/usr/share/systemtap/runtime/stack-i386.c is in systemtap-common 1.6-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 | /* -*- linux-c -*-
* i386 stack tracing functions
* Copyright (C) 2005-2010 Red Hat Inc.
*
* This file is part of systemtap, and is free software. You can
* redistribute it and/or modify it under the terms of the GNU General
* Public License (GPL); either version 2, or (at your option) any
* later version.
*/
#ifdef STAPCONF_LINUX_UACCESS_H
#include <linux/uaccess.h>
#else
#include <asm/uaccess.h>
#endif
#include <linux/types.h>
#define intptr_t long
#define uintptr_t unsigned long
static int _stp_valid_pc_addr(unsigned long addr, struct task_struct *tsk)
{
/* Just a simple check of whether the the address can be accessed
as a user space address. Zero is always bad. */
int ok;
mm_segment_t oldfs = get_fs();
set_fs(USER_DS);
ok = access_ok(VERIFY_READ, (long *) (intptr_t) addr, sizeof(long));
set_fs(oldfs);
return addr != 0L && tsk != NULL ? ok : ! ok;
}
static int _stp_valid_stack_ptr(unsigned long context, unsigned long p)
{
return p > context && p < context + THREAD_SIZE - 3;
}
/* DWARF unwinder failed. Just dump intereting addresses on kernel stack. */
#if !defined(STAPCONF_KERNEL_STACKTRACE)
static void _stp_stack_print_fallback(unsigned long stack, int verbose, int levels)
{
unsigned long addr;
while (levels && stack & (THREAD_SIZE-1)) {
if (unlikely(_stp_read_address(addr, (unsigned long *)stack,
KERNEL_DS))
|| ! _stp_valid_pc_addr(addr, NULL)) {
/* cannot access stack. give up. */
return;
}
_stp_print_addr(addr, verbose | _STP_SYM_INEXACT, NULL);
levels--;
stack++;
}
}
#endif
static void __stp_stack_print(struct pt_regs *regs, int verbose, int levels,
struct task_struct *tsk,
struct unwind_context *uwcontext,
struct uretprobe_instance *ri, int uregs_valid)
{
unsigned long context = (unsigned long)®_SP(regs) & ~(THREAD_SIZE - 1);
#ifdef STP_USE_FRAME_POINTER
unsigned long addr;
unsigned long next_fp, fp = REG_FP(regs);
while (levels && _stp_valid_stack_ptr(context, (unsigned long)fp)) {
if (unlikely(_stp_read_address(addr, (unsigned long *)(fp + 4), KERNEL_DS))) {
/* cannot access stack. give up. */
return;
}
_stp_print_addr(addr, verbose | _STP_SYM_INEXACT, NULL);
if (unlikely(_stp_read_address(next_fp, (unsigned long *)fp, KERNEL_DS))) {
/* cannot access stack. give up. */
return;
}
levels--;
/* frame pointers move upwards */
if (next_fp <= fp)
break;
fp = next_fp;
}
#else
#ifdef STP_USE_DWARF_UNWINDER
struct unwind_frame_info *info = &uwcontext->info;
int sanitize = tsk && ! uregs_valid;
arch_unw_init_frame_info(info, regs, sanitize);
while (levels) {
int ret = unwind(uwcontext, tsk);
#ifdef STAPCONF_UPROBE_GET_PC
unsigned long maybe_pc = 0;
if (ri) {
maybe_pc = uprobe_get_pc(ri, UNW_PC(info),
UNW_SP(info));
if (!maybe_pc)
printk("SYSTEMTAP ERROR: uprobe_get_return returned 0\n");
else
UNW_PC(info) = maybe_pc;
}
#endif
dbug_unwind(1, "ret=%d PC=%lx SP=%lx\n", ret, UNW_PC(info), UNW_SP(info));
if (ret == 0 && _stp_valid_pc_addr(UNW_PC(info), tsk)) {
_stp_print_addr(UNW_PC(info), verbose, tsk);
levels--;
if (UNW_PC(info) != _stp_kretprobe_trampoline)
continue;
}
/* If an error happened or we hit a kretprobe trampoline,
* and the current pc frame address is still valid kernel
* address use fallback backtrace, unless user task backtrace.
* FIXME: is there a way to unwind across kretprobe
* trampolines? PR9999. */
if ((ret < 0 || UNW_PC(info) == _stp_kretprobe_trampoline)
&& ! tsk)
_stp_stack_print_fallback(UNW_SP(info), verbose, levels);
return;
}
#else /* ! STP_USE_DWARF_UNWINDER */
_stp_stack_print_fallback((unsigned long)®_SP(regs), verbose, levels);
#endif /* STP_USE_FRAME_POINTER */
#endif
}
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