1 // SPDX-License-Identifier: GPL-2.0 2 3 /* 4 * Stack trace utility functions etc. 5 * 6 * Copyright 2008 Christoph Hellwig, IBM Corp. 7 * Copyright 2018 SUSE Linux GmbH 8 * Copyright 2018 Nick Piggin, Michael Ellerman, IBM Corp. 9 */ 10 11 #include <linux/export.h> 12 #include <linux/kallsyms.h> 13 #include <linux/module.h> 14 #include <linux/nmi.h> 15 #include <linux/sched.h> 16 #include <linux/sched/debug.h> 17 #include <linux/sched/task_stack.h> 18 #include <linux/stacktrace.h> 19 #include <asm/ptrace.h> 20 #include <asm/processor.h> 21 #include <linux/ftrace.h> 22 #include <asm/kprobes.h> 23 24 #include <asm/paca.h> 25 26 /* 27 * Save stack-backtrace addresses into a stack_trace buffer. 28 */ 29 static void save_context_stack(struct stack_trace *trace, unsigned long sp, 30 struct task_struct *tsk, int savesched) 31 { 32 for (;;) { 33 unsigned long *stack = (unsigned long *) sp; 34 unsigned long newsp, ip; 35 36 if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD)) 37 return; 38 39 newsp = stack[0]; 40 ip = stack[STACK_FRAME_LR_SAVE]; 41 42 if (savesched || !in_sched_functions(ip)) { 43 if (!trace->skip) 44 trace->entries[trace->nr_entries++] = ip; 45 else 46 trace->skip--; 47 } 48 49 if (trace->nr_entries >= trace->max_entries) 50 return; 51 52 sp = newsp; 53 } 54 } 55 56 void save_stack_trace(struct stack_trace *trace) 57 { 58 unsigned long sp; 59 60 sp = current_stack_pointer(); 61 62 save_context_stack(trace, sp, current, 1); 63 } 64 EXPORT_SYMBOL_GPL(save_stack_trace); 65 66 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 67 { 68 unsigned long sp; 69 70 if (!try_get_task_stack(tsk)) 71 return; 72 73 if (tsk == current) 74 sp = current_stack_pointer(); 75 else 76 sp = tsk->thread.ksp; 77 78 save_context_stack(trace, sp, tsk, 0); 79 80 put_task_stack(tsk); 81 } 82 EXPORT_SYMBOL_GPL(save_stack_trace_tsk); 83 84 void 85 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) 86 { 87 save_context_stack(trace, regs->gpr[1], current, 0); 88 } 89 EXPORT_SYMBOL_GPL(save_stack_trace_regs); 90 91 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE 92 /* 93 * This function returns an error if it detects any unreliable features of the 94 * stack. Otherwise it guarantees that the stack trace is reliable. 95 * 96 * If the task is not 'current', the caller *must* ensure the task is inactive. 97 */ 98 static int __save_stack_trace_tsk_reliable(struct task_struct *tsk, 99 struct stack_trace *trace) 100 { 101 unsigned long sp; 102 unsigned long newsp; 103 unsigned long stack_page = (unsigned long)task_stack_page(tsk); 104 unsigned long stack_end; 105 int graph_idx = 0; 106 bool firstframe; 107 108 stack_end = stack_page + THREAD_SIZE; 109 if (!is_idle_task(tsk)) { 110 /* 111 * For user tasks, this is the SP value loaded on 112 * kernel entry, see "PACAKSAVE(r13)" in _switch() and 113 * system_call_common()/EXCEPTION_PROLOG_COMMON(). 114 * 115 * Likewise for non-swapper kernel threads, 116 * this also happens to be the top of the stack 117 * as setup by copy_thread(). 118 * 119 * Note that stack backlinks are not properly setup by 120 * copy_thread() and thus, a forked task() will have 121 * an unreliable stack trace until it's been 122 * _switch()'ed to for the first time. 123 */ 124 stack_end -= STACK_FRAME_OVERHEAD + sizeof(struct pt_regs); 125 } else { 126 /* 127 * idle tasks have a custom stack layout, 128 * c.f. cpu_idle_thread_init(). 