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Fri, 16 Jan 2026 02:46:43 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: A42RL7jkrr-J Date: Fri, 16 Jan 2026 08:46:22 +0100 From: "Arnd Bergmann" To: =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , "David S . Miller" , "Andreas Larsson" , "Andy Lutomirski" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , x86@kernel.org, "H. Peter Anvin" , "Heiko Carstens" , "Vasily Gorbik" , "Alexander Gordeev" , "Christian Borntraeger" , "Sven Schnelle" Cc: sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, Linux-Arch , linux-s390@vger.kernel.org Message-Id: <5424652d-3607-4718-b32a-a9591437c133@app.fastmail.com> In-Reply-To: <20260116-vdso-compat-checkflags-v1-4-4a83b4fbb0d3@linutronix.de> References: <20260116-vdso-compat-checkflags-v1-0-4a83b4fbb0d3@linutronix.de> <20260116-vdso-compat-checkflags-v1-4-4a83b4fbb0d3@linutronix.de> Subject: Re: [PATCH 4/4] asm-generic/bitsperlong.h: Add sanity checks for __BITS_PER_LONG Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Fri, Jan 16, 2026, at 08:40, Thomas Wei=C3=9Fschuh wrote: > The value of __BITS_PER_LONG from architecture-specific logic should > always match the generic one if that is available. It should also match > the actual C type 'long'. > > Mismatches can happen for example when building the compat vDSO. Either > during the compilation, see commit 9a6d3ff10f7f ("arm64: uapi: Provide > correct __BITS_PER_LONG for the compat vDSO"), or when running sparse > when mismatched CHECKFLAGS are inherited from the kernel build. > > Add some consistency checks which detect such issues early and clearly. > The tests are added to the UAPI header to make sure it is also used wh= en > building the vDSO as that is not supposed to use regular kernel header= s. > > The kernel-interal BITS_PER_LONG is not checked as it is derived from > CONFIG_64BIT and therefore breaks for the compat vDSO. See the similar, > deactivated check in include/asm-generic/bitsperlong.h. > > Signed-off-by: Thomas Wei=C3=9Fschuh Acked-by: Arnd Bergmann