On Thu, Sep 04, 2025 at 10:00:52AM +0000, ChenMiao wrote:
> From: chenmiao <chenmiao.ku@xxxxxxxxx>
>
> Supported a complete jump_label implementation based on the ARM64 and
> RV64 version and add the CONFIG_JUMP_LABEL=y to the defconfig.
>
> Testing was conducted using a dedicated test module (jump-label-test,
> provided in the link below) with the following environment: Below is
> a brief usage and test report of this module. For detailed steps,
> please refer to the README in the provided link.
Maybe you can shorten to:
Testing was conducted using a dedicated test module jump-label-test,
provided in the link below. For detailed steps, please refer to the
README also at the provided link.
> Link: https://github.com/ChenMiaoi/GSoC-2025-Final-Report/tree/main/tests/jump-label-test
>
> Test Environment:
> - Hardware: QEMU emulated OR1K
> - Kernel Version: 6.17.0-rc3-dirty
> - Configs: CONFIG_MODULES=y,CONFIG_MODULE_UNLOAD=y
> - Toolchain: or1k-none-linux-musl-gcc 15.1.0
>
> Test Procedure:
> 1. Build and install modules (make modules_install)
> 2. Build the jump-label-test module
> 3. Boot kernel in QEMU
> 4. Transfer jump_label_test.ko via NFS
> 5. Load module and observe results
The procedure is in the readme, maybe its not needed here.
> Test Results:
> $ insmod jump_label_test.ko
> [ 32.590000] Jump label performance test module loaded
> [ 35.250000] Normal branch time: 1241327150 ns (124 ns per iteration)
> [ 35.250000] Jump label (false) time: 706422700 ns (70 ns per iteration)
> [ 35.250000] Jump label (true) time: 708913450 ns (70 ns per iteration)
> $ rmmod jump_label_test.ko
> [ 72.210000] Jump label test module unloaded
>
> The results show approximately 43% improvement in branch performance
> when using jump labels compared to traditional branches.
This is good.
> Link: https://lore.kernel.org/openrisc/aK3O6kOMqgDb6zZj@antec/T/#u
> Signed-off-by: chenmiao <chenmiao.ku@xxxxxxxxx>
>
> ---
> Changes in V4:
> - Add appropriate comments.
> - Added testing for jump_label
>
> Changes in V3:
> - Ensure the two defconfig using the make savedefconfig.
> - modify the __ASSEMBLY__ to __ASSEMBLER__, modify the
> __ASM_JUMP_LABEL_H to __ASM_OPENRISC_JUMP_LABEL_H and remove
> invalid comment.
>
> Changes in V2:
> - using the patch_insn_write(void *addr, u32 insn) not the
> const void *insn.
> - add new macro OPENRISC_INSN_NOP in insn-def.h to use.
>
> Signed-off-by: chenmiao <chenmiao.ku@xxxxxxxxx>
> ---
> .../core/jump-labels/arch-support.txt | 2 +-
> arch/openrisc/Kconfig | 2 +
> arch/openrisc/configs/or1ksim_defconfig | 1 +
> arch/openrisc/configs/virt_defconfig | 1 +
> arch/openrisc/include/asm/insn-def.h | 3 +
> arch/openrisc/include/asm/jump_label.h | 72 +++++++++++++++++++
> arch/openrisc/kernel/Makefile | 1 +
> arch/openrisc/kernel/jump_label.c | 52 ++++++++++++++
> arch/openrisc/kernel/setup.c | 2 +
> 9 files changed, 135 insertions(+), 1 deletion(-)
> create mode 100644 arch/openrisc/include/asm/jump_label.h
> create mode 100644 arch/openrisc/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 ccada815569f..683de7c15058 100644
> --- a/Documentation/features/core/jump-labels/arch-support.txt
> +++ b/Documentation/features/core/jump-labels/arch-support.txt
> @@ -17,7 +17,7 @@
> | microblaze: | TODO |
> | mips: | ok |
> | nios2: | TODO |
> - | openrisc: | TODO |
> + | openrisc: | ok |
> | parisc: | ok |
> | powerpc: | ok |
> | riscv: | ok |
> diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
> index b38fee299bc4..9156635dd264 100644
> --- a/arch/openrisc/Kconfig
> +++ b/arch/openrisc/Kconfig
> @@ -24,6 +24,8 @@ config OPENRISC
> select GENERIC_PCI_IOMAP
> select GENERIC_IOREMAP
> select GENERIC_CPU_DEVICES
> + select HAVE_ARCH_JUMP_LABEL
> + select HAVE_ARCH_JUMP_LABEL_RELATIVE
> select HAVE_PCI
> select HAVE_UID16
> select HAVE_PAGE_SIZE_8KB
