[ltt-dev] [RFC PATCH] Propose a new kernel tracing framework
Mathieu Desnoyers
mathieu.desnoyers at polymtl.ca
Mon Mar 16 20:01:38 EDT 2009
* Jiaying Zhang (jiayingz at google.com) wrote:
> Hi Mathieu,
>
> First, I apologize that I did not forward you my original email. I assumed
> that the email would be noticed by interested people when it was sent
> to lkml. Now I see that is a mistake.
>
Hi Jiaying,
Apologies accepted, no hard feeling :) I have just been surprised when I
found out about the numbers you posted.
> On Fri, Mar 13, 2009 at 10:04 AM, Mathieu Desnoyers
> <mathieu.desnoyers at polymtl.ca> wrote:
> > Hi Jiaying,
> >
> > I'm very interested to hear about the details of your test-case, because
> > what you are talking about here, and the numbers that you get, are, at
> > the very least, not representative of the current LTTng. Perharps you
> > used a version right after the kernel summit and stopped following the
> > improvements we have done since then ? I also wonder about the instrumentation
> > set you enabled in your tests, and whether it's exactly the same in the ktrace
> > and LTTng runs (especially system call tracing). Please note that following the
> > Kernel Summit 2008, a more active development cycle began, and the time was not
> > right for optimisation. But since then a lot of improvement has been done on
> > this side.
>
> Sorry that I omitted a lot of details in my test description. I did use an old
> version of LTTng in my tests. The LTTng version I used was the 0.21 lttng
> patches for 2.6.27 kernel. I used 2.6.26 kernel in my tests, with the ported
> lttng-2.6.27-rc6-0.21 patches.
>
> I enabled the same set of trace events in ktrace and LTTng runs. Here is
> the list of enabled events: syscall entry/exit, irq entry/exit, trap
> entry/exit,
> kernel_sched_switch, kernel_process_fork, kernel_process_wait,
> kernel_process_free, kernel_process_exit.
>
> We are glad to see the improvements coming from the LTTng community.
> I haven't got time to sync with the latest LTTng code and re-run my tests.
> I will let you know when I have such data available.
>
On my side, with flight recorder activated, same instrumentation you
use, with LTTng 0.111 :
arm-google script :
#!/bin/sh
DIR=/mnt/debugfs/ltt/markers
for a in \
syscall_entry syscall_exit \
irq_entry irq_exit \
trap_entry trap_exit \
page_fault_entry page_fault_exit \
page_fault_nosem_entry page_fault_nosem_exit \
page_fault_get_user_entry page_fault_get_user_exit \
sched_schedule process_fork process_wait \
process_free process_exit;
do
echo 1 > ${DIR}/kernel/$a/enable
done
running tbench -t 200 8
Vanilla kernel : 2070 MB/sec
Flight recorder : 1693 MB/sec Performance impact : 18.2 %
Normal : 1620 MB/sec Performance impact : 21.7 % (8 lttd threads)
So now we are comparing apples with apples :-)
> >
> > First I'd like to express my concern about the way you posted your
> > numbers :
> >
> > 1 - You did not CC anyone from the LTTng project.
> > 2 - You did not tell which LTTng version you used as a comparison basis.
> > 3 - You did not look at the current state of code before posting your
> > comparison. (as shows the comment in your patch header)
> That is indeed my mistake.
>
> > 4 - You did not tell the instrumentation set that you enabled from LTTng. Is it
> > the default instrumentation ? Did you also enable system call tracing
> > with your tracer using set_kernel_trace_flag_all_tasks() ? If not, this
> > makes a huge difference on the amount of information gathered.
> Yes. We also enable syscall tracing via set_kernel_trace_flag_all_tasks().
>
> >
> > So let's have a close look at them. I'm re-doing the benchmarks based on
> > the current LTTng version below.
> >
> >> Hello All,
> >>
> >> We have been working on building a kernel tracer for a production environment.
> >> We first considered to use the existing markers code, but found it a bit
> >> heavyweight.
> >
> > Have you looked at :
> >
> > 1 - The tracepoints currently in the kernel
> > 2 - The _current_ version of markers in the LTTng tree ?
>
> I looked at the tracepoints currently in the kernel. It is great to see that
> some trace instrumentation code is finally available in the mainline kernel.
> But I still don't like an additional tracepoint layer on top of the
> actual tracing
> (ktrace or markers or ftrace) layer. That seems to add unnecessary overhead.
> The markers code I referred to in my email is the current code in the mainline
> kernel. I had a look at the LTTng markers code but still saw that va_list
> argument is used in marker_probe_func. It sounds a nice improvement
> if the LTTng markers avoids the use of va_arg whenever possible.
>
Yes, vs_args is only there as a commodity for slow paths.
> >
> >> So we developed a new kernel tracing prototype that shares
> >> many similarities as markers but also includes several simplifications that
> >> give us considerable performance benefits. For example, we pass the size of
> >> trace event directly to the probe function instead of using va_arg as that
> >> used in markers, which saves us the overhead of variable passing.
> >
> > The markers in the LTTng tree only use va_args for "debug-style"
> > tracing. All the tracing fast paths are now done with custom probe
> > functions which takes the arguments from the tracepoint and write them
> > in the trace buffers directly in C. When the event payload size is already
> > known statically, there is no dynamic computation cost at all : it's
> > simply passed to the ltt-relay write function.
> But this raises another concern that sub-system developers may need
> to write a bunch of custom probe functions to avoid the argument parsing
> overhead. Can you instead have a general probe function or macro that
> does this work?
>
Well, considering the amount of care we have to take when we consider
adding a tracepoint in the mainline kernel, I think it's even a *good*
thing that someone has to stop and write a small callback to deal with
the information he wants to export. I think debug-style tracing should
be very, very quick and easy to add, but tracepoints meant to make it
into the mainline does not share this requirement.
> >
> >> Also, we
> >> associate a single probe function to each event, so we can directly call the
> >> probe function when tracing is enabled.
> >
> > You seem to imply that being stuck with a single probe function is
> > somehow superior to have tiny per-event callbacks which then call into a
> > buffer write function ? Why ?
> That is indeed my thinking, because we saw that some platforms are
> very sensitive to function call overhead and we haven't seen use cases
> where multi probe functions prove necessary.
>
Hrm, so your plan is to embed the tracing code at the caller site, or to
keep one single function call ?
> >
> >> Our measurements show that our
> >> current tracing prototype introduces much lower overhead compared with
> >> lttng (we use lttng as a comparison because markers does not provide the
> >> implementation to record trace data).
> >
> > Why LTTng version, kernel version, LTTng config and runtime options do
> > you use ?
> See above for LTTng and kernel versions. I was using the default LTTng
> config options and 'normal' recorder mode.
>
> >
> >> E.g., with dbench, lttng introduces
> >> 20~80% overhead on our testing platforms while the overhead with our
> >> kernel tracer is within 10%; with tbench, lttng usually adds more than 30%
> >> overhead while the overhead added by our kernel tracer is usually within
> >> 15%; with kernbench (time to compile a Linux kernel), the overhead
> >> added by lttng is around 4%~18% while the overhead added by our
> >> kernel tracer is within 2.5%.
