1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #include <linux/sched.h> 3 #include <linux/sched/task.h> 4 #include <linux/sched/task_stack.h> 5 #include <linux/interrupt.h> 6 #include <asm/sections.h> 7 #include <asm/ptrace.h> 8 #include <asm/bitops.h> 9 #include <asm/stacktrace.h> 10 #include <asm/unwind.h> 11 12 unsigned long unwind_get_return_address(struct unwind_state *state) 13 { 14 if (unwind_done(state)) 15 return 0; 16 return __kernel_text_address(state->ip) ? state->ip : 0; 17 } 18 EXPORT_SYMBOL_GPL(unwind_get_return_address); 19 20 static bool outside_of_stack(struct unwind_state *state, unsigned long sp) 21 { 22 return (sp <= state->sp) || 23 (sp > state->stack_info.end - sizeof(struct stack_frame)); 24 } 25 26 static bool update_stack_info(struct unwind_state *state, unsigned long sp) 27 { 28 struct stack_info *info = &state->stack_info; 29 unsigned long *mask = &state->stack_mask; 30 31 /* New stack pointer leaves the current stack */ 32 if (get_stack_info(sp, state->task, info, mask) != 0 || 33 !on_stack(info, sp, sizeof(struct stack_frame))) 34 /* 'sp' does not point to a valid stack */ 35 return false; 36 return true; 37 } 38 39 static inline bool is_task_pt_regs(struct unwind_state *state, 40 struct pt_regs *regs) 41 { 42 return task_pt_regs(state->task) == regs; 43 } 44 45 bool unwind_next_frame(struct unwind_state *state) 46 { 47 struct stack_info *info = &state->stack_info; 48 struct stack_frame *sf; 49 struct pt_regs *regs; 50 unsigned long sp, ip; 51 bool reliable; 52 53 regs = state->regs; 54 if (unlikely(regs)) { 55 sp = state->sp; 56 sf = (struct stack_frame *) sp; 57 ip = READ_ONCE_NOCHECK(sf->gprs[8]); 58 reliable = false; 59 regs = NULL; 60 if (!__kernel_text_address(ip)) { 61 /* skip bogus %r14 */ 62 state->regs = NULL; 63 return unwind_next_frame(state); 64 } 65 } else { 66 sf = (struct stack_frame *) state->sp; 67 sp = READ_ONCE_NOCHECK(sf->back_chain); 68 if (likely(sp)) { 69 /* Non-zero back-chain points to the previous frame */ 70 if (unlikely(outside_of_stack(state, sp))) { 71 if (!update_stack_info(state, sp)) 72 goto out_err; 73 } 74 sf = (struct stack_frame *) sp; 75 ip = READ_ONCE_NOCHECK(sf->gprs[8]); 76 reliable = true; 77 } else { 78 /* No back-chain, look for a pt_regs structure */ 79 sp = state->sp + STACK_FRAME_OVERHEAD; 80 if (!on_stack(info, sp, sizeof(struct pt_regs))) 81 goto out_err; 82 regs = (struct pt_regs *) sp; 83 if (is_task_pt_regs(state, regs)) 84 goto out_stop; 85 ip = READ_ONCE_NOCHECK(regs->psw.addr); 86 sp = READ_ONCE_NOCHECK(regs->gprs[15]); 87 if (unlikely(outside_of_stack(state, sp))) { 88 if (!update_stack_info(state, sp)) 89 goto out_err; 90 } 91 reliable = true; 92 } 93 } 94 95 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, (void *) sp); 96 97 /* Update unwind state */ 98 state->sp = sp; 99 state->ip = ip; 100 state->regs = regs; 101 state->reliable = reliable; 102 return true; 103 104 out_err: 105 state->error = true; 106 out_stop: 107 state->stack_info.type = STACK_TYPE_UNKNOWN; 108 return false; 109 } 110 EXPORT_SYMBOL_GPL(unwind_next_frame); 111 112 void __unwind_start(struct unwind_state *state, struct task_struct *task, 113 struct pt_regs *regs, unsigned long first_frame) 114 { 115 struct stack_info *info = &state->stack_info; 116 struct stack_frame *sf; 117 unsigned long ip, sp; 118 119 memset(state, 0, sizeof(*state)); 120 state->task = task; 121 state->regs = regs; 122 123 /* Don't even attempt to start from user mode regs: */ 124 if (regs && user_mode(regs)) { 125 info->type = STACK_TYPE_UNKNOWN; 126 return; 127 } 128 129 /* Get the instruction pointer from pt_regs or the stack frame */ 130 if (regs) { 131 ip = regs->psw.addr; 132 sp = regs->gprs[15]; 133 } else if (task == current) { 134 sp = current_frame_address(); 135 } else { 136 sp = task->thread.ksp; 137 } 138 139 /* Get current stack pointer and initialize stack info */ 140 if (!update_stack_info(state, sp)) { 141 /* Something is wrong with the stack pointer */ 142 info->type = STACK_TYPE_UNKNOWN; 143 state->error = true; 144 return; 145 } 146 147 if (!regs) { 148 /* Stack frame is within valid stack */ 149 sf = (struct stack_frame *)sp; 150 ip = READ_ONCE_NOCHECK(sf->gprs[8]); 151 } 152 153 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL); 154 155 /* Update unwind state */ 156 state->sp = sp; 157 state->ip = ip; 158 state->reliable = true; 159 160 if (!first_frame) 161 return; 162 /* Skip through the call chain to the specified starting frame */ 163 while (!unwind_done(state)) { 164 if (on_stack(&state->stack_info, first_frame, sizeof(struct stack_frame))) { 165 if (state->sp >= first_frame) 166 break; 167 } 168 unwind_next_frame(state); 169 } 170 } 171 EXPORT_SYMBOL_GPL(__unwind_start); 172