| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Stack tracing support |
| * |
| * Copyright (C) 2012 ARM Ltd. |
| */ |
| #include <linux/kernel.h> |
| #include <linux/export.h> |
| #include <linux/ftrace.h> |
| #include <linux/kprobes.h> |
| #include <linux/sched.h> |
| #include <linux/sched/debug.h> |
| #include <linux/sched/task_stack.h> |
| #include <linux/stacktrace.h> |
| |
| #include <asm/irq.h> |
| #include <asm/pointer_auth.h> |
| #include <asm/stack_pointer.h> |
| #include <asm/stacktrace.h> |
| |
| /* |
| * AArch64 PCS assigns the frame pointer to x29. |
| * |
| * A simple function prologue looks like this: |
| * sub sp, sp, #0x10 |
| * stp x29, x30, [sp] |
| * mov x29, sp |
| * |
| * A simple function epilogue looks like this: |
| * mov sp, x29 |
| * ldp x29, x30, [sp] |
| * add sp, sp, #0x10 |
| */ |
| |
| |
| void start_backtrace(struct stackframe *frame, unsigned long fp, |
| unsigned long pc) |
| { |
| frame->fp = fp; |
| frame->pc = pc; |
| #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| frame->graph = 0; |
| #endif |
| |
| /* |
| * Prime the first unwind. |
| * |
| * In unwind_frame() we'll check that the FP points to a valid stack, |
| * which can't be STACK_TYPE_UNKNOWN, and the first unwind will be |
| * treated as a transition to whichever stack that happens to be. The |
| * prev_fp value won't be used, but we set it to 0 such that it is |
| * definitely not an accessible stack address. |
| */ |
| bitmap_zero(frame->stacks_done, __NR_STACK_TYPES); |
| frame->prev_fp = 0; |
| frame->prev_type = STACK_TYPE_UNKNOWN; |
| } |
| |
| /* |
| * Unwind from one frame record (A) to the next frame record (B). |
| * |
| * We terminate early if the location of B indicates a malformed chain of frame |
| * records (e.g. a cycle), determined based on the location and fp value of A |
| * and the location (but not the fp value) of B. |
| */ |
| int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) |
| { |
| unsigned long fp = frame->fp; |
| struct stack_info info; |
| |
| if (!tsk) |
| tsk = current; |
| |
| /* Final frame; nothing to unwind */ |
| if (fp == (unsigned long)task_pt_regs(tsk)->stackframe) |
| return -ENOENT; |
| |
| if (fp & 0x7) |
| return -EINVAL; |
| |
| if (!on_accessible_stack(tsk, fp, 16, &info)) |
| return -EINVAL; |
| |
| if (test_bit(info.type, frame->stacks_done)) |
| return -EINVAL; |
| |
| /* |
| * As stacks grow downward, any valid record on the same stack must be |
| * at a strictly higher address than the prior record. |
| * |
| * Stacks can nest in several valid orders, e.g. |
| * |
| * TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL |
| * TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW |
| * |
| * ... but the nesting itself is strict. Once we transition from one |
| * stack to another, it's never valid to unwind back to that first |
| * stack. |
| */ |
| if (info.type == frame->prev_type) { |
| if (fp <= frame->prev_fp) |
| return -EINVAL; |
| } else { |
| set_bit(frame->prev_type, frame->stacks_done); |
| } |
| |
| /* |
| * Record this frame record's values and location. The prev_fp and |
| * prev_type are only meaningful to the next unwind_frame() invocation. |
| */ |
| frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp)); |
| frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8)); |
| frame->prev_fp = fp; |
| frame->prev_type = info.type; |
| |
| #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| if (tsk->ret_stack && |
| (ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) { |
| struct ftrace_ret_stack *ret_stack; |
| /* |
| * This is a case where function graph tracer has |
| * modified a return address (LR) in a stack frame |
| * to hook a function return. |
| * So replace it to an original value. |
| */ |
| ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++); |
| if (WARN_ON_ONCE(!ret_stack)) |
| return -EINVAL; |
| frame->pc = ret_stack->ret; |
| } |
| #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |
| |
| frame->pc = ptrauth_strip_insn_pac(frame->pc); |
| |
| return 0; |
| } |
| NOKPROBE_SYMBOL(unwind_frame); |
| |
| void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame, |
| bool (*fn)(void *, unsigned long), void *data) |
| { |
| while (1) { |
| int ret; |
| |
| if (!fn(data, frame->pc)) |
| break; |
| ret = unwind_frame(tsk, frame); |
| if (ret < 0) |
| break; |
| } |
| } |
| NOKPROBE_SYMBOL(walk_stackframe); |
| |
| static void dump_backtrace_entry(unsigned long where, const char *loglvl) |
| { |
| printk("%s %pS\n", loglvl, (void *)where); |
| } |
| |
| void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, |
| const char *loglvl) |
| { |
| struct stackframe frame; |
| int skip = 0; |
| |
| pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); |
| |
| if (regs) { |
| if (user_mode(regs)) |
| return; |
| skip = 1; |
| } |
| |
| if (!tsk) |
| tsk = current; |
| |
| if (!try_get_task_stack(tsk)) |
| return; |
| |
| if (tsk == current) { |
| start_backtrace(&frame, |
| (unsigned long)__builtin_frame_address(0), |
| (unsigned long)dump_backtrace); |
| } else { |
| /* |
| * task blocked in __switch_to |
| */ |
| start_backtrace(&frame, |
| thread_saved_fp(tsk), |
| thread_saved_pc(tsk)); |
| } |
| |
| printk("%sCall trace:\n", loglvl); |
| do { |
| /* skip until specified stack frame */ |
| if (!skip) { |
| dump_backtrace_entry(frame.pc, loglvl); |
| } else if (frame.fp == regs->regs[29]) { |
| skip = 0; |
| /* |
| * Mostly, this is the case where this function is |
| * called in panic/abort. As exception handler's |
| * stack frame does not contain the corresponding pc |
| * at which an exception has taken place, use regs->pc |
| * instead. |
| */ |
| dump_backtrace_entry(regs->pc, loglvl); |
| } |
| } while (!unwind_frame(tsk, &frame)); |
| |
| put_task_stack(tsk); |
| } |
| |
| void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl) |
| { |
| dump_backtrace(NULL, tsk, loglvl); |
| barrier(); |
| } |
| |
| #ifdef CONFIG_STACKTRACE |
| |
| noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, |
| void *cookie, struct task_struct *task, |
| struct pt_regs *regs) |
| { |
| struct stackframe frame; |
| |
| if (regs) |
| start_backtrace(&frame, regs->regs[29], regs->pc); |
| else if (task == current) |
| start_backtrace(&frame, |
| (unsigned long)__builtin_frame_address(1), |
| (unsigned long)__builtin_return_address(0)); |
| else |
| start_backtrace(&frame, thread_saved_fp(task), |
| thread_saved_pc(task)); |
| |
| walk_stackframe(task, &frame, consume_entry, cookie); |
| } |
| |
| #endif |