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Tue, 11 Dec 2018 13:41:18 -0800 (PST) MIME-Version: 1.0 References: <20181129170530.37789-1-vincenzo.frascino@arm.com> <20181129170530.37789-7-vincenzo.frascino@arm.com> <64ff3b50-ce55-ff69-ac3a-61f221299895@arm.com> In-Reply-To: <64ff3b50-ce55-ff69-ac3a-61f221299895@arm.com> From: Arnd Bergmann Date: Tue, 11 Dec 2018 22:41:01 +0100 Message-ID: Subject: Re: [PATCH v2 06/28] kernel: Define gettimeofday vdso common code To: Vincenzo Frascino X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181211_134130_777343_3576A1A9 X-CRM114-Status: GOOD ( 19.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , Catalin Marinas , Daniel Lezcano , Will Deacon , Russell King - ARM Linux , Ralf Baechle , Mark Salyzyn , Paul Burton , Thomas Gleixner , Peter Collingbourne , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Dec 11, 2018 at 2:39 PM Vincenzo Frascino wrote: > On 29/11/2018 20:42, Arnd Bergmann wrote: > > On Thu, Nov 29, 2018 at 6:06 PM Vincenzo Frascino > > wrote: > > > >> +/* > >> + * The definitions below are required to overcome the limitations > >> + * of time_t on 32 bit architectures, which overflows in 2038. > >> + * The new code should use the replacements based on time64_t and > >> + * timespec64. > >> + * > >> + * The abstraction below will be updated once the migration to > >> + * time64_t is complete. > >> + */ > >> +#ifdef CONFIG_GENERIC_VDSO_32 > >> +#define __vdso_timespec old_timespec32 > >> +#define __vdso_timeval old_timeval32 > >> +#else > >> +#ifdef ENABLE_COMPAT_VDSO > >> +#define __vdso_timespec old_timespec32 > >> +#define __vdso_timeval old_timeval32 > >> +#else > >> +#define __vdso_timespec __kernel_timespec > >> +#define __vdso_timeval __kernel_old_timeval > >> +#endif /* CONFIG_COMPAT_VDSO */ > >> +#endif /* CONFIG_GENERIC_VDSO_32 */ > >> > > > > Have you considered doing this in the reverse way, by including > > the common parts from multiple implementations (32 and 64 > > bit), instead of compiling the same source file multiple > > times with different macros set? I think that would make it > > easier to understand. > > > > The common code is never compiled as standalone. It includes arch specific code > (for the fallbacks) and it is included in the arch specific vdso library (for > both 32 and 64 bit where it makes sense). Hence it is built once or twice. > > If I understand correctly your question, seems inline with what I am doing. The result is very similar, it's just a question of which file includes which other file. If I understand your current method right, you use Makefile logic to build multiple object files from a single source file, and setting ENABLE_COMPAT_VDSO on one of them, right? My preference would be to keep that Makefile simpler and have one source file per object file, but have each one define a set of macros before including the common source file, similarly to how we deal with fs/compat_binfmt_elf.c. If that turns out to be worse than what you have here, I'm not overly attached to that solution since including C files is still ugly, but I think it's worth trying if that lets you end up with more easily understandable source code. Arnd _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel