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/* -*- linux-c -*-
* Print Functions
* Copyright (C) 2007-2018 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.
*/
#ifndef _STAPLINUX_PRINT_C_
#define _STAPLINUX_PRINT_C_
#include "stp_string.h"
#include "print.h"
#include "transport/transport.c"
#include "vsprintf.c"
/** @file print.c
* Printing Functions.
*/
/** @addtogroup print Print Functions
* The print buffer is for collecting output to send to the user daemon.
* This is a per-cpu static buffer. The buffer is sent when
* _stp_print_flush() is called.
*
* The reason to do this is to allow multiple small prints to be combined then
* timestamped and sent together to staprun. This is more efficient than sending
* numerous small packets.
*
* This function is called automatically when the print buffer is full.
* It MUST also be called at the end of every probe that prints something.
* @{
*/
struct _stp_log {
unsigned int len; /* Bytes used in the buffer */
char buf[STP_BUFFER_SIZE];
atomic_t reentrancy_lock;
};
#include "print_flush.c"
static struct _stp_log *_stp_log_pcpu;
/*
* An atomic counter is used to synchronize every possible print buffer usage
* with the _stp_print_cleanup() function. The cleanup function sets the counter
* to INT_MAX after waiting for everything using the print buffer to finish. We
* cannot use a lock primitive to implement this because lock_acquire() contains
* tracepoints and print statements are used both inside and outside of probes.
* If the lock were only used inside probes, the runtime context would protect
* us from recursing into the lock_acquire() tracepoints and deadlocking. We
* instead use _stp_print_ctr as if it were a read-write lock.
*/
static atomic_t _stp_print_ctr = ATOMIC_INIT(0);
/*
* This disables IRQs to make per-CPU print buffer accesses atomic. There is a
* reentrancy protection mechanism specifically for NMIs, since they can violate
* our atomic guarantee. Reentrancy is otherwise allowed within code sections
* that have the runtime context held (via _stp_runtime_entryfn_get_context()).
*/
static bool _stp_print_trylock_irqsave(unsigned long *flags)
{
bool context_held = false;
struct _stp_log *log;
local_irq_save(*flags);
if (!atomic_add_unless(&_stp_print_ctr, 1, INT_MAX))
goto irq_restore;
/*
* Check the per-CPU reentrancy lock for contention, unless the runtime
* context is already held, in which case we already have reentrancy
* protection. Otherwise, if the reentrancy lock is contented, that
* means we're either inside an NMI that fired while the current CPU was
* accessing the log buffer, or something is trying to nest calls to
* _stp_print_trylock_irqsave(). Our only choice is to reject the log
* access attempt in this case because log buffer corruption and panics
* could ensue if we're inside an NMI.
*/
if (_stp_runtime_context_trylock()) {
struct context *c = _stp_runtime_get_context();
context_held = c && atomic_read(&c->busy);
_stp_runtime_context_unlock();
}
/* Fall back onto the reentrancy lock if the context isn't held */
if (!context_held) {
log = per_cpu_ptr(_stp_log_pcpu, raw_smp_processor_id());
if (atomic_cmpxchg(&log->reentrancy_lock, 0, 1))
goto print_unlock;
}
return true;
print_unlock:
atomic_dec(&_stp_print_ctr);
irq_restore:
local_irq_restore(*flags);
return false;
}
static void _stp_print_unlock_irqrestore(unsigned long *flags)
{
bool context_held = false;
struct _stp_log *log;
if (_stp_runtime_context_trylock()) {
struct context *c = _stp_runtime_get_context();
context_held = c && atomic_read(&c->busy);
_stp_runtime_context_unlock();
}
if (!context_held) {
log = per_cpu_ptr(_stp_log_pcpu, raw_smp_processor_id());
atomic_set(&log->reentrancy_lock, 0);
}
atomic_dec(&_stp_print_ctr);
local_irq_restore(*flags);
}
/* create percpu print and io buffers */
static int _stp_print_init (void)
{
unsigned int cpu;
_stp_log_pcpu = _stp_alloc_percpu(sizeof(*_stp_log_pcpu));
if (!_stp_log_pcpu)
return -ENOMEM;
for_each_possible_cpu(cpu) {
struct _stp_log *log = per_cpu_ptr(_stp_log_pcpu, cpu);
log->reentrancy_lock = (atomic_t)ATOMIC_INIT(0);
}
return 0;
}
static void _stp_print_cleanup (void)
{
unsigned int cpu;
/* Wait for the loggers to finish modifying the print buffers */
while (atomic_cmpxchg(&_stp_print_ctr, 0, INT_MAX))
cpu_relax();
for_each_possible_cpu(cpu) {
struct _stp_log *log = per_cpu_ptr(_stp_log_pcpu, cpu);
/*
* Flush anything that could be left in the print buffer. It is
* safe to do this without any kind of synchronization mechanism
* because nothing is using this print buffer anymore.
