From: Steven Rostedt <rostedt@goodmis.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Nicolas Boichat <drinkcat@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@chromium.org>, Jason Gunthorpe <jgg@ziepe.ca>,
Daniel Vetter <daniel.vetter@ffwll.ch>,
Peter Zijlstra <peterz@infradead.org>,
Vinod Koul <vkoul@kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
Tiezhu Yang <yangtiezhu@loongson.cn>,
Thomas Gleixner <tglx@linutronix.de>,
"Guilherme G . Piccoli" <gpiccoli@canonical.com>,
Will Deacon <will@kernel.org>,
Douglas Anderson <dianders@chromium.org>,
Guenter Roeck <groeck@chromium.org>,
bpf@vger.kernel.org
Subject: Re: [PATCH] kernel/trace: Add TRACING_ALLOW_PRINTK config option
Date: Sun, 28 Jun 2020 19:43:34 -0400 [thread overview]
Message-ID: <20200628194334.6238b933@oasis.local.home> (raw)
In-Reply-To: <20200628182842.2abb0de2@oasis.local.home>
On Sun, 28 Jun 2020 18:28:42 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> You create a bpf event just like you create any other event. When a bpf
> program that uses a bpf_trace_printk() is loaded, you can enable that
> event from within the kernel. Yes, there's internal interfaces to
> enabled and disable events just like echoing 1 into
> tracefs/events/system/event/enable. See trace_set_clr_event().
I just started playing with what the code would look like and have
this. It can be optimized with per-cpu sets of buffers to remove the
spin lock. I also didn't put in the enabling of the event, but I'm sure
you can figure that out.
Warning, not even compiled tested.
-- Steve
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 6575bb0a0434..aeba5ee7325a 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -31,6 +31,8 @@ ifdef CONFIG_GCOV_PROFILE_FTRACE
GCOV_PROFILE := y
endif
+CFLAGS_bpf_trace.o := -I$(src)
+
CFLAGS_trace_benchmark.o := -I$(src)
CFLAGS_trace_events_filter.o := -I$(src)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index dc05626979b8..01bedf335b2e 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -19,6 +19,9 @@
#include "trace_probe.h"
#include "trace.h"
+#define CREATE_TRACE_EVENTS
+#include "bpf_trace.h"
+
#define bpf_event_rcu_dereference(p) \
rcu_dereference_protected(p, lockdep_is_held(&bpf_event_mutex))
@@ -473,13 +476,29 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
fmt_cnt++;
}
+static DEFINE_SPINLOCK(trace_printk_lock);
+#define BPF_TRACE_PRINTK_SIZE 1024
+
+static inline void do_trace_printk(const char *fmt, ...)
+{
+ static char buf[BPF_TRACE_PRINT_SIZE];
+ unsigned long flags;
+
+ spin_lock_irqsave(&trace_printk_lock, flags);
+ va_start(ap, fmt);
+ vsnprintf(buf, BPF_TRACE_PRINT_SIZE, fmt, ap);
+ va_end(ap);
+
+ trace_bpf_trace_printk(buf);
+ spin_unlock_irqrestore(&trace_printk_lock, flags);
+}
+
/* Horrid workaround for getting va_list handling working with different
* argument type combinations generically for 32 and 64 bit archs.
*/
#define __BPF_TP_EMIT() __BPF_ARG3_TP()
#define __BPF_TP(...) \
- __trace_printk(0 /* Fake ip */, \
- fmt, ##__VA_ARGS__)
+ do_trace_printk(fmt, ##__VA_ARGS__)
#define __BPF_ARG1_TP(...) \
((mod[0] == 2 || (mod[0] == 1 && __BITS_PER_LONG == 64)) \
diff --git a/kernel/trace/bpf_trace.h b/kernel/trace/bpf_trace.h
new file mode 100644
index 000000000000..09088bb92fe1
--- /dev/null
+++ b/kernel/trace/bpf_trace.h
@@ -0,0 +1,27 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM bpf_trace
+
+#if !defined(_TRACE_BPF_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_BPF_TRACE_H
+
+TRACE_EVENT(bpf_trace_printk,
+
+ TP_PROTO(bpf_string),
+
+ TP_ARGS(secs, err),
+
+ TP_STRUCT__entry(
+ __string(bpf_string, bpf_string)
+ ),
+
+ TP_fast_assign(
+ __assign_string(bpf_string, bpf_string);
+ ),
+
+ TP_printk("%s", __get_str(bpf_string))
+);
+
+#endif /* _TRACE_BPF_TRACE_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
next prev parent reply other threads:[~2020-06-28 23:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200624084524.259560-1-drinkcat@chromium.org>
[not found] ` <20200624120408.12c8fa0d@oasis.local.home>
[not found] ` <CAADnVQKDJb5EXZtEONaXx4XHtMMgEezPOuRUvEo18Rc7K+2_Pw@mail.gmail.com>
[not found] ` <CANMq1KCAUfxy-njMJj0=+02Jew_1rJGwxLzp6BRTE=9CL2DZNA@mail.gmail.com>
2020-06-25 3:59 ` [PATCH] kernel/trace: Add TRACING_ALLOW_PRINTK config option Alexei Starovoitov
2020-06-26 22:14 ` Steven Rostedt
2020-06-28 17:27 ` Alexei Starovoitov
2020-06-28 18:46 ` Steven Rostedt
2020-06-28 19:00 ` Steven Rostedt
2020-06-28 19:21 ` Alexei Starovoitov
2020-06-28 19:43 ` Steven Rostedt
2020-06-28 22:02 ` Alexei Starovoitov
2020-06-28 22:28 ` Steven Rostedt
2020-06-28 23:43 ` Steven Rostedt [this message]
2020-06-30 5:16 ` Alexei Starovoitov
2020-06-30 12:39 ` Steven Rostedt
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