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Date: Thu, 11 May 2023 09:33:37 +0800
From: Youling Tang <tangyouling@...ngson.cn>
To: WANG Xuerui <kernel@...0n.name>
Cc: Huacai Chen <chenhuacai@...nel.org>,
Jonathan Corbet <corbet@....net>,
Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Jason Baron <jbaron@...mai.com>,
Zhangjin Wu <falcon@...ylab.org>, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev
Subject: Re: [PATCH v2] LoongArch: Add jump-label implementation
Hi, Xuerui
On 05/10/2023 05:28 PM, WANG Xuerui wrote:
> Hi Youling,
>
> On 2023/5/10 17:16, Youling Tang wrote:
>> Add jump-label implementation based on the ARM64 version.
>
> "Add support for jump labels based on ..." sounds better IMO.
OK.
>
>>
>> Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
>> ---
>> Changes in v2:
>> - Fix build errors.
>> - fix comment.
>>
>> .../core/jump-labels/arch-support.txt | 2 +-
>> arch/loongarch/Kconfig | 2 +
>> arch/loongarch/configs/loongson3_defconfig | 1 +
>> arch/loongarch/include/asm/jump_label.h | 51 +++++++++++++++++++
>> arch/loongarch/kernel/Makefile | 2 +
>> arch/loongarch/kernel/jump_label.c | 23 +++++++++
>> 6 files changed, 80 insertions(+), 1 deletion(-)
>> create mode 100644 arch/loongarch/include/asm/jump_label.h
>> create mode 100644 arch/loongarch/kernel/jump_label.c
>>
>> diff --git a/Documentation/features/core/jump-labels/arch-support.txt
>> b/Documentation/features/core/jump-labels/arch-support.txt
>> index 2328eada3a49..94d9dece580f 100644
>> --- a/Documentation/features/core/jump-labels/arch-support.txt
>> +++ b/Documentation/features/core/jump-labels/arch-support.txt
>> @@ -13,7 +13,7 @@
>> | csky: | ok |
>> | hexagon: | TODO |
>> | ia64: | TODO |
>> - | loongarch: | TODO |
>> + | loongarch: | ok |
>
> +1 for updating the docs along with the implementation!
>
>> | m68k: | TODO |
>> | microblaze: | TODO |
>> | mips: | ok |
>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
>> index d38b066fc931..193a959a5611 100644
>> --- a/arch/loongarch/Kconfig
>> +++ b/arch/loongarch/Kconfig
>> @@ -83,6 +83,8 @@ config LOONGARCH
>> select GPIOLIB
>> select HAS_IOPORT
>> select HAVE_ARCH_AUDITSYSCALL
>> + select HAVE_ARCH_JUMP_LABEL
>> + select HAVE_ARCH_JUMP_LABEL_RELATIVE
>> select HAVE_ARCH_MMAP_RND_BITS if MMU
>> select HAVE_ARCH_SECCOMP_FILTER
>> select HAVE_ARCH_TRACEHOOK
>> diff --git a/arch/loongarch/configs/loongson3_defconfig
>> b/arch/loongarch/configs/loongson3_defconfig
>> index 6cd26dd3c134..33a0f5f742f6 100644
>> --- a/arch/loongarch/configs/loongson3_defconfig
>> +++ b/arch/loongarch/configs/loongson3_defconfig
>> @@ -63,6 +63,7 @@ CONFIG_EFI_ZBOOT=y
>> CONFIG_EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER=y
>> CONFIG_EFI_CAPSULE_LOADER=m
>> CONFIG_EFI_TEST=m
>> +CONFIG_JUMP_LABEL=y
>> CONFIG_MODULES=y
>> CONFIG_MODULE_FORCE_LOAD=y
>> CONFIG_MODULE_UNLOAD=y
>> diff --git a/arch/loongarch/include/asm/jump_label.h
>> b/arch/loongarch/include/asm/jump_label.h
>> new file mode 100644
>> index 000000000000..2f9fdec256c5
>> --- /dev/null
>> +++ b/arch/loongarch/include/asm/jump_label.h
>> @@ -0,0 +1,51 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (C) 2023 Loongson Technology Corporation Limited
>> + *
>> + * Based on arch/arm64/include/asm/jump_label.h
>> + */
>> +#ifndef __ASM_JUMP_LABEL_H
>> +#define __ASM_JUMP_LABEL_H
>> +
>> +#ifndef __ASSEMBLY__
>> +
>> +#include <linux/types.h>
>> +
>> +#define JUMP_LABEL_NOP_SIZE 4
>
> Saying LOONGARCH_INSN_SIZE here might be better for reducing redundancy,
> although that'll necessitate an extra include of <asm/inst.h>. Leaving
> the 4 alone won't cause much harm so I'm fine with either.
