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Annotation of linux/include/sys/user.h, revision 1.1.1.1

1.1       root        1: #include <sys/ptrace.h>
                      2: /* Core file format: The core file is written in such a way that gdb
                      3:    can understand it and provide useful information to the user (under
                      4:    linux we use the 'trad-core' bfd).  There are quite a number of
                      5:    obstacles to being able to view the contents of the floating point
                      6:    registers, and until these are solved you will not be able to view the
                      7:    contents of them.  Actually, you can read in the core file and look at
                      8:    the contents of the user struct to find out what the floating point
                      9:    registers contain.
                     10:    The actual file contents are as follows:
                     11:    UPAGE: 1 page consisting of a user struct that tells gdb what is present
                     12:    in the file.  Directly after this is a copy of the task_struct, which
                     13:    is currently not used by gdb, but it may come in useful at some point.
                     14:    All of the registers are stored as part of the upage.  The upage should
                     15:    always be only one page.
                     16:    DATA: The data area is stored.  We use current->end_text to
                     17:    current->brk to pick up all of the user variables, plus any memory
                     18:    that may have been malloced.  No attempt is made to determine if a page
                     19:    is demand-zero or if a page is totally unused, we just cover the entire
                     20:    range.  All of the addresses are rounded in such a way that an integral
                     21:    number of pages is written.
                     22:    STACK: We need the stack information in order to get a meaningful
                     23:    backtrace.  We need to write the data from (esp) to
                     24:    current->start_stack, so we round each of these off in order to be able
                     25:    to write an integer number of pages.
                     26:    The minimum core file size is 3 pages, or 12288 bytes.
                     27: */
                     28: 
                     29: struct user_i387_struct {
                     30:        long    cwd;
                     31:        long    swd;
                     32:        long    twd;
                     33:        long    fip;
                     34:        long    fcs;
                     35:        long    foo;
                     36:        long    fos;
                     37:        long    st_space[20];   /* 8*10 bytes for each FP-reg = 80 bytes */
                     38: };
                     39: 
                     40: /* When the kernel dumps core, it starts by dumping the user struct -
                     41:    this will be used by gdb to figure out where the data and stack segments
                     42:    are within the file, and what virtual addresses to use. */
                     43: struct user{
                     44: /* We start with the registers, to mimic the way that "memory" is returned
                     45:    from the ptrace(3,...) function.  */
                     46:   struct pt_regs regs;         /* Where the registers are actually stored */
                     47: /* ptrace does not yet supply these.  Someday.... */
                     48:   int u_fpvalid;               /* True if math co-processor being used. */
                     49:                                 /* for this mess. Not yet used. */
                     50:   struct user_i387_struct i387;        /* Math Co-processor registers. */
                     51: /* The rest of this junk is to help gdb figure out what goes where */
                     52:   unsigned long int u_tsize;   /* Text segment size (pages). */
                     53:   unsigned long int u_dsize;   /* Data segment size (pages). */
                     54:   unsigned long int u_ssize;   /* Stack segment size (pages). */
                     55:   unsigned long start_code;     /* Starting virtual address of text. */
                     56:   unsigned long start_stack;   /* Starting virtual address of stack area.
                     57:                                   This is actually the bottom of the stack,
                     58:                                   the top of the stack is always found in the
                     59:                                   esp register.  */
                     60:   long int signal;                     /* Signal that caused the core dump. */
                     61:   char * u_comm;               /* User command that was responsible */
                     62:   struct pt_regs * u_ar0;      /* Used by gdb to help find the values for */
                     63:                                /* the registers. */
                     64:   struct user_i387_struct* u_fpstate;  /* Math Co-processor pointer. */
                     65: };
                     66: #define NBPG 4096
                     67: #define UPAGES 1
                     68: #define HOST_TEXT_START_ADDR (u.start_code)
                     69: #define HOST_STACK_END_ADDR (u.start_stack + u.u_ssize * NBPG)

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