> >>
> >
> > I'm re-running the dbench and tbench tests :
> >
> > With LTTng 0.106, kernel 2.6.29-rc7
> > 8-cores Intel(R) Xeon(R) CPU E5405 @ 2.00GHz, 16GB ram
> >
> > Arming all the default LTTng instrumentation (168 tracepoints),
> > Tracing in flight recorder mode, including system call entry/exit
> > tracing and block I/O tracing (blktrace instrumentation), I get :
> >
> > Test / config | Vanilla kernel | LTTng 0.106 | slowdown
> > dbench 8 -t 200 | 1361 MB/s | 1193 MB/s | 12.3 %
> >
> > As an example of the effect of custom probe vs va_args based probes,
> > let's take the tbench example
> >
> > | Vanilla | LTTng 0.106 | slowdown
> > tbench 8 -t 200 | 2074 MB/s | 997 MB/s | 52 %
> >
> > The LTTng trace statistics shows the top high event rate events :
> >
> > Some are usual (therefore lttng already implements custom probes for them) :
> >
> > 42004 sched_try_wakeup
> > 79754 timer_set
> > 83973 sched_schedule
> > 84317 softirq_exit
> > 84318 softirq_entry
> > 95370 page_free
> > 95412 page_alloc
> > 267247 syscall_entry
> > 267247 syscall_exit
> >
> > Some are more tbench workload-specific :
> >
> > 16915 socket_sendmsg
> > 18911 napi_complete
> > 18911 napi_schedule
> > 18912 dev_receive
> > 18914 dev_xmit
> > 18920 napi_poll
> > 33831 socket_recvmsg
> > 59860 read
> >
> >
> > So let's see what happens if I implement those as custom probes and do a bit of
> > tuning in the tracer hot path :
> Could you give more details about the custom probe you used?
They are available in the lttng tree on git.kernel.org in
ltt/probes/*-trace.c. Their API is in include/linux/ltt-type-serialize.h
> Do you need to write a custom probe for each tracepoint?
>
Yes. But it's not such a big deal. It looks a bit like Steve's
TRACE_EVENT macro-fu, but written in a simple C callback :
void probe_sched_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next);
DEFINE_MARKER_TP(kernel, sched_schedule, sched_switch, probe_sched_switch,
"prev_pid %d next_pid %d prev_state #2d%ld");
notrace void probe_sched_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
struct marker *marker;
struct serialize_int_int_short data;
data.f1 = prev->pid;
data.f2 = next->pid;
data.f3 = prev->state;
marker = &GET_MARKER(kernel, sched_schedule);
ltt_specialized_trace(marker, marker->single.probe_private,
&data, serialize_sizeof(data), sizeof(int));
}
Best regards,
Mathieu
> Jiaying
>
> >
> > | Vanilla | LTTng 0.107 | slowdown
> > Custom probes :
> > tbench 8 -t 200 | 2074 MB/s | 1275 MB/s | 38.5 %
> >
> > With tracer hot path tuning (inline hot path, function calls for slow path, will
> > be in 0.108) :
> > tbench 8 -t 200 | 2074 MB/s | 1335 MB/s | 35.6 %
> >
> > kernbench :
> > Average Optimal load -j 32 Run
> >
> > Vanilla 2.6.29-rc7 :
> > Elapsed Time 48.238 (0.117346)
> >
> > With flight recorder tracing, default lttng instrumentation, lttng 0.108 :
> > Elapsed Time 50.226 (0.0750333)
> >
> > Slowdown : 4.1 %
> >
> > So except the tbench workload on LTTng 0.106, which still had a 52% performance
> > impact (brought it down to 35 % for the next LTTng release) due to
> > specific workload and not having specialized probes implemented, the
> > dbench impact is well below your results (12.3 % vs 20-80%)
> >
> > So given the huge result discrepancies between your tests and mine, could you
> > give us more detail about your benchmarks ? Especially knowing the enabled
> > instrumentation set, and the amount of MB/s generated by both ktrace and LTTng
> > runs (to make sure we are comparing the same traffic) and the LTTng versions you
> > are using as a comparison basis would be good.
> >
> > Thanks,
> >
> > Mathieu
> >
> >
> >> The patch below is the current prototype we have implemented. It uses
> >> Steve's unified trace buffer code with some small extensions to support
> >> buffer mmap. The patch is probably still buggy, but we would like to get
> >> some early feedback from the community.
> >>
> >> Signed-off-by: Jiaying Zhang <jiayingz at google.com>
> >>
> >> Index: git-linux/init/Kconfig
> >> ===================================================================
> >> --- git-linux.orig/init/Kconfig 2009-02-19 14:58:37.000000000 -0800
> >> +++ git-linux/init/Kconfig 2009-02-19 15:50:15.000000000 -0800
> >> @@ -950,6 +950,15 @@
> >> Place an empty function call at each marker site. Can be
> >> dynamically changed for a probe function.
> >>
> >> +config KTRACE
> >> + bool "Enable ktrace support"
> >> + select DEBUG_FS
> >> + select TRACING
> >> + select RING_BUFFER
> >> + help
> >> + Ktrace is a kernel tracing tool that allows you to trace
> >> + kernel events by inserting trace points at proper places.
