root/include/linux/user.h

/* */

INCLUDED FROM

   1 #ifndef _LINUX_USER_H
   2 #define _LINUX_USER_H
   3 
   4 #include <linux/ptrace.h>
   5 /* Core file format: The core file is written in such a way that gdb
   6    can understand it and provide useful information to the user (under
   7    linux we use the 'trad-core' bfd).  There are quite a number of
   8    obstacles to being able to view the contents of the floating point
   9    registers, and until these are solved you will not be able to view the
  10    contents of them.  Actually, you can read in the core file and look at
  11    the contents of the user struct to find out what the floating point
  12    registers contain.
  13    The actual file contents are as follows:
  14    UPAGE: 1 page consisting of a user struct that tells gdb what is present
  15    in the file.  Directly after this is a copy of the task_struct, which
  16    is currently not used by gdb, but it may come in useful at some point.
  17    All of the registers are stored as part of the upage.  The upage should
  18    always be only one page.
  19    DATA: The data area is stored.  We use current->end_text to
  20    current->brk to pick up all of the user variables, plus any memory
  21    that may have been malloced.  No attempt is made to determine if a page
  22    is demand-zero or if a page is totally unused, we just cover the entire
  23    range.  All of the addresses are rounded in such a way that an integral
  24    number of pages is written.
  25    STACK: We need the stack information in order to get a meaningful
  26    backtrace.  We need to write the data from (esp) to
  27    current->start_stack, so we round each of these off in order to be able
  28    to write an integer number of pages.
  29    The minimum core file size is 3 pages, or 12288 bytes.
  30 */
  31 
  32 struct user_i387_struct {
  33         long    cwd;
  34         long    swd;
  35         long    twd;
  36         long    fip;
  37         long    fcs;
  38         long    foo;
  39         long    fos;
  40         long    st_space[20];   /* 8*10 bytes for each FP-reg = 80 bytes */
  41 };
  42 
  43 /* When the kernel dumps core, it starts by dumping the user struct -
  44    this will be used by gdb to figure out where the data and stack segments
  45    are within the file, and what virtual addresses to use. */
  46 struct user{
  47 /* We start with the registers, to mimic the way that "memory" is returned
  48    from the ptrace(3,...) function.  */
  49   struct pt_regs regs;          /* Where the registers are actually stored */
  50 /* ptrace does not yet supply these.  Someday.... */
  51   int u_fpvalid;                /* True if math co-processor being used. */
  52                                 /* for this mess. Not yet used. */
  53   struct user_i387_struct i387; /* Math Co-processor registers. */
  54 /* The rest of this junk is to help gdb figure out what goes where */
  55   unsigned long int u_tsize;    /* Text segment size (pages). */
  56   unsigned long int u_dsize;    /* Data segment size (pages). */
  57   unsigned long int u_ssize;    /* Stack segment size (pages). */
  58   unsigned long start_code;     /* Starting virtual address of text. */
  59   unsigned long start_stack;    /* Starting virtual address of stack area.
  60                                    This is actually the bottom of the stack,
  61                                    the top of the stack is always found in the
  62                                    esp register.  */
  63   long int signal;              /* Signal that caused the core dump. */
  64   char * u_comm;                /* User command that was responsible */
  65   struct pt_regs * u_ar0;       /* Used by gdb to help find the values for */
  66                                 /* the registers. */
  67   struct user_i387_struct* u_fpstate;   /* Math Co-processor pointer. */
  68   unsigned long magic;          /* To uniquely identify a core file */
  69 };
  70 #define NBPG 4096
  71 #define UPAGES 1
  72 #define HOST_TEXT_START_ADDR (u.start_code)
  73 #define HOST_STACK_END_ADDR (u.start_stack + u.u_ssize * NBPG)
  74 
  75 #endif

/* */