For now, ctx[-1] is used to store the nr_args in the trampoline. However,
1-byte is enough to store such information. Therefor, we use only the last
byts of ctx[-1] to store the nr_args, and reverve the rest for other
usages.
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
kernel/bpf/verifier.c | 35 +++++++++++++++++++----------------
kernel/trace/bpf_trace.c | 4 ++--
2 files changed, 21 insertions(+), 18 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d399bfd2413f..96753833c090 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -23275,15 +23275,16 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
insn->imm == BPF_FUNC_get_func_arg) {
/* Load nr_args from ctx - 8 */
insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
- insn_buf[1] = BPF_JMP32_REG(BPF_JGE, BPF_REG_2, BPF_REG_0, 6);
- insn_buf[2] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_2, 3);
- insn_buf[3] = BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_1);
- insn_buf[4] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_2, 0);
- insn_buf[5] = BPF_STX_MEM(BPF_DW, BPF_REG_3, BPF_REG_0, 0);
- insn_buf[6] = BPF_MOV64_IMM(BPF_REG_0, 0);
- insn_buf[7] = BPF_JMP_A(1);
- insn_buf[8] = BPF_MOV64_IMM(BPF_REG_0, -EINVAL);
- cnt = 9;
+ insn_buf[1] = BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xFF);
+ insn_buf[2] = BPF_JMP32_REG(BPF_JGE, BPF_REG_2, BPF_REG_0, 6);
+ insn_buf[3] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_2, 3);
+ insn_buf[4] = BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_1);
+ insn_buf[5] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_2, 0);
+ insn_buf[6] = BPF_STX_MEM(BPF_DW, BPF_REG_3, BPF_REG_0, 0);
+ insn_buf[7] = BPF_MOV64_IMM(BPF_REG_0, 0);
+ insn_buf[8] = BPF_JMP_A(1);
+ insn_buf[9] = BPF_MOV64_IMM(BPF_REG_0, -EINVAL);
+ cnt = 10;
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
@@ -23303,12 +23304,13 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
eatype == BPF_MODIFY_RETURN) {
/* Load nr_args from ctx - 8 */
insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
- insn_buf[1] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_0, 3);
- insn_buf[2] = BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1);
- insn_buf[3] = BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_0, 0);
- insn_buf[4] = BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_3, 0);
- insn_buf[5] = BPF_MOV64_IMM(BPF_REG_0, 0);
- cnt = 6;
+ insn_buf[1] = BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xFF);
+ insn_buf[2] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_0, 3);
+ insn_buf[3] = BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1);
+ insn_buf[4] = BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_0, 0);
+ insn_buf[5] = BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_3, 0);
+ insn_buf[6] = BPF_MOV64_IMM(BPF_REG_0, 0);
+ cnt = 7;
} else {
insn_buf[0] = BPF_MOV64_IMM(BPF_REG_0, -EOPNOTSUPP);
cnt = 1;
@@ -23329,8 +23331,9 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
insn->imm == BPF_FUNC_get_func_arg_cnt) {
/* Load nr_args from ctx - 8 */
insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8);
+ insn_buf[1] = BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xFF);
- new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 1);
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, 2);
if (!new_prog)
return -ENOMEM;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d57727abaade..10c9992d2745 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1194,7 +1194,7 @@ const struct bpf_func_proto bpf_get_branch_snapshot_proto = {
BPF_CALL_3(get_func_arg, void *, ctx, u32, n, u64 *, value)
{
/* This helper call is inlined by verifier. */
- u64 nr_args = ((u64 *)ctx)[-1];
+ u64 nr_args = ((u64 *)ctx)[-1] & 0xFF;
if ((u64) n >= nr_args)
return -EINVAL;
@@ -1214,7 +1214,7 @@ static const struct bpf_func_proto bpf_get_func_arg_proto = {
BPF_CALL_2(get_func_ret, void *, ctx, u64 *, value)
{
/* This helper call is inlined by verifier. */
- u64 nr_args = ((u64 *)ctx)[-1];
+ u64 nr_args = ((u64 *)ctx)[-1] & 0xFF;
*value = ((u64 *)ctx)[nr_args];
return 0;
--
2.52.0