From: Anton Blanchard <anton@samba.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Nicholas Piggin <npiggin@gmail.com>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: BUILD_BUG_ON(!__builtin_constant_p(feature)) breaks bcc trace tool
Date: Sat, 21 Jan 2017 12:03:39 +1100 [thread overview]
Message-ID: <20170121120339.1c774b28@kryten> (raw)
Hi,
We added:
BUILD_BUG_ON(!__builtin_constant_p(feature))
to cpu_has_feature() and mmu_has_feature() in order to catch usage
issues (such as cpu_has_feature(cpu_has_feature(X)). Unfortunately LLVM
isn't smart enough to resolve this, and it errors out.
I work around it in my clang/LLVM builds of the kernel, but I have just
discovered that it causes a lot of issues for the bcc (eBPF) trace tool
(which uses LLVM).
How should we work around this? Wrap the checks in !clang perhaps?
Anton
next reply other threads:[~2017-01-21 1:04 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-21 1:03 Anton Blanchard [this message]
2017-01-21 9:49 ` BUILD_BUG_ON(!__builtin_constant_p(feature)) breaks bcc trace tool Anton Blanchard
2017-01-24 6:15 ` Michael Ellerman
2017-01-24 9:45 ` Arnd Bergmann
2017-01-25 10:35 ` David Laight
2017-01-25 15:44 ` Arnd Bergmann
2017-01-24 5:36 ` Michael Ellerman
2017-01-24 10:47 ` Naveen N. Rao
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