Messages in this thread | | | Date | Tue, 26 Apr 2022 23:39:44 +0800 | Subject | Re: [PATCH] arm64: kcsan: Fix kcsan test_barrier fail and panic | From | Kefeng Wang <> |
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On 2022/4/26 20:42, Mark Rutland wrote: > Hi, > > On Tue, Apr 26, 2022 at 08:17:00AM +0000, Kefeng Wang wrote: >> As "kcsan: Support detecting a subset of missing memory barriers" >> introduced KCSAN_STRICT which make kcsan detects more missing memory >> barrier, but arm64 don't have KCSAN instrumentation for barriers, so >> the new selftest test_barrier() will fail, then panic. >> >> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h >> defined the final instrumented version of these barriers, which will >> fix the above issues. >> >> Fixes: dd03762ab608 ("arm64: Enable KCSAN") >> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> > I don't think the Fixes tag is necessary given this is a new feature > which depends upon EXPERT, and I'm worried it encourages backporting > this into a kernel where it would be broken, so I'd prefer we drop that > tag. > > IIUC when we originially looked at this the instrumentation wasn't safe > and would violate noinstr requirements. Looking at linux/kcsan-checks.h, > the comments block for __KCSAN_BARRIER_TO_SIGNAL_FENCE() say that it > will respect __nokcsan, so it looks like that might be safe now. > > It looks like that's the case as of commit: > > bd3d5bd1a0ad3864 ("kcsan: Support WEAK_MEMORY with Clang where no objtool support exists") > > ... which requires clang 14.0.0+. > > That looks to have gone in concurrently with dd03762ab608, but is > clearly a prerequisite, so as above I'd strongly prefer we drop the > Fixes tag.
Sure, the "kcsan: Support detecting a subset of missing memory barriers"[1] and
dd03762ab608 "arm64: Enable KCSAN" are both merged in v5.17. I will drop the Fixes tag.
> It would be good if we could note that explicitly in the commit message. I will add some message into v2. > > Have you eyeballed the generated assembly to verify that this works as > expected for __no_kcsan ? Look good, will recheck it. > > Thanks, > Mark. [1] https://patchwork.kernel.org/project/linux-mm/cover/20211130114433.2580590-1-elver@google.com/
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