App 的本质和 Mach-O 文件

struct proc {
    LIST_ENTRY(proc) p_list;                /* List of all processes. */

    void *          XNU_PTRAUTH_SIGNED_PTR("proc.task") task;       /* corresponding task (static)*/
    struct  proc *  XNU_PTRAUTH_SIGNED_PTR("proc.p_pptr") p_pptr;   /* Pointer to parent process.(LL) */
    pid_t           p_ppid;                 /* process's parent pid number */
    pid_t           p_original_ppid;        /* process's original parent pid number, doesn't change if reparented */
    pid_t           p_pgrpid;               /* process group id of the process (LL)*/
    uid_t           p_uid;
    gid_t           p_gid;
    uid_t           p_ruid;
    gid_t           p_rgid;
    uid_t           p_svuid;
    gid_t           p_svgid;
    uint64_t        p_uniqueid;             /* process unique ID - incremented on fork/spawn/vfork, remains same across exec. */
    uint64_t        p_puniqueid;            /* parent's unique ID - set on fork/spawn/vfork, doesn't change if reparented. */

    lck_mtx_t       p_mlock;                /* mutex lock for proc */
    pid_t           p_pid;                  /* Process identifier. (static)*/
    char            p_stat;                 /* S* process status. (PL)*/
    char            p_shutdownstate;
    char            p_kdebug;               /* P_KDEBUG eq (CC)*/
    char            p_btrace;               /* P_BTRACE eq (CC)*/
    /* 以下其他字段已省略 */
};

struct fat_header {
  uint32_t  magic;    /* FAT_MAGIC */
  uint32_t  nfat_arch;  /* number of structs that follow */
};
// Fat Binary 包含了多个 fat_arch 组成的 Mach-O 文件
struct fat_arch {
  cpu_type_t  cputype;  /* cpu specifier (int) */
  cpu_subtype_t  cpusubtype;  /* machine specifier (int) */
  uint32_t  offset;    /* file offset to this object file */
  uint32_t  size;    /* size of this object file */
  uint32_t  align;    /* alignment as a power of 2 */
};

/*
 * The 32-bit mach header appears at the very beginning of the object file for
 * 32-bit architectures.
 */
struct mach_header {
  uint32_t  magic;    /* mach magic number identifier */
  cpu_type_t  cputype;  /* cpu specifier */
  cpu_subtype_t  cpusubtype;  /* machine specifier */
  uint32_t  filetype;  /* type of file */
  uint32_t  ncmds;    /* number of load commands */
  uint32_t  sizeofcmds;  /* the size of all the load commands */
  uint32_t  flags;    /* flags */
};
/* Constant for the magic field of the mach_header (32-bit architectures) */
#define  MH_MAGIC  0xfeedface  /* the mach magic number */
#define MH_CIGAM  0xcefaedfe  /* NXSwapInt(MH_MAGIC) */
/*
 * The 64-bit mach header appears at the very beginning of object files for
 * 64-bit architectures.
 */
struct mach_header_64 {
  uint32_t  magic;    /* mach magic number identifier */
  cpu_type_t  cputype;  /* cpu specifier */
  cpu_subtype_t  cpusubtype;  /* machine specifier */
  uint32_t  filetype;  /* type of file */
  uint32_t  ncmds;    /* number of load commands */
  uint32_t  sizeofcmds;  /* the size of all the load commands */
  uint32_t  flags;    /* flags */
  uint32_t  reserved;  /* reserved */
};
/* Constant for the magic field of the mach_header_64 (64-bit architectures) */
#define MH_MAGIC_64 0xfeedfacf /* the 64-bit mach magic number */
#define MH_CIGAM_64 0xcffaedfe /* NXSwapInt(MH_MAGIC_64) */

struct load_command {
  uint32_t cmd;    /* type of load command */
  uint32_t cmdsize;  /* total size of command in bytes */
};

struct segment_command_64 { /* for 64-bit architectures */
  uint32_t  cmd;    /* LC_SEGMENT_64 */
  uint32_t  cmdsize;  /* includes sizeof section_64 structs */
  char    segname[16];  /* segment name */
  uint64_t  vmaddr;    /* memory address of this segment */
  uint64_t  vmsize;    /* memory size of this segment */
  uint64_t  fileoff;  /* file offset of this segment */
  uint64_t  filesize;  /* amount to map from the file */
  int32_t    maxprot;  /* maximum VM protection */
  int32_t    initprot;  /* initial VM protection */
  uint32_t  nsects;    /* number of sections in segment */
  uint32_t  flags;    /* flags */
};

struct section_64 { /* for 64-bit architectures */
  char    sectname[16];  /* name of this section */
  char    segname[16];  /* segment this section goes in */
  uint64_t  addr;    /* memory address of this section */
  uint64_t  size;    /* size in bytes of this section */
  uint32_t  offset;    /* file offset of this section */
  uint32_t  align;    /* section alignment (power of 2) */
  uint32_t  reloff;    /* file offset of relocation entries */
  uint32_t  nreloc;    /* number of relocation entries */
  uint32_t  flags;    /* flags (section type and attributes)*/
  uint32_t  reserved1;  /* reserved (for offset or index) */
  uint32_t  reserved2;  /* reserved (for count or sizeof) */
  uint32_t  reserved3;  /* reserved */
};