227 lines
6.2 KiB
C
227 lines
6.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Stack tracing support
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*
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* Copyright (C) 2012 ARM Ltd.
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*/
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/ftrace.h>
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#include <linux/kprobes.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.h>
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#include <linux/sched/task_stack.h>
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#include <linux/stacktrace.h>
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#include <asm/irq.h>
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#include <asm/pointer_auth.h>
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#include <asm/stack_pointer.h>
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#include <asm/stacktrace.h>
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/*
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* A snapshot of a frame record or fp/lr register values, along with some
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* accounting information necessary for robust unwinding.
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*
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* @fp: The fp value in the frame record (or the real fp)
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* @pc: The lr value in the frame record (or the real lr)
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*
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* @stacks_done: Stacks which have been entirely unwound, for which it is no
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* longer valid to unwind to.
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*
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* @prev_fp: The fp that pointed to this frame record, or a synthetic value
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* of 0. This is used to ensure that within a stack, each
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* subsequent frame record is at an increasing address.
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* @prev_type: The type of stack this frame record was on, or a synthetic
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* value of STACK_TYPE_UNKNOWN. This is used to detect a
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* transition from one stack to another.
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*
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* @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
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* associated with the most recently encountered replacement lr
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* value.
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*/
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struct unwind_state {
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unsigned long fp;
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unsigned long pc;
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DECLARE_BITMAP(stacks_done, __NR_STACK_TYPES);
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unsigned long prev_fp;
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enum stack_type prev_type;
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#ifdef CONFIG_KRETPROBES
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struct llist_node *kr_cur;
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#endif
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};
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static notrace void unwind_init(struct unwind_state *state, unsigned long fp,
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unsigned long pc)
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{
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state->fp = fp;
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state->pc = pc;
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#ifdef CONFIG_KRETPROBES
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state->kr_cur = NULL;
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#endif
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/*
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* Prime the first unwind.
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*
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* In unwind_next() we'll check that the FP points to a valid stack,
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* which can't be STACK_TYPE_UNKNOWN, and the first unwind will be
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* treated as a transition to whichever stack that happens to be. The
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* prev_fp value won't be used, but we set it to 0 such that it is
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* definitely not an accessible stack address.
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*/
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bitmap_zero(state->stacks_done, __NR_STACK_TYPES);
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state->prev_fp = 0;
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state->prev_type = STACK_TYPE_UNKNOWN;
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}
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NOKPROBE_SYMBOL(unwind_init);
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/*
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* Unwind from one frame record (A) to the next frame record (B).
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*
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* We terminate early if the location of B indicates a malformed chain of frame
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* records (e.g. a cycle), determined based on the location and fp value of A
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* and the location (but not the fp value) of B.
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*/
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static int notrace unwind_next(struct task_struct *tsk,
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struct unwind_state *state)
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{
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unsigned long fp = state->fp;
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struct stack_info info;
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/* Final frame; nothing to unwind */
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if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
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return -ENOENT;
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if (fp & 0x7)
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return -EINVAL;
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if (!on_accessible_stack(tsk, fp, 16, &info))
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return -EINVAL;
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if (test_bit(info.type, state->stacks_done))
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return -EINVAL;
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/*
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* As stacks grow downward, any valid record on the same stack must be
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* at a strictly higher address than the prior record.
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*
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* Stacks can nest in several valid orders, e.g.
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*
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* TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL
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* TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW
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*
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* ... but the nesting itself is strict. Once we transition from one
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* stack to another, it's never valid to unwind back to that first
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* stack.
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*/
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if (info.type == state->prev_type) {
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if (fp <= state->prev_fp)
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return -EINVAL;
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} else {
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set_bit(state->prev_type, state->stacks_done);
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}
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/*
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* Record this frame record's values and location. The prev_fp and
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* prev_type are only meaningful to the next unwind_next() invocation.
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*/
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state->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
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state->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
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state->prev_fp = fp;
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state->prev_type = info.type;
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state->pc = ptrauth_strip_insn_pac(state->pc);
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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if (tsk->ret_stack &&
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(state->pc == (unsigned long)return_to_handler)) {
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unsigned long orig_pc;
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/*
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* This is a case where function graph tracer has
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* modified a return address (LR) in a stack frame
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* to hook a function return.
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* So replace it to an original value.
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*/
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orig_pc = ftrace_graph_ret_addr(tsk, NULL, state->pc,
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(void *)state->fp);
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if (WARN_ON_ONCE(state->pc == orig_pc))
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return -EINVAL;
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state->pc = orig_pc;
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}
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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#ifdef CONFIG_KRETPROBES
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if (is_kretprobe_trampoline(state->pc))
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state->pc = kretprobe_find_ret_addr(tsk, (void *)state->fp, &state->kr_cur);
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#endif
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return 0;
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}
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NOKPROBE_SYMBOL(unwind_next);
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static void notrace unwind(struct task_struct *tsk,
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struct unwind_state *state,
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stack_trace_consume_fn consume_entry, void *cookie)
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{
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while (1) {
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int ret;
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if (!consume_entry(cookie, state->pc))
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break;
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ret = unwind_next(tsk, state);
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if (ret < 0)
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break;
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}
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}
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NOKPROBE_SYMBOL(unwind);
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static bool dump_backtrace_entry(void *arg, unsigned long where)
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{
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char *loglvl = arg;
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printk("%s %pSb\n", loglvl, (void *)where);
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return true;
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}
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void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
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const char *loglvl)
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{
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pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
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if (regs && user_mode(regs))
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return;
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if (!tsk)
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tsk = current;
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if (!try_get_task_stack(tsk))
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return;
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printk("%sCall trace:\n", loglvl);
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arch_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs);
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put_task_stack(tsk);
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}
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void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
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{
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dump_backtrace(NULL, tsk, loglvl);
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barrier();
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}
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noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
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void *cookie, struct task_struct *task,
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struct pt_regs *regs)
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{
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struct unwind_state state;
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if (regs)
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unwind_init(&state, regs->regs[29], regs->pc);
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else if (task == current)
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unwind_init(&state,
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(unsigned long)__builtin_frame_address(1),
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(unsigned long)__builtin_return_address(0));
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else
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unwind_init(&state, thread_saved_fp(task),
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thread_saved_pc(task));
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unwind(task, &state, consume_entry, cookie);
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}
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