Linux文件命令：SYSV意味着什么？

Question

我正在挖掘两个传统的交叉编译的ARM Linux版本。没有比“使用VM映像构建源”等多文档文件命令输出之间的唯一区别是“（SYSV）”

# file Executable 
Executable: ELF 32-bit LSB executable, ARM, version 1 (SYSV) ... 

我应该能有什么存在的假设基础在字符串中是否存在SYSV？

Answer 1

如果你看到(SYSV)字符串，这意味着在ELF头的e_ident[EI_OSABI]字段设置为0。从ELF spec (PDF link)：

Table 5. Operating System and ABI Identifiers, e_ident[EI_OSABI] 
Name     Value Meaning 
ELFOSABI_SYSV   0  System V ABI 
ELFOSABI_HPUX   1  HP-UX operating system 
ELFOSABI_STANDALONE 255 Standalone (embedded) application 

我的本地机器的/usr/share/file/magic/elf文件具有更长的名单：

# Up to now only 0, 1 and 2 are defined; I've seen a file with 0x83, it seemed 
# like proper ELF, but extracting the string had bad results. 
>4  byte   <0x80 
>>8 string  >\0  (%s) 
>8 string  \0 
>>7 byte  0  (SYSV) 
>>7 byte  1  (HP-UX) 
>>7 byte  2  (NetBSD) 
>>7 byte  3  (GNU/Linux) 
>>7 byte  4  (GNU/Hurd) 
>>7 byte  5  (86Open) 
>>7 byte  6  (Solaris) 
>>7 byte  7  (Monterey) 
>>7 byte  8  (IRIX) 
>>7 byte  9  (FreeBSD) 
>>7 byte  10  (Tru64) 
>>7 byte  11  (Novell Modesto) 
>>7 byte  12  (OpenBSD) 
>8  string   \2 
>>7  byte   13    (OpenVMS) 
>>7 byte  97  (ARM) 
>>7 byte  255  (embedded) 

下面是ELF头和偏移以供参考（从this link）：

#define EI_NIDENT 16 

typedef struct { 
     unsigned char e_ident[EI_NIDENT]; 
     Elf32_Half  e_type; 
     Elf32_Half  e_machine; 
     Elf32_Word  e_version; 
     Elf32_Addr  e_entry; 
     Elf32_Off  e_phoff; 
     Elf32_Off  e_shoff; 
     Elf32_Word  e_flags; 
     Elf32_Half  e_ehsize; 
     Elf32_Half  e_phentsize; 
     Elf32_Half  e_phnum; 
     Elf32_Half  e_shentsize; 
     Elf32_Half  e_shnum; 
     Elf32_Half  e_shstrndx; 
} Elf32_Ehdr; 


Figure 4-4: e_ident[] Identification Indexes 
Name  Value Purpose 
EI_MAG0  0  File identification 
EI_MAG1  1  File identification 
EI_MAG2  2  File identification 
EI_MAG3  3  File identification 
EI_CLASS  4  File class 
EI_DATA  5  Data encoding 
EI_VERSION 6  File version 
EI_OSABI  7  Operating system/ABI identification 
EI_ABIVERSION 8  ABI version 
EI_PAD  9  Start of padding bytes 
EI_NIDENT  16 Size of e_ident[]