kernel/arch/xtensa/oprofile/backtrace.c

   1 /**
   2  * @file backtrace.c
   3  *
   4  * @remark Copyright 2008 Tensilica Inc.
   5  * @remark Read the file COPYING
   6  *
   7  */
   8
   9 #include <linux/oprofile.h>
  10 #include <linux/sched.h>
  11 #include <linux/mm.h>
  12 #include <asm/ptrace.h>
  13 #include <asm/uaccess.h>
  14 #include <asm/traps.h>
  15
  16 /* Address of common_exception_return, used to check the
  17  * transition from kernel to user space.
  18  */
  19 extern int common_exception_return;
  20
  21 /* A struct that maps to the part of the frame containing the a0 and
  22  * a1 registers.
  23  */
  24 struct frame_start {
  25         unsigned long a0;
  26         unsigned long a1;
  27 };
  28
  29 static void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth)
  30 {
  31         unsigned long windowstart = regs->windowstart;
  32         unsigned long windowbase = regs->windowbase;
  33         unsigned long a0 = regs->areg[0];
  34         unsigned long a1 = regs->areg[1];
  35         unsigned long pc = MAKE_PC_FROM_RA(a0, regs->pc);
  36         int index;
  37
  38         /* First add the current PC to the trace. */
  39         if (pc != 0 && pc <= TASK_SIZE)
  40                 oprofile_add_trace(pc);
  41         else
  42                 return;
  43
  44         /* Two steps:
  45          *
  46          * 1. Look through the register window for the
  47          * previous PCs in the call trace.
  48          *
  49          * 2. Look on the stack.
  50          */
  51
  52         /* Step 1.  */
  53         /* Rotate WINDOWSTART to move the bit corresponding to
  54          * the current window to the bit #0.
  55          */
  56         windowstart = (windowstart << WSBITS | windowstart) >> windowbase;
  57
  58         /* Look for bits that are set, they correspond to
  59          * valid windows.
  60          */
  61         for (index = WSBITS - 1; (index > 0) && depth; depth--, index--)
  62                 if (windowstart & (1 << index)) {
  63                         /* Read a0 and a1 from the
  64                          * corresponding position in AREGs.
  65                          */
  66                         a0 = regs->areg[index * 4];
  67                         a1 = regs->areg[index * 4 + 1];
  68                         /* Get the PC from a0 and a1. */
  69                         pc = MAKE_PC_FROM_RA(a0, pc);
  70
  71                         /* Add the PC to the trace. */
  72                         if (pc != 0 && pc <= TASK_SIZE)
  73                                 oprofile_add_trace(pc);
  74                         else
  75                                 return;
  76                 }
  77
  78         /* Step 2. */
  79         /* We are done with the register window, we need to
  80          * look through the stack.
  81          */
  82         if (depth > 0) {
  83                 /* Start from the a1 register. */
  84                 /* a1 = regs->areg[1]; */
  85                 while (a0 != 0 && depth--) {
  86
  87                         struct frame_start frame_start;
  88                         /* Get the location for a1, a0 for the
  89                          * previous frame from the current a1.
  90                          */
  91                         unsigned long *psp = (unsigned long *)a1;
  92                         psp -= 4;
  93
  94                         /* Check if the region is OK to access. */
  95                         if (!access_ok(VERIFY_READ, psp, sizeof(frame_start)))
  96                                 return;
  97                         /* Copy a1, a0 from user space stack frame. */
  98                         if (__copy_from_user_inatomic(&frame_start, psp,
  99                                                 sizeof(frame_start)))
 100                                 return;
 101
 102                         a0 = frame_start.a0;
 103                         a1 = frame_start.a1;
 104                         pc = MAKE_PC_FROM_RA(a0, pc);
 105
 106                         if (pc != 0 && pc <= TASK_SIZE)
 107                                 oprofile_add_trace(pc);
 108                         else
 109                                 return;
 110                 }
 111         }
 112 }
 113
 114 static void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth)
 115 {
 116         unsigned long pc = regs->pc;
 117         unsigned long *psp;
 118         unsigned long sp_start, sp_end;
 119         unsigned long a0 = regs->areg[0];
 120         unsigned long a1 = regs->areg[1];
 121
 122         sp_start = a1 & ~(THREAD_SIZE-1);
 123         sp_end = sp_start + THREAD_SIZE;
 124
 125         /* Spill the register window to the stack first. */
 126         spill_registers();
 127
 128         /* Read the stack frames one by one and create the PC
 129          * from the a0 and a1 registers saved there.
 130          */
 131         while (a1 > sp_start && a1 < sp_end && depth--) {
 132                 pc = MAKE_PC_FROM_RA(a0, pc);
 133
 134                 /* Add the PC to the trace. */
 135                 oprofile_add_trace(pc);
 136                 if (pc == (unsigned long) &common_exception_return) {
 137                         regs = (struct pt_regs *)a1;
 138                         if (user_mode(regs)) {
 139                                 pc = regs->pc;
 140                                 if (pc != 0 && pc <= TASK_SIZE)
 141                                         oprofile_add_trace(pc);
 142                                 else
 143                                         return;
 144                                 return xtensa_backtrace_user(regs, depth);
 145                         }
 146                         a0 = regs->areg[0];
 147                         a1 = regs->areg[1];
 148                         continue;
 149                 }
 150
 151                 psp = (unsigned long *)a1;
 152
 153                 a0 = *(psp - 4);
 154                 a1 = *(psp - 3);
 155
 156                 if (a1 <= (unsigned long)psp)
 157                         return;
 158
 159         }
 160         return;
 161 }
 162
 163 void xtensa_backtrace(struct pt_regs * const regs, unsigned int depth)
 164 {
 165         if (user_mode(regs))
 166                 xtensa_backtrace_user(regs, depth);
 167         else
 168                 xtensa_backtrace_kernel(regs, depth);
 169 }