filehdr.5

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 5 代码 · 共 55 行

.TH filehdr 5 RISC
.SH Name
filehdr \- file header for RISC object files
.SH Syntax
.B "#include < filehdr.h>"
.SH Description
Every RISC object file begins with a 20-byte header.  The following C
struct declaration is used:
.EX 0
struct filehdr
{
   unsigned short  f_magic;     /* magic number */
   unsigned short  f_nscns;     /* number of sections */
   long            f_timdat;    /* time & date stamp */
   long            f_symptr;    /* file pointer to symbolic header */
   long            f_nsyms;     /* sizeof(symbolic header) */
   unsigned short  f_opthdr;    /* sizeof(optional header) */
   unsigned short  f_flags;     /* flags */
};
.EE
.PP
The byte offset into the file at which the symbolic header can be found is
.I f_symptr.
Its value can be used as the offset in
.MS fseek 3s
to position an I/O stream to the symbolic header.  The ULTRIX system optional
header is 56 bytes.  The valid magic numbers are given below:
.EX 0
#define MIPSEBMAGIC 0x0160 /* objects for big-endian machines */
#define MIPSELMAGIC 0x0162 /* objects for little-endian machines */
#define MIPSEBUMAGIC 0x0180 /* ucode objects for big-endian machines */
#define MIPSELUMAGIC 0x0182 /* ucode objects for little-endian machines */
.EE
RISC object files can be loaded and examined on machines differing from the
object's target byte sex.  
Therefore, for object file magic numbers, the byte-swapped 
values have define constants associated with them:
.EX 0
#define SMIPSEBMAGIC 0x6001
#define SMIPSELMAGIC 0x6201
.EE
The value in
.I f_timdat
is obtained from the
.MS time 2
system call.  Flag bits used in RISC objects are:
.EX 0
#define F_RELFLG 0000001  /* relocation entries stripped */
#define F_EXEC   0000002  /* file is executable */
#define F_LNNO   0000004  /* line numbers stripped */
#define F_LSYMS  0000010  /* local symbols stripped */
.EE
.SH See Also
time(2), fseek(3s), a.out(5)