In order to let eBPF programs call skb_vlan_push/pop via helper functions
eBPF JITs need to recognize helpers that change skb->data, since
skb->data and hlen are cached as part of JIT code generation.
- arm64 JIT is using bpf_load_pointer() without caching, so it's ok as-is.
- x64 JIT recognizes bpf_skb_vlan_push/pop() calls and re-caches skb->data/hlen
after such calls (experiments showed that conditional re-caching is slower).
- s390 JIT falls back to interpreter for now when bpf_skb_vlan_push() is present
in the program (re-caching is tbd).
Signed-off-by: Alexei Starovoitov <a...@plumgrid.com>
---
with these helpers the phys2virt gateway I showed at nfws can be done
in scalable way without creating a ton of vlan netdevs.
arch/s390/net/bpf_jit_comp.c | 4 +++
arch/x86/net/bpf_jit_comp.c | 80 ++++++++++++++++++++++--------------------
include/linux/bpf.h | 2 ++
include/linux/filter.h | 1 +
include/uapi/linux/bpf.h | 2 ++
net/core/filter.c | 47 +++++++++++++++++++++++++
6 files changed, 98 insertions(+), 38 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index fee782acc2ee..79c731e8d178 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -973,6 +973,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit,
struct bpf_prog *fp, int i
*/
const u64 func = (u64)__bpf_call_base + imm;
+ if (bpf_helper_changes_skb_data((void *)func))
+ /* TODO reload skb->data, hlen */
+ return -1;
+
REG_SET_SEEN(BPF_REG_5);
jit->seen |= SEEN_FUNC;
/* lg %w1,<d(imm)>(%l) */
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 579a8fd74be0..6c335a8fc086 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -315,6 +315,26 @@ static void emit_bpf_tail_call(u8 **pprog)
*pprog = prog;
}
+
+static void emit_load_skb_data_hlen(u8 **pprog)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ /* r9d = skb->len - skb->data_len (headlen)
+ * r10 = skb->data
+ */
+ /* mov %r9d, off32(%rdi) */
+ EMIT3_off32(0x44, 0x8b, 0x8f, offsetof(struct sk_buff, len));
+
+ /* sub %r9d, off32(%rdi) */
+ EMIT3_off32(0x44, 0x2b, 0x8f, offsetof(struct sk_buff, data_len));
+
+ /* mov %r10, off32(%rdi) */
+ EMIT3_off32(0x4c, 0x8b, 0x97, offsetof(struct sk_buff, data));
+ *pprog = prog;
+}
+
static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
int oldproglen, struct jit_context *ctx)
{
@@ -329,36 +349,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs,
u8 *image,
emit_prologue(&prog);
- if (seen_ld_abs) {
- /* r9d : skb->len - skb->data_len (headlen)
- * r10 : skb->data
- */
- if (is_imm8(offsetof(struct sk_buff, len)))
- /* mov %r9d, off8(%rdi) */
- EMIT4(0x44, 0x8b, 0x4f,
- offsetof(struct sk_buff, len));
- else
- /* mov %r9d, off32(%rdi) */
- EMIT3_off32(0x44, 0x8b, 0x8f,
- offsetof(struct sk_buff, len));
-
- if (is_imm8(offsetof(struct sk_buff, data_len)))
- /* sub %r9d, off8(%rdi) */
- EMIT4(0x44, 0x2b, 0x4f,
- offsetof(struct sk_buff, data_len));
- else
- EMIT3_off32(0x44, 0x2b, 0x8f,
- offsetof(struct sk_buff, data_len));
-
- if (is_imm8(offsetof(struct sk_buff, data)))
- /* mov %r10, off8(%rdi) */
- EMIT4(0x4c, 0x8b, 0x57,
- offsetof(struct sk_buff, data));
- else
- /* mov %r10, off32(%rdi) */
- EMIT3_off32(0x4c, 0x8b, 0x97,
- offsetof(struct sk_buff, data));
- }
+ if (seen_ld_abs)
+ emit_load_skb_data_hlen(&prog);
for (i = 0; i < insn_cnt; i++, insn++) {
const s32 imm32 = insn->imm;
@@ -367,6 +359,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8
*image,
u8 b1 = 0, b2 = 0, b3 = 0;
s64 jmp_offset;
u8 jmp_cond;
+ bool reload_skb_data;
int ilen;
u8 *func;
@@ -818,12 +811,18 @@ xadd: if (is_imm8(insn->off))
func = (u8 *) __bpf_call_base + imm32;
jmp_offset = func - (image + addrs[i]);
if (seen_ld_abs) {
- EMIT2(0x41, 0x52); /* push %r10 */
- EMIT2(0x41, 0x51); /* push %r9 */
- /* need to adjust jmp offset, since
- * pop %r9, pop %r10 take 4 bytes after call
insn
- */
- jmp_offset += 4;
+ reload_skb_data =
