LXR linux/arch/ia64/oprofile/backtrace.c

   1/**
   2 * @file backtrace.c
   3 *
   4 * @remark Copyright 2004 Silicon Graphics Inc.  All Rights Reserved.
   5 * @remark Read the file COPYING
   6 *
   7 * @author Greg Banks <gnb@melbourne.sgi.com>
   8 * @author Keith Owens <kaos@melbourne.sgi.com>
   9 * Based on work done for the ia64 port of the SGI kernprof patch, which is
  10 *    Copyright (c) 2003-2004 Silicon Graphics Inc.  All Rights Reserved.
  11 */
  12
  13#include <linux/oprofile.h>
  14#include <linux/sched.h>
  15#include <linux/mm.h>
  16#include <asm/ptrace.h>
  17#include <asm/system.h>
  18
  19/*
  20 * For IA64 we need to perform a complex little dance to get both
  21 * the struct pt_regs and a synthetic struct switch_stack in place
  22 * to allow the unwind code to work.  This dance requires our unwind
  23 * using code to be called from a function called from unw_init_running().
  24 * There we only get a single void* data pointer, so use this struct
  25 * to hold all the data we need during the unwind.
  26 */
  27typedef struct
  28{
  29        unsigned int depth;
  30        struct pt_regs *regs;
  31        struct unw_frame_info frame;
  32        u64 *prev_pfs_loc;      /* state for WAR for old spinlock ool code */
  33} ia64_backtrace_t;
  34
  35/* Returns non-zero if the PC is in the Interrupt Vector Table */
  36static __inline__ int in_ivt_code(unsigned long pc)
  37{
  38        extern char ia64_ivt[];
  39        return (pc >= (u_long)ia64_ivt && pc < (u_long)ia64_ivt+32768);
  40}
  41
  42/*
  43 * Unwind to next stack frame.
  44 */
  45static __inline__ int next_frame(ia64_backtrace_t *bt)
  46{
  47        /*
  48         * Avoid unsightly console message from unw_unwind() when attempting
  49         * to unwind through the Interrupt Vector Table which has no unwind
  50         * information.
  51         */
  52        if (in_ivt_code(bt->frame.ip))
  53                return 0;
  54
  55        /*
  56         * WAR for spinlock contention from leaf functions.  ia64_spinlock_contention_pre3_4
  57         * has ar.pfs == r0.  Leaf functions do not modify ar.pfs so ar.pfs remains
  58         * as 0, stopping the backtrace.  Record the previous ar.pfs when the current
  59         * IP is in ia64_spinlock_contention_pre3_4 then unwind, if pfs_loc has not changed
  60         * after unwind then use pt_regs.ar_pfs which is where the real ar.pfs is for
  61         * leaf functions.
  62         */
  63        if (bt->prev_pfs_loc && bt->regs && bt->frame.pfs_loc == bt->prev_pfs_loc)
  64                bt->frame.pfs_loc = &bt->regs->ar_pfs;
  65        bt->prev_pfs_loc = NULL;
  66
  67        return unw_unwind(&bt->frame) == 0;
  68}
  69
  70
  71static void do_ia64_backtrace(struct unw_frame_info *info, void *vdata)
  72{
  73        ia64_backtrace_t *bt = vdata;
  74        struct switch_stack *sw;
  75        int count = 0;
  76        u_long pc, sp;
  77
  78        sw = (struct switch_stack *)(info+1);
  79        /* padding from unw_init_running */
  80        sw = (struct switch_stack *)(((unsigned long)sw + 15) & ~15);
  81
  82        unw_init_frame_info(&bt->frame, current, sw);
  83
  84        /* skip over interrupt frame and oprofile calls */
  85        do {
  86                unw_get_sp(&bt->frame, &sp);
  87                if (sp >= (u_long)bt->regs)
  88                        break;
  89                if (!next_frame(bt))
  90                        return;
  91        } while (count++ < 200);
  92
  93        /* finally, grab the actual sample */
  94        while (bt->depth-- && next_frame(bt)) {
  95                unw_get_ip(&bt->frame, &pc);
  96                oprofile_add_trace(pc);
  97                if (unw_is_intr_frame(&bt->frame)) {
  98                        /*
  99                         * Interrupt received on kernel stack; this can
 100                         * happen when timer interrupt fires while processing
 101                         * a softirq from the tail end of a hardware interrupt
 102                         * which interrupted a system call.  Don't laugh, it
 103                         * happens!  Splice the backtrace into two parts to
 104                         * avoid spurious cycles in the gprof output.
 105                         */
 106                        /* TODO: split rather than drop the 2nd half */
 107                        break;
 108                }
 109        }
 110}
 111
 112void
 113ia64_backtrace(struct pt_regs * const regs, unsigned int depth)
 114{
 115        ia64_backtrace_t bt;
 116        unsigned long flags;
 117
 118        /*
 119         * On IA64 there is little hope of getting backtraces from
 120         * user space programs -- the problems of getting the unwind
 121         * information from arbitrary user programs are extreme.
 122         */
 123        if (user_mode(regs))
 124                return;
 125
 126        bt.depth = depth;
 127        bt.regs = regs;
 128        bt.prev_pfs_loc = NULL;
 129        local_irq_save(flags);
 130        unw_init_running(do_ia64_backtrace, &bt);
 131        local_irq_restore(flags);
 132}
 133