diff options
author | Alan Maguire <alan.maguire@oracle.com> | 2020-07-13 14:52:33 +0300 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2020-07-14 02:55:49 +0300 |
commit | ac5a72ea5c8989871e61f6bb0852e0f91de51ebe (patch) | |
tree | dca6c9b98c6653937db455e2c6948e86e3274064 /kernel | |
parent | 93776cb9ee91aeed43ba53dcec97ffed4ae6f1f7 (diff) |
bpf: Use dedicated bpf_trace_printk event instead of trace_printk()
The bpf helper bpf_trace_printk() uses trace_printk() under the hood.
This leads to an alarming warning message originating from trace
buffer allocation which occurs the first time a program using
bpf_trace_printk() is loaded.
We can instead create a trace event for bpf_trace_printk() and enable
it in-kernel when/if we encounter a program using the
bpf_trace_printk() helper. With this approach, trace_printk()
is not used directly and no warning message appears.
This work was started by Steven (see Link) and finished by Alan; added
Steven's Signed-off-by with his permission.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/r/20200628194334.6238b933@oasis.local.home
Link: https://lore.kernel.org/bpf/1594641154-18897-2-git-send-email-alan.maguire@oracle.com
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/trace/Makefile | 2 | ||||
-rw-r--r-- | kernel/trace/bpf_trace.c | 42 | ||||
-rw-r--r-- | kernel/trace/bpf_trace.h | 34 |
3 files changed, 73 insertions, 5 deletions
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 e178e8e32b33..3cc0dcb60ca2 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -11,6 +11,7 @@ #include <linux/uaccess.h> #include <linux/ctype.h> #include <linux/kprobes.h> +#include <linux/spinlock.h> #include <linux/syscalls.h> #include <linux/error-injection.h> #include <linux/btf_ids.h> @@ -20,6 +21,9 @@ #include "trace_probe.h" #include "trace.h" +#define CREATE_TRACE_POINTS +#include "bpf_trace.h" + #define bpf_event_rcu_dereference(p) \ rcu_dereference_protected(p, lockdep_is_held(&bpf_event_mutex)) @@ -375,6 +379,30 @@ static void bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype, } } +static DEFINE_RAW_SPINLOCK(trace_printk_lock); + +#define BPF_TRACE_PRINTK_SIZE 1024 + +static inline __printf(1, 0) int bpf_do_trace_printk(const char *fmt, ...) +{ + static char buf[BPF_TRACE_PRINTK_SIZE]; + unsigned long flags; + va_list ap; + int ret; + + raw_spin_lock_irqsave(&trace_printk_lock, flags); + va_start(ap, fmt); + ret = vsnprintf(buf, sizeof(buf), fmt, ap); + va_end(ap); + /* vsnprintf() will not append null for zero-length strings */ + if (ret == 0) + buf[0] = '\0'; + trace_bpf_trace_printk(buf); + raw_spin_unlock_irqrestore(&trace_printk_lock, flags); + + return ret; +} + /* * Only limited trace_printk() conversion specifiers allowed: * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %pB %pks %pus %s @@ -484,8 +512,7 @@ fmt_next: */ #define __BPF_TP_EMIT() __BPF_ARG3_TP() #define __BPF_TP(...) \ - __trace_printk(0 /* Fake ip */, \ - fmt, ##__VA_ARGS__) + bpf_do_trace_printk(fmt, ##__VA_ARGS__) #define __BPF_ARG1_TP(...) \ ((mod[0] == 2 || (mod[0] == 1 && __BITS_PER_LONG == 64)) \ @@ -522,10 +549,15 @@ static const struct bpf_func_proto bpf_trace_printk_proto = { const struct bpf_func_proto *bpf_get_trace_printk_proto(void) { /* - * this program might be calling bpf_trace_printk, - * so allocate per-cpu printk buffers + * This program might be calling bpf_trace_printk, + * so enable the associated bpf_trace/bpf_trace_printk event. + * Repeat this each time as it is possible a user has + * disabled bpf_trace_printk events. By loading a program + * calling bpf_trace_printk() however the user has expressed + * the intent to see such events. */ - trace_printk_init_buffers(); + if (trace_set_clr_event("bpf_trace", "bpf_trace_printk", 1)) + pr_warn_ratelimited("could not enable bpf_trace_printk events"); return &bpf_trace_printk_proto; } diff --git a/kernel/trace/bpf_trace.h b/kernel/trace/bpf_trace.h new file mode 100644 index 000000000000..9acbc11ac7bb --- /dev/null +++ b/kernel/trace/bpf_trace.h @@ -0,0 +1,34 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM bpf_trace + +#if !defined(_TRACE_BPF_TRACE_H) || defined(TRACE_HEADER_MULTI_READ) + +#define _TRACE_BPF_TRACE_H + +#include <linux/tracepoint.h> + +TRACE_EVENT(bpf_trace_printk, + + TP_PROTO(const char *bpf_string), + + TP_ARGS(bpf_string), + + TP_STRUCT__entry( + __string(bpf_string, bpf_string) + ), + + TP_fast_assign( + __assign_str(bpf_string, bpf_string); + ), + + TP_printk("%s", __get_str(bpf_string)) +); + +#endif /* _TRACE_BPF_TRACE_H */ + +#undef TRACE_INCLUDE_PATH +#define TRACE_INCLUDE_PATH . +#define TRACE_INCLUDE_FILE bpf_trace + +#include <trace/define_trace.h> |