bpf_helper_changes_skb_data(func);
+ if (reload_skb_data) {
+ EMIT1(0x57); /* push %rdi */
+ jmp_offset += 22; /* pop, mov, sub, mov
*/
+ } else {
+ EMIT2(0x41, 0x52); /* push %r10 */
+ EMIT2(0x41, 0x51); /* push %r9 */
+ /* need to adjust jmp offset, since
+ * pop %r9, pop %r10 take 4 bytes after
call insn
+ */
+ jmp_offset += 4;
+ }
}
if (!imm32 || !is_simm32(jmp_offset)) {
pr_err("unsupported bpf func %d addr %p image
%p\n",
@@ -832,8 +831,13 @@ xadd: if (is_imm8(insn->off))
}
EMIT1_off32(0xE8, jmp_offset);
if (seen_ld_abs) {
- EMIT2(0x41, 0x59); /* pop %r9 */
- EMIT2(0x41, 0x5A); /* pop %r10 */
+ if (reload_skb_data) {
+ EMIT1(0x5F); /* pop %rdi */
+ emit_load_skb_data_hlen(&prog);
+ } else {
+ EMIT2(0x41, 0x59); /* pop %r9 */
+ EMIT2(0x41, 0x5A); /* pop %r10 */
+ }
}
break;
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4383476a0d48..139d6d2e123f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -192,5 +192,7 @@ extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
extern const struct bpf_func_proto bpf_get_current_pid_tgid_proto;
extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
extern const struct bpf_func_proto bpf_get_current_comm_proto;
+extern const struct bpf_func_proto bpf_skb_vlan_push_proto;
+extern const struct bpf_func_proto bpf_skb_vlan_pop_proto;
#endif /* _LINUX_BPF_H */
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 17724f6ea983..69d00555ce35 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -411,6 +411,7 @@ void sk_filter_uncharge(struct sock *sk, struct sk_filter
*fp);
u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
void bpf_int_jit_compile(struct bpf_prog *fp);
+bool bpf_helper_changes_skb_data(void *func);
#ifdef CONFIG_BPF_JIT
typedef void (*bpf_jit_fill_hole_t)(void *area, unsigned int size);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2de87e58b12b..2f6c83d714e9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -256,6 +256,8 @@ enum bpf_func_id {
* Return: classid if != 0
*/
BPF_FUNC_get_cgroup_classid,
+ BPF_FUNC_skb_vlan_push, /* bpf_skb_vlan_push(skb, vlan_proto, vlan_tci)
*/
+ BPF_FUNC_skb_vlan_pop, /* bpf_skb_vlan_pop(skb) */
__BPF_FUNC_MAX_ID,
};
diff --git a/net/core/filter.c b/net/core/filter.c
index 247450a5e387..3683ab09a48a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1437,6 +1437,49 @@ static const struct bpf_func_proto
bpf_get_cgroup_classid_proto = {
.arg1_type = ARG_PTR_TO_CTX,
};
+static u64 bpf_skb_vlan_push(u64 r1, u64 vlan_proto, u64 vlan_tci, u64 r4, u64
r5)
+{
+ struct sk_buff *skb = (struct sk_buff *) (long) r1;
+
+ if (unlikely(vlan_proto != htons(ETH_P_8021Q) &&
+ vlan_proto != htons(ETH_P_8021AD)))
+ vlan_proto = htons(ETH_P_8021Q);
+
+ return skb_vlan_push(skb, vlan_proto, vlan_tci);
+}
+
+const struct bpf_func_proto bpf_skb_vlan_push_proto = {
+ .func = bpf_skb_vlan_push,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+};
+
+static u64 bpf_skb_vlan_pop(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ struct sk_buff *skb = (struct sk_buff *) (long) r1;
+
+ return skb_vlan_pop(skb);
+}
+
+const struct bpf_func_proto bpf_skb_vlan_pop_proto = {
+ .func = bpf_skb_vlan_pop,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+};
+
+bool bpf_helper_changes_skb_data(void *func)
+{
+ if (func == bpf_skb_vlan_push)
+ return true;
+ if (func == bpf_skb_vlan_pop)
+ return true;
+ return false;
+}
+
static const struct bpf_func_proto *
sk_filter_func_proto(enum bpf_func_id func_id)
{
@@ -1476,6 +1519,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
return &bpf_clone_redirect_proto;
case BPF_FUNC_get_cgroup_classid:
return &bpf_get_cgroup_classid_proto;
+ case BPF_FUNC_skb_vlan_push:
+ return &bpf_skb_vlan_push_proto;
+ case BPF_FUNC_skb_vlan_pop:
+ return &bpf_skb_vlan_pop_proto;
default:
return sk_filter_func_proto(func_id);
}
--
1.7.9.5
--
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