6 /* Core file format: The core file is written in such a way that gdb
7 can understand it and provide useful information to the user (under
8 linux we use the 'trad-core' bfd). There are quite a number of
9 obstacles to being able to view the contents of the floating point
10 registers, and until these are solved you will not be able to view the
11 contents of them. Actually, you can read in the core file and look at
12 the contents of the user struct to find out what the floating point
14 The actual file contents are as follows:
15 UPAGE: 1 page consisting of a user struct that tells gdb what is present
16 in the file. Directly after this is a copy of the task_struct, which
17 is currently not used by gdb, but it may come in useful at some point.
18 All of the registers are stored as part of the upage. The upage should
19 always be only one page.
20 DATA: The data area is stored. We use current->end_text to
21 current->brk to pick up all of the user variables, plus any memory
22 that may have been malloced. No attempt is made to determine if a page
23 is demand-zero or if a page is totally unused, we just cover the entire
24 range. All of the addresses are rounded in such a way that an integral
25 number of pages is written.
26 STACK: We need the stack information in order to get a meaningful
27 backtrace. We need to write the data from (esp) to
28 current->start_stack, so we round each of these off in order to be able
29 to write an integer number of pages.
30 The minimum core file size is 3 pages, or 12288 bytes.
33 /* This is the old layout of "struct pt_regs" as of Linux 1.x, and
34 is still the layout used by user (the new pt_regs doesn't have
36 struct user_regs_struct
{
37 long er1
,er2
,er3
,er4
,er5
,er6
;
46 /* When the kernel dumps core, it starts by dumping the user struct -
47 this will be used by gdb to figure out where the data and stack segments
48 are within the file, and what virtual addresses to use. */
50 /* We start with the registers, to mimic the way that "memory" is returned
51 from the ptrace(3,...) function. */
52 struct user_regs_struct regs
; /* Where the registers are actually stored */
53 /* ptrace does not yet supply these. Someday.... */
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
63 long int signal
; /* Signal that caused the core dump. */
64 int reserved
; /* No longer used */
65 struct user_regs_struct
*u_ar0
;
66 /* Used by gdb to help find the values for */
68 unsigned long magic
; /* To uniquely identify a core file */
69 char u_comm
[32]; /* User command that was responsible */
71 #define NBPG PAGE_SIZE
73 #define HOST_TEXT_START_ADDR (u.start_code)
74 #define HOST_STACK_END_ADDR (u.start_stack + u.u_ssize * NBPG)
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