> >> +
> >> source "arch/Kconfig"
> >>
> >> endmenu # General setup
> >> Index: git-linux/kernel/Makefile
> >> ===================================================================
> >> --- git-linux.orig/kernel/Makefile 2009-02-19 14:58:37.000000000 -0800
> >> +++ git-linux/kernel/Makefile 2009-02-19 14:58:39.000000000 -0800
> >> @@ -86,6 +86,7 @@
> >> obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
> >> obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
> >> obj-$(CONFIG_MARKERS) += marker.o
> >> +obj-$(CONFIG_KTRACE) += ktrace.o
> >> obj-$(CONFIG_TRACEPOINTS) += tracepoint.o
> >> obj-$(CONFIG_LATENCYTOP) += latencytop.o
> >> obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
> >> Index: git-linux/include/asm-generic/vmlinux.lds.h
> >> ===================================================================
> >> --- git-linux.orig/include/asm-generic/vmlinux.lds.h 2009-02-19
> >> 14:58:37.000000000 -0800
> >> +++ git-linux/include/asm-generic/vmlinux.lds.h 2009-02-19
> >> 14:58:39.000000000 -0800
> >> @@ -73,6 +73,9 @@
> >> MEM_KEEP(init.data) \
> >> MEM_KEEP(exit.data) \
> >> . = ALIGN(8); \
> >> + VMLINUX_SYMBOL(__start___ktraces) = .; \
> >> + *(__ktrace) \
> >> + VMLINUX_SYMBOL(__stop___ktraces) = .; \
> >> VMLINUX_SYMBOL(__start___markers) = .; \
> >> *(__markers) \
> >> VMLINUX_SYMBOL(__stop___markers) = .; \
> >> @@ -89,6 +92,7 @@
> >> VMLINUX_SYMBOL(__start_rodata) = .; \
> >> *(.rodata) *(.rodata.*) \
> >> *(__vermagic) /* Kernel version magic */ \
> >> + *(__ktrace_strings) /* Ktrace: strings */ \
> >> *(__markers_strings) /* Markers: strings */ \
> >> *(__tracepoints_strings)/* Tracepoints: strings */ \
> >> } \
> >> Index: git-linux/kernel/module.c
> >> ===================================================================
> >> --- git-linux.orig/kernel/module.c 2009-02-19 14:58:37.000000000 -0800
> >> +++ git-linux/kernel/module.c 2009-02-19 14:58:39.000000000 -0800
> >> @@ -50,6 +50,7 @@
> >> #include <asm/sections.h>
> >> #include <linux/tracepoint.h>
> >> #include <linux/ftrace.h>
> >> +#include <linux/ktrace.h>
> >> #include <linux/async.h>
> >>
> >> #if 0
> >> @@ -2145,6 +2146,10 @@
> >> sizeof(*mod->tracepoints),
> >> &mod->num_tracepoints);
> >> #endif
> >> +#ifdef CONFIG_KTRACE
> >> + mod->ktrace = section_objs(hdr, sechdrs, secstrings, "__ktrace",
> >> + sizeof(*mod->ktrace), &mod->num_ktrace);
> >> +#endif
> >>
> >> #ifdef CONFIG_MODVERSIONS
> >> if ((mod->num_syms && !mod->crcs)
> >> Index: git-linux/include/linux/module.h
> >> ===================================================================
> >> --- git-linux.orig/include/linux/module.h 2009-02-19
> >> 14:58:37.000000000 -0800
> >> +++ git-linux/include/linux/module.h 2009-02-19 14:58:39.000000000 -0800
> >> @@ -44,6 +44,7 @@
> >> };
> >>
> >> struct module;
> >> +struct kernel_trace;
> >>
> >> struct module_attribute {
> >> struct attribute attr;
> >> @@ -347,6 +348,11 @@
> >> /* Reference counts */
> >> struct module_ref ref[NR_CPUS];
> >> #endif
> >> +#ifdef CONFIG_KTRACE
> >> + struct kernel_trace *ktrace;
> >> + unsigned int num_ktrace;
> >> +#endif
> >> +
> >> };
> >> #ifndef MODULE_ARCH_INIT
> >> #define MODULE_ARCH_INIT {}
> >> Index: git-linux/include/linux/ktrace.h
> >> ===================================================================
> >> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> >> +++ git-linux/include/linux/ktrace.h 2009-02-19 15:36:39.000000000 -0800
> >> @@ -0,0 +1,83 @@
> >> +#ifndef _LINUX_KTRACE_H
> >> +#define _LINUX_KTRACE_H
> >> +
> >> +#include <linux/types.h>
> >> +
> >> +struct kernel_trace;
> >> +
> >> +typedef void ktrace_probe_func(struct kernel_trace *, void *, size_t);
> >> +
> >> +struct kernel_trace {
> >> + const char *name;
> >> + const char *format; /* format string describing variable list */
> >> + size_t *stroff; /* offsets of string variables */
> >> + /* 31 bit event_id is converted to 16 bit when entering to the buffer */
> >> + u32 enabled:1, event_id:31;
> >> + ktrace_probe_func *func; /* probe function */
> >> + struct list_head list; /* list head linked to the hash table entry */
> >> +} __attribute__((aligned(8)));
> >> +
> >> +extern int ktrace_enabled;
> >> +
> >> +/*
> >> + * Make sure the alignment of the structure in the __ktrace section will
> >> + * not add unwanted padding between the beginning of the section and the
> >> + * structure. Force alignment to the same alignment as the section start.
> >> + */
> >> +
> >> +#define DEFINE_KTRACE_STRUCT(name) \
> >> + struct __attribute__((packed)) ktrace_struct_##name
> >> +
> >> +#ifdef CONFIG_KTRACE
> >> +/*
> >> + * DO_TRACE is the macro that is called from each trace point. Each trace
> >> + * point is associated with a static ktrace object that is located in a
> >> + * special __ktrace section and is uniquely identified by the event name and
> >> + * event format. Take a look at the files under include/trace for example
> >> + * usage. Note that we call the trace probe function only if the global
> >> + * tracing is enabled and the tracing for the associated event is enabled,
> >> + * so we only introduce the overhead of a predicted condition judge when
> >> + * tracing is disabled.
> >> + */
> >> +#define DO_TRACE(name, format, args...)
> >> \
> >> + do { \
> >> + static const char __kstrtab_##name[] \
> >> + __attribute__((section("__ktrace_strings"))) \
> >> + = #name "\0" format; \
> >> + static struct kernel_trace __ktrace_##name \
> >> + __attribute__((section("__ktrace"), aligned(8))) = \
> >> + { __kstrtab_##name, &__kstrtab_##name[sizeof(#name)], \
> >> + NULL, 0, 0, NULL, LIST_HEAD_INIT(__ktrace_##name.list) }; \
> >> + __ktrace_check_format(format, ## args); \
> >> + if (unlikely(ktrace_enabled) && \
> >> + unlikely(__ktrace_##name.enabled)) { \
> >> + struct ktrace_struct_##name karg = { args }; \
> >> + (*__ktrace_##name.func) \
> >> + (&__ktrace_##name, &karg, sizeof(karg)); \
> >> + } \
> >> + } while (0)
> >> +
> >> +#else /* !CONFIG_KTRACE */
> >> +#define DO_TRACE(name, format, args...)
> >> +#endif
> >> +
> >> +/* To be used for string format validity checking with gcc */
> >> +static inline void __printf(1, 2) ___ktrace_check_format(const char *fmt, ...)
> >> +{
> >> +}
> >> +
> >> +#define __ktrace_check_format(format, args...) \
> >> + do { \
> >> + if (0) \
> >> + ___ktrace_check_format(format, ## args); \
> >> + } while (0)
> >> +
> >> +
> >> +/* get the trace buffer information */
> >> +#define KTRACE_BUF_GET_SIZE _IOR(0xF5, 0x00, __u32)
> >> +#define KTRACE_BUF_GET_PRODUCED _IOR(0xF5, 0x01, __u32)
> >> +#define KTRACE_BUF_GET_CONSUMED _IOR(0xF5, 0x02, __u32)
> >> +#define KTRACE_BUF_PUT_PRODUCED _IOW(0xF5, 0x03, __u32)
> >> +#define KTRACE_BUF_PUT_CONSUMED _IOW(0xF5, 0x04, __u32)
> >> +
> >> +#endif
> >> Index: git-linux/kernel/ktrace.c
> >> ===================================================================
> >> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> >> +++ git-linux/kernel/ktrace.c 2009-02-19 15:45:20.000000000 -0800
> >> @@ -0,0 +1,872 @@
> >> +/*
> >> + * kernel/ktrace.c
> >> + *
> >> + * Implementation of the kernel tracing for linux kernel 2.6.
