Messages in this thread | | | From | Miguel Ojeda <> | Date | Wed, 12 Sep 2018 06:19:08 +0200 | Subject | Re: [PATCH] include/linux/compiler-clang.h: define __naked |
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Hi Arnd, Nick, Stefan,
On Mon, Sep 10, 2018 at 2:14 PM, Arnd Bergmann <arnd@arndb.de> wrote: > On Mon, Sep 10, 2018 at 8:05 AM Stefan Agner <stefan@agner.ch> wrote: >> >> ARM32 arch code uses the __naked attribute. This has previously been >> defined in include/linux/compiler-gcc.h, which is no longer included >> for Clang. Define __naked for Clang. Conservatively add all attributes >> previously used (and supported by Clang). >> >> This fixes compile errors when building ARM32 using Clang: >> arch/arm/mach-exynos/mcpm-exynos.c:193:13: error: variable has incomplete type 'void' >> static void __naked exynos_pm_power_up_setup(unsigned int affinity_level) >> ^ >> >> Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive") >> Signed-off-by: Stefan Agner <stefan@agner.ch> > >> +/* >> + * ARM32 is currently the only user of __naked supported by Clang. Follow >> + * gcc: Do not trace naked functions and make sure they don't get inlined. >> + */ >> +#define __naked __attribute__((naked)) noinline notrace >> + > > Please see patches 5 and 6 of the series that Miguel posted: > > https://lore.kernel.org/lkml/20180908212459.19736-6-miguel.ojeda.sandonis@gmail.com/ > > I suppose we want the patch to fix clang build as soon as possible though, > and follow up with the cleanup for the next merge window, right?
Not sure what the plans of Linus et. al. are, if they have any; but that would be a safe bet.
In case they want to speed this up and put the entire series into v4.19 (instead of the two patches), I have done a binary & objdump diff between -rc2 and v4 (based on -rc2) on all object files (with UTS_RELEASE fixed to avoid some differences).
In a x86_64 tinyconfig with gcc 7.3, the differences I found are:
$ ./compare.py linux-rc2 linux-v4 [2018-09-12 06:16:39,483] [INFO] [arch/x86/boot/compressed/piggy.o] Binary diff (use 'bash -c "cmp linux-rc2/arch/x86/boot/compressed/piggy.o linux-v4/arch/x86/boot/compressed/piggy.o"' to replicate) [2018-09-12 06:16:39,606] [INFO] [arch/x86/boot/header.o] Binary diff (use 'bash -c "cmp linux-rc2/arch/x86/boot/header.o linux-v4/arch/x86/boot/header.o"' to replicate) [2018-09-12 06:16:39,659] [INFO] [arch/x86/boot/version.o] Binary diff (use 'bash -c "cmp linux-rc2/arch/x86/boot/version.o linux-v4/arch/x86/boot/version.o"' to replicate) [2018-09-12 06:16:40,483] [INFO] [init/version.o] Binary diff (use 'bash -c "cmp linux-rc2/init/version.o linux-v4/init/version.o"' to replicate)
I will do a bigger one tomorrow or so and see if there are any important differences. Regardless of what we do, I will send the __naked patches separately as well (requested by Nick on GitHub).
Cheers, Miguel
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