Merge tag 'docs-5.5a' of git://git.lwn.net/linux
[linux-2.6-microblaze.git] / arch / mips / oprofile / backtrace.c
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/oprofile.h>
3 #include <linux/sched.h>
4 #include <linux/mm.h>
5 #include <linux/uaccess.h>
6 #include <asm/ptrace.h>
7 #include <asm/stacktrace.h>
8 #include <linux/stacktrace.h>
9 #include <linux/kernel.h>
10 #include <asm/sections.h>
11 #include <asm/inst.h>
12
13 struct stackframe {
14         unsigned long sp;
15         unsigned long pc;
16         unsigned long ra;
17 };
18
19 static inline int get_mem(unsigned long addr, unsigned long *result)
20 {
21         unsigned long *address = (unsigned long *) addr;
22         if (!access_ok(address, sizeof(unsigned long)))
23                 return -1;
24         if (__copy_from_user_inatomic(result, address, sizeof(unsigned long)))
25                 return -3;
26         return 0;
27 }
28
29 /*
30  * These two instruction helpers were taken from process.c
31  */
32 static inline int is_ra_save_ins(union mips_instruction *ip)
33 {
34         /* sw / sd $ra, offset($sp) */
35         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op)
36                 && ip->i_format.rs == 29 && ip->i_format.rt == 31;
37 }
38
39 static inline int is_sp_move_ins(union mips_instruction *ip)
40 {
41         /* addiu/daddiu sp,sp,-imm */
42         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
43                 return 0;
44         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
45                 return 1;
46         return 0;
47 }
48
49 /*
50  * Looks for specific instructions that mark the end of a function.
51  * This usually means we ran into the code area of the previous function.
52  */
53 static inline int is_end_of_function_marker(union mips_instruction *ip)
54 {
55         /* jr ra */
56         if (ip->r_format.func == jr_op && ip->r_format.rs == 31)
57                 return 1;
58         /* lui gp */
59         if (ip->i_format.opcode == lui_op && ip->i_format.rt == 28)
60                 return 1;
61         return 0;
62 }
63
64 /*
65  * TODO for userspace stack unwinding:
66  * - handle cases where the stack is adjusted inside a function
67  *     (generally doesn't happen)
68  * - find optimal value for max_instr_check
69  * - try to find a better way to handle leaf functions
70  */
71
72 static inline int unwind_user_frame(struct stackframe *old_frame,
73                                     const unsigned int max_instr_check)
74 {
75         struct stackframe new_frame = *old_frame;
76         off_t ra_offset = 0;
77         size_t stack_size = 0;
78         unsigned long addr;
79
80         if (old_frame->pc == 0 || old_frame->sp == 0 || old_frame->ra == 0)
81                 return -9;
82
83         for (addr = new_frame.pc; (addr + max_instr_check > new_frame.pc)
84                 && (!ra_offset || !stack_size); --addr) {
85                 union mips_instruction ip;
86
87                 if (get_mem(addr, (unsigned long *) &ip))
88                         return -11;
89
90                 if (is_sp_move_ins(&ip)) {
91                         int stack_adjustment = ip.i_format.simmediate;
92                         if (stack_adjustment > 0)
93                                 /* This marks the end of the previous function,
94                                    which means we overran. */
95                                 break;
96                         stack_size = (unsigned long) stack_adjustment;
97                 } else if (is_ra_save_ins(&ip)) {
98                         int ra_slot = ip.i_format.simmediate;
99                         if (ra_slot < 0)
100                                 /* This shouldn't happen. */
101                                 break;
102                         ra_offset = ra_slot;
103                 } else if (is_end_of_function_marker(&ip))
104                         break;
105         }
106
107         if (!ra_offset || !stack_size)
108                 goto done;
109
110         if (ra_offset) {
111                 new_frame.ra = old_frame->sp + ra_offset;
112                 if (get_mem(new_frame.ra, &(new_frame.ra)))
113                         return -13;
114         }
115
116         if (stack_size) {
117                 new_frame.sp = old_frame->sp + stack_size;
118                 if (get_mem(new_frame.sp, &(new_frame.sp)))
119                         return -14;
120         }
121
122         if (new_frame.sp > old_frame->sp)
123                 return -2;
124
125 done:
126         new_frame.pc = old_frame->ra;
127         *old_frame = new_frame;
128
129         return 0;
130 }
131
132 static inline void do_user_backtrace(unsigned long low_addr,
133                                      struct stackframe *frame,
134                                      unsigned int depth)
135 {
136         const unsigned int max_instr_check = 512;
137         const unsigned long high_addr = low_addr + THREAD_SIZE;
138
139         while (depth-- && !unwind_user_frame(frame, max_instr_check)) {
140                 oprofile_add_trace(frame->ra);
141                 if (frame->sp < low_addr || frame->sp > high_addr)
142                         break;
143         }
144 }
145
146 #ifndef CONFIG_KALLSYMS
147 static inline void do_kernel_backtrace(unsigned long low_addr,
148                                        struct stackframe *frame,
149                                        unsigned int depth) { }
150 #else
151 static inline void do_kernel_backtrace(unsigned long low_addr,
152                                        struct stackframe *frame,
153                                        unsigned int depth)
154 {
155         while (depth-- && frame->pc) {
156                 frame->pc = unwind_stack_by_address(low_addr,
157                                                     &(frame->sp),
158                                                     frame->pc,
159                                                     &(frame->ra));
160                 oprofile_add_trace(frame->ra);
161         }
162 }
163 #endif
164
165 void notrace op_mips_backtrace(struct pt_regs *const regs, unsigned int depth)
166 {
167         struct stackframe frame = { .sp = regs->regs[29],
168                                     .pc = regs->cp0_epc,
169                                     .ra = regs->regs[31] };
170         const int userspace = user_mode(regs);
171         const unsigned long low_addr = ALIGN(frame.sp, THREAD_SIZE);
172
173         if (userspace)
174                 do_user_backtrace(low_addr, &frame, depth);
175         else
176                 do_kernel_backtrace(low_addr, &frame, depth);
177 }