*/
__stp_print_flush(log);
}
_stp_free_percpu(_stp_log_pcpu);
}
static inline void _stp_print_flush(void)
{
struct _stp_log *log;
unsigned long flags;
if (!_stp_print_trylock_irqsave(&flags))
return;
log = per_cpu_ptr(_stp_log_pcpu, raw_smp_processor_id());
__stp_print_flush(log);
_stp_print_unlock_irqrestore(&flags);
}
#ifndef STP_MAXBINARYARGS
#define STP_MAXBINARYARGS 127
#endif
/** Reserves space in the output buffer for direct I/O. Must be called with
* _stp_print_trylock_irqsave() held.
*/
static void * _stp_reserve_bytes (int numbytes)
{
struct _stp_log *log;
char *ret;
if (unlikely(numbytes == 0 || numbytes > STP_BUFFER_SIZE))
return NULL;
log = per_cpu_ptr(_stp_log_pcpu, raw_smp_processor_id());
if (unlikely(numbytes > (STP_BUFFER_SIZE - log->len)))
__stp_print_flush(log);
ret = &log->buf[log->len];
log->len += numbytes;
return ret;
}
static void _stp_unreserve_bytes (int numbytes)
{
struct _stp_log *log;
log = per_cpu_ptr(_stp_log_pcpu, raw_smp_processor_id());
if (numbytes <= log->len)
log->len -= numbytes;
}
/** Write 64-bit args directly into the output stream.
* This function takes a variable number of 64-bit arguments
* and writes them directly into the output stream. Marginally faster
* than doing the same in _stp_vsnprintf().
* @sa _stp_vsnprintf()
*/
static void _stp_print_binary (int num, ...)
{
unsigned long flags;
va_list vargs;
int i;
int64_t *args;
if (unlikely(num > STP_MAXBINARYARGS))
num = STP_MAXBINARYARGS;
if (!_stp_print_trylock_irqsave(&flags))
return;
args = _stp_reserve_bytes(num * sizeof(int64_t));
if (args) {
va_start(vargs, num);
for (i = 0; i < num; i++)
args[i] = va_arg(vargs, int64_t);
va_end(vargs);
}
_stp_print_unlock_irqrestore(&flags);
}
/** Print into the print buffer.
* Like C printf.
*
* @sa _stp_print_flush()
*/
static void _stp_printf (const char *fmt, ...)
{
va_list args;
va_start(args, fmt);
_stp_vsnprintf(NULL, 0, fmt, args);
va_end(args);
}
/** Write a string into the print buffer.
* @param str A C string (char *)
*/
static void _stp_print (const char *str)
{
struct _stp_log *log;
unsigned long flags;
if (!_stp_print_trylock_irqsave(&flags))
return;
log = per_cpu_ptr(_stp_log_pcpu, raw_smp_processor_id());
while (1) {
while (log->len < STP_BUFFER_SIZE && *str)
log->buf[log->len++] = *str++;
if (likely(!*str))
break;
__stp_print_flush(log);
}
_stp_print_unlock_irqrestore(&flags);
}
static void _stp_print_char (const char c)
{
struct _stp_log *log;
unsigned long flags;
if (!_stp_print_trylock_irqsave(&flags))
return;
log = per_cpu_ptr(_stp_log_pcpu, raw_smp_processor_id());
if (unlikely(log->len == STP_BUFFER_SIZE))
__stp_print_flush(log);
log->buf[log->len++] = c;
_stp_print_unlock_irqrestore(&flags);
}
static void _stp_print_kernel_info(char *sname, char *vstr, int ctx, int num_probes)
{
printk(KERN_DEBUG
"%s (%s): systemtap: %s, base: %lx"
", memory: %ludata/%lutext/%uctx/%unet/%ualloc kb"
", probes: %d"
#if ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPDEV)
", unpriv-uid: %d"
#endif
"\n",
THIS_MODULE->name,
sname, /* name of source file */
vstr, /* stap version */
#ifdef STAPCONF_MODULE_LAYOUT
(unsigned long) THIS_MODULE->core_layout.base,
(unsigned long) (THIS_MODULE->core_layout.size - THIS_MODULE->core_layout.text_size)/1024,
(unsigned long) (THIS_MODULE->core_layout.text_size)/1024,
#else
#ifndef STAPCONF_GRSECURITY
(unsigned long) THIS_MODULE->module_core,
(unsigned long) (THIS_MODULE->core_size - THIS_MODULE->core_text_size)/1024,
(unsigned long) (THIS_MODULE->core_text_size)/1024,
#else
(unsigned long) THIS_MODULE->module_core_rx,
(unsigned long) (THIS_MODULE->core_size_rw - THIS_MODULE->core_size_rx)/1024,
(unsigned long) (THIS_MODULE->core_size_rx)/1024,
#endif
#endif
ctx/1024,
_stp_allocated_net_memory/1024,
(_stp_allocated_memory - _stp_allocated_net_memory - ctx)/1024,
/* (un-double-counting net/ctx because they're also stp_alloc'd) */
num_probes
#if ! STP_PRIVILEGE_CONTAINS (STP_PRIVILEGE, STP_PR_STAPDEV)
, _stp_uid
#endif
);
}
/** @} */
#endif /* _STAPLINUX_PRINT_C_ */