arch/arm/lib/backtrace.S

   1 /*
   2  *  linux/arch/arm/lib/backtrace.S
   3  *
   4  *  Copyright (C) 1995, 1996 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * 27/03/03 Ian Molton Clean up CONFIG_CPU
  11  *
  12  */
  13 #include <linux/linkage.h>
  14 #include <asm/assembler.h>
  15                 .text
  16
  17 @ fp is 0 or stack frame
  18
  19 #define frame   r4
  20 #define sv_fp   r5
  21 #define sv_pc   r6
  22 #define mask    r7
  23 #define offset  r8
  24
  25 ENTRY(__backtrace)
  26                 mov     r1, #0x10
  27                 mov     r0, fp
  28
  29 ENTRY(c_backtrace)
  30
  31 #if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
  32                 mov     pc, lr
  33 ENDPROC(__backtrace)
  34 ENDPROC(c_backtrace)
  35 #else
  36                 stmfd   sp!, {r4 - r8, lr}      @ Save an extra register so we have a location...
  37                 movs    frame, r0               @ if frame pointer is zero
  38                 beq     no_frame                @ we have no stack frames
  39
  40                 tst     r1, #0x10               @ 26 or 32-bit mode?
  41  ARM(           moveq   mask, #0xfc000003       )
  42  THUMB(         moveq   mask, #0xfc000000       )
  43  THUMB(         orreq   mask, #0x03             )
  44                 movne   mask, #0                @ mask for 32-bit
  45
  46 1:              stmfd   sp!, {pc}               @ calculate offset of PC stored
  47                 ldr     r0, [sp], #4            @ by stmfd for this CPU
  48                 adr     r1, 1b
  49                 sub     offset, r0, r1
  50
  51 /*
  52  * Stack frame layout:
  53  *             optionally saved caller registers (r4 - r10)
  54  *             saved fp
  55  *             saved sp
  56  *             saved lr
  57  *    frame => saved pc
  58  *             optionally saved arguments (r0 - r3)
  59  * saved sp => <next word>
  60  *
  61  * Functions start with the following code sequence:
  62  *                  mov   ip, sp
  63  *                  stmfd sp!, {r0 - r3} (optional)
  64  * corrected pc =>  stmfd sp!, {..., fp, ip, lr, pc}
  65  */
  66 for_each_frame: tst     frame, mask             @ Check for address exceptions
  67                 bne     no_frame
  68
  69 1001:           ldr     sv_pc, [frame, #0]      @ get saved pc
  70 1002:           ldr     sv_fp, [frame, #-12]    @ get saved fp
  71
  72                 sub     sv_pc, sv_pc, offset    @ Correct PC for prefetching
  73                 bic     sv_pc, sv_pc, mask      @ mask PC/LR for the mode
  74
  75 1003:           ldr     r2, [sv_pc, #-4]        @ if stmfd sp!, {args} exists,
  76                 ldr     r3, .Ldsi+4             @ adjust saved 'pc' back one
  77                 teq     r3, r2, lsr #10         @ instruction
  78                 subne   r0, sv_pc, #4           @ allow for mov
  79                 subeq   r0, sv_pc, #8           @ allow for mov + stmia
  80
  81                 ldr     r1, [frame, #-4]        @ get saved lr
  82                 mov     r2, frame
  83                 bic     r1, r1, mask            @ mask PC/LR for the mode
  84                 bl      dump_backtrace_entry
  85
  86                 ldr     r1, [sv_pc, #-4]        @ if stmfd sp!, {args} exists,
  87                 ldr     r3, .Ldsi+4
  88                 teq     r3, r1, lsr #10
  89                 ldreq   r0, [frame, #-8]        @ get sp
  90                 subeq   r0, r0, #4              @ point at the last arg
  91                 bleq    .Ldumpstm               @ dump saved registers
  92
  93 1004:           ldr     r1, [sv_pc, #0]         @ if stmfd sp!, {..., fp, ip, lr, pc}
  94                 ldr     r3, .Ldsi               @ instruction exists,
  95                 teq     r3, r1, lsr #10
  96                 subeq   r0, frame, #16
  97                 bleq    .Ldumpstm               @ dump saved registers
  98
  99                 teq     sv_fp, #0               @ zero saved fp means
 100                 beq     no_frame                @ no further frames
 101
 102                 cmp     sv_fp, frame            @ next frame must be
 103                 mov     frame, sv_fp            @ above the current frame
 104                 bhi     for_each_frame
 105
 106 1006:           adr     r0, .Lbad
 107                 mov     r1, frame
 108                 bl      printk
 109 no_frame:       ldmfd   sp!, {r4 - r8, pc}
 110 ENDPROC(__backtrace)
 111 ENDPROC(c_backtrace)
 112
 113                 .pushsection __ex_table,"a"
 114                 .align  3
 115                 .long   1001b, 1006b
 116                 .long   1002b, 1006b
 117                 .long   1003b, 1006b
 118                 .long   1004b, 1006b
 119                 .popsection
 120
 121 #define instr r4
 122 #define reg   r5
 123 #define stack r6
 124
 125 .Ldumpstm:      stmfd   sp!, {instr, reg, stack, r7, lr}
 126                 mov     stack, r0
 127                 mov     instr, r1
 128                 mov     reg, #10
 129                 mov     r7, #0
 130 1:              mov     r3, #1
 131  ARM(           tst     instr, r3, lsl reg      )
 132  THUMB(         lsl     r3, reg                 )
 133  THUMB(         tst     instr, r3               )
 134                 beq     2f
 135                 add     r7, r7, #1
 136                 teq     r7, #6
 137                 moveq   r7, #1
 138                 moveq   r1, #'\n'
 139                 movne   r1, #' '
 140                 ldr     r3, [stack], #-4
 141                 mov     r2, reg
 142                 adr     r0, .Lfp
 143                 bl      printk
 144 2:              subs    reg, reg, #1
 145                 bpl     1b
 146                 teq     r7, #0
 147                 adrne   r0, .Lcr
 148                 blne    printk
 149                 ldmfd   sp!, {instr, reg, stack, r7, pc}
 150
 151 .Lfp:           .asciz  "%cr%d:%08x"
 152 .Lcr:           .asciz  "\n"
 153 .Lbad:          .asciz  "Backtrace aborted due to bad frame pointer <%p>\n"
 154                 .align
 155 .Ldsi:          .word   0xe92dd800 >> 10        @ stmfd sp!, {... fp, ip, lr, pc}
 156                 .word   0xe92d0000 >> 10        @ stmfd sp!, {}
 157
 158 #endif