[PATCH bpf-next v4 13/25] bpf: Enable r11 based insns

[Yonghong Song <yonghong.song@linux.dev>]

BPF_REG_PARAMS (r11) is used for stack argument accesses and
the following are only insns with r11 presence:
    - load incoming stack arg
    - store register to outgoing stack arg
    - store immediate to outgoing stack arg

The detailed insn format can be found in is_stack_arg_ldx/st/stx()
helpers. After this patch, stack arg ldx/st/stx insns become valid
for kernel and these insns can be properly checked by verifier.

The LLVM compiler [1] implemented the above BPF_REG_PARAMS insns.

  [1] https://github.com/llvm/llvm-project/pull/189060

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 kernel/bpf/verifier.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 30143bea6a86..18bbc5b6c2d2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18006,11 +18006,12 @@ static int check_and_resolve_insns(struct bpf_verifier_env *env)
 		return err;
 
 	for (i = 0; i < insn_cnt; i++, insn++) {
-		if (insn->dst_reg >= MAX_BPF_REG) {
+		if (insn->dst_reg >= MAX_BPF_REG &&
+		    !is_stack_arg_st(insn) && !is_stack_arg_stx(insn)) {
 			verbose(env, "R%d is invalid\n", insn->dst_reg);
 			return -EINVAL;
 		}
-		if (insn->src_reg >= MAX_BPF_REG) {
+		if (insn->src_reg >= MAX_BPF_REG && !is_stack_arg_ldx(insn)) {
 			verbose(env, "R%d is invalid\n", insn->src_reg);
 			return -EINVAL;
 		}
-- 
2.53.0-Meta