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bpf: make bpf_xdp_adjust_head support mandatory

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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 c2002f9837 ("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>
This commit is contained in:
Daniel Borkmann 2017-04-24 22:14:35 +02:00 committed by David S. Miller
parent 91ec701a55
commit e390b55d5a
2 changed files with 1 additions and 5 deletions
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3
include/linux/filter.h
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@ -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 */

3
kernel/bpf/verifier.c
View file

@ -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