bpf: make bpf_xdp_adjust_head support mandatory

Now that also the last in-tree user of the xdp_adjust_head bit has
been removed, we can remove the flag from struct bpf_prog altogether.

This, at the same time, also makes sure that any future driver for
XDP comes with bpf_xdp_adjust_head() support right away.

A rejection based on this flag would also mean that tail calls
couldn't be used with such driver as per c2002f983767 ("bpf: fix
checking xdp_adjust_head on tail calls") fix, thus lets not allow
for it in the first place.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 511fe91..9a7786d 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -413,8 +413,7 @@ struct bpf_prog {
                                locked:1,       /* Program image locked? */
                                gpl_compatible:1, /* Is filter GPL compatible? */
                                cb_access:1,    /* Is control block accessed? */
-                               dst_needed:1,   /* Do we need dst entry? */
-                               xdp_adjust_head:1; /* Adjusting pkt head? */
+                               dst_needed:1;   /* Do we need dst entry? */
        kmemcheck_bitfield_end(meta);
        enum bpf_prog_type      type;           /* Type of BPF program */
        u32                     len;            /* Number of filter blocks */

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ca15cf2..6f8b6ed 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3346,8 +3346,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
                        prog->dst_needed = 1;
                if (insn->imm == BPF_FUNC_get_prandom_u32)
                        bpf_user_rnd_init_once();
-               if (insn->imm == BPF_FUNC_xdp_adjust_head)
-                       prog->xdp_adjust_head = 1;
                if (insn->imm == BPF_FUNC_tail_call) {
                        /* If we tail call into other programs, we
                         * cannot make any assumptions since they can
@@ -3355,7 +3353,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
                         * the program array.
                         */
                        prog->cb_access = 1;
-                       prog->xdp_adjust_head = 1;
 
                        /* mark bpf_tail_call as different opcode to avoid
                         * conditional branch in the interpeter for every normal