> >> + *
> >> + * Copyright 2008- Google Inc.
> >> + * Original Author: Jiaying Zhang
> >> + */
> >> +
> >> +#include <linux/module.h>
> >> +#include <linux/kernel.h>
> >> +#include <linux/bitmap.h>
> >> +#include <linux/poll.h>
> >> +#include <linux/errno.h>
> >> +#include <linux/sched.h>
> >> +#include <linux/linkage.h>
> >> +#include <linux/debugfs.h>
> >> +#include <linux/timer.h>
> >> +#include <linux/delay.h>
> >> +#include <linux/jhash.h>
> >> +#include <linux/ctype.h>
> >> +#include <linux/namei.h>
> >> +#include <linux/ktrace.h>
> >> +#include <linux/ring_buffer.h>
> >> +
> >> +static char *ktrace_version = "1.0.0";
> >> +int ktrace_enabled;
> >> +EXPORT_SYMBOL(ktrace_enabled);
> >> +static uint16_t ktrace_next_id;
> >> +
> >> +extern struct kernel_trace __start___ktraces[];
> >> +extern struct kernel_trace __stop___ktraces[];
> >> +
> >> +static DEFINE_MUTEX(ktrace_mutex);
> >> +
> >> +/* ktrace hash table entry structure and variables */
> >> +struct ktrace_entry {
> >> + struct hlist_node hlist;
> >> + char *name;
> >> + char *format;
> >> + size_t *stroff;
> >> + ktrace_probe_func *func;
> >> + u32 enabled:1, event_id:31;
> >> + struct list_head klist; /* list of loaded ktraces */
> >> +};
> >> +
> >> +#define KTRACE_HASH_BITS 6
> >> +#define KTRACE_HASH_SIZE (1 << KTRACE_HASH_BITS)
> >> +static struct hlist_head ktrace_table[KTRACE_HASH_SIZE];
> >> +
> >> +/* debugfs directory variables */
> >> +static struct dentry *tracedir;
> >> +static struct dentry *eventdir;
> >> +typedef void tracecontrol_handle_func(struct file *, unsigned long, size_t *);
> >> +
> >> +/* ring buffer code */
> >> +static unsigned long trace_buf_size = 65536UL;
> >> +struct ring_buffer *trace_buffer;
> >> +static DECLARE_WAIT_QUEUE_HEAD(trace_wait); /* waitqueue for trace_data_poll */
> >> +static struct timer_list trace_timer; /* reader wake-up timer */
> >> +#define TRACEREAD_WAKEUP_INTERVAL 1000 /* time interval in jiffies */
> >> +static struct kref ktrace_kref;
> >> +
> >> +static void
> >> +ring_buffer_probe(struct kernel_trace *kt, void *data, size_t event_size)
> >> +{
> >> + struct ring_buffer_event *event;
> >> + void *trace_event;
> >> + unsigned long flag;
> >> +
> >> + event = ring_buffer_lock_reserve(trace_buffer,
> >> + sizeof(uint16_t) + event_size, &flag);
> >> + if (!event)
> >> + return;
> >> + trace_event = ring_buffer_event_data(event);
> >> + *(uint16_t *) trace_event = (uint16_t) kt->event_id;
> >> + memcpy(trace_event + sizeof(uint16_t), data, event_size);
> >> + ring_buffer_unlock_commit(trace_buffer, event, flag);
> >> +}
> >> +
> >> +/* special probe function for events that contain string arguments */
> >> +static void
> >> +string_probe(struct kernel_trace *kt, void *data, size_t event_size)
> >> +{
> >> + struct ring_buffer_event *event;
> >> + void *trace_event, *p;
> >> + unsigned long flag;
> >> + size_t *offset, scanned;
> >> + char *string;
> >> +
> >> + /*
> >> + * Get the real length of the event, i.e., we use stroff array to
> >> + * locate string variables in the passed-in trace data and use their
> >> + * length to replace the size of the string pointers.
> >> + */
> >> + for (offset = kt->stroff; *offset != -1; offset++) {
> >> + string = *(char **) (data + *offset);
> >> + event_size += strlen(string) + 1 - sizeof(char *);
> >> + }
> >> + event = ring_buffer_lock_reserve(trace_buffer,
> >> + sizeof(uint16_t) + event_size, &flag);
> >> + if (!event)
> >> + return;
> >> + trace_event = ring_buffer_event_data(event);
> >> + *(uint16_t *) trace_event = (uint16_t) kt->event_id;
> >> + p = trace_event + sizeof(uint16_t);
> >> + /*
> >> + * Copy the trace data into buffer. For string variables, we enter the
> >> + * string into the buffer. Otherwise, the passed in data is copied.
> >> + */
> >> + for (offset = kt->stroff, scanned = 0; *offset != -1; offset++) {
> >> + memcpy(p, data + scanned, *offset - scanned);
> >> + p += *offset - scanned;
> >> + string = *(char **) (data + *offset);
> >> + memcpy(p, string, strlen(string) + 1);
> >> + p += strlen(string) + 1;
> >> + scanned = *offset + sizeof(char *);
> >> + }
> >> + memcpy(p, data + scanned,
> >> + trace_event + sizeof(uint16_t) + event_size - p);
> >> + ring_buffer_unlock_commit(trace_buffer, event, flag);
> >> +}
> >> +
> >> +/* timer function used to defer ring buffer reader waking */
> >> +static void wakeup_readers(unsigned long data)
> >> +{
> >> + if (trace_buffer && !ring_buffer_empty(trace_buffer))
> >> + wake_up_interruptible(&trace_wait);
> >> + mod_timer(&trace_timer, jiffies + TRACEREAD_WAKEUP_INTERVAL);
> >> +}
> >> +
> >> +/* function for reading ktrace metadata info */
> >> +static void *tracing_info_start(struct seq_file *seq, loff_t *pos)
> >> +{
> >> + seq_printf(seq, "version %s\n", ktrace_version);
> >> + return (*pos >= KTRACE_HASH_SIZE) ? NULL : &ktrace_table[*pos];
> >> +}
> >> +
> >> +static void *tracing_info_next(struct seq_file *seq, void *v, loff_t *pos)
> >> +{
> >> + ++*pos;
> >> + return (*pos >= KTRACE_HASH_SIZE) ? NULL : &ktrace_table[*pos];
> >> +}
> >> +
> >> +static int tracing_info_show(struct seq_file *seq, void *v)
> >> +{
> >> + struct hlist_head *head = v;
> >> + struct hlist_node *node;
> >> + struct ktrace_entry *entry;
> >> + hlist_for_each_entry(entry, node, head, hlist)
> >> + seq_printf(seq, "name '%s' format '%s' id %u %s\n",
> >> + entry->name, entry->format, entry->event_id,
> >> + entry->enabled ? "enabled" : "disabled");
> >> + return 0;
> >> +}
> >> +
> >> +static void tracing_info_stop(struct seq_file *seq, void *v)
> >> +{
> >> +}
> >> +
> >> +static const struct seq_operations tracing_info_seq_ops = {
> >> + .start = tracing_info_start,
> >> + .next = tracing_info_next,
> >> + .show = tracing_info_show,
> >> + .stop = tracing_info_stop,
> >> +};
> >> +
> >> +static int tracing_info_open(struct inode *inode, struct file *file)
> >> +{
> >> + return seq_open(file, &tracing_info_seq_ops);
> >> +}
> >> +
> >> +static const struct file_operations traceinfo_file_operations = {
> >> + .open = tracing_info_open,
> >> + .read = seq_read,
> >> + .llseek = seq_lseek,
> >> + .release = seq_release,
> >> +};
> >> +
> >> +/*
> >> + * wrapper function used by debugfs write operation.
