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 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         /* Sanity check: ABI requires SP to be aligned 8 bytes. */
  96         if (sp & 0x7)
  97                 goto out_err;
  98
  99         ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, (void *) sp);
 100
 101         /* Update unwind state */
 102         state->sp = sp;
 103         state->ip = ip;
 104         state->regs = regs;
 105         state->reliable = reliable;
 106         return true;
 107
 108 out_err:
 109         state->error = true;
 110 out_stop:
 111         state->stack_info.type = STACK_TYPE_UNKNOWN;
 112         return false;
 113 }
 114 EXPORT_SYMBOL_GPL(unwind_next_frame);
 115
 116 void __unwind_start(struct unwind_state *state, struct task_struct *task,
 117                     struct pt_regs *regs, unsigned long first_frame)
 118 {
 119         struct stack_info *info = &state->stack_info;
 120         struct stack_frame *sf;
 121         unsigned long ip, sp;
 122
 123         memset(state, 0, sizeof(*state));
 124         state->task = task;
 125         state->regs = regs;
 126
 127         /* Don't even attempt to start from user mode regs: */
 128         if (regs && user_mode(regs)) {
 129                 info->type = STACK_TYPE_UNKNOWN;
 130                 return;
 131         }
 132
 133         /* Get the instruction pointer from pt_regs or the stack frame */
 134         if (regs) {
 135                 ip = regs->psw.addr;
 136                 sp = regs->gprs[15];
 137         } else if (task == current) {
 138                 sp = current_frame_address();
 139         } else {
 140                 sp = task->thread.ksp;
 141         }
 142
 143         /* Get current stack pointer and initialize stack info */
 144         if (!update_stack_info(state, sp)) {
 145                 /* Something is wrong with the stack pointer */
 146                 info->type = STACK_TYPE_UNKNOWN;
 147                 state->error = true;
 148                 return;
 149         }
 150
 151         if (!regs) {
 152                 /* Stack frame is within valid stack */
 153                 sf = (struct stack_frame *)sp;
 154                 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
 155         }
 156
 157         ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL);
 158
 159         /* Update unwind state */
 160         state->sp = sp;
 161         state->ip = ip;
 162         state->reliable = true;
 163
 164         if (!first_frame)
 165                 return;
 166         /* Skip through the call chain to the specified starting frame */
 167         while (!unwind_done(state)) {
 168                 if (on_stack(&state->stack_info, first_frame, sizeof(struct stack_frame))) {
 169                         if (state->sp >= first_frame)
 170                                 break;
 171                 }
 172                 unwind_next_frame(state);
 173         }
 174 }
 175 EXPORT_SYMBOL_GPL(__unwind_start);