Re: [PATCH v6 6/7] arm64, jump label: optimize jump labelimplementation

[Will Deacon]

Hi Jiang Liu,

Thanks for the updated patches! I still have some small comments, but I
don't think they will cause you much work. See inline.

On Tue, Dec 10, 2013 at 04:03:52PM +0000, Jiang Liu wrote:
> Optimize jump label implementation for ARM64 by dynamically patching
> kernel text.
> 
> Signed-off-by: Jiang Liu <liuj97@xxxxxxxxx>
> ---
>  arch/arm64/Kconfig                  |  1 +
>  arch/arm64/include/asm/jump_label.h | 51 ++++++++++++++++++++++++++++++++
>  arch/arm64/kernel/Makefile          |  1 +
>  arch/arm64/kernel/jump_label.c      | 59 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 112 insertions(+)
>  create mode 100644 arch/arm64/include/asm/jump_label.h
>  create mode 100644 arch/arm64/kernel/jump_label.c
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 6d4dd22..5f962e8 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -19,6 +19,7 @@ config ARM64
>  	select GENERIC_SMP_IDLE_THREAD
>  	select GENERIC_TIME_VSYSCALL
>  	select HARDIRQS_SW_RESEND
> +	select HAVE_ARCH_JUMP_LABEL
>  	select HAVE_ARCH_TRACEHOOK
>  	select HAVE_DEBUG_BUGVERBOSE
>  	select HAVE_DEBUG_KMEMLEAK
> diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h
> new file mode 100644
> index 0000000..ca95a3a
> --- /dev/null
> +++ b/arch/arm64/include/asm/jump_label.h
> @@ -0,0 +1,51 @@
> +/*
> + * Copyright (C) 2013 Huawei Ltd.
> + * Author: Jiang Liu <liuj97@xxxxxxxxx>
> + *
> + * Based on arch/arm/include/asm/jump_label.h
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#ifndef _ASM_ARM64_JUMP_LABEL_H
> +#define _ASM_ARM64_JUMP_LABEL_H

Just use __ASM_JUMP_LABEL_H to keep consistent with out other headers.

> +#include <linux/types.h>
> +
> +#ifdef __KERNEL__
> +
> +#define JUMP_LABEL_NOP_SIZE 4

This is the same as AARCH64_INSN_SIZE; just use the latter.

> +
> +static __always_inline bool arch_static_branch(struct static_key *key)
> +{
> +	asm goto("1: nop\n\t"
> +		 ".pushsection __jump_table,  \"aw\"\n\t"
> +		 ".align 3\n\t"
> +		 ".quad 1b, %l[l_yes], %c0\n\t"
> +		 ".popsection\n\t"
> +		 :  :  "i"(key) :  : l_yes);
> +
> +	return false;
> +l_yes:
> +	return true;
> +}
> +
> +#endif /* __KERNEL__ */
> +
> +typedef u64 jump_label_t;
> +
> +struct jump_entry {
> +	jump_label_t code;
> +	jump_label_t target;
> +	jump_label_t key;
> +};
> +
> +#endif	/* _ASM_ARM64_JUMP_LABEL_H */
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index cd95a25..e155d56 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP)			+= smp.o smp_spin_table.o
>  arm64-obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event.o
>  arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)+= hw_breakpoint.o
>  arm64-obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
> +arm64-obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
>  
>  obj-y					+= $(arm64-obj-y) vdso/
>  obj-m					+= $(arm64-obj-m)
> diff --git a/arch/arm64/kernel/jump_label.c b/arch/arm64/kernel/jump_label.c
> new file mode 100644
> index 0000000..b13ef62
> --- /dev/null
> +++ b/arch/arm64/kernel/jump_label.c
> @@ -0,0 +1,59 @@
> +/*
> + * Copyright (C) 2013 Huawei Ltd.
> + * Author: Jiang Liu <liuj97@xxxxxxxxx>
> + *
> + * Based on arch/arm/kernel/jump_label.c
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#include <linux/kernel.h>
> +#include <linux/jump_label.h>
> +#include <asm/jump_label.h>
> +#include <asm/insn.h>
> +
> +#ifdef HAVE_JUMP_LABEL

Slightly worrying... this should be CONFIG_HAVE_JUMP_LABEL, right? How did
you manage to test this code?

Will
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/