> >> + * func: handling function that does real work
> >> + */
> >> +static ssize_t trace_debugfs_write(struct file *filp, const char __user *ubuf,
> >> + size_t cnt, loff_t *ppos, tracecontrol_handle_func *func)
> >> +{
> >> + int ret;
> >> + char buf[64];
> >> + unsigned long val;
> >> +
> >> + if (cnt >= sizeof(buf))
> >> + return -EINVAL;
> >> + if (copy_from_user(&buf, ubuf, cnt))
> >> + return -EFAULT;
> >> + buf[cnt] = 0;
> >> +
> >> + ret = strict_strtoul(buf, 10, &val);
> >> + if (ret < 0)
> >> + return ret;
> >> + val = !!val;
> >> +
> >> + func(filp, val, &cnt);
> >> +
> >> + filp->f_pos += cnt;
> >> + return cnt;
> >> +}
> >> +
> >> +/* functions for reading/writing the global 'enabled' control file */
> >> +static ssize_t tracing_control_read(struct file *filp, char __user *ubuf,
> >> + size_t cnt, loff_t *ppos)
> >> +{
> >> + int ret;
> >> + char buf[64];
> >> + ret = snprintf(buf, 64, "%u\n", ktrace_enabled);
> >> + return simple_read_from_buffer(ubuf, cnt, ppos, buf, ret);
> >> +}
> >> +
> >> +static void __tracing_control_write(struct file *filp,
> >> + unsigned long val, size_t *cnt)
> >> +{
> >> + if (val ^ ktrace_enabled) {
> >> + if (val) {
> >> + trace_timer.expires =
> >> + jiffies + TRACEREAD_WAKEUP_INTERVAL;
> >> + add_timer(&trace_timer);
> >> + ktrace_enabled = 1;
> >> + } else {
> >> + ktrace_enabled = 0;
> >> + del_timer_sync(&trace_timer);
> >> + if (trace_buffer && !ring_buffer_empty(trace_buffer))
> >> + wake_up_interruptible(&trace_wait);
> >> + }
> >> + }
> >> +}
> >> +
> >> +static ssize_t tracing_control_write(struct file *filp, const char
> >> __user *ubuf,
> >> + size_t cnt, loff_t *ppos)
> >> +{
> >> + return trace_debugfs_write(filp, ubuf, cnt, ppos,
> >> + __tracing_control_write);
> >> +}
> >> +
> >> +static const struct file_operations tracecontrol_file_operations = {
> >> + .read = tracing_control_read,
> >> + .write = tracing_control_write,
> >> +};
> >> +
> >> +/* functions for reading/writing a trace event file */
> >> +static int update_ktrace(struct ktrace_entry *entry,
> >> + ktrace_probe_func *func, int enabled)
> >> +{
> >> + struct kernel_trace *iter;
> >> + /* no need to update the list if the tracing is not initialized */
> >> + if (!tracedir)
> >> + return 0;
> >> + entry->enabled = enabled;
> >> + entry->func = func;
> >> + list_for_each_entry(iter, &entry->klist, list) {
> >> + iter->stroff = entry->stroff;
> >> + iter->func = func;
> >> + iter->enabled = enabled;
> >> + }
> >> + return 0;
> >> +}
> >> +
> >> +static int ktrace_probe_register(struct ktrace_entry *entry,
> >> + ktrace_probe_func *probefunc)
> >> +{
> >> + return update_ktrace(entry, probefunc, 1);
> >> +}
> >> +
> >> +static int ktrace_probe_unregister(struct ktrace_entry *entry)
> >> +{
> >> + return update_ktrace(entry, NULL, 0);
> >> +}
> >> +
> >> +static int ktrace_control_open(struct inode *inode, struct file *filp)
> >> +{
> >> + filp->private_data = inode->i_private;
> >> + return 0;
> >> +}
> >> +
> >> +static ssize_t ktrace_control_read(struct file *filp, char __user *ubuf,
> >> + size_t cnt, loff_t *ppos)
> >> +{
> >> + int ret;
> >> + char buf[64];
> >> + struct ktrace_entry *entry = filp->private_data;
> >> +
> >> + ret = snprintf(buf, 64, "%u\n", entry->enabled);
> >> + return simple_read_from_buffer(ubuf, cnt, ppos, buf, ret);
> >> +}
> >> +
> >> +/*
> >> + * Check whether the event contains string arguments. Return 0 if not;
> >> + * otherwise record the offsets of the string arguments in the ktrace
> >> + * structure according to the event format and return 1.
> >> + * The offset info is later used to store the string arguments into
> >> + * the trace buffer during trace probe.
