/usr/share/systemtap/runtime/stack.c is in systemtap-common 1.7-1+deb7u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* Stack tracing functions
* Copyright (C) 2005-2009, 2011 Red Hat Inc.
* Copyright (C) 2005 Intel Corporation.
*
* 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.
*/
/*
The translator will only include this file if the session needs any
of the backtrace functions. Currently indicated by having the session
need_unwind flag, which is set by tapset functions marked with
pragme:unwind.
*/
#ifndef _STACK_C_
#define _STACK_C_
/* Maximum number of backtrace levels. */
#ifndef MAXBACKTRACE
#define MAXBACKTRACE 20
#endif
/** @file stack.c
* @brief Stack Tracing Functions
*/
/** @addtogroup stack Stack Tracing Functions
*
* @{
*/
#include "sym.c"
#include "regs.h"
/* If uprobes isn't in the kernel, pull it in from the runtime. */
#if defined(CONFIG_UTRACE) /* uprobes doesn't work without utrace */
#if defined(CONFIG_UPROBES) || defined(CONFIG_UPROBES_MODULE)
#include <linux/uprobes.h>
#else
#include "uprobes/uprobes.h"
#endif
#ifndef UPROBES_API_VERSION
#define UPROBES_API_VERSION 1
#endif
#else
struct uretprobe_instance;
#endif
#if defined(STAPCONF_KERNEL_STACKTRACE) || defined(STAPCONF_KERNEL_STACKTRACE_NO_BP)
#include <linux/stacktrace.h>
#include <asm/stacktrace.h>
#endif
static void _stp_stack_print_fallback(unsigned long, int, int, int);
#ifdef STP_USE_DWARF_UNWINDER
#include "stack-dwarf.c"
#endif
#if defined (__ia64__)
#include "stack-ia64.c"
#elif defined (__arm__)
#include "stack-arm.c"
#elif defined (__s390__)
#include "stack-s390.c"
#else
#ifndef STP_USE_DWARF_UNWINDER
#error "Unsupported architecture"
#endif
#endif
#if defined(STAPCONF_KERNEL_STACKTRACE) || defined(STAPCONF_KERNEL_STACKTRACE_NO_BP)
struct print_stack_data
{
int flags;
int levels;
int skip;
};
#if defined(STAPCONF_STACKTRACE_OPS_WARNING)
static void print_stack_warning(void *data, char *msg)
{
}
static void
print_stack_warning_symbol(void *data, char *msg, unsigned long symbol)
{
}
#endif
static int print_stack_stack(void *data, char *name)
{
return -1;
}
static void print_stack_address(void *data, unsigned long addr, int reliable)
{
struct print_stack_data *sdata = data;
if (sdata->skip > 0)
sdata->skip--;
else if (sdata->levels > 0) {
_stp_print_addr(addr,
sdata->flags | (reliable ? 0 :_STP_SYM_INEXACT),
NULL);
sdata->levels--;
}
}
static const struct stacktrace_ops print_stack_ops = {
#if defined(STAPCONF_STACKTRACE_OPS_WARNING)
.warning = print_stack_warning,
.warning_symbol = print_stack_warning_symbol,
#endif
.stack = print_stack_stack,
.address = print_stack_address,
#if defined(STAPCONF_WALK_STACK)
.walk_stack = print_context_stack,
#endif
};
/* Used for kernel backtrace printing when other mechanisms fail. */
static void _stp_stack_print_fallback(unsigned long stack,
int sym_flags, int levels, int skip)
{
struct print_stack_data print_data;
print_data.flags = sym_flags;
print_data.levels = levels;
print_data.skip = skip;
#if defined(STAPCONF_KERNEL_STACKTRACE)
dump_trace(current, NULL, (long *)stack, 0, &print_stack_ops,
&print_data);
#else
/* STAPCONF_KERNEL_STACKTRACE_NO_BP */
dump_trace(current, NULL, (long *)stack, &print_stack_ops,
&print_data);
#endif
}
#else
static void _stp_stack_print_fallback(unsigned long s, int v, int l, int k) {
/* Don't guess, just give up. */
_stp_print_addr(0, v | _STP_SYM_INEXACT, NULL);
}
#endif /* defined(STAPCONF_KERNEL_STACKTRACE) || defined(STAPCONF_KERNEL_STACKTRACE_NO_BP) */
// Without KPROBES very little works atm.
// But this file is unconditionally imported, while these two functions are only
// used through context-unwind.stp.
