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Subject[PATCH v3 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 | 60 +++++++++++++++++++++++++++++++++++++
4 files changed, 114 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..74cbc73
--- /dev/null
+++ b/arch/arm64/kernel/jump_label.c
@@ -0,0 +1,60 @@
+/*
+ * 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) {
+ /* no way out if instruction offset is out of range(+/-128M) */
+ insn = aarch64_insn_gen_branch_imm(entry->code,
+ entry->target, 0);
+ BUG_ON(!insn);
+ } 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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