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/stacktrace.h> 33 #include <asm/switch_to.h> 34 35 /*------------------------------------------------------------------------- 36 * Unwinder Iterator 37 *------------------------------------------------------------------------- 38 */ 39 40 #ifdef CONFIG_ARC_DW2_UNWIND 41 42 static int 43 seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs, 44 struct unwind_frame_info *frame_info) 45 { 46 if (regs) { 47 /* 48 * Asynchronous unwinding of intr/exception 49 * - Just uses the pt_regs passed 50 */ 51 frame_info->task = tsk; 52 53 frame_info->regs.r27 = regs->fp; 54 frame_info->regs.r28 = regs->sp; 55 frame_info->regs.r31 = regs->blink; 56 frame_info->regs.r63 = regs->ret; 57 frame_info->call_frame = 0; 58 } else if (tsk == NULL || tsk == current) { 59 /* 60 * synchronous unwinding (e.g. dump_stack) 61 * - uses current values of SP and friends 62 */ 63 unsigned long fp, sp, blink, ret; 64 frame_info->task = current; 65 66 __asm__ __volatile__( 67 "mov %0,r27\n\t" 68 "mov %1,r28\n\t" 69 "mov %2,r31\n\t" 70 "mov %3,r63\n\t" 71 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret) 72 ); 73 74 frame_info->regs.r27 = fp; 75 frame_info->regs.r28 = sp; 76 frame_info->regs.r31 = blink; 77 frame_info->regs.r63 = ret; 78 frame_info->call_frame = 0; 79 } else { 80 /* 81 * Asynchronous unwinding of a likely sleeping task 82 * - first ensure it is actually sleeping 83 * - if so, it will be in __switch_to, kernel mode SP of task 84 * is safe-kept and BLINK at a well known location in there 85 */ 86 87 if (task_is_running(tsk)) 88 return -1; 89 90 frame_info->task = tsk; 91 92 frame_info->regs.r27 = TSK_K_FP(tsk); 93 frame_info->regs.r28 = TSK_K_ESP(tsk); 94 frame_info->regs.r31 = TSK_K_BLINK(tsk); 95 frame_info->regs.r63 = (unsigned int)__switch_to; 96 97 /* In the prologue of __switch_to, first FP is saved on stack 98 * and then SP is copied to FP. Dwarf assumes cfa as FP based 99 * but we didn't save FP. The value retrieved above is FP's 100 * state in previous frame. 101 * As a work around for this, we unwind from __switch_to start 102 * and adjust SP accordingly. The other limitation is that 103 * __switch_to macro is dwarf rules are not generated for inline 104 * assembly code 105 */ 106 frame_info->regs.r27 = 0; 107 frame_info->regs.r28 += 60; 108 frame_info->call_frame = 0; 109 110 } 111 return 0; 112 } 113 114 #endif 115 116 notrace noinline unsigned int 117 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs, 118 int (*consumer_fn) (unsigned int, void *), void *arg) 119 { 120 #ifdef CONFIG_ARC_DW2_UNWIND 121 int ret = 0, cnt = 0; 122 unsigned int address; 123 struct unwind_frame_info frame_info; 124 125 if (seed_unwind_frame_info(tsk, regs, &frame_info)) 126 return 0; 127 128 while (1) { 129 address = UNW_PC(&frame_info); 130 131 if (!address || !__kernel_text_address(address)) 132 break; 133 134 if (consumer_fn(address, arg) == -1) 135 break; 136 137 ret = arc_unwind(&frame_info); 138 if (ret) 139 break; 140 141 frame_info.regs.r63 = frame_info.regs.r31; 142 143 if (cnt++ > 128) { 144 printk("unwinder looping too long, aborting !\n"); 145 return 0; 146 } 147 } 148 149 return address; /* return the last address it saw */ 150 #else 151 /* On ARC, only Dward based unwinder works. fp based backtracing is 152 * not possible (-fno-omit-frame-pointer) because of the way function 153 * prologue is setup (callee regs saved and then fp set and not other 154 * way around 155 */ 156 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n"); 157 return 0; 158 159 #endif 160 } 161 162 /*------------------------------------------------------------------------- 163 * callbacks called by unwinder iterator to implement kernel APIs 164 * 165 * The callback can return -1 to force the iterator to stop, which by default 166 * keeps going till the bottom-most frame. 167 *------------------------------------------------------------------------- 168 */ 169 170 /* Call-back which plugs into unwinding core to dump the stack in 171 * case of panic/OOPs/BUG etc 172 */ 173 static int __print_sym(unsigned int address, void *arg) 174 { 175 const char *loglvl = arg; 176 177 printk("%s %pS\n", loglvl, (void *)address); 178 return 0; 179 } 180 181 #ifdef CONFIG_STACKTRACE 182 183 /* Call-back which plugs into unwinding core to capture the 184 * traces needed by kernel on /proc/<pid>/stack 185 */ 186 static int __collect_all(unsigned int address, void *arg) 187 { 188 struct stack_trace *trace = arg; 189 190 if (trace->skip > 0) 191 trace->skip--; 192 else 193 trace->entries[trace->nr_entries++] = address; 194 195 if (trace->nr_entries >= trace->max_entries) 196 return -1; 197 198 return 0; 199 } 200 201 static int __collect_all_but_sched(unsigned int address, void *arg) 202 { 203 struct stack_trace *trace = arg; 204 205 if (in_sched_functions(address)) 206 return 0; 207 208 if (trace->skip > 0) 209 trace->skip--; 210 else 211 trace->entries[trace->nr_entries++] = address; 212 213 if (trace->nr_entries >= trace->max_entries) 214 return -1; 215 216 return 0; 217 } 218 219 #endif 220 221 static int __get_first_nonsched(unsigned int address, void *unused) 222 { 223 if (in_sched_functions(address)) 224 return 0; 225 226 return -1; 227 } 228 229 /*------------------------------------------------------------------------- 230 * APIs expected by various kernel sub-systems 231 *------------------------------------------------------------------------- 232 */ 233 234 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs, 235 const char *loglvl) 236 { 237 printk("%s\nStack Trace:\n", loglvl); 238 arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl); 239 } 240 EXPORT_SYMBOL(show_stacktrace); 241 242 /* Expected by sched Code */ 243 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl) 244 { 245 show_stacktrace(tsk, NULL, loglvl); 246 } 247 248 /* Another API expected by schedular, shows up in "ps" as Wait Channel 249 * Of course just returning schedule( ) would be pointless so unwind until 250 * the function is not in schedular code 251 */ 252 unsigned int __get_wchan(struct task_struct *tsk) 253 { 254 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL); 255 } 256 257 #ifdef CONFIG_STACKTRACE 258 259 /* 260 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP. 261 * A typical use is when /proc/<pid>/stack is queried by userland 262 */ 263 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 264 { 265 /* Assumes @tsk is sleeping so unwinds from __switch_to */ 266 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace); 267 } 268 269 void save_stack_trace(struct stack_trace *trace) 270 { 271 /* Pass NULL for task so it unwinds the current call frame */ 272 arc_unwind_core(NULL, NULL, __collect_all, trace); 273 } 274 EXPORT_SYMBOL_GPL(save_stack_trace); 275 #endif 276