#if defined (CONFIG_KPROBES)
/** Gets user space registers when available, also sets context probe_flags
* _STP_PROBE_STATE_FULL_UREGS if appropriate. Should be used instead of
* accessing context uregs field directly when (full) uregs are needed
* from kernel context.
*/
static struct pt_regs *_stp_get_uregs(struct context *c)
{
/* When the probe occurred in user context uregs are always complete. */
if (c->uregs && c->probe_flags & _STP_PROBE_STATE_USER_MODE)
c->probe_flags |= _STP_PROBE_STATE_FULL_UREGS;
else if (c->uregs == NULL)
{
/* First try simple recovery through task_pt_regs,
on some platforms that already provides complete uregs. */
c->uregs = _stp_current_pt_regs();
if (c->uregs && _stp_task_pt_regs_valid(current, c->uregs))
c->probe_flags |= _STP_PROBE_STATE_FULL_UREGS;
/* Sadly powerpc does support the dwarf unwinder, but doesn't have enough
CFI in the kernel to recover fully to user space. */
#if defined(STP_USE_DWARF_UNWINDER) && !defined (__powerpc__)
else if (c->uregs != NULL && c->kregs != NULL
&& ! (c->probe_flags & _STP_PROBE_STATE_USER_MODE))
{
struct unwind_frame_info *info = &c->uwcontext.info;
int ret = 0;
int levels;
/* We might be lucky and this probe already ran the kernel
unwind to end up in the user regs. */
if (UNW_PC(info) == REG_IP(c->uregs))
{
levels = 0;
dbug_unwind(1, "feeling lucky, info pc == uregs pc\n");
}
else
{
/* Try to recover the uregs by unwinding from the the kernel
probe location. */
levels = MAXBACKTRACE;
arch_unw_init_frame_info(info, c->kregs, 0);
dbug_unwind(1, "Trying to recover... searching for 0x%lx\n",
REG_IP(c->uregs));
}
while (levels > 0 && ret == 0 && UNW_PC(info) != REG_IP(c->uregs))
{
levels--;
ret = unwind(&c->uwcontext, 0);
dbug_unwind(1, "unwind levels: %d, ret: %d, pc=0x%lx\n",
levels, ret, UNW_PC(info));
}
/* Have we arrived where we think user space currently is? */
if (ret == 0 && UNW_PC(info) == REG_IP(c->uregs))
{
/* Note we need to clear this state again when the unwinder
has been rerun. See __stp_stack_print invocation below. */
UNW_SP(info) = REG_SP(c->uregs); /* Fix up user stack */
c->uregs = &info->regs;
c->probe_flags |= _STP_PROBE_STATE_FULL_UREGS;
dbug_unwind(1, "recovered with pc=0x%lx sp=0x%lx\n",
UNW_PC(info), UNW_SP(info));
}
else
dbug_unwind(1, "failed to recover user reg state\n");
}
#endif
}
return c->uregs;
}
/** Prints the stack backtrace
* @param regs A pointer to the struct pt_regs.
* @param verbose _STP_SYM_FULL or _STP_SYM_BRIEF
*/
static void _stp_stack_kernel_print(struct context *c, int sym_flags)
{
struct pt_regs *regs = NULL;
if (! c->kregs) {
/* For the kernel we can use an inexact fallback.
