Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc
[linux-2.6.git] / 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 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) 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                 return -1;
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         new_frame.pc = old_frame->ra;
125         *old_frame = new_frame;
126
127         return 0;
128 }
129
130 static inline void do_user_backtrace(unsigned long low_addr,
131                                      struct stackframe *frame,
132                                      unsigned int depth)
133 {
134         const unsigned int max_instr_check = 512;
135         const unsigned long high_addr = low_addr + THREAD_SIZE;
136
137         while (depth-- && !unwind_user_frame(frame, max_instr_check)) {
138                 oprofile_add_trace(frame->ra);
139                 if (frame->sp < low_addr || frame->sp > high_addr)
140                         break;
141         }
142 }
143
144 #ifndef CONFIG_KALLSYMS
145 static inline void do_kernel_backtrace(unsigned long low_addr,
146                                        struct stackframe *frame,
147                                        unsigned int depth) { }
148 #else
149 static inline void do_kernel_backtrace(unsigned long low_addr,
150                                        struct stackframe *frame,
151                                        unsigned int depth)
152 {
153         while (depth-- && frame->pc) {
154                 frame->pc = unwind_stack_by_address(low_addr,
155                                                     &(frame->sp),
156                                                     frame->pc,
157                                                     &(frame->ra));
158                 oprofile_add_trace(frame->ra);
159         }
160 }
161 #endif
162
163 void notrace op_mips_backtrace(struct pt_regs *const regs, unsigned int depth)
164 {
165         struct stackframe frame = { .sp = regs->regs[29],
166                                     .pc = regs->cp0_epc,
167                                     .ra = regs->regs[31] };
168         const int userspace = user_mode(regs);
169         const unsigned long low_addr = ALIGN(frame.sp, THREAD_SIZE);
170
171         if (userspace)
172                 do_user_backtrace(low_addr, &frame, depth);
173         else
174                 do_kernel_backtrace(low_addr, &frame, depth);
175 }