// SPDX-License-Identifier: GPL-2.0-only/* *	stacktrace.c : stacktracing APIs needed by rest of kernel *			(wrappers over ARC dwarf based unwinder) * * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) * *  vineetg: aug 2009 *  -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( ) *   for displaying task's kernel mode call stack in /proc/<pid>/stack *  -Iterator based approach to have single copy of unwinding core and APIs *   needing unwinding, implement the logic in iterator regarding: *      = which frame onwards to start capture *      = which frame to stop capturing (wchan) *      = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc) * *  vineetg: March 2009 *  -Implemented correct versions of thread_saved_pc() and get_wchan() * *  rajeshwarr: 2008 *  -Initial implementation */ #include <linux/ptrace.h>#include <linux/export.h>#include <linux/stacktrace.h>#include <linux/kallsyms.h>#include <linux/sched/debug.h> #include <asm/arcregs.h>#include <asm/unwind.h>#include <asm/switch_to.h> /*------------------------------------------------------------------------- *              Unwinder Iterator *------------------------------------------------------------------------- */ #ifdef CONFIG_ARC_DW2_UNWIND static intseed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs,		       struct unwind_frame_info *frame_info){	if (regs) {		/*		 * Asynchronous unwinding of intr/exception		 *  - Just uses the pt_regs passed		 */		frame_info->task = tsk; 		frame_info->regs.r27 = regs->fp;		frame_info->regs.r28 = regs->sp;		frame_info->regs.r31 = regs->blink;		frame_info->regs.r63 = regs->ret;		frame_info->call_frame = 0;	} else if (tsk == NULL || tsk == current) {		/*		 * synchronous unwinding (e.g. dump_stack)		 *  - uses current values of SP and friends		 */		unsigned long fp, sp, blink, ret;		frame_info->task = current; 		__asm__ __volatile__(			"mov %0,r27\n\t"			"mov %1,r28\n\t"			"mov %2,r31\n\t"			"mov %3,r63\n\t"			: "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)		); 		frame_info->regs.r27 = fp;		frame_info->regs.r28 = sp;		frame_info->regs.r31 = blink;		frame_info->regs.r63 = ret;		frame_info->call_frame = 0;	} else {		/*		 * Asynchronous unwinding of a likely sleeping task		 *  - first ensure it is actually sleeping		 *  - if so, it will be in __switch_to, kernel mode SP of task		 *    is safe-kept and BLINK at a well known location in there		 */ 		if (tsk->state == TASK_RUNNING)			return -1; 		frame_info->task = tsk; 		frame_info->regs.r27 = TSK_K_FP(tsk);		frame_info->regs.r28 = TSK_K_ESP(tsk);		frame_info->regs.r31 = TSK_K_BLINK(tsk);		frame_info->regs.r63 = (unsigned int)__switch_to; 		/* In the prologue of __switch_to, first FP is saved on stack		 * and then SP is copied to FP. Dwarf assumes cfa as FP based		 * but we didn't save FP. The value retrieved above is FP's		 * state in previous frame.		 * As a work around for this, we unwind from __switch_to start		 * and adjust SP accordingly. The other limitation is that		 * __switch_to macro is dwarf rules are not generated for inline		 * assembly code		 */		frame_info->regs.r27 = 0;		frame_info->regs.r28 += 60;		frame_info->call_frame = 0; 	}	return 0;} #endif notrace noinline unsigned intarc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,		int (*consumer_fn) (unsigned int, void *), void *arg){#ifdef CONFIG_ARC_DW2_UNWIND	int ret = 0, cnt = 0;	unsigned int address;	struct unwind_frame_info frame_info; 	if (seed_unwind_frame_info(tsk, regs, &frame_info))		return 0; 	while (1) {		address = UNW_PC(&frame_info); 		if (!address || !__kernel_text_address(address))			break; 		if (consumer_fn(address, arg) == -1)			break; 		ret = arc_unwind(&frame_info);		if (ret)			break; 		frame_info.regs.r63 = frame_info.regs.r31; 		if (cnt++ > 128) {			printk("unwinder looping too long, aborting !\n");			return 0;		}	} 	return address;		/* return the last address it saw */#else	/* On ARC, only Dward based unwinder works. fp based backtracing is	 * not possible (-fno-omit-frame-pointer) because of the way function	 * prelogue is setup (callee regs saved and then fp set and not other	 * way around	 */	pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");	return 0; #endif} /*------------------------------------------------------------------------- * callbacks called by unwinder iterator to implement kernel APIs * * The callback can return -1 to force the iterator to stop, which by default * keeps going till the bottom-most frame. *------------------------------------------------------------------------- */ /* Call-back which plugs into unwinding core to dump the stack in * case of panic/OOPs/BUG etc */static int __print_sym(unsigned int address, void *arg){	const char *loglvl = arg; 	printk("%s  %pS\n", loglvl, (void *)address);	return 0;} #ifdef CONFIG_STACKTRACE /* Call-back which plugs into unwinding core to capture the * traces needed by kernel on /proc/<pid>/stack */static int __collect_all(unsigned int address, void *arg){	struct stack_trace *trace = arg; 	if (trace->skip > 0)		trace->skip--;	else		trace->entries[trace->nr_entries++] = address; 	if (trace->nr_entries >= trace->max_entries)		return -1; 	return 0;} static int __collect_all_but_sched(unsigned int address, void *arg){	struct stack_trace *trace = arg; 	if (in_sched_functions(address))		return 0; 	if (trace->skip > 0)		trace->skip--;	else		trace->entries[trace->nr_entries++] = address; 	if (trace->nr_entries >= trace->max_entries)		return -1; 	return 0;} #endif static int __get_first_nonsched(unsigned int address, void *unused){	if (in_sched_functions(address))		return 0; 	return -1;} /*------------------------------------------------------------------------- *              APIs expected by various kernel sub-systems *------------------------------------------------------------------------- */ noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs,			      const char *loglvl){	printk("%s\nStack Trace:\n", loglvl);	arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl);}EXPORT_SYMBOL(show_stacktrace); /* Expected by sched Code */void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl){	show_stacktrace(tsk, NULL, loglvl);} /* Another API expected by schedular, shows up in "ps" as Wait Channel * Of course just returning schedule( ) would be pointless so unwind until * the function is not in schedular code */unsigned int get_wchan(struct task_struct *tsk){	return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);} #ifdef CONFIG_STACKTRACE /* * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP. * A typical use is when /proc/<pid>/stack is queried by userland */void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace){	/* Assumes @tsk is sleeping so unwinds from __switch_to */	arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);} void save_stack_trace(struct stack_trace *trace){	/* Pass NULL for task so it unwinds the current call frame */	arc_unwind_core(NULL, NULL, __collect_all, trace);}EXPORT_SYMBOL_GPL(save_stack_trace);#endif