Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e390b55d authored Apr 24, 2017 by Daniel Borkmann Committed by David S. Miller Apr 24, 2017

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 c2002f98 ("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>

parent 91ec701a

include/linux/filter.h

+1 −2

Original line number	Diff line number	Diff line
		@@ -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 */

kernel/bpf/verifier.c

+0 −3

Original line number	Diff line number	Diff line
		@@ -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