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    Subject[PATCH v5 6/7] arm64, jump label: optimize jump label implementation
    Date
    From: Jiang Liu <jiang.liu@huawei.com>

    Optimize jump label implementation for ARM64 by dynamically patching
    kernel text.

    Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
    Cc: Jiang Liu <liuj97@gmail.com>
    ---
    arch/arm64/Kconfig | 1 +
    arch/arm64/include/asm/jump_label.h | 52 +++++++++++++++++++++++++++++++++
    arch/arm64/kernel/Makefile | 1 +
    arch/arm64/kernel/jump_label.c | 58 +++++++++++++++++++++++++++++++++++++
    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 c044548..da388e4 100644
    --- a/arch/arm64/Kconfig
    +++ b/arch/arm64/Kconfig
    @@ -17,6 +17,7 @@ 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..d268fab
    --- /dev/null
    +++ b/arch/arm64/include/asm/jump_label.h
    @@ -0,0 +1,52 @@
    +/*
    + * Copyright (C) 2013 Huawei Ltd.
    + * Author: Jiang Liu <jiang.liu@huawei.com>
    + *
    + * 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
    +#include <linux/types.h>
    +
    +#ifdef __KERNEL__
    +
    +#define JUMP_LABEL_NOP_SIZE 4
    +
    +static __always_inline bool arch_static_branch(struct static_key *key)
    +{
    + asm goto("1:\n\t"
    + "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 9af6cb3..b7db65e 100644
    --- a/arch/arm64/kernel/Makefile
    +++ b/arch/arm64/kernel/Makefile
    @@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP) += smp.o smp_spin_table.o smp_psci.o
    arm64-obj-$(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..871786a
    --- /dev/null
    +++ b/arch/arm64/kernel/jump_label.c
    @@ -0,0 +1,58 @@
    +/*
    + * Copyright (C) 2013 Huawei Ltd.
    + * Author: Jiang Liu <jiang.liu@huawei.com>
    + *
    + * 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
    +
    +static void __arch_jump_label_transform(struct jump_entry *entry,
    + enum jump_label_type type,
    + bool is_static)
    +{
    + void *addr = (void *)entry->code;
    + u32 insn;
    +
    + if (type == JUMP_LABEL_ENABLE) {
    + insn = aarch64_insn_gen_branch_imm(entry->code,
    + entry->target, 0);
    + } else {
    + insn = aarch64_insn_gen_nop();
    + }
    +
    + if (is_static)
    + aarch64_insn_patch_text_nosync(&addr, &insn, 1);
    + else
    + aarch64_insn_patch_text(&addr, &insn, 1);
    +}
    +
    +void arch_jump_label_transform(struct jump_entry *entry,
    + enum jump_label_type type)
    +{
    + __arch_jump_label_transform(entry, type, false);
    +}
    +
    +void arch_jump_label_transform_static(struct jump_entry *entry,
    + enum jump_label_type type)
    +{
    + __arch_jump_label_transform(entry, type, true);
    +}
    +
    +#endif /* HAVE_JUMP_LABEL */
    --
    1.8.1.2


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