• Flg表示当前program segment的属性
• Align表示当前program segment的对齐大小

$ readelf -lW vmlinux Elf file type is DYN (Shared object file)
Entry point 0xffff800008000000
There are 5 program headers, starting at offset 64Program Headers:Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg AlignLOAD           0x010000 0xffff800008000000 0xffff800008000000 0xd2c000 0xd2c000 RWE 0x10000LOAD           0xd40000 0xffff800008d40000 0xffff800008d40000 0x0588dc 0x0588dc R E 0x10000LOAD           0xda0000 0xffff800008da0000 0xffff800008da0000 0x397808 0x43ea24 RW  0x10000NOTE           0xd3aa50 0xffff800008d2aa50 0xffff800008d2aa50 0x000054 0x000054 R   0x4GNU_STACK      0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW  0x10Section to Segment mapping:Segment Sections...00     .head.text .text .got.plt .rodata __ksymtab __ksymtab_gpl __ksymtab_strings __param __modver __ex_table .notes .hyp.rodata 01     .init.text .exit.text .altinstructions 02     .init.data .data..percpu .hyp.data..percpu .hyp.reloc .rela.dyn .data __bug_table .mmuoff.data.write .mmuoff.data.read .bss 03     .notes 04     
$

1.3 elf program segment数据流向图

2 elf section

2.1 eld section header

typedef struct elf32_shdr {Elf32_Word    sh_name;Elf32_Word    sh_type;Elf32_Word    sh_flags;Elf32_Addr    sh_addr;Elf32_Off     sh_offset;Elf32_Word    sh_size;Elf32_Word    sh_link;Elf32_Word    sh_info;Elf32_Word    sh_addralign;                                                                          Elf32_Word    sh_entsize;
} Elf32_Shdr;typedef struct elf64_shdr {Elf64_Word sh_name;           /* Section name, index in string tbl */Elf64_Word sh_type;           /* Type of section */Elf64_Xword sh_flags;         /* Miscellaneous section attributes */Elf64_Addr sh_addr;           /* Section virtual addr at execution */Elf64_Off sh_offset;          /* Section file offset */Elf64_Xword sh_size;          /* Size of section in bytes */Elf64_Word sh_link;           /* Index of another section */Elf64_Word sh_info;           /* Additional section information */Elf64_Xword sh_addralign;     /* Section alignment */Elf64_Xword sh_entsize;       /* Entry size if section holds table */
} Elf64_Shdr;

2.2 ELF32和ELF64示例

2.2.1 ELF32 section

以test.elf为例来分析

• Off表示对应section数据在elf文件中的偏移地址
• Addr表示要将该section的数据拷贝到的物理地址
• Size表示当前section的大小
• Flg表示当前program segment的属性
• Type表示当前section的类型
• Name表示当前section的名字
• Flg表示当前section的属性

$ readelf -SW test.elf 
There are 23 section headers, starting at offset 0x9b894:Section Headers:[Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al[ 0]                   NULL            00000000 000000 000000 00      0   0  0[ 1] .reset            PROGBITS        00000000 010000 000040 00   A  0   0  1[ 2] .rom              PROGBITS        00000100 010100 000340 00  WA  0   0  1[ 3] .ram_mpu          NOBITS          a0000000 0a0000 004100 00  WA  0   0  1[ 4] .cpu_vectors      PROGBITS        10000000 020000 000800 00  AX  0   0  4[ 5] .init             PROGBITS        10100000 030000 00000c 00  AX  0   0  4[ 6] .text             PROGBITS        10100010 030010 0555c0 00  AX  0   0 16[ 7] .fini             PROGBITS        101555d0 0855d0 00000c 00  AX  0   0  4[ 8] .rodata           PROGBITS        101555e0 0855e0 00d04c 00   A  0   0  8[ 9] .ARM.exidx        ARM_EXIDX       1016262c 09262c 000008 00  AL  6   0  4[10] .eh_frame         PROGBITS        10162634 092634 000004 00   A  0   0  4[11] shell_cmd         PROGBITS        10172740 092740 0000f0 00  WA  0   0 32[12] .data             PROGBITS        10172830 092830 004780 00  WA  0   0 16[13] .init_array       INIT_ARRAY      10176fb0 096fb0 000004 04  WA  0   0  4[14] .fini_array       FINI_ARRAY      10176fb4 096fb4 000004 04  WA  0   0  4[15] .init_array.00000 INIT_ARRAY      10176fb8 096fb8 000004 04  WA  0   0  4[16] .datasafe         PROGBITS        10176fbc 096fbc 004790 00  WA  0   0  1[17] .bss              NOBITS          1017b750 09b74c 07c888 00  WA  0   0 16[18] .stack            NOBITS          101f7fe0 09b74c 090000 00  WA  0   0  1[19] .heap             NOBITS          10287fe0 09b74c 5c00000 00  WA  0   0  1[20] .comment          PROGBITS        00000000 09b74c 000045 01  MS  0   0  1[21] .ARM.attributes   ARM_ATTRIBUTES  00000000 09b791 000035 00      0   0  1[22] .shstrtab         STRTAB          00000000 09b7c6 0000cb 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),y (purecode), p (processor specific)
$

