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