Using LOONGARCH_INSN_SIZE in v1, but causing build errors due to
inclusion of <asm/inst.h> [1].
So I removed the <asm/inst.h> include and used hardcoded 4.
[1]:
https://lore.kernel.org/loongarch/202305100412.gazWW71q-lkp@intel.com/T/#m0d8393aaf529aea0a4dcc5985469e698d63d66b3
>
>> +
>> +static __always_inline bool arch_static_branch(struct static_key *
>> const key,
>> + const bool branch)
>> +{
>> + asm_volatile_goto(
>> + "1: nop \n\t"
>> + " .pushsection __jump_table, \"aw\" \n\t"
>> + " .align 3 \n\t"
>> + " .long 1b - ., %l[l_yes] - . \n\t"
>> + " .quad %0 - . \n\t"
>> + " .popsection \n\t"
>> + : : "i"(&((char *)key)[branch]) : : l_yes);
>> +
>> + return false;
>> +l_yes:
>> + return true;
>> +}
>> +
>> +static __always_inline bool arch_static_branch_jump(struct static_key
>> * const key,
>> + const bool branch)
>> +{
>> + asm_volatile_goto(
>> + "1: b %l[l_yes] \n\t"
>> + " .pushsection __jump_table, \"aw\" \n\t"
>> + " .align 3 \n\t"
>> + " .long 1b - ., %l[l_yes] - . \n\t"
>> + " .quad %0 - . \n\t"
>> + " .popsection \n\t"
>> + : : "i"(&((char *)key)[branch]) : : l_yes);
>> +
>> + return false;
>> +l_yes:
>> + return true;
>> +}
>> +
>> +#endif /* __ASSEMBLY__ */
>> +#endif /* __ASM_JUMP_LABEL_H */
>> diff --git a/arch/loongarch/kernel/Makefile
>> b/arch/loongarch/kernel/Makefile
>> index 9a72d91cd104..64ea76f60e2c 100644
>> --- a/arch/loongarch/kernel/Makefile
>> +++ b/arch/loongarch/kernel/Makefile
>> @@ -54,4 +54,6 @@ obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
>> obj-$(CONFIG_KPROBES) += kprobes.o kprobes_trampoline.o
>> +obj-$(CONFIG_JUMP_LABEL) += jump_label.o
>> +
>> CPPFLAGS_vmlinux.lds := $(KBUILD_CFLAGS)
>> diff --git a/arch/loongarch/kernel/jump_label.c
>> b/arch/loongarch/kernel/jump_label.c
>> new file mode 100644
>> index 000000000000..b06245955f7a
>> --- /dev/null
>> +++ b/arch/loongarch/kernel/jump_label.c
>> @@ -0,0 +1,23 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2023 Loongson Technology Corporation Limited
>> + *
>> + * Based on arch/arm64/kernel/jump_label.c
>> + */
>> +#include <linux/jump_label.h>
>> +#include <linux/kernel.h>
>> +#include <asm/inst.h>
>> +
>> +void arch_jump_label_transform(struct jump_entry *entry,
>> + enum jump_label_type type)
>> +{
>> + void *addr = (void *)jump_entry_code(entry);
>> + u32 insn;
>> +
>> + if (type == JUMP_LABEL_JMP)
>
> Please use a switch for dealing with enum-typed values.
Because the current type only has JUMP_LABEL_NOP and JUMP_LABEL_JMP,
using if may be simpler than switch.
Thanks,
Youling.
>
>> + insn = larch_insn_gen_b(jump_entry_code(entry),
>> jump_entry_target(entry));
>> + else
>> + insn = larch_insn_gen_nop();
>> +
>> + larch_insn_patch_text(addr, insn);
>> +}
>
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