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Diffstat (limited to 'lib/mipsunwinder/backtrace-mips32.c')
-rw-r--r-- | lib/mipsunwinder/backtrace-mips32.c | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/lib/mipsunwinder/backtrace-mips32.c b/lib/mipsunwinder/backtrace-mips32.c new file mode 100644 index 0000000000..c5ab41e628 --- /dev/null +++ b/lib/mipsunwinder/backtrace-mips32.c | |||
@@ -0,0 +1,236 @@ | |||
1 | /*************************************************************************** | ||
2 | * __________ __ ___. | ||
3 | * Open \______ \ ____ ____ | | _\_ |__ _______ ___ | ||
4 | * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / | ||
5 | * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < | ||
6 | * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ | ||
7 | * \/ \/ \/ \/ \/ | ||
8 | * $Id$ | ||
9 | * | ||
10 | * MIPS32 backtrace implementation | ||
11 | * Copyright (C) 2022 Aidan MacDonald | ||
12 | * | ||
13 | * References: | ||
14 | * https://yosefk.com/blog/getting-the-call-stack-without-a-frame-pointer.html | ||
15 | * https://elinux.org/images/6/68/ELC2008_-_Back-tracing_in_MIPS-based_Linux_Systems.pdf | ||
16 | * System V ABI MIPS Supplement, 3rd edition | ||
17 | * | ||
18 | * This program is free software; you can redistribute it and/or | ||
19 | * modify it under the terms of the GNU General Public License | ||
20 | * as published by the Free Software Foundation; either version 2 | ||
21 | * of the License, or (at your option) any later version. | ||
22 | * | ||
23 | * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY | ||
24 | * KIND, either express or implied. | ||
25 | * | ||
26 | ****************************************************************************/ | ||
27 | |||
28 | #include "backtrace.h" | ||
29 | #include "lcd.h" | ||
30 | #include <stdint.h> | ||
31 | #include <stdbool.h> | ||
32 | #include <stdalign.h> | ||
33 | #include <stdarg.h> | ||
34 | #include <stdio.h> | ||
35 | |||
36 | #define MIN_ADDR 0x80000000ul | ||
37 | #define MAX_ADDR (MIN_ADDR + (MEMORYSIZE * 1024 * 1024) - 1) | ||
38 | |||
39 | static bool read_check(const void* addr, size_t alignment) | ||
40 | { | ||
41 | if(addr < (const void*)MIN_ADDR || | ||
42 | addr > (const void*)MAX_ADDR) | ||
43 | return false; | ||
44 | |||
45 | if((uintptr_t)addr & (alignment - 1)) | ||
46 | return false; | ||
47 | |||
48 | return true; | ||
49 | } | ||
50 | |||
51 | static bool read32(const void* addr, uint32_t* val) | ||
52 | { | ||
53 | if(!read_check(addr, alignof(uint32_t))) | ||
54 | return false; | ||
55 | |||
56 | *val = *(const uint32_t*)addr; | ||
57 | return true; | ||
58 | } | ||
59 | |||
60 | #if 0 | ||
61 | static bool read16(const void* addr, uint16_t* val) | ||
62 | { | ||
63 | if(!read_check(addr, alignof(uint16_t))) | ||
64 | return false; | ||
65 | |||
66 | *val = *(const uint16_t*)addr; | ||
67 | return true; | ||
68 | } | ||
69 | |||
70 | static bool read8(const void* addr, uint8_t* val) | ||
71 | { | ||
72 | if(!read_check(addr, alignof(uint8_t))) | ||
73 | return false; | ||
74 | |||
75 | *val = *(const uint8_t*)addr; | ||
76 | return true; | ||
77 | } | ||
78 | #endif | ||
79 | |||
80 | static long extract_s16(uint32_t val) | ||
81 | { | ||
82 | #if 1 | ||
83 | /* not ISO C, but gets GCC to emit 'seh' which is more compact */ | ||
84 | return (int32_t)(val << 16) >> 16; | ||
85 | #else | ||
86 | val &= 0xffff; | ||
87 | |||
88 | if(val > 0x7fff) | ||
89 | return (long)val - 0x10000l; | ||
90 | else | ||
91 | return val; | ||
92 | #endif | ||
93 | } | ||
94 | |||
95 | /* TODO - cases not handled by the backtrace algorithm | ||
96 | * | ||
97 | * 1. functions that save the frame pointer will not be handled correctly | ||
98 | * (need to implement the algorithm specified by the System V ABI). | ||
99 | * | ||
100 | * 2. GCC can generate functions with a "false" stack pointer decrement, | ||
101 | * for some examples see read_bmp_fd and walk_path. those functions | ||
102 | * seem to be more difficult to deal with and the SysV algorithm will | ||
103 | * also get confused by them, but they are not common. | ||
