// SPDX-License-Identifier: GPL-2.0-only#include <linux/export.h>#include <linux/sched.h>#include <linux/sched/debug.h>#include <linux/stacktrace.h> #include <asm/sections.h>#include <asm/stacktrace.h>#include <asm/traps.h> #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)/* * Unwind the current stack frame and store the new register values in the * structure passed as argument. Unwinding is equivalent to a function return, * hence the new PC value rather than LR should be used for backtrace. * * With framepointer enabled, a simple function prologue looks like this: *	mov	ip, sp *	stmdb	sp!, {fp, ip, lr, pc} *	sub	fp, ip, #4 * * A simple function epilogue looks like this: *	ldm	sp, {fp, sp, pc} * * When compiled with clang, pc and sp are not pushed. A simple function * prologue looks like this when built with clang: * *	stmdb	{..., fp, lr} *	add	fp, sp, #x *	sub	sp, sp, #y * * A simple function epilogue looks like this when built with clang: * *	sub	sp, fp, #x *	ldm	{..., fp, pc} * * * Note that with framepointer enabled, even the leaf functions have the same * prologue and epilogue, therefore we can ignore the LR value in this case. */int notrace unwind_frame(struct stackframe *frame){	unsigned long high, low;	unsigned long fp = frame->fp; 	/* only go to a higher address on the stack */	low = frame->sp;	high = ALIGN(low, THREAD_SIZE); #ifdef CONFIG_CC_IS_CLANG	/* check current frame pointer is within bounds */	if (fp < low + 4 || fp > high - 4)		return -EINVAL; 	frame->sp = frame->fp;	frame->fp = *(unsigned long *)(fp);	frame->pc = frame->lr;	frame->lr = *(unsigned long *)(fp + 4);#else	/* check current frame pointer is within bounds */	if (fp < low + 12 || fp > high - 4)		return -EINVAL; 	/* restore the registers from the stack frame */	frame->fp = *(unsigned long *)(fp - 12);	frame->sp = *(unsigned long *)(fp - 8);	frame->pc = *(unsigned long *)(fp - 4);#endif 	return 0;}#endif void notrace walk_stackframe(struct stackframe *frame,		     int (*fn)(struct stackframe *, void *), void *data){	while (1) {		int ret; 		if (fn(frame, data))			break;		ret = unwind_frame(frame);		if (ret < 0)			break;	}}EXPORT_SYMBOL(walk_stackframe); #ifdef CONFIG_STACKTRACEstruct stack_trace_data {	struct stack_trace *trace;	unsigned int no_sched_functions;	unsigned int skip;}; static int save_trace(struct stackframe *frame, void *d){	struct stack_trace_data *data = d;	struct stack_trace *trace = data->trace;	struct pt_regs *regs;	unsigned long addr = frame->pc; 	if (data->no_sched_functions && in_sched_functions(addr))		return 0;	if (data->skip) {		data->skip--;		return 0;	} 	trace->entries[trace->nr_entries++] = addr; 	if (trace->nr_entries >= trace->max_entries)		return 1; 	if (!in_entry_text(frame->pc))		return 0; 	regs = (struct pt_regs *)frame->sp;	if ((unsigned long)&regs[1] > ALIGN(frame->sp, THREAD_SIZE))		return 0; 	trace->entries[trace->nr_entries++] = regs->ARM_pc; 	return trace->nr_entries >= trace->max_entries;} /* This must be noinline to so that our skip calculation works correctly */static noinline void __save_stack_trace(struct task_struct *tsk,	struct stack_trace *trace, unsigned int nosched){	struct stack_trace_data data;	struct stackframe frame; 	data.trace = trace;	data.skip = trace->skip;	data.no_sched_functions = nosched; 	if (tsk != current) {#ifdef CONFIG_SMP		/*		 * What guarantees do we have here that 'tsk' is not		 * running on another CPU?  For now, ignore it as we		 * can't guarantee we won't explode.		 */		return;#else		frame.fp = thread_saved_fp(tsk);		frame.sp = thread_saved_sp(tsk);		frame.lr = 0;		/* recovered from the stack */		frame.pc = thread_saved_pc(tsk);#endif	} else {		/* We don't want this function nor the caller */		data.skip += 2;		frame.fp = (unsigned long)__builtin_frame_address(0);		frame.sp = current_stack_pointer;		frame.lr = (unsigned long)__builtin_return_address(0);		frame.pc = (unsigned long)__save_stack_trace;	} 	walk_stackframe(&frame, save_trace, &data);} void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace){	struct stack_trace_data data;	struct stackframe frame; 	data.trace = trace;	data.skip = trace->skip;	data.no_sched_functions = 0; 	frame.fp = regs->ARM_fp;	frame.sp = regs->ARM_sp;	frame.lr = regs->ARM_lr;	frame.pc = regs->ARM_pc; 	walk_stackframe(&frame, save_trace, &data);} void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace){	__save_stack_trace(tsk, trace, 1);}EXPORT_SYMBOL(save_stack_trace_tsk); void save_stack_trace(struct stack_trace *trace){	__save_stack_trace(current, trace, 0);}EXPORT_SYMBOL_GPL(save_stack_trace);#endif