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/**
* @file backtrace.c
*
* @remark Copyright 2004 Silicon Graphics Inc. All Rights Reserved.
* @remark Read the file COPYING
*
* @author Greg Banks <gnb@melbourne.sgi.com>
* @author Keith Owens <kaos@melbourne.sgi.com>
* Based on work done for the ia64 port of the SGI kernprof patch, which is
* Copyright (c) 2003-2004 Silicon Graphics Inc. All Rights Reserved.
*/
#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/ptrace.h>
#include <asm/system.h>
/*
* For IA64 we need to perform a complex little dance to get both
* the struct pt_regs and a synthetic struct switch_stack in place
* to allow the unwind code to work. This dance requires our unwind
* using code to be called from a function called from unw_init_running().
* There we only get a single void* data pointer, so use this struct
* to hold all the data we need during the unwind.
*/
typedef struct
{
unsigned int depth;
struct pt_regs *regs;
struct unw_frame_info frame;
u64 *prev_pfs_loc; /* state for WAR for old spinlock ool code */
} ia64_backtrace_t;
/* Returns non-zero if the PC is in the Interrupt Vector Table */
static __inline__ int in_ivt_code(unsigned long pc)
{
extern char ia64_ivt[];
return (pc >= (u_long)ia64_ivt && pc < (u_long)ia64_ivt+32768);
}
/*
* Unwind to next stack frame.
*/
static __inline__ int next_frame(ia64_backtrace_t *bt)
{
/*
* Avoid unsightly console message from unw_unwind() when attempting
* to unwind through the Interrupt Vector Table which has no unwind
* information.
*/
if (in_ivt_code(bt->frame.ip))
return 0;
/*
* WAR for spinlock contention from leaf functions. ia64_spinlock_contention_pre3_4
* has ar.pfs == r0. Leaf functions do not modify ar.pfs so ar.pfs remains
* as 0, stopping the backtrace. Record the previous ar.pfs when the current
* IP is in ia64_spinlock_contention_pre3_4 then unwind, if pfs_loc has not changed
* after unwind then use pt_regs.ar_pfs which is where the real ar.pfs is for
* leaf functions.
*/
if (bt->prev_pfs_loc && bt->regs && bt->frame.pfs_loc == bt->prev_pfs_loc)
bt->frame.pfs_loc = &bt->regs->ar_pfs;
bt->prev_pfs_loc = NULL;
return unw_unwind(&bt->frame) == 0;
}
static void do_ia64_backtrace(struct unw_frame_info *info, void *vdata)
{
ia64_backtrace_t *bt = vdata;
struct switch_stack *sw;
int count = 0;
u_long pc, sp;
sw = (struct switch_stack *)(info+1);
/* padding from unw_init_running */
sw = (struct switch_stack *)(((unsigned long)sw + 15) & ~15);
unw_init_frame_info(&bt->frame, current, sw);
/* skip over interrupt frame and oprofile calls */
do {
unw_get_sp(&bt->frame, &sp);
if (sp >= (u_long)bt->regs)
break;
if (!next_frame(bt))
return;
} while (count++ < 200);
/* finally, grab the actual sample */
while (bt->depth-- && next_frame(bt)) {
unw_get_ip(&bt->frame, &pc);
oprofile_add_trace(pc);
if (unw_is_intr_frame(&bt->frame)) {
/*
* Interrupt received on kernel stack; this can
* happen when timer interrupt fires while processing
* a softirq from the tail end of a hardware interrupt
* which interrupted a system call. Don't laugh, it
* happens! Splice the backtrace into two parts to
* avoid spurious cycles in the gprof output.
*/
/* TODO: split rather than drop the 2nd half */
break;
}
}
}
void
ia64_backtrace(struct pt_regs * const regs, unsigned int depth)
{
ia64_backtrace_t bt;
unsigned long flags;
/*
* On IA64 there is little hope of getting backtraces from
* user space programs -- the problems of getting the unwind
* information from arbitrary user programs are extreme.
*/
if (user_mode(regs))
return;
bt.depth = depth;
bt.regs = regs;
bt.prev_pfs_loc = NULL;
local_irq_save(flags);
unw_init_running(do_ia64_backtrace, &bt);
local_irq_restore(flags);
}
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