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 (tsk == current) 71 sp = current_stack_pointer(); 72 else 73 sp = tsk->thread.ksp; 74 75 save_context_stack(trace, sp, tsk, 0); 76 } 77 EXPORT_SYMBOL_GPL(save_stack_trace_tsk); 78 79 void 80 save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace) 81 { 82 save_context_stack(trace, regs->gpr[1], current, 0); 83 } 84 EXPORT_SYMBOL_GPL(save_stack_trace_regs); 85 86 #ifdef CONFIG_HAVE_RELIABLE_STACKTRACE 87 /* 88 * This function returns an error if it detects any unreliable features of the 89 * stack. Otherwise it guarantees that the stack trace is reliable. 90 * 91 * If the task is not 'current', the caller *must* ensure the task is inactive. 92 */ 93 int 94 save_stack_trace_tsk_reliable(struct task_struct *tsk, 95 struct stack_trace *trace) 96 { 97 unsigned long sp; 98 unsigned long newsp; 99 unsigned long stack_page = (unsigned long)task_stack_page(tsk); 100 unsigned long stack_end; 101 int graph_idx = 0; 102 bool firstframe; 103 104 stack_end = stack_page + THREAD_SIZE; 105 if (!is_idle_task(tsk)) { 106 /* 107 * For user tasks, this is the SP value loaded on 108 * kernel entry, see "PACAKSAVE(r13)" in _switch() and 109 * system_call_common()/EXCEPTION_PROLOG_COMMON(). 110 * 111 * Likewise for non-swapper kernel threads, 112 * this also happens to be the top of the stack 113 * as setup by copy_thread(). 114 * 115 * Note that stack backlinks are not properly setup by 116 * copy_thread() and thus, a forked task() will have 117 * an unreliable stack trace until it's been 118 * _switch()'ed to for the first time. 119 */ 120 stack_end -= STACK_FRAME_OVERHEAD + sizeof(struct pt_regs); 121 } else { 122 /* 123 * idle tasks have a custom stack layout, 124 * c.f. cpu_idle_thread_init(). 125 */ 126 stack_end -= STACK_FRAME_OVERHEAD; 127 } 128 129 if (tsk == current) 130 sp = current_stack_pointer(); 131 else 132 sp = tsk->thread.ksp; 133 134 if (sp < stack_page + sizeof(struct thread_struct) || 135 sp > stack_end - STACK_FRAME_MIN_SIZE) { 136 return -EINVAL; 137 } 138 139 for (firstframe = true; sp != stack_end; 140 firstframe = false, sp = newsp) { 141 unsigned long *stack = (unsigned long *) sp; 142 unsigned long ip; 143 144 /* sanity check: ABI requires SP to be aligned 16 bytes. */ 145 if (sp & 0xF) 146 return -EINVAL; 147 148 newsp = stack[0]; 149 /* Stack grows downwards; unwinder may only go up. */ 150 if (newsp <= sp) 151 return -EINVAL; 152 153 if (newsp != stack_end && 154 newsp > stack_end - STACK_FRAME_MIN_SIZE) { 155 return -EINVAL; /* invalid backlink, too far up. */ 156 } 157 158 /* 159 * We can only trust the bottom frame's backlink, the 160 * rest of the frame may be uninitialized, continue to 161 * the next. 162 */ 163 if (firstframe) 164 continue; 165 166 /* Mark stacktraces with exception frames as unreliable. */ 167 if (sp <= stack_end - STACK_INT_FRAME_SIZE && 168 stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) { 169 return -EINVAL; 170 } 171 172 /* Examine the saved LR: it must point into kernel code. */ 173 ip = stack[STACK_FRAME_LR_SAVE]; 174 if (!__kernel_text_address(ip)) 175 return -EINVAL; 176 177 /* 178 * FIXME: IMHO these tests do not belong in 179 * arch-dependent code, they are generic. 180 */ 181 ip = ftrace_graph_ret_addr(tsk, &graph_idx, ip, NULL); 182 #ifdef CONFIG_KPROBES 183 /* 184 * Mark stacktraces with kretprobed functions on them 185 * as unreliable. 186 */ 187 if (ip == (unsigned long)kretprobe_trampoline) 188 return -EINVAL; 189 #endif 190 191 if (trace->nr_entries >= trace->max_entries) 192 return -E2BIG; 193 if (!trace->skip) 194 trace->entries[trace->nr_entries++] = ip; 195 else 196 trace->skip--; 197 } 198 return 0; 199 } 200 EXPORT_SYMBOL_GPL(save_stack_trace_tsk_reliable); 201 #endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */ 202 203 #if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) 204 static void handle_backtrace_ipi(struct pt_regs *regs) 205 { 206 nmi_cpu_backtrace(regs); 207 } 208 209 static void raise_backtrace_ipi(cpumask_t *mask) 210 { 211 unsigned int cpu; 212 213 for_each_cpu(cpu, mask) { 214 if (cpu == smp_processor_id()) 215 handle_backtrace_ipi(NULL); 216 else 217 smp_send_safe_nmi_ipi(cpu, handle_backtrace_ipi, 5 * USEC_PER_SEC); 218 } 219 220 for_each_cpu(cpu, mask) { 221 struct paca_struct *p = paca_ptrs[cpu]; 222 223 cpumask_clear_cpu(cpu, mask); 224 225 pr_warn("CPU %d didn't respond to backtrace IPI, inspecting paca.\n", cpu); 226 if (!virt_addr_valid(p)) { 227 pr_warn("paca pointer appears corrupt? (%px)\n", p); 228 continue; 229 } 230 231 pr_warn("irq_soft_mask: 0x%02x in_mce: %d in_nmi: %d", 232 p->irq_soft_mask, p->in_mce, p->in_nmi); 233 234 if (virt_addr_valid(p->__current)) 235 pr_cont(" current: %d (%s)\n", p->__current->pid, 236 p->__current->comm); 237 else 238 pr_cont(" current pointer corrupt? (%px)\n", p->__current); 239 240 pr_warn("Back trace of paca->saved_r1 (0x%016llx) (possibly stale):\n", p->saved_r1); 241 show_stack(p->__current, (unsigned long *)p->saved_r1); 242 } 243 } 244 245 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) 246 { 247 nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi); 248 } 249 #endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */ 250