arch/mips/oprofile/backtrace.c

   1 #include <linux/oprofile.h>
   2 #include <linux/sched.h>
   3 #include <linux/mm.h>
   4 #include <linux/uaccess.h>
   5 #include <asm/ptrace.h>
   6 #include <asm/stacktrace.h>
   7 #include <linux/stacktrace.h>
   8 #include <linux/kernel.h>
   9 #include <asm/sections.h>
  10 #include <asm/inst.h>
  11
  12 struct stackframe {
  13         unsigned long sp;
  14         unsigned long pc;
  15         unsigned long ra;
  16 };
  17
  18 static inline int get_mem(unsigned long addr, unsigned long *result)
  19 {
  20         unsigned long *address = (unsigned long *) addr;
  21         if (!access_ok(VERIFY_READ, addr, sizeof(unsigned long)))
  22                 return -1;
  23         if (__copy_from_user_inatomic(result, address, sizeof(unsigned long)))
  24                 return -3;
  25         return 0;
  26 }
  27
  28 /*
  29  * These two instruction helpers were taken from process.c
  30  */
  31 static inline int is_ra_save_ins(union mips_instruction *ip)
  32 {
  33         /* sw / sd $ra, offset($sp) */
  34         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op)
  35                 && ip->i_format.rs == 29 && ip->i_format.rt == 31;
  36 }
  37
  38 static inline int is_sp_move_ins(union mips_instruction *ip)
  39 {
  40         /* addiu/daddiu sp,sp,-imm */
  41         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
  42                 return 0;
  43         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
  44                 return 1;
  45         return 0;
  46 }
  47
  48 /*
  49  * Looks for specific instructions that mark the end of a function.
  50  * This usually means we ran into the code area of the previous function.
  51  */
  52 static inline int is_end_of_function_marker(union mips_instruction *ip)
  53 {
  54         /* jr ra */
  55         if (ip->r_format.func == jr_op && ip->r_format.rs == 31)
  56                 return 1;
  57         /* lui gp */
  58         if (ip->i_format.opcode == lui_op && ip->i_format.rt == 28)
  59                 return 1;
  60         return 0;
  61 }
  62
  63 /*
  64  * TODO for userspace stack unwinding:
  65  * - handle cases where the stack is adjusted inside a function
  66  *     (generally doesn't happen)
  67  * - find optimal value for max_instr_check
  68  * - try to find a better way to handle leaf functions
  69  */
  70
  71 static inline int unwind_user_frame(struct stackframe *old_frame,
  72                                     const unsigned int max_instr_check)
  73 {
  74         struct stackframe new_frame = *old_frame;
  75         off_t ra_offset = 0;
  76         size_t stack_size = 0;
  77         unsigned long addr;
  78
  79         if (old_frame->pc == 0 || old_frame->sp == 0 || old_frame->ra == 0)
  80                 return -9;
  81
  82         for (addr = new_frame.pc; (addr + max_instr_check > new_frame.pc)
  83                 && (!ra_offset || !stack_size); --addr) {
  84                 union mips_instruction ip;
  85
  86                 if (get_mem(addr, (unsigned long *) &ip))
  87                         return -11;
  88
  89                 if (is_sp_move_ins(&ip)) {
  90                         int stack_adjustment = ip.i_format.simmediate;
  91                         if (stack_adjustment > 0)
  92                                 /* This marks the end of the previous function,
  93                                    which means we overran. */
  94                                 break;
  95                         stack_size = (unsigned long) stack_adjustment;
  96                 } else if (is_ra_save_ins(&ip)) {
  97                         int ra_slot = ip.i_format.simmediate;
  98                         if (ra_slot < 0)
  99                                 /* This shouldn't happen. */
 100                                 break;
 101                         ra_offset = ra_slot;
 102                 } else if (is_end_of_function_marker(&ip))
 103                         break;
 104         }
 105
 106         if (!ra_offset || !stack_size)
 107                 goto done;
 108
 109         if (ra_offset) {
 110                 new_frame.ra = old_frame->sp + ra_offset;
 111                 if (get_mem(new_frame.ra, &(new_frame.ra)))
 112                         return -13;
 113         }
 114
 115         if (stack_size) {
 116                 new_frame.sp = old_frame->sp + stack_size;
 117                 if (get_mem(new_frame.sp, &(new_frame.sp)))
 118                         return -14;
 119         }
 120
 121         if (new_frame.sp > old_frame->sp)
 122                 return -2;
 123
 124 done:
 125         new_frame.pc = old_frame->ra;
 126         *old_frame = new_frame;
 127
 128         return 0;
 129 }
 130
 131 static inline void do_user_backtrace(unsigned long low_addr,
 132                                      struct stackframe *frame,
 133                                      unsigned int depth)
 134 {
 135         const unsigned int max_instr_check = 512;
 136         const unsigned long high_addr = low_addr + THREAD_SIZE;
 137
 138         while (depth-- && !unwind_user_frame(frame, max_instr_check)) {
 139                 oprofile_add_trace(frame->ra);
 140                 if (frame->sp < low_addr || frame->sp > high_addr)
 141                         break;
 142         }
 143 }
 144
 145 #ifndef CONFIG_KALLSYMS
 146 static inline void do_kernel_backtrace(unsigned long low_addr,
 147                                        struct stackframe *frame,
 148                                        unsigned int depth) { }
 149 #else
 150 static inline void do_kernel_backtrace(unsigned long low_addr,
 151                                        struct stackframe *frame,
 152                                        unsigned int depth)
 153 {
 154         while (depth-- && frame->pc) {
 155                 frame->pc = unwind_stack_by_address(low_addr,
 156                                                     &(frame->sp),
 157                                                     frame->pc,
 158                                                     &(frame->ra));
 159                 oprofile_add_trace(frame->ra);
 160         }
 161 }
 162 #endif
 163
 164 void notrace op_mips_backtrace(struct pt_regs *const regs, unsigned int depth)
 165 {
 166         struct stackframe frame = { .sp = regs->regs[29],
 167                                     .pc = regs->cp0_epc,
 168                                     .ra = regs->regs[31] };
 169         const int userspace = user_mode(regs);
 170         const unsigned long low_addr = ALIGN(frame.sp, THREAD_SIZE);
 171
 172         if (userspace)
 173                 do_user_backtrace(low_addr, &frame, depth);
 174         else
 175                 do_kernel_backtrace(low_addr, &frame, depth);
 176 }