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
get_mem(unsigned long addr,unsigned long * result)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 */
is_ra_save_ins(union mips_instruction * ip)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
is_sp_move_ins(union mips_instruction * ip)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 */
is_end_of_function_marker(union mips_instruction * ip)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
unwind_user_frame(struct stackframe * old_frame,const unsigned int max_instr_check)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
do_user_backtrace(unsigned long low_addr,struct stackframe * frame,unsigned int depth)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
do_kernel_backtrace(unsigned long low_addr,struct stackframe * frame,unsigned int depth)147 static inline void do_kernel_backtrace(unsigned long low_addr,
148 struct stackframe *frame,
149 unsigned int depth) { }
150 #else
do_kernel_backtrace(unsigned long low_addr,struct stackframe * frame,unsigned int depth)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
op_mips_backtrace(struct pt_regs * const regs,unsigned int depth)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 }
178