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@xxxxxxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 11 +++++++++++
kernel/bpf/helpers.c | 16 ++++++++++++++++
tools/include/uapi/linux/bpf.h | 11 +++++++++++
4 files changed, 39 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a7cbc29b0994..685c8fe5c0be 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2165,6 +2165,7 @@ extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
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_strncmp_proto;
const struct bpf_func_proto *tracing_prog_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index a69e4b04ffeb..afdc52efa4a1 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4957,6 +4957,16 @@ union bpf_attr {
* **-ENOENT** if *task->mm* is NULL, or no vma contains *addr*.
* **-EBUSY** if failed to try lock mmap_lock.
* **-EINVAL** for invalid **flags**.
+ *
+ * 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), \
@@ -5140,6 +5150,7 @@ union bpf_attr {
FN(skc_to_unix_sock), \
FN(kallsyms_lookup_name), \
FN(find_vma), \
+ FN(strncmp), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1ffd469c217f..a7d3a8d48e00 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -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_ringbuf_query_proto;
case BPF_FUNC_for_each_map_elem:
return &bpf_for_each_map_elem_proto;
+ case BPF_FUNC_strncmp:
+ return &bpf_strncmp_proto;
default:
break;
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a69e4b04ffeb..afdc52efa4a1 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4957,6 +4957,16 @@ union bpf_attr {
* **-ENOENT** if *task->mm* is NULL, or no vma contains *addr*.
* **-EBUSY** if failed to try lock mmap_lock.
* **-EINVAL** for invalid **flags**.
+ *
+ * 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), \
@@ -5140,6 +5150,7 @@ union bpf_attr {
FN(skc_to_unix_sock), \
FN(kallsyms_lookup_name), \
FN(find_vma), \
+ FN(strncmp), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.29.2
