Messages in this thread | | | Date | Wed, 30 Oct 2013 00:55:58 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v5 6/7] arm64, jump label: optimize jump label implementation |
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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?
> + ".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'.
> + } 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.
Will
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