104 | */ | ||
105 | int mips_bt_step(struct mips_bt_context* ctx) | ||
106 | { | ||
107 | /* go backward and look for the stack pointer decrement */ | ||
108 | uint32_t* pc = ctx->pc; | ||
109 | uint32_t insn; | ||
110 | long sp_off; | ||
111 | |||
112 | while(true) { | ||
113 | if(!read32(pc, &insn)) | ||
114 | return 0; | ||
115 | |||
116 | /* addiu sp, sp, sp_off */ | ||
117 | if((insn >> 16) == 0x27bd) { | ||
118 | sp_off = extract_s16(insn); | ||
119 | if(sp_off < 0) | ||
120 | break; | ||
121 | } | ||
122 | |||
123 | /* jr ra */ | ||
124 | if(insn == 0x03e00008) { | ||
125 | /* end if this is not a leaf or we lack register info */ | ||
126 | if(ctx->depth > 0 || !(ctx->valid & (1 << MIPSBT_RA))) { | ||
127 | mips_bt_debug(ctx, "unexpected leaf function"); | ||
128 | return 0; | ||
129 | } | ||
130 | |||
131 | /* this is a leaf function - ra contains the return address | ||
132 | * and sp is unchanged */ | ||
133 | ctx->pc = (void*)ctx->reg[MIPSBT_RA] - 8; | ||
134 | ctx->depth++; | ||
135 | return 1; | ||
136 | } | ||
137 | |||
138 | --pc; | ||
139 | } | ||
140 | |||
141 | mips_bt_debug(ctx, "found sp_off=%ld at %p", sp_off, pc); | ||
142 | |||
143 | /* now go forward and find the saved return address */ | ||
144 | while((void*)pc < ctx->pc) { | ||
145 | if(!read32(pc, &insn)) | ||
146 | return 0; | ||
147 | |||
148 | /* sw ra, ra_off(sp) */ | ||
149 | if((insn >> 16) == 0xafbf) { | ||
150 | long ra_off = extract_s16(insn); | ||
151 | uint32_t save_ra; | ||
152 | |||
153 | /* load the saved return address */ | ||
154 | mips_bt_debug(ctx, "load ra from %p+%ld", ctx->sp, ra_off); | ||
155 | if(!read32(ctx->sp + ra_off, &save_ra)) | ||
156 | return 0; | ||
157 | |||
158 | if(save_ra == 0) { | ||
159 | mips_bt_debug("hit root"); | ||
160 | return 0; | ||
161 | } | ||
162 | |||
163 | /* update bt context */ | ||
164 | ctx->pc = (void*)save_ra - 8; | ||
165 | ctx->sp -= sp_off; | ||
166 | |||
167 | /* update saved register info */ | ||
168 | ctx->reg[MIPSBT_RA] = save_ra; | ||
169 | ctx->valid |= (1 << MIPSBT_RA); | ||
170 | |||
171 | ctx->depth++; | ||
172 | return 1; | ||
173 | } | ||
174 | |||
175 | ++pc; | ||
176 | } | ||
177 | |||
178 | /* sometimes an exception occurs before ra is saved - in this case | ||
179 | * the ra register should contain the caller PC, but we still need | ||
180 | * to adjust the stack frame. */ | ||
181 | if(ctx->depth == 0 && (ctx->valid & (1 << MIPSBT_RA))) { | ||
182 | ctx->pc = (void*)ctx->reg[MIPSBT_RA] - 8; | ||
183 | ctx->sp -= sp_off; | ||
184 | |||
185 | ctx->depth++; | ||
186 | return 1; | ||
187 | } | ||
188 | |||
189 | mips_bt_debug(ctx, "ra not found"); | ||
190 | return 0; | ||
191 | } | ||
192 | |||
193 | #ifdef MIPSUNWINDER_DEBUG | ||
194 | static void rb_backtrace_debugf(void* arg, const char* fmt, ...) | ||
195 | { | ||
196 | static char buf[64]; | ||
197 | va_list ap; | ||
198 | va_start(ap, fmt); | ||
199 | vsnprintf(buf, sizeof(buf), fmt, ap); | ||
200 | va_end(ap); | ||
201 | |||
202 | unsigned int* line = arg; | ||
203 | lcd_putsf(4, (*line)++, "%s", buf); | ||
204 | lcd_update(); | ||
205 | } | ||
206 | #endif | ||
207 | |||
208 | void rb_backtrace_ctx(void* arg, unsigned* line) | ||
209 | { | ||
210 | struct mips_bt_context* ctx = arg; | ||
211 | #ifdef MIPSUNWINDER_DEBUG | ||
212 | ctx->debugf = rb_backtrace_debugf; | ||
213 | ctx->debug_arg = line; | ||
214 | #endif | ||
215 | |||
216 | do { | ||
217 | lcd_putsf(0, (*line)++, "%02d pc:%08lx sp:%08lx", | ||
218 | ctx->depth, (unsigned long)ctx->pc, (unsigned long)ctx->sp); | ||
219 | lcd_update(); | ||
220 | } while(mips_bt_step(ctx)); | ||
221 | |||
222 | lcd_puts(0, (*line)++, "bt end"); | ||
223 | lcd_update(); | ||
224 | } | ||
225 | |||
226 | void rb_backtrace(int pcAddr, int spAddr, unsigned* line) | ||
227 | { | ||
228 | (void)pcAddr; | ||
229 | (void)spAddr; | ||
230 | |||
231 | struct mips_bt_context ctx; | ||
232 | mips_bt_start(&ctx); | ||
233 | mips_bt_step(&ctx); /* step over this function */ | ||
234 | |||
235 | rb_backtrace_ctx(&ctx, line); | ||
236 | } | ||