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 + sizeof(struct stack_frame) > state->stack_info.end); 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 bool unwind_next_frame(struct unwind_state *state) 40 { 41 struct stack_info *info = &state->stack_info; 42 struct stack_frame *sf; 43 struct pt_regs *regs; 44 unsigned long sp, ip; 45 bool reliable; 46 47 regs = state->regs; 48 if (unlikely(regs)) { 49 sp = READ_ONCE_NOCHECK(regs->gprs[15]); 50 if (unlikely(outside_of_stack(state, sp))) { 51 if (!update_stack_info(state, sp)) 52 goto out_err; 53 } 54 sf = (struct stack_frame *) sp; 55 ip = READ_ONCE_NOCHECK(sf->gprs[8]); 56 reliable = false; 57 regs = NULL; 58 } else { 59 sf = (struct stack_frame *) state->sp; 60 sp = READ_ONCE_NOCHECK(sf->back_chain); 61 if (likely(sp)) { 62 /* Non-zero back-chain points to the previous frame */ 63 if (unlikely(outside_of_stack(state, sp))) { 64 if (!update_stack_info(state, sp)) 65 goto out_err; 66 } 67 sf = (struct stack_frame *) sp; 68 ip = READ_ONCE_NOCHECK(sf->gprs[8]); 69 reliable = true; 70 } else { 71 /* No back-chain, look for a pt_regs structure */ 72 sp = state->sp + STACK_FRAME_OVERHEAD; 73 if (!on_stack(info, sp, sizeof(struct pt_regs))) 74 goto out_stop; 75 regs = (struct pt_regs *) sp; 76 if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE) 77 goto out_stop; 78 ip = READ_ONCE_NOCHECK(regs->psw.addr); 79 reliable = true; 80 } 81 } 82 83 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 84 /* Decode any ftrace redirection */ 85 if (ip == (unsigned long) return_to_handler) 86 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, 87 ip, (void *) sp); 88 #endif 89 90 /* Update unwind state */ 91 state->sp = sp; 92 state->ip = ip; 93 state->regs = regs; 94 state->reliable = reliable; 95 return true; 96 97 out_err: 98 state->error = true; 99 out_stop: 100 state->stack_info.type = STACK_TYPE_UNKNOWN; 101 return false; 102 } 103 EXPORT_SYMBOL_GPL(unwind_next_frame); 104 105 void __unwind_start(struct unwind_state *state, struct task_struct *task, 106 struct pt_regs *regs, unsigned long sp) 107 { 108 struct stack_info *info = &state->stack_info; 109 unsigned long *mask = &state->stack_mask; 110 struct stack_frame *sf; 111 unsigned long ip; 112 bool reliable; 113 114 memset(state, 0, sizeof(*state)); 115 state->task = task; 116 state->regs = regs; 117 118 /* Don't even attempt to start from user mode regs: */ 119 if (regs && user_mode(regs)) { 120 info->type = STACK_TYPE_UNKNOWN; 121 return; 122 } 123 124 /* Get current stack pointer and initialize stack info */ 125 if (get_stack_info(sp, task, info, mask) != 0 || 126 !on_stack(info, sp, sizeof(struct stack_frame))) { 127 /* Something is wrong with the stack pointer */ 128 info->type = STACK_TYPE_UNKNOWN; 129 state->error = true; 130 return; 131 } 132 133 /* Get the instruction pointer from pt_regs or the stack frame */ 134 if (regs) { 135 ip = READ_ONCE_NOCHECK(regs->psw.addr); 136 reliable = true; 137 } else { 138 sf = (struct stack_frame *) sp; 139 ip = READ_ONCE_NOCHECK(sf->gprs[8]); 140 reliable = false; 141 } 142 143 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 144 /* Decode any ftrace redirection */ 145 if (ip == (unsigned long) return_to_handler) 146 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, 147 ip, NULL); 148 #endif 149 150 /* Update unwind state */ 151 state->sp = sp; 152 state->ip = ip; 153 state->reliable = reliable; 154 } 155 EXPORT_SYMBOL_GPL(__unwind_start); 156