When compiled with frame pointers we can do
a pretty good guess at the stack value,
otherwise let dump_stack guess it
(and skip some framework frames). */
#if defined(STAPCONF_KERNEL_STACKTRACE) || defined(STAPCONF_KERNEL_STACKTRACE_NO_BP)
unsigned long sp;
int skip;
#ifdef CONFIG_FRAME_POINTER
sp = *(unsigned long *) __builtin_frame_address (0);
skip = 1; /* Skip just this frame. */
#else
sp = 0;
skip = 5; /* yes, that many framework frames. */
#endif
_stp_stack_print_fallback(sp, sym_flags,
MAXBACKTRACE, skip);
#else
if (sym_flags & _STP_SYM_SYMBOL)
_stp_printf("<no kernel backtrace at %s>\n",
c->probe_point);
else
_stp_print("\n");
#endif
return;
} else {
regs = c->kregs;
}
/* print the current address */
if (c->probe_type == _STP_PROBE_HANDLER_KRETPROBE && c->ips.krp.pi) {
if ((sym_flags & _STP_SYM_FULL) == _STP_SYM_FULL) {
_stp_print("Returning from: ");
_stp_print_addr((unsigned long)_stp_probe_addr_r(c->ips.krp.pi),
sym_flags, NULL);
_stp_print("Returning to : ");
}
_stp_print_addr((unsigned long)_stp_ret_addr_r(c->ips.krp.pi),
sym_flags, NULL);
} else {
_stp_print_addr(REG_IP(regs), sym_flags, NULL);
}
/* print rest of stack... */
#ifdef STP_USE_DWARF_UNWINDER
if (c->uregs == &c->uwcontext.info.regs) {
/* Unwinder needs the reg state, clear uregs ref. */
c->uregs = NULL;
c->probe_flags &= ~_STP_PROBE_STATE_FULL_UREGS;
}
__stp_dwarf_stack_kernel_print(regs, sym_flags, MAXBACKTRACE,
&c->uwcontext);
#else
/* Arch specific fallback for kernel backtraces. */
__stp_stack_print(regs, sym_flags, MAXBACKTRACE);
#endif
}
static void _stp_stack_user_print(struct context *c, int sym_flags)
{
struct pt_regs *regs = NULL;
int uregs_valid = 0;
struct uretprobe_instance *ri = NULL;
if (c->probe_type == _STP_PROBE_HANDLER_URETPROBE)
ri = c->ips.ri;
#ifdef STAPCONF_UPROBE_GET_PC
else if (c->probe_type == _STP_PROBE_HANDLER_UPROBE)
ri = GET_PC_URETPROBE_NONE;
#endif
regs = _stp_get_uregs(c);
uregs_valid = c->probe_flags & _STP_PROBE_STATE_FULL_UREGS;
if (! current->mm || ! regs) {
if (sym_flags & _STP_SYM_SYMBOL)
_stp_printf("<no user backtrace at %s>\n",
c->probe_point);
else
_stp_print("\n");
return;
}
/* print the current address */
#ifdef STAPCONF_UPROBE_GET_PC
if (c->probe_type == _STP_PROBE_HANDLER_URETPROBE && ri) {
if ((sym_flags & _STP_SYM_FULL) == _STP_SYM_FULL) {
_stp_print("Returning from: ");
/* ... otherwise this dereference fails */
_stp_print_addr(ri->rp->u.vaddr, sym_flags, current);
_stp_print("Returning to : ");
_stp_print_addr(ri->ret_addr, sym_flags, current);
} else
_stp_print_addr(ri->ret_addr, sym_flags, current);
} else {
_stp_print_addr(REG_IP(regs), sym_flags, current);
}
#else
_stp_print_addr(REG_IP(regs), sym_flags, current);
#endif
/* print rest of stack... */
#ifdef STP_USE_DWARF_UNWINDER
if (c->uregs == &c->uwcontext.info.regs) {
/* Unwinder needs the reg state, clear uregs ref. */
c->uregs = NULL;
c->probe_flags &= ~_STP_PROBE_STATE_FULL_UREGS;
}
__stp_dwarf_stack_user_print(regs, sym_flags, MAXBACKTRACE,
&c->uwcontext, ri, uregs_valid);
#else
/* User stack traces only supported for arches with dwarf unwinder. */
if (sym_flags & _STP_SYM_SYMBOL)
_stp_printf("<no user backtrace support on arch>\n");
else
_stp_print("\n");
#endif
}
/** Writes stack backtrace to a string
*
* @param str string
* @param regs A pointer to the struct pt_regs.
* @returns void
*/
static void _stp_stack_kernel_sprint(char *str, int size, struct context* c,
int sym_flags)
{
/* To get an hex string, we use a simple trick.
* First flush the print buffer,
* then call _stp_stack_print,
* then copy the result into the output string
* and clear the print buffer. */
_stp_pbuf *pb = per_cpu_ptr(Stp_pbuf, smp_processor_id());
_stp_print_flush();
_stp_stack_kernel_print(c, sym_flags);
strlcpy(str, pb->buf, size < (int)pb->len ? size : (int)pb->len);
pb->len = 0;
}
static void _stp_stack_user_sprint(char *str, int size, struct context* c,
int sym_flags)
{
/* To get an hex string, we use a simple trick.
* First flush the print buffer,
* then call _stp_stack_print,
* then copy the result into the output string
* and clear the print buffer. */
_stp_pbuf *pb = per_cpu_ptr(Stp_pbuf, smp_processor_id());
_stp_print_flush();
_stp_stack_user_print(c, sym_flags);
strlcpy(str, pb->buf, size < (int)pb->len ? size : (int)pb->len);
pb->len = 0;
}
#endif /* CONFIG_KPROBES */
#endif /* _STACK_C_ */
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