stacktrace.c
/*
* 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/<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 void 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 (tsk == NULL && regs == NULL) {
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 sleeping task
* - Gets SP etc from task's pt_regs (saved bottom of kernel
* mode stack of task)
*/
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;
}
}
#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;
unsigned int address;
struct unwind_frame_info frame_info;
seed_unwind_frame_info(tsk, regs, &frame_info);
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;
}
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/<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)
{
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/<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
