1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * stacktrace.c : stacktracing APIs needed by rest of kernel 4 * (wrappers over ARC dwarf based unwinder) 5 * 6 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 7 * 8 * vineetg: aug 2009 9 * -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( ) 10 * for displaying task's kernel mode call stack in /proc/<pid>/stack 11 * -Iterator based approach to have single copy of unwinding core and APIs 12 * needing unwinding, implement the logic in iterator regarding: 13 * = which frame onwards to start capture 14 * = which frame to stop capturing (wchan) 15 * = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc) 16 * 17 * vineetg: March 2009 18 * -Implemented correct versions of thread_saved_pc() and get_wchan() 19 * 20 * rajeshwarr: 2008 21 * -Initial implementation 22 */ 23 24 #include <linux/ptrace.h> 25 #include <linux/export.h> 26 #include <linux/stacktrace.h> 27 #include <linux/kallsyms.h> 28 #include <linux/sched/debug.h> 29 30 #include <asm/arcregs.h> 31 #include <asm/unwind.h> 32 #include <asm/switch_to.h> 33 34 /*------------------------------------------------------------------------- 35 * Unwinder Iterator 36 *------------------------------------------------------------------------- 37 */ 38 39 #ifdef CONFIG_ARC_DW2_UNWIND 40 41 static void seed_unwind_frame_info(struct task_struct *tsk, 42 struct pt_regs *regs, 43 struct unwind_frame_info *frame_info) 44 { 45 /* 46 * synchronous unwinding (e.g. dump_stack) 47 * - uses current values of SP and friends 48 */ 49 if (tsk == NULL && regs == NULL) { 50 unsigned long fp, sp, blink, ret; 51 frame_info->task = current; 52 53 __asm__ __volatile__( 54 "mov %0,r27\n\t" 55 "mov %1,r28\n\t" 56 "mov %2,r31\n\t" 57 "mov %3,r63\n\t" 58 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret) 59 ); 60 61 frame_info->regs.r27 = fp; 62 frame_info->regs.r28 = sp; 63 frame_info->regs.r31 = blink; 64 frame_info->regs.r63 = ret; 65 frame_info->call_frame = 0; 66 } else if (regs == NULL) { 67 /* 68 * Asynchronous unwinding of sleeping task 69 * - Gets SP etc from task's pt_regs (saved bottom of kernel 70 * mode stack of task) 71 */ 72 73 frame_info->task = tsk; 74 75 frame_info->regs.r27 = TSK_K_FP(tsk); 76 frame_info->regs.r28 = TSK_K_ESP(tsk); 77 frame_info->regs.r31 = TSK_K_BLINK(tsk); 78 frame_info->regs.r63 = (unsigned int)__switch_to; 79 80 /* In the prologue of __switch_to, first FP is saved on stack 81 * and then SP is copied to FP. Dwarf assumes cfa as FP based 82 * but we didn't save FP. The value retrieved above is FP's 83 * state in previous frame. 84 * As a work around for this, we unwind from __switch_to start 85 * and adjust SP accordingly. The other limitation is that 86 * __switch_to macro is dwarf rules are not generated for inline 87 * assembly code 88 */ 89 frame_info->regs.r27 = 0; 90 frame_info->regs.r28 += 60; 91 frame_info->call_frame = 0; 92 93 } else { 94 /* 95 * Asynchronous unwinding of intr/exception 96 * - Just uses the pt_regs passed 97 */ 98 frame_info->task = tsk; 99 100 frame_info->regs.r27 = regs->fp; 101 frame_info->regs.r28 = regs->sp; 102 frame_info->regs.r31 = regs->blink; 103 frame_info->regs.r63 = regs->ret; 104 frame_info->call_frame = 0; 105 } 106 } 107 108 #endif 109 110 notrace noinline unsigned int 111 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs, 112 int (*consumer_fn) (unsigned int, void *), void *arg) 113 { 114 #ifdef CONFIG_ARC_DW2_UNWIND 115 int ret = 0, cnt = 0; 116 unsigned int address; 117 struct unwind_frame_info frame_info; 118 119 seed_unwind_frame_info(tsk, regs, &frame_info); 120 121 while (1) { 122 address = UNW_PC(&frame_info); 123 124 if (!address || !