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