Commit a1852ce0 authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

Merge branch 'add support for writable bare tracepoint' 

Hou Tao says:

====================

From: Hou Tao <houtao1@huawei.com>

Hi,

The patchset series supports writable context for bare tracepoint.

The main idea comes from patchset "writable contexts for bpf raw
tracepoints" [1], but it only supports normal tracepoint with
associated trace event under tracefs. Now we have one use case
in which we add bare tracepoint in VFS layer, and update
file::f_mode for specific files. The reason using bare tracepoint
is that it doesn't form a ABI and we can change it freely. So
add support for it in BPF.

Comments are always welcome.

[1]: https://lore.kernel.org/lkml/20190426184951.21812-1-mmullins@fb.com

Change log:
v5:
 * rebased on bpf-next
 * patch 1: add Acked-by tag
 * patch 2: handle invalid section name, make prefixes array being const

v4: https://www.spinics.net/lists/bpf/msg47021.html
 * rebased on bpf-next
 * update patch 2 to add support for writable raw tracepoint attachment
   in attach_raw_tp().
 * update patch 3 to add Acked-by tag

v3: https://www.spinics.net/lists/bpf/msg46824.html
  * use raw_tp.w instead of raw_tp_writable as section
    name of writable tp
  * use ASSERT_XXX() instead of CHECK()
  * define a common macro for "/sys/kernel/bpf_testmod"

v2: https://www.spinics.net/lists/bpf/msg46356.html
  * rebase on bpf-next tree
  * address comments from Yonghong Song
  * rename bpf_testmode_test_writable_ctx::ret as early_ret to reflect
    its purpose better.

v1: https://www.spinics.net/lists/bpf/msg46221.html


====================

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parents 1c8dab7d fa7f17d0

include/trace/bpf_probe.h

+15 −4
Original line number Diff line number Diff line
@@ -93,8 +93,7 @@ __section("__bpf_raw_tp_map") = { \ 


#define FIRST(x, ...) x



#undef DEFINE_EVENT_WRITABLE

#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size)	\

#define __CHECK_WRITABLE_BUF_SIZE(call, proto, args, size)		\

static inline void bpf_test_buffer_##call(void)				\

{									\

	/* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
@@ -103,7 +102,11 @@ static inline void bpf_test_buffer_##call(void) \ 
	 */								\

	FIRST(proto);							\

	(void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args)));		\

}									\

}



#undef DEFINE_EVENT_WRITABLE

#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \

	__CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \

	__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)



#undef DEFINE_EVENT
@@ -119,9 +122,17 @@ __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size) 
	__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))		\

	__DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), 0)



#undef DECLARE_TRACE_WRITABLE

#define DECLARE_TRACE_WRITABLE(call, proto, args, size) \

	__CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \

	__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \

	__DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), size)



#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)



#undef DECLARE_TRACE_WRITABLE

#undef DEFINE_EVENT_WRITABLE

#undef __CHECK_WRITABLE_BUF_SIZE

#undef __DEFINE_EVENT

#undef FIRST

tools/lib/bpf/libbpf.c

+21 −5
Original line number Diff line number Diff line
@@ -8077,6 +8077,8 @@ static const struct bpf_sec_def section_defs[] = { 
	SEC_DEF("tp/",			TRACEPOINT, 0, SEC_NONE, attach_tp),

	SEC_DEF("raw_tracepoint/",	RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tp/",		RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tracepoint.w/",	RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tp.w/",		RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("tp_btf/",		TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fentry/",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fmod_ret/",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),
@@ -9846,12 +9848,26 @@ struct bpf_link *bpf_program__attach_raw_tracepoint(const struct bpf_program *pr 


static struct bpf_link *attach_raw_tp(const struct bpf_program *prog, long cookie)

{

	const char *tp_name;

	static const char *const prefixes[] = {

		"raw_tp/",

		"raw_tracepoint/",

		"raw_tp.w/",

		"raw_tracepoint.w/",

	};

	size_t i;

	const char *tp_name = NULL;



	if (str_has_pfx(prog->sec_name, "raw_tp/"))

		tp_name = prog->sec_name + sizeof("raw_tp/") - 1;

	else

		tp_name = prog->sec_name + sizeof("raw_tracepoint/") - 1;

	for (i = 0; i < ARRAY_SIZE(prefixes); i++) {

		if (str_has_pfx(prog->sec_name, prefixes[i])) {

			tp_name = prog->sec_name + strlen(prefixes[i]);

			break;

		}

	}

	if (!tp_name) {

		pr_warn("prog '%s': invalid section name '%s'\n",

			prog->name, prog->sec_name);

		return libbpf_err_ptr(-EINVAL);

	}



	return bpf_program__attach_raw_tracepoint(prog, tp_name);

}

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h

+15 −0
Original line number Diff line number Diff line
@@ -34,6 +34,21 @@ DECLARE_TRACE(bpf_testmod_test_write_bare, 
	TP_ARGS(task, ctx)

);



#undef BPF_TESTMOD_DECLARE_TRACE

#ifdef DECLARE_TRACE_WRITABLE

#define BPF_TESTMOD_DECLARE_TRACE(call, proto, args, size) \

	DECLARE_TRACE_WRITABLE(call, PARAMS(proto), PARAMS(args), size)

#else

#define BPF_TESTMOD_DECLARE_TRACE(call, proto, args, size) \

	DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))

#endif



BPF_TESTMOD_DECLARE_TRACE(bpf_testmod_test_writable_bare,

	TP_PROTO(struct bpf_testmod_test_writable_ctx *ctx),

	TP_ARGS(ctx),

	sizeof(struct bpf_testmod_test_writable_ctx)

);



#endif /* _BPF_TESTMOD_EVENTS_H */



#undef TRACE_INCLUDE_PATH

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

+10 −0
Original line number Diff line number Diff line
@@ -50,6 +50,16 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, 
	if (bpf_testmod_loop_test(101) > 100)

		trace_bpf_testmod_test_read(current, &ctx);



	/* Magic number to enable writable tp */

	if (len == 64) {

		struct bpf_testmod_test_writable_ctx writable = {

			.val = 1024,

		};

		trace_bpf_testmod_test_writable_bare(&writable);

		if (writable.early_ret)

			return snprintf(buf, len, "%d\n", writable.val);

	}



	return -EIO; /* always fail */

}

EXPORT_SYMBOL(bpf_testmod_test_read);

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h

+5 −0
Original line number Diff line number Diff line
@@ -17,4 +17,9 @@ struct bpf_testmod_test_write_ctx { 
	size_t len;

};



struct bpf_testmod_test_writable_ctx {

	bool early_ret;

	int val;

};



#endif /* _BPF_TESTMOD_H */