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/delay.h> 12 #include <linux/export.h> 13 #include <linux/kallsyms.h> 14 #include <linux/module.h> 15 #include <linux/nmi.h> 16 #include <linux/sched.h> 17 #include <linux/sched/debug.h> 18 #include <linux/sched/task_stack.h> 19 #include <linux/stacktrace.h> 20 #include <asm/ptrace.h> 21 #include <asm/processor.h> 22 #include <linux/ftrace.h> 23 #include <asm/kprobes.h> 24 25 #include <asm/paca.h> 26 27 void __no_sanitize_address arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, 28 struct task_struct *task, struct pt_regs *regs) 29 { 30 unsigned long sp; 31 32 if (regs && !consume_entry(cookie, regs->nip)) 33 return; 34 35 if (regs) 36 sp = regs->gpr[1]; 37 else if (task == current) 38 sp = current_stack_frame(); 39 else 40 sp = task->thread.ksp; 41 42 for (;;) { 43 unsigned long *stack = (unsigned long *) sp; 44 unsigned long newsp, ip; 45 46 if (!validate_sp(sp, task)) 47 return; 48 49 newsp = stack[0]; 50 ip = stack[STACK_FRAME_LR_SAVE]; 51 52 if (!consume_entry(cookie, ip)) 53 return; 54 55 sp = newsp; 56 } 57 } 58 59 /* 60 * This function returns an error if it detects any unreliable features of the 61 * stack. Otherwise it guarantees that the stack trace is reliable. 62 * 63 * If the task is not 'current', the caller *must* ensure the task is inactive. 64 */ 65 int __no_sanitize_address arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, 66 void *cookie, struct task_struct *task) 67 { 68 unsigned long sp; 69 unsigned long newsp; 70 unsigned long stack_page = (unsigned long)task_stack_page(task); 71 unsigned long stack_end; 72 int graph_idx = 0; 73 bool firstframe; 74 75 stack_end = stack_page + THREAD_SIZE; 76 77 // See copy_thread() for details. 78 if (task->flags & PF_KTHREAD) 79 stack_end -= STACK_FRAME_MIN_SIZE; 80 else 81 stack_end -= STACK_USER_INT_FRAME_SIZE; 82 83 if (task == current) 84 sp = current_stack_frame(); 85 else 86 sp = task->thread.ksp; 87 88 if (sp < stack_page + sizeof(struct thread_struct) || 89 sp > stack_end - STACK_FRAME_MIN_SIZE) { 90 return -EINVAL; 91 } 92 93 for (firstframe = true; sp != stack_end; 94 firstframe = false, sp = newsp) { 95 unsigned long *stack = (unsigned long *) sp; 96 unsigned long ip; 97 98 /* sanity check: ABI requires SP to be aligned 16 bytes. */ 99 if (sp & 0xF) 100 return -EINVAL; 101 102 newsp = stack[0]; 103 /* Stack grows downwards; unwinder may only go up. */ 104 if (newsp <= sp) 105 return -EINVAL; 106 107 if (newsp != stack_end && 108 newsp > stack_end - STACK_FRAME_MIN_SIZE) { 109 return -EINVAL; /* invalid backlink, too far up. */ 110 } 111 112 /* 113 * We can only trust the bottom frame's backlink, the 114 * rest of the frame may be uninitialized, continue to 115 * the next. 116 */ 117 if (firstframe) 118 continue; 119 120 /* Mark stacktraces with exception frames as unreliable. */ 121 if (sp <= stack_end - STACK_INT_FRAME_SIZE && 122 stack[STACK_INT_FRAME_MARKER_LONGS] == STACK_FRAME_REGS_MARKER) { 123 return -EINVAL; 124 } 125 126 /* Examine the saved LR: it must point into kernel code. */ 127 ip = stack[STACK_FRAME_LR_SAVE]; 128 if (!__kernel_text_address(ip)) 129 return -EINVAL; 130 131 /* 132 * FIXME: IMHO these tests do not belong in 133 * arch-dependent code, they are generic. 134 */ 135 ip = ftrace_graph_ret_addr(task, &graph_idx, ip, stack); 136 #ifdef CONFIG_KPROBES 137 /* 138 * Mark stacktraces with kretprobed functions on them 139 * as unreliable. 140 */ 141 if (ip == (unsigned long)__kretprobe_trampoline) 142 return -EINVAL; 143 #endif 144 145 if (!consume_entry(cookie, ip)) 146 return -EINVAL; 147 } 148 return 0; 149 } 150 151 #if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) 152 static void handle_backtrace_ipi(struct pt_regs *regs) 153 { 154 nmi_cpu_backtrace(regs); 155 } 156 157 static void raise_backtrace_ipi(cpumask_t *mask) 158 { 159 struct paca_struct *p; 160 unsigned int cpu; 161 u64 delay_us; 162 163 for_each_cpu(cpu, mask) { 164 if (cpu == smp_processor_id()) { 165 handle_backtrace_ipi(NULL); 166 continue; 167 } 168 169 delay_us = 5 * USEC_PER_SEC; 170 171 if (smp_send_safe_nmi_ipi(cpu, handle_backtrace_ipi, delay_us)) { 172 // Now wait up to 5s for the other CPU to do its backtrace 173 while (cpumask_test_cpu(cpu, mask) && delay_us) { 174 udelay(1); 175 delay_us--; 176 } 177 178 // Other CPU cleared itself from the mask 179 if (delay_us) 180 continue; 181 } 182 183 p = paca_ptrs[cpu]; 184 185 cpumask_clear_cpu(cpu, mask); 186 187 pr_warn("CPU %d didn't respond to backtrace IPI, inspecting paca.\n", cpu); 188 if (!virt_addr_valid(p)) { 189 pr_warn("paca pointer appears corrupt? (%px)\n", p); 190 continue; 191 } 192 193 pr_warn("irq_soft_mask: 0x%02x in_mce: %d in_nmi: %d", 194 p->irq_soft_mask, p->in_mce, p->in_nmi); 195 196 if (virt_addr_valid(p->__current)) 197 pr_cont(" current: %d (%s)\n", p->__current->pid, 198 p->__current->comm); 199 else 200 pr_cont(" current pointer corrupt? (%px)\n", p->__current); 201 202 pr_warn("Back trace of paca->saved_r1 (0x%016llx) (possibly stale):\n", p->saved_r1); 203 show_stack(p->__current, (unsigned long *)p->saved_r1, KERN_WARNING); 204 } 205 } 206 207 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) 208 { 209 nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace_ipi); 210 } 211 #endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */ 212