linux/arch/arc/kernel/stacktrace.c
Alexey Brodkin 9bd54517ee arc: unwind: warn only once if DW2_UNWIND is disabled
If CONFIG_ARC_DW2_UNWIND is disabled every time arc_unwind_core()
gets called following message gets printed in debug console:
----------------->8---------------
CONFIG_ARC_DW2_UNWIND needs to be enabled
----------------->8---------------

That message makes sense if user indeed wants to see a backtrace or
get nice function call-graphs in perf but what if user disabled
unwinder for the purpose? Why pollute his debug console?

So instead we'll warn user about possibly missing feature once and
let him decide if that was what he or she really wanted.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
2016-06-28 11:11:44 +05:30

262 lines
6.9 KiB
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 <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)
{
__print_symbol(" %s\n", 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