arch/s390/kernel/unwind_bc.c

   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 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                 if (state->reuse_sp) {
  50                         sp = state->sp;
  51                         state->reuse_sp = false;
  52                 } else {
  53                         sp = READ_ONCE_NOCHECK(regs->gprs[15]);
  54                         if (unlikely(outside_of_stack(state, sp))) {
  55                                 if (!update_stack_info(state, sp))
  56                                         goto out_err;
  57                         }
  58                 }
  59                 sf = (struct stack_frame *) sp;
  60                 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
  61                 reliable = false;
  62                 regs = NULL;
  63         } else {
  64                 sf = (struct stack_frame *) state->sp;
  65                 sp = READ_ONCE_NOCHECK(sf->back_chain);
  66                 if (likely(sp)) {
  67                         /* Non-zero back-chain points to the previous frame */
  68                         if (unlikely(outside_of_stack(state, sp))) {
  69                                 if (!update_stack_info(state, sp))
  70                                         goto out_err;
  71                         }
  72                         sf = (struct stack_frame *) sp;
  73                         ip = READ_ONCE_NOCHECK(sf->gprs[8]);
  74                         reliable = true;
  75                 } else {
  76                         /* No back-chain, look for a pt_regs structure */
  77                         sp = state->sp + STACK_FRAME_OVERHEAD;
  78                         if (!on_stack(info, sp, sizeof(struct pt_regs)))
  79                                 goto out_stop;
  80                         regs = (struct pt_regs *) sp;
  81                         if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE)
  82                                 goto out_stop;
  83                         ip = READ_ONCE_NOCHECK(regs->psw.addr);
  84                         reliable = true;
  85                 }
  86         }
  87
  88 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  89         /* Decode any ftrace redirection */
  90         if (ip == (unsigned long) return_to_handler)
  91                 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
  92                                            ip, (void *) sp);
  93 #endif
  94
  95         /* Update unwind state */
  96         state->sp = sp;
  97         state->ip = ip;
  98         state->regs = regs;
  99         state->reliable = reliable;
 100         return true;
 101
 102 out_err:
 103         state->error = true;
 104 out_stop:
 105         state->stack_info.type = STACK_TYPE_UNKNOWN;
 106         return false;
 107 }
 108 EXPORT_SYMBOL_GPL(unwind_next_frame);
 109
 110 void __unwind_start(struct unwind_state *state, struct task_struct *task,
 111                     struct pt_regs *regs, unsigned long sp)
 112 {
 113         struct stack_info *info = &state->stack_info;
 114         unsigned long *mask = &state->stack_mask;
 115         bool reliable, reuse_sp;
 116         struct stack_frame *sf;
 117         unsigned long ip;
 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 current stack pointer and initialize stack info */
 130         if (get_stack_info(sp, task, info, mask) != 0 ||
 131             !on_stack(info, sp, sizeof(struct stack_frame))) {
 132                 /* Something is wrong with the stack pointer */
 133                 info->type = STACK_TYPE_UNKNOWN;
 134                 state->error = true;
 135                 return;
 136         }
 137
 138         /* Get the instruction pointer from pt_regs or the stack frame */
 139         if (regs) {
 140                 ip = READ_ONCE_NOCHECK(regs->psw.addr);
 141                 reliable = true;
 142                 reuse_sp = true;
 143         } else {
 144                 sf = (struct stack_frame *) sp;
 145                 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
 146                 reliable = false;
 147                 reuse_sp = false;
 148         }
 149
 150 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 151         /* Decode any ftrace redirection */
 152         if (ip == (unsigned long) return_to_handler)
 153                 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
 154                                            ip, NULL);
 155 #endif
 156
 157         /* Update unwind state */
 158         state->sp = sp;
 159         state->ip = ip;
 160         state->reliable = reliable;
 161         state->reuse_sp = reuse_sp;
 162 }
 163 EXPORT_SYMBOL_GPL(__unwind_start);