summaryrefslogtreecommitdiff
path: root/kernel/bpf
diff options
context:
space:
mode:
authorBrendan Jackman <jackmanb@google.com>2021-02-17 13:45:09 +0300
committerAlexei Starovoitov <ast@kernel.org>2021-02-26 23:05:07 +0300
commite6ac593372aadacc14e02b198e4a1acfef1db595 (patch)
tree2c4784ea0af06554e8b81f0ebe0b6dde72fcdc6c /kernel/bpf
parent523a4cf491b3c9e2d546040d57250f1a0ca84f03 (diff)
downloadlinux-e6ac593372aadacc14e02b198e4a1acfef1db595.tar.xz
bpf: Rename fixup_bpf_calls and add some comments
This function has become overloaded, it actually does lots of diverse things in a single pass. Rename it to avoid confusion, and add some concise commentary. Signed-off-by: Brendan Jackman <jackmanb@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20210217104509.2423183-1-jackmanb@google.com
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/verifier.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9f7e35590fc6..9336bac39027 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5877,7 +5877,7 @@ static int update_alu_sanitation_state(struct bpf_insn_aux_data *aux,
aux->alu_limit != alu_limit))
return -EACCES;
- /* Corresponding fixup done in fixup_bpf_calls(). */
+ /* Corresponding fixup done in do_misc_fixups(). */
aux->alu_state = alu_state;
aux->alu_limit = alu_limit;
return 0;
@@ -11535,12 +11535,10 @@ static int fixup_call_args(struct bpf_verifier_env *env)
return err;
}
-/* fixup insn->imm field of bpf_call instructions
- * and inline eligible helpers as explicit sequence of BPF instructions
- *
- * this function is called after eBPF program passed verification
+/* Do various post-verification rewrites in a single program pass.
+ * These rewrites simplify JIT and interpreter implementations.
*/
-static int fixup_bpf_calls(struct bpf_verifier_env *env)
+static int do_misc_fixups(struct bpf_verifier_env *env)
{
struct bpf_prog *prog = env->prog;
bool expect_blinding = bpf_jit_blinding_enabled(prog);
@@ -11555,6 +11553,7 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
int i, ret, cnt, delta = 0;
for (i = 0; i < insn_cnt; i++, insn++) {
+ /* Make divide-by-zero exceptions impossible. */
if (insn->code == (BPF_ALU64 | BPF_MOD | BPF_X) ||
insn->code == (BPF_ALU64 | BPF_DIV | BPF_X) ||
insn->code == (BPF_ALU | BPF_MOD | BPF_X) ||
@@ -11595,6 +11594,7 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
continue;
}
+ /* Implement LD_ABS and LD_IND with a rewrite, if supported by the program type. */
if (BPF_CLASS(insn->code) == BPF_LD &&
(BPF_MODE(insn->code) == BPF_ABS ||
BPF_MODE(insn->code) == BPF_IND)) {
@@ -11614,6 +11614,7 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
continue;
}
+ /* Rewrite pointer arithmetic to mitigate speculation attacks. */
if (insn->code == (BPF_ALU64 | BPF_ADD | BPF_X) ||
insn->code == (BPF_ALU64 | BPF_SUB | BPF_X)) {
const u8 code_add = BPF_ALU64 | BPF_ADD | BPF_X;
@@ -11835,6 +11836,7 @@ patch_map_ops_generic:
goto patch_call_imm;
}
+ /* Implement bpf_jiffies64 inline. */
if (prog->jit_requested && BITS_PER_LONG == 64 &&
insn->imm == BPF_FUNC_jiffies64) {
struct bpf_insn ld_jiffies_addr[2] = {
@@ -12645,7 +12647,7 @@ skip_full_check:
ret = convert_ctx_accesses(env);
if (ret == 0)
- ret = fixup_bpf_calls(env);
+ ret = do_misc_fixups(env);
/* do 32-bit optimization after insn patching has done so those patched
* insns could be handled correctly.