1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Stack tracing support 4 * 5 * Copyright (C) 2012 ARM Ltd. 6 */ 7 #include <linux/kernel.h> 8 #include <linux/export.h> 9 #include <linux/ftrace.h> 10 #include <linux/sched.h> 11 #include <linux/sched/debug.h> 12 #include <linux/sched/task_stack.h> 13 #include <linux/stacktrace.h> 14 15 #include <asm/irq.h> 16 #include <asm/stack_pointer.h> 17 #include <asm/stacktrace.h> 18 19 /* 20 * Start an unwind from a pt_regs. 21 * 22 * The unwind will begin at the PC within the regs. 23 * 24 * The regs must be on a stack currently owned by the calling task. 25 */ 26 static __always_inline void unwind_init_from_regs(struct unwind_state *state, 27 struct pt_regs *regs) 28 { 29 unwind_init_common(state, current); 30 31 state->fp = regs->regs[29]; 32 state->pc = regs->pc; 33 } 34 35 /* 36 * Start an unwind from a caller. 37 * 38 * The unwind will begin at the caller of whichever function this is inlined 39 * into. 40 * 41 * The function which invokes this must be noinline. 42 */ 43 static __always_inline void unwind_init_from_caller(struct unwind_state *state) 44 { 45 unwind_init_common(state, current); 46 47 state->fp = (unsigned long)__builtin_frame_address(1); 48 state->pc = (unsigned long)__builtin_return_address(0); 49 } 50 51 /* 52 * Start an unwind from a blocked task. 53 * 54 * The unwind will begin at the blocked tasks saved PC (i.e. the caller of 55 * cpu_switch_to()). 56 * 57 * The caller should ensure the task is blocked in cpu_switch_to() for the 58 * duration of the unwind, or the unwind will be bogus. It is never valid to 59 * call this for the current task. 60 */ 61 static __always_inline void unwind_init_from_task(struct unwind_state *state, 62 struct task_struct *task) 63 { 64 unwind_init_common(state, task); 65 66 state->fp = thread_saved_fp(task); 67 state->pc = thread_saved_pc(task); 68 } 69 70 /* 71 * Unwind from one frame record (A) to the next frame record (B). 72 * 73 * We terminate early if the location of B indicates a malformed chain of frame 74 * records (e.g. a cycle), determined based on the location and fp value of A 75 * and the location (but not the fp value) of B. 76 */ 77 static int notrace unwind_next(struct unwind_state *state) 78 { 79 struct task_struct *tsk = state->task; 80 unsigned long fp = state->fp; 81 int err; 82 83 /* Final frame; nothing to unwind */ 84 if (fp == (unsigned long)task_pt_regs(tsk)->stackframe) 85 return -ENOENT; 86 87 err = unwind_next_frame_record(state); 88 if (err) 89 return err; 90 91 state->pc = ptrauth_strip_insn_pac(state->pc); 92 93 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 94 if (tsk->ret_stack && 95 (state->pc == (unsigned long)return_to_handler)) { 96 unsigned long orig_pc; 97 /* 98 * This is a case where function graph tracer has 99 * modified a return address (LR) in a stack frame 100 * to hook a function return. 101 * So replace it to an original value. 102 */ 103 orig_pc = ftrace_graph_ret_addr(tsk, NULL, state->pc, 104 (void *)state->fp); 105 if (WARN_ON_ONCE(state->pc == orig_pc)) 106 return -EINVAL; 107 state->pc = orig_pc; 108 } 109 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 110 #ifdef CONFIG_KRETPROBES 111 if (is_kretprobe_trampoline(state->pc)) 112 state->pc = kretprobe_find_ret_addr(tsk, (void *)state->fp, &state->kr_cur); 113 #endif 114 115 return 0; 116 } 117 NOKPROBE_SYMBOL(unwind_next); 118 119 static void notrace unwind(struct unwind_state *state, 120 stack_trace_consume_fn consume_entry, void *cookie) 121 { 122 while (1) { 123 int ret; 124 125 if (!consume_entry(cookie, state->pc)) 126 break; 127 ret = unwind_next(state); 128 if (ret < 0) 129 break; 130 } 131 } 132 NOKPROBE_SYMBOL(unwind); 133 134 static bool dump_backtrace_entry(void *arg, unsigned long where) 135 { 136 char *loglvl = arg; 137 printk("%s %pSb\n", loglvl, (void *)where); 138 return true; 139 } 140 141 void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, 142 const char *loglvl) 143 { 144 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 145 146 if (regs && user_mode(regs)) 147 return; 148 149 if (!tsk) 150 tsk = current; 151 152 if (!try_get_task_stack(tsk)) 153 return; 154 155 printk("%sCall trace:\n", loglvl); 156 arch_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs); 157 158 put_task_stack(tsk); 159 } 160 161 void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl) 162 { 163 dump_backtrace(NULL, tsk, loglvl); 164 barrier(); 165 } 166 167 /* 168 * Per-cpu stacks are only accessible when unwinding the current task in a 169 * non-preemptible context. 170 */ 171 #define STACKINFO_CPU(name) \ 172 ({ \ 173 ((task == current) && !preemptible()) \ 174 ? stackinfo_get_##name() \ 175 : stackinfo_get_unknown(); \ 176 }) 177 178 /* 179 * SDEI stacks are only accessible when unwinding the current task in an NMI 180 * context. 181 */ 182 #define STACKINFO_SDEI(name) \ 183 ({ \ 184 ((task == current) && in_nmi()) \ 185 ? stackinfo_get_sdei_##name() \ 186 : stackinfo_get_unknown(); \ 187 }) 188 189 noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, 190 void *cookie, struct task_struct *task, 191 struct pt_regs *regs) 192 { 193 struct stack_info stacks[] = { 194 stackinfo_get_task(task), 195 STACKINFO_CPU(irq), 196 #if defined(CONFIG_VMAP_STACK) 197 STACKINFO_CPU(overflow), 198 #endif 199 #if defined(CONFIG_VMAP_STACK) && defined(CONFIG_ARM_SDE_INTERFACE) 200 STACKINFO_SDEI(normal), 201 STACKINFO_SDEI(critical), 202 #endif 203 }; 204 struct unwind_state state = { 205 .stacks = stacks, 206 .nr_stacks = ARRAY_SIZE(stacks), 207 }; 208 209 if (regs) { 210 if (task != current) 211 return; 212 unwind_init_from_regs(&state, regs); 213 } else if (task == current) { 214 unwind_init_from_caller(&state); 215 } else { 216 unwind_init_from_task(&state, task); 217 } 218 219 unwind(&state, consume_entry, cookie); 220 } 221