From: Alexei Starovoitov <redacted>
Date: Sat, 29 Apr 2017 22:52:42 -0700

From: Yonghong Song <redacted>

llvm 4.0 and above generates the code like below:
....
440: (b7) r1 = 15
441: (05) goto pc+73
515: (79) r6 = *(u64 *)(r10 -152)
516: (bf) r7 = r10
517: (07) r7 += -112
518: (bf) r2 = r7
519: (0f) r2 += r1
520: (71) r1 = *(u8 *)(r8 +0)
521: (73) *(u8 *)(r2 +45) = r1
....
and the verifier complains "R2 invalid mem access 'inv'" for insn #521.
This is because verifier marks register r2 as unknown value after #519
where r2 is a stack pointer and r1 holds a constant value.

Teach verifier to recognize "stack_ptr + imm" and
"stack_ptr + reg with const val" as valid stack_ptr with new offset.

Signed-off-by: Yonghong Song <redacted>
Acked-by: Martin KaFai Lau <redacted>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
technically it's 'net' material, but it's too late for 'net',
hence 'net-next' tag.
No 'Fixes' tag, since it's only seen with newer llvm.

Applied to net-next, but I'll queue this up to -stable.