Commit 84ef3f0b authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

Merge branch 'introduce bpf_strncmp() helper' 

Hou Tao says:

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

Hi,

The motivation for introducing bpf_strncmp() helper comes from
two aspects:

(1) clang doesn't always replace strncmp() automatically
In tracing program, sometimes we need to using a home-made
strncmp() to check whether or not the file name is expected.

(2) the performance of home-made strncmp is not so good
As shown in the benchmark in patch #4, the performance of
bpf_strncmp() helper is 18% or 33% better than home-made strncmp()
under x86-64 or arm64 when the compared string length is 64. When
the string length grows to 4095, the performance win will be
179% or 600% under x86-64 or arm64.

Any comments are welcome.
Regards,
Tao

Change Log:
v2:
 * rebased on bpf-next
 * drop patch "selftests/bpf: factor out common helpers for benchmarks"
   (suggested by Andrii)
 * remove unnecessary inline functions and add comments for programs which
   will be rejected by verifier in patch 4 (suggested by Andrii)
 * rename variables used in will-fail programs to clarify the purposes.

v1: https://lore.kernel.org/bpf/20211130142215.1237217-1-houtao1@huawei.com
 * change API to bpf_strncmp(const char *s1, u32 s1_sz, const char *s2)
 * add benchmark refactor and benchmark between bpf_strncmp() and strncmp()

RFC: https://lore.kernel.org/bpf/20211106132822.1396621-1-houtao1@huawei.com/


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

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parents 259172bb bdbee82b

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -2163,6 +2163,7 @@ extern const struct bpf_func_proto bpf_sk_getsockopt_proto; 
extern const struct bpf_func_proto bpf_kallsyms_lookup_name_proto;

extern const struct bpf_func_proto bpf_find_vma_proto;

extern const struct bpf_func_proto bpf_loop_proto;

extern const struct bpf_func_proto bpf_strncmp_proto;



const struct bpf_func_proto *tracing_prog_func_proto(

  enum bpf_func_id func_id, const struct bpf_prog *prog);

include/uapi/linux/bpf.h

+11 −0
Original line number Diff line number Diff line
@@ -4983,6 +4983,16 @@ union bpf_attr { 
 *	Return

 *		The number of loops performed, **-EINVAL** for invalid **flags**,

 *		**-E2BIG** if **nr_loops** exceeds the maximum number of loops.

 *

 * long bpf_strncmp(const char *s1, u32 s1_sz, const char *s2)

 *	Description

 *		Do strncmp() between **s1** and **s2**. **s1** doesn't need

 *		to be null-terminated and **s1_sz** is the maximum storage

 *		size of **s1**. **s2** must be a read-only string.

 *	Return

 *		An integer less than, equal to, or greater than zero

 *		if the first **s1_sz** bytes of **s1** is found to be

 *		less than, to match, or be greater than **s2**.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -5167,6 +5177,7 @@ union bpf_attr { 
	FN(kallsyms_lookup_name),	\

	FN(find_vma),			\

	FN(loop),			\

	FN(strncmp),			\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

kernel/bpf/helpers.c

+16 −0
Original line number Diff line number Diff line
@@ -565,6 +565,20 @@ const struct bpf_func_proto bpf_strtoul_proto = { 
};

#endif



BPF_CALL_3(bpf_strncmp, const char *, s1, u32, s1_sz, const char *, s2)

{

	return strncmp(s1, s2, s1_sz);

}



const struct bpf_func_proto bpf_strncmp_proto = {

	.func		= bpf_strncmp,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_MEM,

	.arg2_type	= ARG_CONST_SIZE,

	.arg3_type	= ARG_PTR_TO_CONST_STR,

};



BPF_CALL_4(bpf_get_ns_current_pid_tgid, u64, dev, u64, ino,

	   struct bpf_pidns_info *, nsdata, u32, size)

{
@@ -1378,6 +1392,8 @@ bpf_base_func_proto(enum bpf_func_id func_id) 
		return &bpf_for_each_map_elem_proto;

	case BPF_FUNC_loop:

		return &bpf_loop_proto;

	case BPF_FUNC_strncmp:

		return &bpf_strncmp_proto;

	default:

		break;

	}

tools/include/uapi/linux/bpf.h

+11 −0
Original line number Diff line number Diff line
@@ -4983,6 +4983,16 @@ union bpf_attr { 
 *	Return

 *		The number of loops performed, **-EINVAL** for invalid **flags**,

 *		**-E2BIG** if **nr_loops** exceeds the maximum number of loops.

 *

 * long bpf_strncmp(const char *s1, u32 s1_sz, const char *s2)

 *	Description

 *		Do strncmp() between **s1** and **s2**. **s1** doesn't need

 *		to be null-terminated and **s1_sz** is the maximum storage

 *		size of **s1**. **s2** must be a read-only string.

 *	Return

 *		An integer less than, equal to, or greater than zero

 *		if the first **s1_sz** bytes of **s1** is found to be

 *		less than, to match, or be greater than **s2**.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -5167,6 +5177,7 @@ union bpf_attr { 
	FN(kallsyms_lookup_name),	\

	FN(find_vma),			\

	FN(loop),			\

	FN(strncmp),			\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

tools/testing/selftests/bpf/Makefile

+3 −1
Original line number Diff line number Diff line
@@ -537,6 +537,7 @@ $(OUTPUT)/bench_ringbufs.o: $(OUTPUT)/ringbuf_bench.skel.h \ 
			    $(OUTPUT)/perfbuf_bench.skel.h

$(OUTPUT)/bench_bloom_filter_map.o: $(OUTPUT)/bloom_filter_bench.skel.h

$(OUTPUT)/bench_bpf_loop.o: $(OUTPUT)/bpf_loop_bench.skel.h

$(OUTPUT)/bench_strncmp.o: $(OUTPUT)/strncmp_bench.skel.h

$(OUTPUT)/bench.o: bench.h testing_helpers.h $(BPFOBJ)

$(OUTPUT)/bench: LDLIBS += -lm

$(OUTPUT)/bench: $(OUTPUT)/bench.o \
@@ -547,7 +548,8 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o \ 
		 $(OUTPUT)/bench_trigger.o \

		 $(OUTPUT)/bench_ringbufs.o \

		 $(OUTPUT)/bench_bloom_filter_map.o \

		 $(OUTPUT)/bench_bpf_loop.o

		 $(OUTPUT)/bench_bpf_loop.o \

		 $(OUTPUT)/bench_strncmp.o

	$(call msg,BINARY,,$@)

	$(Q)$(CC) $(LDFLAGS) $(filter %.a %.o,$^) $(LDLIBS) -o $@