__kernel_text_address(address)) 125 break; 126 127 if (consumer_fn(address, arg) == -1) 128 break; 129 130 ret = arc_unwind(&frame_info); 131 if (ret) 132 break; 133 134 frame_info.regs.r63 = frame_info.regs.r31; 135 136 if (cnt++ > 128) { 137 printk("unwinder looping too long, aborting !\n"); 138 return 0; 139 } 140 } 141 142 return address; /* return the last address it saw */ 143 #else 144 /* On ARC, only Dward based unwinder works. fp based backtracing is 145 * not possible (-fno-omit-frame-pointer) because of the way function 146 * prelogue is setup (callee regs saved and then fp set and not other 147 * way around 148 */ 149 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n"); 150 return 0; 151 152 #endif 153 } 154 155 /*------------------------------------------------------------------------- 156 * callbacks called by unwinder iterator to implement kernel APIs 157 * 158 * The callback can return -1 to force the iterator to stop, which by default 159 * keeps going till the bottom-most frame. 160 *------------------------------------------------------------------------- 161 */ 162 163 /* Call-back which plugs into unwinding core to dump the stack in 164 * case of panic/OOPs/BUG etc 165 */ 166 static int __print_sym(unsigned int address, void *arg) 167 { 168 const char *loglvl = arg; 169 170 printk("%s %pS\n", loglvl, (void *)address); 171 return 0; 172 } 173 174 #ifdef CONFIG_STACKTRACE 175 176 /* Call-back which plugs into unwinding core to capture the 177 * traces needed by kernel on /proc/<pid>/stack 178 */ 179 static int __collect_all(unsigned int address, void *arg) 180 { 181 struct stack_trace *trace = arg; 182 183 if (trace->skip > 0) 184 trace->skip--; 185 else 186 trace->entries[trace->nr_entries++] = address; 187 188 if (trace->nr_entries >= trace->max_entries) 189 return -1; 190 191 return 0; 192 } 193 194 static int __collect_all_but_sched(unsigned int address, void *arg) 195 { 196 struct stack_trace *trace = arg; 197 198 if (in_sched_functions(address)) 199 return 0; 200 201 if (trace->skip > 0) 202 trace->skip--; 203 else 204 trace->entries[trace->nr_entries++] = address; 205 206 if (trace->nr_entries >= trace->max_entries) 207 return -1; 208 209 return 0; 210 } 211 212 #endif 213 214 static int __get_first_nonsched(unsigned int address, void *unused) 215 { 216 if (in_sched_functions(address)) 217 return 0; 218 219 return -1; 220 } 221 222 /*------------------------------------------------------------------------- 223 * APIs expected by various kernel sub-systems 224 *------------------------------------------------------------------------- 225 */ 226 227 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs, 228 const char *loglvl) 229 { 230 printk("%s\nStack Trace:\n", loglvl); 231 arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl); 232 } 233 EXPORT_SYMBOL(show_stacktrace); 234 235 /* Expected by sched Code */ 236 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl) 237 { 238 show_stacktrace(tsk, NULL, loglvl); 239 } 240 241 /* Another API expected by schedular, shows up in "ps" as Wait Channel 242 * Of course just returning schedule( ) would be pointless so unwind until 243 * the function is not in schedular code 244 */ 245 unsigned int get_wchan(struct task_struct *tsk) 246 { 247 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL); 248 } 249 250 #ifdef CONFIG_STACKTRACE 251 252 /* 253 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP. 254 * A typical use is when /proc/<pid>/stack is queried by userland 255 */ 256 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 257 { 258 /* Assumes @tsk is sleeping so unwinds from __switch_to */ 259 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace); 260 } 261 262 void save_stack_trace(struct stack_trace *trace) 263 { 264 /* Pass NULL for task so it unwinds the current call frame */ 265 arc_unwind_core(NULL, NULL, __collect_all, trace); 266 } 267 EXPORT_SYMBOL_GPL(save_stack_trace); 268 #endif 269