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bpf: Add bpf_strncmp helper

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The helper compares two strings: one string is a null-terminated
read-only string, and another string has const max storage size
but doesn't need to be null-terminated. It can be used to compare
file name in tracing or LSM program.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211210141652.877186-2-houtao1@huawei.com
This commit is contained in:
Hou Tao 2021-12-10 22:16:49 +08:00 committed by Alexei Starovoitov
parent 259172bb65
commit c5fb199374
4 changed files with 39 additions and 0 deletions
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1
include/linux/bpf.h
View File

@ -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);

11
include/uapi/linux/bpf.h
View File

@ -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

16
kernel/bpf/helpers.c
View File

@ -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;
}

11
tools/include/uapi/linux/bpf.h
View File

@ -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