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_final_pt_regs(struct unwind_state *state,
  40                                     struct pt_regs *regs)
  41 {
  42         /* user mode or kernel thread pt_regs at the bottom of task stack */
  43         if (task_pt_regs(state->task) == regs)
  44                 return true;
  45
  46         /* user mode pt_regs at the bottom of irq stack */
  47         return state->stack_info.type == STACK_TYPE_IRQ &&
  48                state->stack_info.end - sizeof(struct pt_regs) == (unsigned long)regs &&
  49                READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE;
  50 }
  51
  52 bool unwind_next_frame(struct unwind_state *state)
  53 {
  54         struct stack_info *info = &state->stack_info;
  55         struct stack_frame *sf;
  56         struct pt_regs *regs;
  57         unsigned long sp, ip;
  58         bool reliable;
  59
  60         regs = state->regs;
  61         if (unlikely(regs)) {
  62                 sp = state->sp;
  63                 sf = (struct stack_frame *) sp;
  64                 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
  65                 reliable = false;
  66                 regs = NULL;
  67                 if (!__kernel_text_address(ip)) {
  68                         /* skip bogus %r14 */
  69                         state->regs = NULL;
  70                         return unwind_next_frame(state);
  71                 }
  72         } else {
  73                 sf = (struct stack_frame *) state->sp;
  74                 sp = READ_ONCE_NOCHECK(sf->back_chain);
  75                 if (likely(sp)) {
  76                         /* Non-zero back-chain points to the previous frame */
  77                         if (unlikely(outside_of_stack(state, sp))) {
  78                                 if (!update_stack_info(state, sp))
  79                                         goto out_err;
  80                         }
  81                         sf = (struct stack_frame *) sp;
  82                         ip = READ_ONCE_NOCHECK(sf->gprs[8]);
  83                         reliable = true;
  84                 } else {
  85                         /* No back-chain, look for a pt_regs structure */
  86                         sp = state->sp + STACK_FRAME_OVERHEAD;
  87                         if (!on_stack(info, sp, sizeof(struct pt_regs)))
  88                                 goto out_err;
  89                         regs = (struct pt_regs *) sp;
  90                         if (is_final_pt_regs(state, regs))
  91                                 goto out_stop;
  92                         ip = READ_ONCE_NOCHECK(regs->psw.addr);
  93                         sp = READ_ONCE_NOCHECK(regs->gprs[15]);
  94                         if (unlikely(outside_of_stack(state, sp))) {
  95                                 if (!update_stack_info(state, sp))
  96                                         goto out_err;
  97                         }
  98                         reliable = true;
  99                 }
 100         }
 101
 102         /* Sanity check: ABI requires SP to be aligned 8 bytes. */
 103         if (sp & 0x7)
 104                 goto out_err;
 105
 106         ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, (void *) sp);
 107
 108         /* Update unwind state */
 109         state->sp = sp;
 110         state->ip = ip;
 111         state->regs = regs;
 112         state->reliable = reliable;
 113         return true;
 114
 115 out_err:
 116         state->error = true;
 117 out_stop:
 118         state->stack_info.type = STACK_TYPE_UNKNOWN;
 119         return false;
 120 }
 121 EXPORT_SYMBOL_GPL(unwind_next_frame);
 122
 123 void __unwind_start(struct unwind_state *state, struct task_struct *task,
 124                     struct pt_regs *regs, unsigned long first_frame)
 125 {
 126         struct stack_info *info = &state->stack_info;
 127         struct stack_frame *sf;
 128         unsigned long ip, sp;
 129
 130         memset(state, 0, sizeof(*state));
 131         state->task = task;
 132         state->regs = regs;
 133
 134         /* Don't even attempt to start from user mode regs: */
 135         if (regs && user_mode(regs)) {
 136                 info->type = STACK_TYPE_UNKNOWN;
 137                 return;
 138         }
 139
 140         /* Get the instruction pointer from pt_regs or the stack frame */
 141         if (regs) {
 142                 ip = regs->psw.addr;
 143                 sp = regs->gprs[15];
 144         } else if (task == current) {
 145                 sp = current_frame_address();
 146         } else {
 147                 sp = task->thread.ksp;
 148         }
 149
 150         /* Get current stack pointer and initialize stack info */
 151         if (!update_stack_info(state, sp)) {
 152                 /* Something is wrong with the stack pointer */
 153                 info->type = STACK_TYPE_UNKNOWN;
 154                 state->error = true;
 155                 return;
 156         }
 157
 158         if (!regs) {
 159                 /* Stack frame is within valid stack */
 160                 sf = (struct stack_frame *)sp;
 161                 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
 162         }
 163
 164         ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL);
 165
 166         /* Update unwind state */
 167         state->sp = sp;
 168         state->ip = ip;
 169         state->reliable = true;
 170
 171         if (!first_frame)
 172                 return;
 173         /* Skip through the call chain to the specified starting frame */
 174         while (!unwind_done(state)) {
 175                 if (on_stack(&state->stack_info, first_frame, sizeof(struct stack_frame))) {
 176                         if (state->sp >= first_frame)
 177                                 break;
 178                 }
 179                 unwind_next_frame(state);
 180         }
 181 }
 182 EXPORT_SYMBOL_GPL(__unwind_start);