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