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 int 42 seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs, 43 struct unwind_frame_info *frame_info) 44 { 45 if (regs) { 46 /* 47 * Asynchronous unwinding of intr/exception 48 * - Just uses the pt_regs passed 49 */ 50 frame_info->task = tsk; 51 52 frame_info->regs.r27 = regs->fp; 53 frame_info->regs.r28 = regs->sp; 54 frame_info->regs.r31 = regs->blink; 55 frame_info->regs.r63 = regs->ret; 56 frame_info->call_frame = 0; 57 } else if (tsk == NULL || tsk == current) { 58 /* 59 * synchronous unwinding (e.g. dump_stack) 60 * - uses current values of SP and friends 61 */ 62 unsigned long fp, sp, blink, ret; 63 frame_info->task = current; 64 65 __asm__ __volatile__( 66 "mov %0,r27\n\t" 67 "mov %1,r28\n\t" 68 "mov %2,r31\n\t" 69 "mov %3,r63\n\t" 70 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret) 71 ); 72 73 frame_info->regs.r27 = fp; 74 frame_info->regs.r28 = sp; 75 frame_info->regs.r31 = blink; 76 frame_info->regs.r63 = ret; 77 frame_info->call_frame = 0; 78 } else { 79 /* 80 * Asynchronous unwinding of a likely sleeping task 81 * - first ensure it is actually sleeping 82 * - if so, it will be in __switch_to, kernel mode SP of task 83 * is safe-kept and BLINK at a well known location in there 84 */ 85 86 if (tsk->state == TASK_RUNNING) 87 return -1; 88 89 frame_info->task = tsk; 90 91 frame_info->regs.r27 = TSK_K_FP(tsk); 92 frame_info->regs.r28 = TSK_K_ESP(tsk); 93 frame_info->regs.r31 = TSK_K_BLINK(tsk); 94 frame_info->regs.r63 = (unsigned int)__switch_to; 95 96 /* In the prologue of __switch_to, first FP is saved on stack 97 * and then SP is copied to FP. Dwarf assumes cfa as FP based 98 * but we didn't save FP. The value retrieved above is FP's 99 * state in previous frame. 100 * As a work around for this, we unwind from __switch_to start 101 * and adjust SP accordingly. The other limitation is that 102 * __switch_to macro is dwarf rules are not generated for inline 103 * assembly code 104 */ 105 frame_info->regs.r27 = 0; 106 frame_info->regs.r28 += 60; 107 frame_info->call_frame = 0; 108 109 } 110 return 0; 111 } 112 113 #endif 114 115 notrace noinline unsigned int 116 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs, 117 int (*consumer_fn) (unsigned int, void *), void *arg) 118 { 119 #ifdef CONFIG_ARC_DW2_UNWIND 120 int ret = 0, cnt = 0; 121 unsigned int address; 122 struct unwind_frame_info frame_info; 123 124 if (seed_unwind_frame_info(tsk, regs, &frame_info)) 125 return 0; 126 127 while (1) { 128 address = UNW_PC(&frame_info); 129 130 if (!address || !__kernel_text_address(address)) 131 break; 132 133 if (consumer_fn(address, arg) == -1) 134 break; 135 136 ret = arc_unwind(&frame_info); 137 if (ret) 138 break; 139 140 frame_info.regs.r63 = frame_info.regs.r31; 141 142 if (cnt++ > 128) { 143 printk("unwinder looping too long, aborting !\n"); 144 return 0; 145 } 146 } 147 148 return address; /* return the last address it saw */ 149 #else 150 /* On ARC, only Dward based unwinder works. fp based backtracing is 151 * not possible (-fno-omit-frame-pointer) because of the way function 152 * prelogue is setup (callee regs saved and then fp set and not other 153 * way around 154 */ 155 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n"); 156 return 0; 157 158 #endif 159 } 160 161 /*------------------------------------------------------------------------- 162 * callbacks called by unwinder iterator to implement kernel APIs 163 * 164 * The callback can return -1 to force the iterator to stop, which by default 165 * keeps going till the bottom-most frame. 166 *------------------------------------------------------------------------- 167 */ 168 169 /* Call-back which plugs into unwinding core to dump the stack in 170 * case of panic/OOPs/BUG etc 171 */ 172 static int __print_sym(unsigned int address, void *arg) 173 { 174 const char *loglvl = arg; 175 176 printk("%s %pS\n", loglvl, (void *)address); 177 return 0; 178 } 179 180 #ifdef CONFIG_STACKTRACE 181 182 /* Call-back which plugs into unwinding core to capture the 183 * traces needed by kernel on /proc/<pid>/stack 184 */ 185 static int __collect_all(unsigned int address, void *arg) 186 { 187 struct stack_trace *trace = arg; 188 189 if (trace->skip > 0) 190 trace->skip--; 191 else 192 trace->entries[trace->nr_entries++] = address; 193 194 if (trace->nr_entries >= trace->max_entries) 195 return -1; 196 197 return 0; 198 } 199 200 static int __collect_all_but_sched(unsigned int address, void *arg) 201 { 202 struct stack_trace *trace = arg; 203 204 if (in_sched_functions(address)) 205 return 0; 206 207 if (trace->skip > 0) 208 trace->skip--; 209 else 210 trace->entries[trace->nr_entries++] = address; 211 212 if (trace->nr_entries >= trace->max_entries) 213 return -1; 214 215 return 0; 216 } 217 218 #endif 219 220 static int __get_first_nonsched(unsigned int address, void *unused) 221 { 222 if (in_sched_functions(address)) 223 return 0; 224 225 return -1; 226 } 227 228 /*------------------------------------------------------------------------- 229 * APIs expected by various kernel sub-systems 230 *------------------------------------------------------------------------- 231 */ 232 233 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs, 234 const char *loglvl) 235 { 236 printk("%s\nStack Trace:\n", loglvl); 237 arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl); 238 } 239 EXPORT_SYMBOL(show_stacktrace); 240 241 /* Expected by sched Code */ 242 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl) 243 { 244 show_stacktrace(tsk, NULL, loglvl); 245 } 246 247 /* Another API expected by schedular, shows up in "ps" as Wait Channel 248 * Of course just returning schedule( ) would be pointless so unwind until 249 * the function is not in schedular code 250 */ 251 unsigned int get_wchan(struct task_struct *tsk) 252 { 253 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL); 254 } 255 256 #ifdef CONFIG_STACKTRACE 257 258 /* 259 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP. 260 * A typical use is when /proc/<pid>/stack is queried by userland 261 */ 262 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 263 { 264 /* Assumes @tsk is sleeping so unwinds from __switch_to */ 265 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace); 266 } 267 268 void save_stack_trace(struct stack_trace *trace) 269 { 270 /* Pass NULL for task so it unwinds the current call frame */ 271 arc_unwind_core(NULL, NULL, __collect_all, trace); 272 } 273 EXPORT_SYMBOL_GPL(save_stack_trace); 274 #endif 275