From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arm64: LLVMLinux: Fix inline arm64 assembly for use with clang
Date: Wed, 10 Sep 2014 18:38:29 +0100 [thread overview]
Message-ID: <20140910173829.GI1710@arm.com> (raw)
In-Reply-To: <20140908093051.GA12657@localhost>
On Mon, Sep 08, 2014 at 10:30:51AM +0100, Olof Johansson wrote:
> On Fri, Sep 05, 2014 at 04:24:20PM -0700, behanw at converseincode.com wrote:
> > From: Mark Charlebois <charlebm@gmail•com>
> >
> > Fix variable types for 64-bit inline assembly.
> >
> > This patch now works with both gcc and clang.
> >
> > Signed-off-by: Mark Charlebois <charlebm@gmail•com>
> > Signed-off-by: Behan Webster <behanw@converseincode•com>
> > ---
> > arch/arm64/include/asm/arch_timer.h | 26 +++++++++++++++-----------
> > arch/arm64/include/asm/uaccess.h | 2 +-
> > arch/arm64/kernel/debug-monitors.c | 8 ++++----
> > arch/arm64/kernel/perf_event.c | 34 +++++++++++++++++-----------------
> > arch/arm64/mm/mmu.c | 2 +-
> > 5 files changed, 38 insertions(+), 34 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
> > index 9400596..c1f87e0 100644
> > --- a/arch/arm64/include/asm/arch_timer.h
> > +++ b/arch/arm64/include/asm/arch_timer.h
> > @@ -37,19 +37,23 @@ void arch_timer_reg_write_cp15(int access, enum arch_timer_reg reg, u32 val)
> > if (access == ARCH_TIMER_PHYS_ACCESS) {
> > switch (reg) {
> > case ARCH_TIMER_REG_CTRL:
> > - asm volatile("msr cntp_ctl_el0, %0" : : "r" (val));
> > + asm volatile("msr cntp_ctl_el0, %0"
> > + : : "r" ((u64)val));
>
> Ick. Care to elaborate in the patch description why this is needed with
> LLVM? It's really messy and very annoying having to cast register values
> every time they're passed in, instead of the compiler handling it for you.
>
> Is there a way to catch this with GCC? If not, I expect you to get broken
> all the time on this by people who don't notice.
Question to the clang people (Clangers?): what happens if the %0 above is
rewritten as %x0 and the cast on val is dropped? I could stomach a change
adding that, but it's still likely to regress without regular build testing.
Will
next prev parent reply other threads:[~2014-09-10 17:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-05 23:24 [PATCH] arm64: LLVMLinux: Fix inline arm64 assembly for use with clang behanw at converseincode.com
2014-09-08 9:30 ` Olof Johansson
2014-09-10 17:38 ` Will Deacon [this message]
2014-09-10 17:49 ` Ard Biesheuvel
2014-09-08 10:53 ` Will Deacon
2014-09-08 18:35 ` Mark Charlebois
2014-09-09 10:15 ` Will Deacon
2014-09-15 5:30 ` behanw at converseincode.com
2014-09-15 16:02 ` Will Deacon
2014-09-15 16:26 ` Catalin Marinas
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