[bpf-next,v2,1/2] bpf: Add kfuncs for read-only string operations

Commit Message

Viktor Malik Sept. 26, 2024, 7:29 a.m. UTC

Kernel contains highly optimised implementation of traditional string
operations. Expose them as kfuncs to allow BPF programs leverage the
kernel implementation instead of needing to reimplement the operations.

For now, add kfuncs for all string operations which do not copy memory
around: strcmp, strchr, strrchr, strnchr, strstr, strnstr, strlen,
strnlen, strpbrk, strspn, strcspn. Do not add strncmp as it is already
exposed as a helper.

Signed-off-by: Viktor Malik <[e-mail]>
---
 kernel/bpf/helpers.c | 66 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

Patch

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1a43d06eab28..daa19760d8c8 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -3004,6 +3004,61 @@  __bpf_kfunc int bpf_copy_from_user_str(void *dst, u32 dst__sz, const void __user
 	return ret + 1;
 }
 
+__bpf_kfunc int bpf_strcmp(const char *cs, const char *ct)
+{
+	return strcmp(cs, ct);
+}
+
+__bpf_kfunc char *bpf_strchr(const char *s, int c)
+{
+	return strchr(s, c);
+}
+
+__bpf_kfunc char *bpf_strrchr(const char *s, int c)
+{
+	return strrchr(s, c);
+}
+
+__bpf_kfunc char *bpf_strnchr(const char *s, size_t count, int c)
+{
+	return strnchr(s, count, c);
+}
+
+__bpf_kfunc char *bpf_strstr(const char *s1, const char *s2)
+{
+	return strstr(s1, s2);
+}
+
+__bpf_kfunc char *bpf_strnstr(const char *s1, const char *s2, size_t len)
+{
+	return strnstr(s1, s2, len);
+}
+
+__bpf_kfunc size_t bpf_strlen(const char *s)
+{
+	return strlen(s);
+}
+
+__bpf_kfunc size_t bpf_strnlen(const char *s, size_t count)
+{
+	return strnlen(s, count);
+}
+
+__bpf_kfunc char *bpf_strpbrk(const char *cs, const char *ct)
+{
+	return strpbrk(cs, ct);
+}
+
+__bpf_kfunc size_t bpf_strspn(const char *s, const char *accept)
+{
+	return strspn(s, accept);
+}
+
+__bpf_kfunc size_t bpf_strcspn(const char *s, const char *reject)
+{
+	return strcspn(s, reject);
+}
+
 __bpf_kfunc_end_defs();
 
 BTF_KFUNCS_START(generic_btf_ids)
@@ -3090,6 +3145,17 @@  BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW)
 BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
 BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)
+BTF_ID_FLAGS(func, bpf_strcmp)
+BTF_ID_FLAGS(func, bpf_strchr)
+BTF_ID_FLAGS(func, bpf_strrchr)
+BTF_ID_FLAGS(func, bpf_strnchr)
+BTF_ID_FLAGS(func, bpf_strstr)
+BTF_ID_FLAGS(func, bpf_strnstr)
+BTF_ID_FLAGS(func, bpf_strlen)
+BTF_ID_FLAGS(func, bpf_strnlen)
+BTF_ID_FLAGS(func, bpf_strpbrk)
+BTF_ID_FLAGS(func, bpf_strspn)
+BTF_ID_FLAGS(func, bpf_strcspn)
 BTF_KFUNCS_END(common_btf_ids)
 
 static const struct btf_kfunc_id_set common_kfunc_set = {