From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Ard Biesheuvel <ardb@kernel.org>, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: asm: Rewrite get_thread_info using BIC
Date: Wed, 27 May 2020 14:13:57 +0100 [thread overview]
Message-ID: <20200527131356.GN1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <20200527122201.124090-1-linus.walleij@linaro.org>
On Wed, May 27, 2020 at 02:22:01PM +0200, Linus Walleij wrote:
> By using two BIC instructions we can replace the ARM/thumb
> split instructions with something that works on either
> and also save one instruction.
>
> Based on code from proc-macros.S and an idea from Ard
> Biesheuvel.
>
> We need to include <linux/const.h> to expand the
> THREAD_SIZE definition properly in the preprocessor.
>
> Suggested-by: Russell King <linux@armlinux.org.uk>
> Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Looks good to me, thanks.
> ---
> arch/arm/include/asm/assembler.h | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
> index 99929122dad7..f218e8cf7f88 100644
> --- a/arch/arm/include/asm/assembler.h
> +++ b/arch/arm/include/asm/assembler.h
> @@ -17,6 +17,7 @@
> #error "Only include this from assembly code"
> #endif
>
> +#include <linux/const.h>
> #include <asm/ptrace.h>
> #include <asm/domain.h>
> #include <asm/opcodes-virt.h>
> @@ -203,10 +204,8 @@
> * Get current thread_info.
> */
> .macro get_thread_info, rd
> - ARM( mov \rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT )
> - THUMB( mov \rd, sp )
> - THUMB( lsr \rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT )
> - mov \rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT
> + bic \rd, sp, #(THREAD_SIZE - 1) & ~63
> + bic \rd, \rd, #63
> .endm
>
> /*
> --
> 2.25.4
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2020-05-27 13:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 12:22 [PATCH] ARM: asm: Rewrite get_thread_info using BIC Linus Walleij
2020-05-27 13:13 ` Russell King - ARM Linux admin [this message]
2020-07-21 13:37 ` Dmitry Osipenko
2020-07-21 13:38 ` Russell King - ARM Linux admin
2020-07-21 13:39 ` Dmitry Osipenko
2020-07-21 13:54 ` Linus Walleij
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