2.2.2 ELF64 section

以linux的vmlinux为例来分析

• Off表示对应section数据在elf文件中的偏移地址
• Addr表示要将该section的数据拷贝到的物理地址
• Size表示当前section的大小
• Flg表示当前program segment的属性
• Type表示当前section的类型
• Name表示当前section的名字
• Flg表示当前section的属性

$ readelf -SW vmlinux 
There are 40 section headers, starting at offset 0xd59a938:Section Headers:[Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al[ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0[ 1] .head.text        PROGBITS        ffff800008000000 010000 000040 00  AX  0   0  4[ 2] .text             PROGBITS        ffff800008010000 020000 a63d60 08  AX  0   0 65536[ 3] .got.plt          PROGBITS        ffff800008a73d60 a83d60 000018 08  WA  0   0  8[ 4] .rodata           PROGBITS        ffff800008a80000 a90000 25af18 00  WA  0   0 4096[ 5] __ksymtab         PROGBITS        ffff800008cdaf18 ceaf18 00d374 00   A  0   0  4[ 6] __ksymtab_gpl     PROGBITS        ffff800008ce828c cf828c 00fe10 00   A  0   0  4[ 7] __ksymtab_strings PROGBITS        ffff800008cf809c d0809c 02e361 01 AMS  0   0  1[ 8] __param           PROGBITS        ffff800008d26400 d36400 0028a0 00   A  0   0  8[ 9] __modver          PROGBITS        ffff800008d28ca0 d38ca0 000318 00  WA  0   0  8[10] __ex_table        PROGBITS        ffff800008d28fb8 d38fb8 001a98 00   A  0   0  8[11] .notes            NOTE            ffff800008d2aa50 d3aa50 000054 00   A  0   0  4[12] .hyp.rodata       PROGBITS        ffff800008d2b000 d3b000 001000 00  WA  0   0  8[13] .init.text        PROGBITS        ffff800008d40000 d40000 03fcf4 00  AX  0   0  4[14] .exit.text        PROGBITS        ffff800008d7fcf4 d7fcf4 0031c8 00  AX  0   0  4[15] .altinstructions  PROGBITS        ffff800008d82ebc d82ebc 015a20 00   A  0   0  1[16] .init.data        PROGBITS        ffff800008da0000 da0000 013298 00  WA  0   0 256[17] .data..percpu     PROGBITS        ffff800008db4000 db4000 009b58 00  WA  0   0 64[18] .hyp.data..percpu PROGBITS        ffff800008dbe000 dbe000 000ed0 00  WA  0   0 16[19] .hyp.reloc        PROGBITS        ffff800008dbeed0 dbeed0 000060 00   A  0   0  4[20] .rela.dyn         RELA            ffff800008dbef30 dbef30 1fa280 18   A 37   0  8[21] .data             PROGBITS        ffff800008fc0000 fc0000 162b20 00  WA  0   0 4096[22] __bug_table       PROGBITS        ffff800009122b20 1122b20 013e18 00  WA  0   0  4[23] .mmuoff.data.write PROGBITS        ffff800009137000 1137000 000018 00  WA  0   0 2048[24] .mmuoff.data.read PROGBITS        ffff800009137800 1137800 000008 00  WA  0   0  8[25] .bss              NOBITS          ffff800009138000 1137808 0a6a24 00  WA  0   0 4096[26] .debug_aranges    PROGBITS        0000000000000000 1137810 01f600 00      0   0 16[27] .debug_info       PROGBITS        0000000000000000 1156e10 8f735c0 00      0   0  1[28] .debug_abbrev     PROGBITS        0000000000000000 a0ca3d0 449e7e 00      0   0  1[29] .debug_line       PROGBITS        0000000000000000 a51424e f522ac 00      0   0  1[30] .debug_frame      PROGBITS        0000000000000000 b466500 261300 00      0   0  8[31] .debug_str        PROGBITS        0000000000000000 b6c7800 29f3dc 01  MS  0   0  1[32] .debug_ranges     PROGBITS        0000000000000000 b966be0 000230 00      0   0 16[33] .debug_line_str   PROGBITS        0000000000000000 b966e10 010dda 01  MS  0   0  1[34] .debug_loclists   PROGBITS        0000000000000000 b977bea 152ec46 00      0   0  1[35] .debug_rnglists   PROGBITS        0000000000000000 cea6830 2e8174 00      0   0  1[36] .comment          PROGBITS        0000000000000000 d18e9a4 000045 01  MS  0   0  1[37] .symtab           SYMTAB          0000000000000000 d18e9f0 26caa8 18     38 85372  8[38] .strtab           STRTAB          0000000000000000 d3fb498 19f2f0 00      0   0  1[39] .shstrtab         STRTAB          0000000000000000 d59a788 0001ab 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),p (processor specific)
$

2.3 elf section数据流向图

对于elf section的数据在boot阶段的流向是按照从elf文件的offset处，按照size大小去拷贝数据到addr的内存处，当各个section拷贝完成之后即可以触发复位操作，启动对应的core。