/* * 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) * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * vineetg: aug 2009 * -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( ) * for displaying task's kernel mode call stack in /proc//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 #include #include #include #include #include #include #include /*------------------------------------------------------------------------- * Unwinder Iterator *------------------------------------------------------------------------- */ #ifdef CONFIG_ARC_DW2_UNWIND static int seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs, struct unwind_frame_info *frame_info) { /* * synchronous unwinding (e.g. dump_stack) * - uses current values of SP and friends */ if (regs == NULL && (tsk == NULL || tsk == current)) { 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 if (regs == NULL) { /* * 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; } else { /* * 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; } return 0; } #endif notrace noinline unsigned int arc_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 *unused) { printk(" %pS\n", (void *)address); return 0; } #ifdef CONFIG_STACKTRACE /* Call-back which plugs into unwinding core to capture the * traces needed by kernel on /proc//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) { pr_info("\nStack Trace:\n"); arc_unwind_core(tsk, regs, __print_sym, NULL); } EXPORT_SYMBOL(show_stacktrace); /* Expected by sched Code */ void show_stack(struct task_struct *tsk, unsigned long *sp) { show_stacktrace(tsk, NULL); } /* 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//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