tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
12struct stackframe {
13 unsigned long sp;
14 unsigned long pc;
15 unsigned long ra;
16};
17
18static 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 */
31static 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
38static 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 */
52static 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
71static 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
130static 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
145static inline void do_kernel_backtrace(unsigned long low_addr,
146 struct stackframe *frame,
147 unsigned int depth) { }
148#else
149static 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
163void 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}