Messages in this thread | | | Date | Thu, 07 Nov 2013 00:38:57 +0800 | From | Jiang Liu <> | Subject | Re: [PATCH v5 6/7] arm64, jump label: optimize jump label implementation |
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On 10/30/2013 08:55 AM, Will Deacon wrote: > On Fri, Oct 18, 2013 at 04:20:00PM +0100, Jiang Liu wrote: >> 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" > > Minor nit: can you put the label on the same line as the nop please? Sure, will refine it.
> >> + ".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); > > Maybe have an enum or #define for the last parameter -- it's not at all > obvious that '0' means `no link'. Thanks, will improve it.
> >> + } else { >> + insn = aarch64_insn_gen_nop(); >> + } >> + >> + if (is_static) >> + aarch64_insn_patch_text_nosync(&addr, &insn, 1); > > I think I mentioned this before, but is it ever safe to patch more than one > instruction in the _nosync case? If not, I wouldn't even bother with that > last argument. I originally plan to optimize jump_label implementation with the third parameter. But for now, I will remove the third parameter to make code simple and add them back in future when needed. Thanks!
> > Will >
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