> >> + */
> >> +static int contain_string_arguments(struct ktrace_entry *entry)
> >> +{
> >> + int count = 0;
> >> + char *fmt;
> >> + int qualifier; /* 'h', 'l', or 'L' for integer fields */
> >> + size_t offset = 0;
> >> +
> >> + for (fmt = strstr(entry->format, "%s"); fmt; fmt = strstr(++fmt, "%s"))
> >> + count++;
> >> + if (!count)
> >> + return 0;
> >> + entry->stroff = kmalloc(sizeof(size_t) * (count + 1), GFP_KERNEL);
> >> + if (!entry->stroff)
> >> + return -ENOMEM;
> >> +
> >> + for (fmt = entry->format, count = 0; *fmt ; ++fmt) {
> >> + if (*fmt != '%')
> >> + continue;
> >> +repeat:
> >> + ++fmt;
> >> + switch (*fmt) {
> >> + case '-':
> >> + case '+':
> >> + case ' ':
> >> + case '#':
> >> + case '0':
> >> + ++fmt;
> >> + goto repeat;
> >> + }
> >> +
> >> + while (isdigit(*fmt))
> >> + fmt++;
> >> +
> >> + /* get the conversion qualifier */
> >> + qualifier = -1;
> >> + if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
> >> + qualifier = *fmt;
> >> + ++fmt;
> >> + if (qualifier == 'l' && *fmt == 'l') {
> >> + qualifier = 'L';
> >> + ++fmt;
> >> + }
> >> + }
> >> +
> >> + switch (*fmt) {
> >> + case 'c':
> >> + offset += sizeof(char);
> >> + continue;
> >> + case 's':
> >> + entry->stroff[count] = offset;
> >> + count++;
> >> + offset += sizeof(char *);
> >> + continue;
> >> + case 'p':
> >> + offset += sizeof(void *);
> >> + continue;
> >> + case 'd':
> >> + case 'i':
> >> + case 'o':
> >> + case 'u':
> >> + case 'x':
> >> + case 'X':
> >> + switch (qualifier) {
> >> + case 'L':
> >> + offset += sizeof(long long);
> >> + break;
> >> + case 'l':
> >> + offset += sizeof(long);
> >> + break;
> >> + case 'h':
> >> + offset += sizeof(short);
> >> + break;
> >> + default:
> >> + offset += sizeof(int);
> >> + break;
> >> + }
> >> + break;
> >> + default:
> >> + printk(KERN_WARNING "unknown format '%c'", *fmt);
> >> + continue;
> >> + }
> >> + }
> >> + entry->stroff[count] = -1;
> >> + return 1;
> >> +}
> >> +
> >> +static void __ktrace_control_write(struct file *filp,
> >> + unsigned long val, size_t *cnt)
> >> +{
> >> + struct ktrace_entry *entry = filp->private_data;
> >> + int ret;
> >> +
> >> + mutex_lock(&ktrace_mutex);
> >> + if (val ^ entry->enabled) {
> >> + if (val) {
> >> + ret = contain_string_arguments(entry);
> >> + if (ret == 0)
> >> + ktrace_probe_register(entry, ring_buffer_probe);
> >> + else if (ret > 0)
> >> + ktrace_probe_register(entry, string_probe);
> >> + else
> >> + *cnt = ret;
> >> + } else
> >> + ktrace_probe_unregister(entry);
> >> + }
> >> + mutex_unlock(&ktrace_mutex);
> >> +}
> >> +
> >> +static ssize_t ktrace_control_write(struct file *filp, const char __user *ubuf,
> >> + size_t cnt, loff_t *ppos)
> >> +{
> >> + return trace_debugfs_write(filp, ubuf, cnt, ppos,
> >> + __ktrace_control_write);
> >> +}
> >> +
> >> +static const struct file_operations ktracecontrol_file_operations = {
> >> + .open = ktrace_control_open,
> >> + .read = ktrace_control_read,
> >> + .write = ktrace_control_write,
> >> +};
> >> +
> >> +/* functions for adding/removing a trace event. Protected by mutex lock.
> >> + * Called during initialization or after loading a module */
> >> +static struct ktrace_entry *add_ktrace(struct kernel_trace *ktrace)
> >> +{
> >> + struct ktrace_entry *entry;
> >> + size_t name_len = strlen(ktrace->name) + 1;
> >> + u32 hash = jhash(ktrace->name, name_len-1, 0);
> >> + struct hlist_head *head;
> >> + struct hlist_node *node;
> >> + struct dentry *dentry;
> >> +
> >> + if (!tracedir)
> >> + return 0;
> >> + head = &ktrace_table[hash & ((1 << KTRACE_HASH_BITS)-1)];
> >> + hlist_for_each_entry(entry, node, head, hlist) {
> >> + if (!strcmp(ktrace->name, entry->name)) {
> >> + if (strcmp(ktrace->format, entry->format)) {
> >> + printk(KERN_WARNING "the format of tracepoint "
> >> + "\'%s\' changes from \'%s\' to \'%s\'."
> >> + "Dynamic changing of trace format is "
> >> + "not supported yet!\n",
> >> + ktrace->name, entry->format,
> >> + ktrace->format);
> >> + return ERR_PTR(-EINVAL);
> >> + }
> >> + ktrace->enabled = entry->enabled;
> >> + ktrace->func = entry->func;
> >> + ktrace->event_id = entry->event_id;
> >> + if (list_empty(&entry->klist))
> >> + goto add_head;
> >> + list_add_tail(&ktrace->list, &entry->klist);
> >> + return entry;
> >> + }
> >> + }
> >> + entry = kmalloc(sizeof(struct ktrace_entry), GFP_KERNEL);
> >> + if (!entry)
> >> + return ERR_PTR(-ENOMEM);
> >> + entry->name = kmalloc(name_len, GFP_KERNEL);
> >> + if (!entry->name) {
> >> + kfree(entry);
> >> + return ERR_PTR(-ENOMEM);
> >> + }
> >> + memcpy(entry->name, ktrace->name, name_len);
> >> + if (ktrace->format) {
> >> + size_t format_len = strlen(ktrace->format) + 1;
> >> + entry->format = kmalloc(format_len, GFP_KERNEL);
> >> + if (!entry->format) {
> >> + kfree(entry->name);
> >> + kfree(entry);
> >> + return ERR_PTR(-ENOMEM);
> >> + }
> >> + memcpy(entry->format, ktrace->format, format_len);
> >> + } else
> >> + entry->format = NULL;
> >> + entry->func = ktrace->func;
> >> + entry->enabled = 0;
> >> + ktrace->event_id = entry->event_id = ktrace_next_id++;
> >> + entry->stroff = NULL;
> >> + INIT_LIST_HEAD(&entry->klist);
> >> + hlist_add_head(&entry->hlist, head);
> >> +add_head:
> >> + list_add(&ktrace->list, &entry->klist);
> >> + dentry = debugfs_create_file(entry->name, 0660, eventdir,
> >> + entry, &ktracecontrol_file_operations);
> >> + if (!dentry)
> >> + printk(KERN_WARNING "Couldn't create debugfs '%s' entry\n",
> >> + entry->name);
> >> + return entry;
> >> +}
> >> +
> >> +static int remove_ktrace(struct kernel_trace *ktrace, int free)
> >> +{
> >> + struct ktrace_entry *entry;
> >> + size_t name_len = strlen(ktrace->name) + 1;
> >> + u32 hash = jhash(ktrace->name, name_len-1, 0);
> >> + struct hlist_head *head;
> >> + struct hlist_node *node, *temp;
> >> + struct dentry *dentry;
> >> +
> >> + if (!tracedir)
> >> + return 0;
> >> + list_del(&ktrace->list);
> >> + head = &ktrace_table[hash & ((1 << KTRACE_HASH_BITS)-1)];
> >> + hlist_for_each_entry_safe(entry, node, temp, head, hlist)
> >> + if (!strcmp(ktrace->name, entry->name)) {
> >> + if (list_empty(&entry->klist)) {
> >> + dentry = lookup_one_len(entry->name,
> >> + eventdir, strlen(entry->name));
> >> + if (dentry && !IS_ERR(dentry)) {
> >> + debugfs_remove(dentry);
> >> + dput(dentry);
> >> + }
> >> + entry->enabled = 0;
> >> + if (free) {
> >> + hlist_del(&entry->hlist);
> >> + kfree(entry->name);
> >> + kfree(entry->format);
> >> + kfree(entry->stroff);
> >> + kfree(entry);
> >> + }
> >> + }
> >> + return 0;
> >> + }
> >> + return -1;
> >> +}
> >> +
> >> +/* Add/remove tracepoints contained in a module to the ktrace hash table.
