[PATCH v2] bpf: make function do_misc_fixups as noinline_for_stack

[flyingpenghao@gmail.com]

From: Peng Hao <flyingpeng@tencent.com>

When KASAN is enabled and built with clang:
kernel/bpf/verifier.c:21486:5: error: stack frame size (2264) exceeds limit (2048) in 'bpf_check' [-Werror,-Wframe-larger-than]
int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_size)
    ^

By tracing the call chain, we found that do_misc_fixups consumed a lot
of stack space. mark it as noinline_for_stack to prevent it from spreading
to bpf_check's stack size.

Signed-off-by: Peng Hao <flyingpeng@tencent.com>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 48f3a9acdef3..ba1bf742a33d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19791,7 +19791,7 @@ static int add_hidden_subprog(struct bpf_verifier_env *env, struct bpf_insn *pat
 /* Do various post-verification rewrites in a single program pass.
  * These rewrites simplify JIT and interpreter implementations.
  */
-static int do_misc_fixups(struct bpf_verifier_env *env)
+static noinline_for_stack int do_misc_fixups(struct bpf_verifier_env *env)
 {
 	struct bpf_prog *prog = env->prog;
 	enum bpf_attach_type eatype = prog->expected_attach_type;
-- 
2.27.0