Add BPF helper that allows to calculate jhash of arbitrary (initialized)
memory slice.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 8 ++++++++
kernel/bpf/helpers.c | 23 +++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 8 ++++++++
3 files changed, 39 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2e3048488feb..7b17e46b0be2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4913,6 +4913,13 @@ union bpf_attr {
* Return
* The number of bytes written to the buffer, or a negative error
* in case of failure.
+ *
+ * u64 bpf_jhash_mem(const void *data, u32 sz, u32 seed)
+ * Description
+ * Calculate jhash of a given memory slice.
+ *
+ * Return
+ * Calculated hash value.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5093,6 +5100,7 @@ union bpf_attr {
FN(task_pt_regs), \
FN(get_branch_snapshot), \
FN(trace_vprintk), \
+ FN(jhash_mem), \
/* */
/* 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 2c604ff8c7fb..00fb1b69595c 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -15,9 +15,30 @@
#include <linux/pid_namespace.h>
#include <linux/proc_ns.h>
#include <linux/security.h>
+#include <linux/jhash.h>
#include "../../lib/kstrtox.h"
+BPF_CALL_3(bpf_jhash_mem, const void *, data, u32, sz, u32, seed)
+{
+ if (unlikely((uintptr_t)data % 4 || sz % 4))
+ return jhash(data, sz, seed);
+
+ /* optimized 4-byte version */
+ return jhash2(data, sz / 4, seed);
+}
+
+
+static const struct bpf_func_proto bpf_jhash_mem_proto = {
+ .func = bpf_jhash_mem,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_CONST_SIZE_OR_ZERO,
+ .arg3_type = ARG_ANYTHING,
+};
+
+
/* If kernel subsystem is allowing eBPF programs to call this function,
* inside its own verifier_ops->get_func_proto() callback it should return
* bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
@@ -1341,6 +1362,8 @@ const struct bpf_func_proto *
bpf_base_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
+ case BPF_FUNC_jhash_mem:
+ return &bpf_jhash_mem_proto;
case BPF_FUNC_map_lookup_elem:
return &bpf_map_lookup_elem_proto;
case BPF_FUNC_map_update_elem:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 2e3048488feb..7b17e46b0be2 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4913,6 +4913,13 @@ union bpf_attr {
* Return
* The number of bytes written to the buffer, or a negative error
* in case of failure.
+ *
+ * u64 bpf_jhash_mem(const void *data, u32 sz, u32 seed)
+ * Description
+ * Calculate jhash of a given memory slice.
+ *
+ * Return
+ * Calculated hash value.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5093,6 +5100,7 @@ union bpf_attr {
FN(task_pt_regs), \
FN(get_branch_snapshot), \
FN(trace_vprintk), \
+ FN(jhash_mem), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.30.2
