From: John Fastabend <john.fastabend@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>, davem@davemloft.net
Cc: daniel@iogearbox.net, john.fastabend@gmail.com,
netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com
Subject: RE: [PATCH v2 bpf-next 2/4] bpf: Track spill/fill of bounded scalars.
Date: Fri, 09 Oct 2020 12:49:20 -0700 [thread overview]
Message-ID: <5f80bec0c60a0_ed7420896@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20201009011240.48506-3-alexei.starovoitov@gmail.com>
Alexei Starovoitov wrote:
> From: Yonghong Song <yhs@fb.com>
>
> Under register pressure the llvm may spill registers with bounds into the stack.
> The verifier has to track them through spill/fill otherwise many kinds of bound
> errors will be seen. The spill/fill of induction variables was already
> happening. This patch extends this logic from tracking spill/fill of a constant
> into any bounded register. There is no need to track spill/fill of unbounded,
> since no new information will be retrieved from the stack during register fill.
>
> Though extra stack difference could cause state pruning to be less effective, no
> adverse affects were seen from this patch on selftests and on cilium programs.
>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> ---
> kernel/bpf/verifier.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
LGTM and will be useful.
Acked-by: John Fastabend <john.fastabend@gmail.com>
next prev parent reply other threads:[~2020-10-09 19:49 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-09 1:12 [PATCH v2 bpf-next 0/4] bpf: Make the verifier recognize llvm register allocation patterns Alexei Starovoitov
2020-10-09 1:12 ` [PATCH v2 bpf-next 1/4] bpf: Propagate scalar ranges through register assignments Alexei Starovoitov
2020-10-09 19:42 ` John Fastabend
2020-10-09 1:12 ` [PATCH v2 bpf-next 2/4] bpf: Track spill/fill of bounded scalars Alexei Starovoitov
2020-10-09 19:49 ` John Fastabend [this message]
2020-10-09 1:12 ` [PATCH v2 bpf-next 3/4] selftests/bpf: Add profiler test Alexei Starovoitov
2020-10-09 6:49 ` Yonghong Song
2020-10-09 15:08 ` Alexei Starovoitov
2020-10-09 15:13 ` Yonghong Song
2020-10-13 19:56 ` Jiri Olsa
2020-10-13 21:03 ` Alexei Starovoitov
2020-10-13 21:56 ` Andrii Nakryiko
2020-10-15 6:09 ` Song Liu
2020-11-04 16:45 ` Jiri Olsa
2020-11-04 20:50 ` Andrii Nakryiko
2020-11-04 21:57 ` Jiri Olsa
2020-10-13 21:59 ` Jiri Olsa
2020-10-14 0:21 ` Song Liu
2020-10-09 1:12 ` [PATCH v2 bpf-next 4/4] selftests/bpf: Asm tests for the verifier regalloc tracking Alexei Starovoitov
2020-10-09 20:06 ` John Fastabend
2020-10-09 20:10 ` [PATCH v2 bpf-next 0/4] bpf: Make the verifier recognize llvm register allocation patterns patchwork-bot+netdevbpf
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