129 */ 130 stack_end -= STACK_FRAME_OVERHEAD; 131 } 132 133 if (tsk == current) 134 sp = current_stack_pointer(); 135 else 136 sp = tsk->thread.ksp; 137 138 if (sp < stack_page + sizeof(struct thread_struct) || 139 sp > stack_end - STACK_FRAME_MIN_SIZE) { 140 return -EINVAL; 141 } 142 143 for (firstframe = true; sp != stack_end; 144 firstframe = false, sp = newsp) { 145 unsigned long *stack = (unsigned long *) sp; 146 unsigned long ip; 147 148 /* sanity check: ABI requires SP to be aligned 16 bytes. */ 149 if (sp & 0xF) 150 return -EINVAL; 151 152 newsp = stack[0]; 153 /* Stack grows downwards; unwinder may only go up. */ 154 if (newsp <= sp) 155 return -EINVAL; 156 157 if (newsp != stack_end && 158 newsp > stack_end - STACK_FRAME_MIN_SIZE) { 159 return -EINVAL; /* invalid backlink, too far up. */ 160 } 161 162 /* 163 * We can only trust the bottom frame's backlink, the 164 * rest of the frame may be uninitialized, continue to 165 * the next. 166 */ 167 if (firstframe) 168 continue; 169 170 /* Mark stacktraces with exception frames as unreliable. */ 171 if (sp <= stack_end - STACK_INT_FRAME_SIZE && 172 stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) { 173 return -EINVAL; 174 } 175 176 /* Examine the saved LR: it must point into kernel code. */ 177 ip = stack[STACK_FRAME_LR_SAVE]; 178 if (!__kernel_text_address(ip)) 179 return -EINVAL; 180 181 /* 182 * FIXME: IMHO these tests do not belong in 183 * arch-dependent code, they are generic. 184 */ 185 ip = ftrace_graph_ret_addr(tsk, &graph_idx, ip, stack); 186 #ifdef CONFIG_KPROBES 187 /* 188 * Mark stacktraces with kretprobed functions on them 189 * as unreliable. 190 */ 191 if (ip == (unsigned long)kretprobe_trampoline) 192 return -EINVAL; 193 #endif 194 195 if (trace->nr_entries >= trace->max_entries) 196 return -E2BIG; 197 if (!trace->skip) 198 trace->entries[trace->nr_entries++] = ip; 199 else 200 trace->skip--; 201 } 202 return 0; 203 } 204 205 int save_stack_trace_tsk_reliable(struct task_struct *tsk, 206 struct stack_trace *trace) 207 { 208 int ret; 209 210 /* 211 * If the task doesn't have a stack (e.g., a zombie), the stack is 212 * "reliably" empty. 213 */ 214 if (!try_get_task_stack(tsk)) 215 return 0; 216 217 ret = __save_stack_trace_tsk_reliable(tsk, trace); 218 219 put_task_stack(tsk); 220 221 return ret; 222 } 223 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */ 224 225 #if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) 226 static void handle_backtrace_ipi(struct pt_regs *regs) 227 { 228 nmi_cpu_backtrace(regs); 229 } 230 231 static void raise_backtrace_ipi(cpumask_t *mask) 232 { 233 unsigned int cpu; 234 235 for_each_cpu(cpu, mask) { 236 if (cpu == smp_processor_id()) 237 handle_backtrace_ipi(NULL); 238 else 239 smp_send_safe_nmi_ipi(cpu, handle_backtrace_ipi, 5 * USEC_PER_SEC); 240 } 241 242 for_each_cpu(cpu, mask) { 243 struct paca_struct *p = paca_ptrs[cpu]; 244 245 cpumask_clear_cpu(cpu, mask); 246 247 pr_warn("CPU %d didn't respond to backtrace IPI, inspecting paca.\n", cpu); 248 if (!virt_addr_valid(p)) { 249 pr_warn("paca pointer appears corrupt? (%px)\n", p); 250 continue; 251 } 252 253 pr_warn("irq_soft_mask: 0x%02x in_mce: %d in_nmi: %d", 254 p->irq_soft_mask, p->in_mce, p->in_nmi); 255 256 if (virt_addr_valid(p->__current)) 257 pr_cont(" current: %d (%s)\n", p->__current->pid, 258 p->__current->comm); 259 else 260 pr_cont(" current pointer corrupt? (%px)\n", p->__current); 261 262 pr_warn("Back trace of paca->saved_r1 (0x%016llx) (possibly stale):\n", p->saved_r1); 263 show_stack(p->__current, (unsigned long *)p->saved_r1); 264 } 265 } 266 267 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) 268 { 269 nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi); 270 } 271 #endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */ 272