> >> + * Called at the end of module load/unload. */
> >> +static int ktrace_module_notify(struct notifier_block *self,
> >> + unsigned long val, void *data)
> >> +{
> >> +#ifdef CONFIG_MODULES
> >> + struct kernel_trace *iter;
> >> + struct module *mod = data;
> >> +
> >> + if (val != MODULE_STATE_COMING && val != MODULE_STATE_GOING)
> >> + return 0;
> >> + mutex_lock(&ktrace_mutex);
> >> + for (iter = mod->ktrace; iter < mod->ktrace + mod->num_ktrace; iter++)
> >> + if (val == MODULE_STATE_COMING)
> >> + add_ktrace(iter);
> >> + else
> >> + remove_ktrace(iter, 0);
> >> + mutex_unlock(&ktrace_mutex);
> >> +#endif
> >> + return 0;
> >> +}
> >> +
> >> +static struct notifier_block ktrace_module_nb = {
> >> + .notifier_call = ktrace_module_notify,
> >> +};
> >> +
> >> +/* functions for user-space programs to read data from tracing buffer */
> >> +static int trace_data_open(struct inode *inode, struct file *filp)
> >> +{
> >> + filp->private_data = inode->i_private;
> >> + kref_get(&ktrace_kref);
> >> + return 0;
> >> +}
> >> +
> >> +static void release_trace_buffer(struct kref *kref)
> >> +{
> >> + ring_buffer_free(trace_buffer);
> >> + trace_buffer = NULL;
> >> +}
> >> +
> >> +static int trace_data_release(struct inode *inode, struct file *filp)
> >> +{
> >> + kref_put(&ktrace_kref, release_trace_buffer);
> >> + return 0;
> >> +}
> >> +
> >> +static unsigned int trace_data_poll(struct file *filp, poll_table *poll_table)
> >> +{
> >> + struct ring_buffer_per_cpu *cpu_buffer = filp->private_data;
> >> + if (filp->f_mode & FMODE_READ) {
> >> + if (!ring_buffer_per_cpu_empty(cpu_buffer))
> >> + return POLLIN | POLLRDNORM;
> >> + poll_wait(filp, &trace_wait, poll_table);
> >> + if (!ring_buffer_per_cpu_empty(cpu_buffer))
> >> + return POLLIN | POLLRDNORM;
> >> + }
> >> + return 0;
> >> +}
> >> +
> >> +static int trace_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> >> +{
> >> + struct ring_buffer_per_cpu *cpu_buffer = vma->vm_private_data;
> >> + pgoff_t pgoff = vmf->pgoff;
> >> + struct page *page;
> >> +
> >> + if (!trace_buffer)
> >> + return VM_FAULT_OOM;
> >> + page = ring_buffer_get_page(cpu_buffer, pgoff);
> >> + if (page == NULL)
> >> + return VM_FAULT_SIGBUS;
> >> + get_page(page);
> >> + vmf->page = page;
> >> + return 0;
> >> +}
> >> +
> >> +static struct vm_operations_struct trace_data_mmap_ops = {
> >> + .fault = trace_buf_fault,
> >> +};
> >> +
> >> +static int trace_data_mmap(struct file *filp, struct vm_area_struct *vma)
> >> +{
> >> + struct ring_buffer_per_cpu *cpu_buffer = filp->private_data;
> >> +
> >> + vma->vm_ops = &trace_data_mmap_ops;
> >> + vma->vm_flags |= VM_DONTEXPAND;
> >> + vma->vm_private_data = cpu_buffer;
> >> + return 0;
> >> +}
> >> +
> >> +static int trace_data_ioctl(struct inode *inode, struct file *filp,
> >> + unsigned int cmd, unsigned long arg)
> >> +{
> >> + u32 __user *argp = (u32 __user *)arg;
> >> + struct ring_buffer_per_cpu *cpu_buffer = filp->private_data;
> >> +
> >> + if (!trace_buffer || !tracedir)
> >> + return -EINVAL;
> >> + switch (cmd) {
> >> + case KTRACE_BUF_GET_SIZE:
> >> + {
> >> + unsigned long bufsize;
> >> + bufsize = ring_buffer_size(trace_buffer);
> >> + return put_user((u32)bufsize, argp);
> >> + }
> >> + case KTRACE_BUF_GET_PRODUCED:
> >> + return put_user(ring_buffer_get_produced(cpu_buffer), argp);
> >> + case KTRACE_BUF_GET_CONSUMED:
> >> + return put_user(ring_buffer_get_consumed(cpu_buffer), argp);
> >> + case KTRACE_BUF_PUT_CONSUMED:
> >> + {
> >> + u32 consumed, consumed_old;
> >> + int ret;
> >> +
> >> + ret = get_user(consumed, argp);
> >> + if (ret) {
> >> + printk(KERN_WARNING
> >> + "error getting consumed value: %d\n", ret);
> >> + return ret;
> >> + }
> >> + consumed_old = ring_buffer_get_consumed(cpu_buffer);
> >> + if (consumed == consumed_old)
> >> + return 0;
> >> + ring_buffer_advance_reader(cpu_buffer, consumed - consumed_old);
> >> + return 0;
> >> + }
> >> + default:
> >> + return -ENOIOCTLCMD;
> >> + }
> >> + return 0;
> >> +}
> >> +
> >> +static const struct file_operations tracedata_file_operations = {
> >> + .open = trace_data_open,
> >> + .poll = trace_data_poll,
> >> + .mmap = trace_data_mmap,
> >> + .ioctl = trace_data_ioctl,
> >> + .release = trace_data_release,
> >> +};
> >> +
> >> +/* function to report the number of lost events due to buffer overflow */
> >> +static ssize_t trace_overflow_read(struct file *filp, char __user *ubuf,
> >> + size_t cnt, loff_t *ppos)
> >> +{
> >> + int ret;
> >> + char buf[64];
> >> + ret = snprintf(buf, 64, "%lu\n", ring_buffer_overruns(trace_buffer));
> >> + return simple_read_from_buffer(ubuf, cnt, ppos, buf, ret);
> >> +}
> >> +
> >> +static const struct file_operations traceoverflow_file_operations = {
> >> + .read = trace_overflow_read,
> >> +};
> >> +
> >> +/* function to re-initialize trace buffer */
> >> +static void __trace_buffer_reset(struct file *filp,
> >> + unsigned long val, size_t *cnt)
> >> +{
> >> + if (val && trace_buffer)
> >> + ring_buffer_reset(trace_buffer);
> >> +}
> >> +
> >> +static ssize_t trace_buffer_reset(struct file *filp, const char __user *ubuf,
> >> + size_t cnt, loff_t *ppos)
> >> +{
> >> + return trace_debugfs_write(filp, ubuf, cnt, ppos,
> >> + __trace_buffer_reset);
> >> +}
> >> +
> >> +static const struct file_operations tracereset_file_operations = {
> >> + .write = trace_buffer_reset,
> >> +};
> >> +
> >> +/*
> >> + * We use debugfs for kernel-user communication. All of the control/info
> >> + * files are under debugfs/ktrace directory.
