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bpf: add bpf_patch_insn_single helper

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Move the functionality to patch instructions out of the verifier
code and into the core as the new bpf_patch_insn_single() helper
will be needed later on for blinding as well. No changes in
functionality.

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
2016-05-13 19:08:30 +02:00
committed by David S. Miller
parent 93a73d442d
commit c237ee5eb3
3 changed files with 83 additions and 44 deletions
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53
kernel/bpf/verifier.c
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@@ -2587,26 +2587,6 @@ static void convert_pseudo_ld_imm64(struct verifier_env *env)
insn->src_reg = 0;
}
static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
{
struct bpf_insn *insn = prog->insnsi;
int insn_cnt = prog->len;
int i;
for (i = 0; i < insn_cnt; i++, insn++) {
if (BPF_CLASS(insn->code) != BPF_JMP ||
BPF_OP(insn->code) == BPF_CALL ||
BPF_OP(insn->code) == BPF_EXIT)
continue;
/* adjust offset of jmps if necessary */
if (i < pos && i + insn->off + 1 > pos)
insn->off += delta;
else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
insn->off -= delta;
}
}
/* convert load instructions that access fields of 'struct __sk_buff'
* into sequence of instructions that access fields of 'struct sk_buff'
*/
@@ -2616,14 +2596,15 @@ static int convert_ctx_accesses(struct verifier_env *env)
int insn_cnt = env->prog->len;
struct bpf_insn insn_buf[16];
struct bpf_prog *new_prog;
u32 cnt;
int i;
enum bpf_access_type type;
int i;
if (!env->prog->aux->ops->convert_ctx_access)
return 0;
for (i = 0; i < insn_cnt; i++, insn++) {
u32 insn_delta, cnt;
if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
type = BPF_READ;
else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
@@ -2645,34 +2626,18 @@ static int convert_ctx_accesses(struct verifier_env *env)
return -EINVAL;
}
if (cnt == 1) {
memcpy(insn, insn_buf, sizeof(*insn));
continue;
}
/* several new insns need to be inserted. Make room for them */
insn_cnt += cnt - 1;
new_prog = bpf_prog_realloc(env->prog,
bpf_prog_size(insn_cnt),
GFP_USER);
new_prog = bpf_patch_insn_single(env->prog, i, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
new_prog->len = insn_cnt;
memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
sizeof(*insn) * (insn_cnt - i - cnt));
/* copy substitute insns in place of load instruction */
memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
/* adjust branches in the whole program */
adjust_branches(new_prog, i, cnt - 1);
insn_delta = cnt - 1;
/* keep walking new program and skip insns we just inserted */
env->prog = new_prog;
insn = new_prog->insnsi + i + cnt - 1;
i += cnt - 1;
insn = new_prog->insnsi + i + insn_delta;
insn_cnt += insn_delta;
i += insn_delta;
}
return 0;