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#if (__GNUC__ == 3 && __GNUC_MINOR__ < 3)
  36/*
  37 * Returns non-zero if the PC is in the spinlock contention out-of-line code
  38 * with non-standard calling sequence (on older compilers).
  39 */
  40static __inline__ int in_old_ool_spinlock_code(unsigned long pc)
  41{
  42        extern const char ia64_spinlock_contention_pre3_4[] __attribute__ ((weak));
  43        extern const char ia64_spinlock_contention_pre3_4_end[] __attribute__ ((weak));
  44        unsigned long sc_start = (unsigned long)ia64_spinlock_contention_pre3_4;
  45        unsigned long sc_end = (unsigned long)ia64_spinlock_contention_pre3_4_end;
  46        return (sc_start && sc_end && pc >= sc_start && pc < sc_end);
  47}
  48#else
  49/* Newer spinlock code does a proper br.call and works fine with the unwinder */
  50#define in_old_ool_spinlock_code(pc)    0
  51#endif
  52
  53/* Returns non-zero if the PC is in the Interrupt Vector Table */
  54static __inline__ int in_ivt_code(unsigned long pc)
  55{
  56        extern char ia64_ivt[];
  57        return (pc >= (u_long)ia64_ivt && pc < (u_long)ia64_ivt+32768);
  58}
  59
  60/*
  61 * Unwind to next stack frame.
  62 */
  63static __inline__ int next_frame(ia64_backtrace_t *bt)
  64{
  65        /*
  66         * Avoid unsightly console message from unw_unwind() when attempting
  67         * to unwind through the Interrupt Vector Table which has no unwind
  68         * information.
  69         */
  70        if (in_ivt_code(bt->frame.ip))
  71                return 0;
  72
  73        /*
  74         * WAR for spinlock contention from leaf functions.  ia64_spinlock_contention_pre3_4
  75         * has ar.pfs == r0.  Leaf functions do not modify ar.pfs so ar.pfs remains
  76         * as 0, stopping the backtrace.  Record the previous ar.pfs when the current
  77         * IP is in ia64_spinlock_contention_pre3_4 then unwind, if pfs_loc has not changed
  78         * after unwind then use pt_regs.ar_pfs which is where the real ar.pfs is for
  79         * leaf functions.
  80         */
  81        if (bt->prev_pfs_loc && bt->regs && bt->frame.pfs_loc == bt->prev_pfs_loc)
  82                bt->frame.pfs_loc = &bt->regs->ar_pfs;
  83        bt->prev_pfs_loc = (in_old_ool_spinlock_code(bt->frame.ip) ? bt->frame.pfs_loc : NULL);
  84
  85        return unw_unwind(&bt->frame) == 0;
  86}
  87
  88
  89static void do_ia64_backtrace(struct unw_frame_info *info, void *vdata)
  90{
  91        ia64_backtrace_t *bt = vdata;
  92        struct switch_stack *sw;
  93        int count = 0;
  94        u_long pc, sp;
  95
  96        sw = (struct switch_stack *)(info+1);
  97        /* padding from unw_init_running */
  98        sw = (struct switch_stack *)(((unsigned long)sw + 15) & ~15);
  99
 100        unw_init_frame_info(&bt->frame, current, sw);
 101
 102        /* skip over interrupt frame and oprofile calls */
 103        do {
 104                unw_get_sp(&bt->frame, &sp);
 105                if (sp >= (u_long)bt->regs)
 106                        break;
 107                if (!next_frame(bt))
 108                        return;
 109        } while (count++ < 200);
 110
 111        /* finally, grab the actual sample */
 112        while (bt->depth-- && next_frame(bt)) {
 113                unw_get_ip(&bt->frame, &pc);
 114                oprofile_add_trace(pc);
 115                if (unw_is_intr_frame(&bt->frame)) {
 116                        /*
 117                         * Interrupt received on kernel stack; this can
 118                         * happen when timer interrupt fires while processing
 119                         * a softirq from the tail end of a hardware interrupt
 120                         * which interrupted a system call.  Don't laugh, it
 121                         * happens!  Splice the backtrace into two parts to
 122                         * avoid spurious cycles in the gprof output.
 123                         */
 124                        /* TODO: split rather than drop the 2nd half */
 125                        break;
 126                }
 127        }
 128}
 129
 130void
 131ia64_backtrace(struct pt_regs * const regs, unsigned int depth)
 132{
 133        ia64_backtrace_t bt;
 134        unsigned long flags;
 135
 136        /*
 137         * On IA64 there is little hope of getting backtraces from
 138         * user space programs -- the problems of getting the unwind
 139         * information from arbitrary user programs are extreme.
 140         */
 141        if (user_mode(regs))
 142                return;
 143
 144        bt.depth = depth;
 145        bt.regs = regs;
 146        bt.prev_pfs_loc = NULL;
 147        local_irq_save(flags);
 148        unw_init_running(do_ia64_backtrace, &bt);
 149        local_irq_restore(flags);
 150}
 151