[PATCH openEuler-1.0-LTS 1/3] bpf: Use dedicated bpf_trace_printk event instead of trace_printk()
From: Alan Maguire alan.maguire@oracle.com
mainline inclusion from mainline-v5.10.78 commit ac5a72ea5c8989871e61f6bb0852e0f91de51ebe category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4PKDW CVE: NA
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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@o... Signed-off-by: Liu Xinpeng liuxp11@chinatelecom.cn # openEuler_contributor Signed-off-by: Ctyun Kernel ctyuncommiter01@chinatelecom.cn # openEuler_contributor --- kernel/trace/Makefile | 2 ++ kernel/trace/bpf_trace.c | 42 +++++++++++++++++++++++++++++++++++++----- kernel/trace/bpf_trace.h | 34 ++++++++++++++++++++++++++++++++++ 3 files changed, 73 insertions(+), 5 deletions(-) create mode 100644 kernel/trace/bpf_trace.h
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index f81dadbc7..846b6b0 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -28,6 +28,8 @@ 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 e0b0e92..f359f79 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -11,12 +11,16 @@ #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 "trace_probe.h" #include "trace.h"
+#define CREATE_TRACE_POINTS +#include "bpf_trace.h" + #ifdef CONFIG_MODULES struct bpf_trace_module { struct module *module; @@ -318,6 +322,30 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void) return &bpf_probe_write_user_proto; }
+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 %s @@ -408,8 +436,7 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void) */ #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)) \ @@ -446,10 +473,15 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void) 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 00000000..9acbc11 --- /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>
From: Stanislav Fomichev sdf@google.com
mainline inclusion from mainline-v5.10.78 commit ac5a72ea5c8989871e61f6bb0852e0f91de51ebe category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4PKDW CVE: NA
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I get the following error during compilation on my side: kernel/trace/bpf_trace.c: In function 'bpf_do_trace_printk': kernel/trace/bpf_trace.c:386:34: error: function 'bpf_do_trace_printk' can never be inlined because it uses variable argument lists static inline __printf(1, 0) int bpf_do_trace_printk(const char *fmt, ...) ^
Fixes: ac5a72ea5c89 ("bpf: Use dedicated bpf_trace_printk event instead of trace_printk()") Signed-off-by: Stanislav Fomichev sdf@google.com Signed-off-by: Alexei Starovoitov ast@kernel.org Link: https://lore.kernel.org/bpf/20200806182612.1390883-1-sdf@google.com Signed-off-by: Liu Xinpeng liuxp11@chinatelecom.cn # openEuler_contributor Signed-off-by: Ctyun Kernel ctyuncommiter01@chinatelecom.cn # openEuler_contributor --- kernel/trace/bpf_trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index f359f79..f45e0ca 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -326,7 +326,7 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
#define BPF_TRACE_PRINTK_SIZE 1024
-static inline __printf(1, 0) int bpf_do_trace_printk(const char *fmt, ...) +static __printf(1, 0) int bpf_do_trace_printk(const char *fmt, ...) { static char buf[BPF_TRACE_PRINTK_SIZE]; unsigned long flags;
From: Alan Maguire alan.maguire@oracle.com
mainline inclusion from mainline-v5.10.78 commit ac5a72ea5c8989871e61f6bb0852e0f91de51ebe category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4PKDW CVE: NA
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The BPF helper bpf_trace_printk() no longer uses trace_printk(); it is now triggers a dedicated trace event. Hence the described warning is no longer present, so remove the discussion of it as it may confuse people.
Fixes: ac5a72ea5c89 ("bpf: Use dedicated bpf_trace_printk event instead of trace_printk()") Signed-off-by: Alan Maguire alan.maguire@oracle.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/1596801029-32395-1-git-send-email-alan.maguire@o... Signed-off-by: Liu Xinpeng liuxp11@chinatelecom.cn # openEuler_contributor Signed-off-by: Ctyun Kernel ctyuncommiter01@chinatelecom.cn # openEuler_contributor --- Documentation/bpf/bpf_design_QA.rst | 11 ----------- 1 file changed, 11 deletions(-)
diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst index e2cc405..bc405f7 100644 --- a/Documentation/bpf/bpf_design_QA.rst +++ b/Documentation/bpf/bpf_design_QA.rst @@ -208,17 +208,6 @@ program is loaded the kernel will print warning message, so this helper is only useful for experiments and prototypes. Tracing BPF programs are root only.
-Q: bpf_trace_printk() helper warning ------------------------------------- -Q: When bpf_trace_printk() helper is used the kernel prints nasty -warning message. Why is that? - -A: This is done to nudge program authors into better interfaces when -programs need to pass data to user space. Like bpf_perf_event_output() -can be used to efficiently stream data via perf ring buffer. -BPF maps can be used for asynchronous data sharing between kernel -and user space. bpf_trace_printk() should only be used for debugging. - Q: New functionality via kernel modules? ---------------------------------------- Q: Can BPF functionality such as new program or map types, new
-
Liu Xinpeng