> >> + */
> >> +static int create_debugfs(void)
> >> +{
> >> + struct dentry *entry, *bufdir;
> >> + struct ring_buffer_per_cpu *cpu_buffer;
> >> + char *tmpname;
> >> + int cpu;
> >> +
> >> + tracedir = debugfs_create_dir("ktrace", NULL);
> >> + if (!tracedir) {
> >> + printk(KERN_WARNING "Couldn't create debugfs directory\n");
> >> + return -ENOMEM;
> >> + }
> >> +
> >> + /* 'buffers' is the directory that holds trace buffer debugfs files */
> >> + bufdir = debugfs_create_dir("buffers", tracedir);
> >> + if (!bufdir) {
> >> + printk(KERN_WARNING "Couldn't create 'buffers' directory\n");
> >> + return -ENOMEM;
> >> + }
> >> +
> >> + tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
> >> + if (!tmpname)
> >> + return -ENOMEM;
> >> + /* create a debugfs file for each cpu buffer */
> >> + for_each_possible_cpu(cpu) {
> >> + snprintf(tmpname, NAME_MAX, "%s%d", "cpu", cpu);
> >> + cpu_buffer = ring_buffer_cpu(trace_buffer, cpu);
> >> + entry = debugfs_create_file(tmpname, 0440, bufdir, cpu_buffer,
> >> + &tracedata_file_operations);
> >> + if (!entry) {
> >> + printk(KERN_WARNING
> >> + "Couldn't create debugfs \'%s\' entry\n",
> >> + tmpname);
> >> + return -ENOMEM;
> >> + }
> >> + }
> >> + kfree(tmpname);
> >> +
> >> + /* the control file for users to enable/disable global tracing. */
> >> + entry = debugfs_create_file("enabled", 0664, tracedir, NULL,
> >> + &tracecontrol_file_operations);
> >> + if (!entry) {
> >> + printk(KERN_WARNING
> >> + "Couldn't create debugfs 'enabled' entry\n");
> >> + return -ENOMEM;
> >> + }
> >> +
> >> + /*
> >> + * the debugfs file that displays the name, format etc. of every
> >> + * supported trace event. The file is to be used by the user-space
> >> + * trace parser to analyze the collected trace data.
> >> + */
> >> + entry = debugfs_create_file("info", 0444, tracedir, NULL,
> >> + &traceinfo_file_operations);
> >> + if (!entry) {
> >> + printk(KERN_WARNING "Couldn't create debugfs 'info' entry\n");
> >> + return -ENOMEM;
> >> + }
> >> +
> >> + /*
> >> + * the debugfs file that reports the number of events
> >> + * lost due to buffer overflow
> >> + */
> >> + entry = debugfs_create_file("overflow", 0444, tracedir, NULL,
> >> + &traceoverflow_file_operations);
> >> + if (!entry) {
> >> + printk(KERN_WARNING
> >> + "Couldn't create debugfs 'overflow' entry\n");
> >> + return -ENOMEM;
> >> + }
> >> +
> >> + /* the debugfs file that resets trace buffer upon write */
> >> + entry = debugfs_create_file("reset", 0220, tracedir, NULL,
> >> + &tracereset_file_operations);
> >> + if (!entry) {
> >> + printk(KERN_WARNING "Couldn't create debugfs 'reset' entry\n");
> >> + return -ENOMEM;
> >> + }
> >> +
> >> + /* create the directory that holds the control files for every event */
> >> + eventdir = debugfs_create_dir("events", tracedir);
> >> + if (!eventdir) {
> >> + printk(KERN_WARNING "Couldn't create 'events' directory\n");
> >> + return -ENOMEM;
> >> + }
> >> + return 0;
> >> +}
> >> +
> >> +static void remove_debugfs_file(struct dentry *dir, char *name)
> >> +{
> >> + struct dentry *dentry;
> >> + dentry = lookup_one_len(name, dir, strlen(name));
> >> + if (dentry && !IS_ERR(dentry)) {
> >> + debugfs_remove(dentry);
> >> + dput(dentry);
> >> + }
> >> +}
> >> +
> >> +static int remove_debugfs(void)
> >> +{
> >> + struct dentry *bufdir;
> >> + char *tmpname;
> >> + int cpu;
> >> +
> >> + bufdir = lookup_one_len("buffers", tracedir, strlen("buffers"));
> >> + if (!bufdir || IS_ERR(bufdir))
> >> + return -EIO;
> >> + tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
> >> + if (!tmpname)
> >> + return -ENOMEM;
> >> + for_each_possible_cpu(cpu) {
> >> + snprintf(tmpname, NAME_MAX, "%s%d", "cpu", cpu);
> >> + remove_debugfs_file(bufdir, tmpname);
> >> + }
> >> + kfree(tmpname);
> >> + debugfs_remove(bufdir);
> >> +
> >> + remove_debugfs_file(tracedir, "enabled");
> >> + remove_debugfs_file(tracedir, "info");
> >> + debugfs_remove(eventdir);
> >> + debugfs_remove(tracedir);
> >> + return 0;
> >> +}
> >> +
> >> +static int __init init_ktrace(void)
> >> +{
> >> + struct kernel_trace *iter;
> >> + int i, err;
> >> +
> >> + ktrace_next_id = 0;
> >> + kref_set(&ktrace_kref, 1);
> >> + trace_buffer = ring_buffer_alloc(trace_buf_size, RB_FL_OVERWRITE);
> >> + if (trace_buffer == NULL)
> >> + return -ENOMEM;
> >> + setup_timer(&trace_timer, wakeup_readers, 0);
> >> + for (i = 0; i < KTRACE_HASH_SIZE; i++)
> >> + INIT_HLIST_HEAD(&ktrace_table[i]);
> >> +
> >> + mutex_lock(&ktrace_mutex);
> >> + err = create_debugfs();
> >> + if (err != 0)
> >> + goto out;
> >> + for (iter = __start___ktraces; iter < __stop___ktraces; iter++)
> >> + add_ktrace(iter);
> >> + err = register_module_notifier(&ktrace_module_nb);
> >> +out:
> >> + mutex_unlock(&ktrace_mutex);
> >> + return err;
> >> +}
> >> +module_init(init_ktrace);
> >> +
> >> +static void __exit exit_ktrace(void)
> >> +{
> >> + struct kernel_trace *iter;
> >> +
> >> + if (ktrace_enabled) {
> >> + ktrace_enabled = 0;
> >> + del_timer_sync(&trace_timer);
> >> + }
> >> + mutex_lock(&ktrace_mutex);
> >> + for (iter = __start___ktraces; iter < __stop___ktraces; iter++)
> >> + remove_ktrace(iter, 1);
> >> + unregister_module_notifier(&ktrace_module_nb);
> >> + remove_debugfs();
> >> + mutex_unlock(&ktrace_mutex);
> >> +
> >> + kref_put(&ktrace_kref, release_trace_buffer);
> >> +}
> >
> > --
> > Mathieu Desnoyers
> > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
> >
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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