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240 lines
5.8 KiB
240 lines
5.8 KiB
// 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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* AArch64 PCS assigns the frame pointer to x29. |
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* |
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* A simple function prologue looks like this: |
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* sub sp, sp, #0x10 |
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* stp x29, x30, [sp] |
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* mov x29, sp |
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* |
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* A simple function epilogue looks like this: |
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* mov sp, x29 |
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* ldp x29, x30, [sp] |
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* add sp, sp, #0x10 |
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*/ |
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void start_backtrace(struct stackframe *frame, unsigned long fp, |
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unsigned long pc) |
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{ |
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frame->fp = fp; |
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frame->pc = pc; |
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER |
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frame->graph = 0; |
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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_frame() 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(frame->stacks_done, __NR_STACK_TYPES); |
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frame->prev_fp = 0; |
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frame->prev_type = STACK_TYPE_UNKNOWN; |
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} |
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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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int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) |
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{ |
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unsigned long fp = frame->fp; |
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struct stack_info info; |
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if (!tsk) |
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tsk = current; |
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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, frame->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 == frame->prev_type) { |
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if (fp <= frame->prev_fp) |
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return -EINVAL; |
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} else { |
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set_bit(frame->prev_type, frame->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_frame() invocation. |
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*/ |
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frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp)); |
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frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8)); |
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frame->prev_fp = fp; |
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frame->prev_type = info.type; |
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER |
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if (tsk->ret_stack && |
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(ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) { |
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struct ftrace_ret_stack *ret_stack; |
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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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ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++); |
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if (WARN_ON_ONCE(!ret_stack)) |
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return -EINVAL; |
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frame->pc = ret_stack->ret; |
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} |
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |
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frame->pc = ptrauth_strip_insn_pac(frame->pc); |
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return 0; |
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} |
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NOKPROBE_SYMBOL(unwind_frame); |
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void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame, |
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bool (*fn)(void *, unsigned long), void *data) |
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{ |
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while (1) { |
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int ret; |
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if (!fn(data, frame->pc)) |
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break; |
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ret = unwind_frame(tsk, frame); |
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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(walk_stackframe); |
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static void dump_backtrace_entry(unsigned long where, const char *loglvl) |
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{ |
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printk("%s %pSb\n", loglvl, (void *)where); |
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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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struct stackframe frame; |
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int skip = 0; |
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pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); |
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if (regs) { |
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if (user_mode(regs)) |
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return; |
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skip = 1; |
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} |
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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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if (tsk == current) { |
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start_backtrace(&frame, |
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(unsigned long)__builtin_frame_address(0), |
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(unsigned long)dump_backtrace); |
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} else { |
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/* |
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* task blocked in __switch_to |
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*/ |
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start_backtrace(&frame, |
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thread_saved_fp(tsk), |
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thread_saved_pc(tsk)); |
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} |
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printk("%sCall trace:\n", loglvl); |
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do { |
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/* skip until specified stack frame */ |
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if (!skip) { |
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dump_backtrace_entry(frame.pc, loglvl); |
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} else if (frame.fp == regs->regs[29]) { |
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skip = 0; |
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/* |
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* Mostly, this is the case where this function is |
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* called in panic/abort. As exception handler's |
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* stack frame does not contain the corresponding pc |
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* at which an exception has taken place, use regs->pc |
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* instead. |
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*/ |
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dump_backtrace_entry(regs->pc, loglvl); |
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} |
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} while (!unwind_frame(tsk, &frame)); |
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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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#ifdef CONFIG_STACKTRACE |
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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 stackframe frame; |
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if (regs) |
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start_backtrace(&frame, regs->regs[29], regs->pc); |
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else if (task == current) |
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start_backtrace(&frame, |
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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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start_backtrace(&frame, thread_saved_fp(task), |
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thread_saved_pc(task)); |
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walk_stackframe(task, &frame, consume_entry, cookie); |
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} |
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#endif
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