> diff --git a/arch/openrisc/configs/or1ksim_defconfig b/arch/openrisc/configs/or1ksim_defconfig
> index 58e27d8fdb4e..769705ac24d5 100644
> --- a/arch/openrisc/configs/or1ksim_defconfig
> +++ b/arch/openrisc/configs/or1ksim_defconfig
> @@ -10,6 +10,7 @@ CONFIG_EXPERT=y
> # CONFIG_KALLSYMS is not set
> CONFIG_BUILTIN_DTB_NAME="or1ksim"
> CONFIG_HZ_100=y
> +CONFIG_JUMP_LABEL=y
> CONFIG_MODULES=y
> # CONFIG_BLOCK is not set
> CONFIG_SLUB_TINY=y
> diff --git a/arch/openrisc/configs/virt_defconfig b/arch/openrisc/configs/virt_defconfig
> index 8a581e932766..a93a3e1e4f87 100644
> --- a/arch/openrisc/configs/virt_defconfig
> +++ b/arch/openrisc/configs/virt_defconfig
> @@ -12,6 +12,7 @@ CONFIG_NR_CPUS=8
> CONFIG_SMP=y
> CONFIG_HZ_100=y
> # CONFIG_OPENRISC_NO_SPR_SR_DSX is not set
> +CONFIG_JUMP_LABEL=y
> # CONFIG_COMPAT_BRK is not set
> CONFIG_NET=y
> CONFIG_PACKET=y
> diff --git a/arch/openrisc/include/asm/insn-def.h b/arch/openrisc/include/asm/insn-def.h
> index e28a9a9604fc..1e0c028a5b95 100644
> --- a/arch/openrisc/include/asm/insn-def.h
> +++ b/arch/openrisc/include/asm/insn-def.h
> @@ -9,4 +9,7 @@
> /* or1k instructions are always 32 bits. */
> #define OPENRISC_INSN_SIZE 4
>
> +/* or1k nop instruction code */
> +#define OPENRISC_INSN_NOP 0x15000000U
> +
> #endif /* __ASM_OPENRISC_INSN_DEF_H */
> diff --git a/arch/openrisc/include/asm/jump_label.h b/arch/openrisc/include/asm/jump_label.h
> new file mode 100644
> index 000000000000..3ec0f4e19f9c
> --- /dev/null
> +++ b/arch/openrisc/include/asm/jump_label.h
> @@ -0,0 +1,72 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2025 Chen Miao
> + *
> + * Based on arch/arm/include/asm/jump_label.h
> + */
> +#ifndef __ASM_OPENRISC_JUMP_LABEL_H
> +#define __ASM_OPENRISC_JUMP_LABEL_H
> +
> +#ifndef __ASSEMBLER__
> +
> +#include <linux/types.h>
> +#include <asm/insn-def.h>
> +
> +#define HAVE_JUMP_LABEL_BATCH
> +
> +#define JUMP_LABEL_NOP_SIZE OPENRISC_INSN_SIZE
> +
> +/**
> + * JUMP_TABLE_ENTRY - Create a jump table entry
> + * @key: Jump key identifier (typically a symbol address)
> + * @label: Target label address
> + *
> + * This macro creates a jump table entry in the dedicated kernel section (__jump_table).
> + * Each entry contains the following information:
> + * Offset from current instruction to jump instruction (1b - .)
> + * Offset from current instruction to target label (label - .)
> + * Offset from current instruction to key identifier (key - .)
> + */
> +#define JUMP_TABLE_ENTRY(key, label) \
> + ".pushsection __jump_table, \"aw\" \n\t" \
> + ".align 4 \n\t" \
> + ".long 1b - ., " label " - . \n\t" \
> + ".long " key " - . \n\t" \
> + ".popsection \n\t"
> +
> +#define ARCH_STATIC_BRANCH_ASM(key, label) \
> + ".align 4 \n\t" \
> + "1: l.nop \n\t" \
> + " l.nop \n\t" \
> + JUMP_TABLE_ENTRY(key, label)
> +
> +static __always_inline bool arch_static_branch(struct static_key *const key,
> + const bool branch)
> +{
> + asm goto (ARCH_STATIC_BRANCH_ASM("%0", "%l[l_yes]")
> + ::"i"(&((char *)key)[branch])::l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +#define ARCH_STATIC_BRANCH_JUMP_ASM(key, label) \
> + ".align 4 \n\t" \
> + "1: l.j " label " \n\t" \
> + " l.nop \n\t" \
> + JUMP_TABLE_ENTRY(key, label)
> +
> +static __always_inline bool
> +arch_static_branch_jump(struct static_key *const key, const bool branch)
> +{
> + asm goto (ARCH_STATIC_BRANCH_JUMP_ASM("%0", "%l[l_yes]")
> + ::"i"(&((char *)key)[branch])::l_yes);
> +
> + return false;
> +l_yes:
> + return true;
> +}
> +
> +#endif /* __ASSEMBLER__ */
> +#endif /* __ASM_OPENRISC_JUMP_LABEL_H */
> diff --git a/arch/openrisc/kernel/Makefile b/arch/openrisc/kernel/Makefile
> index f0957ce16d6b..19e0eb94f2eb 100644
> --- a/arch/openrisc/kernel/Makefile
> +++ b/arch/openrisc/kernel/Makefile
> @@ -9,6 +9,7 @@ obj-y := head.o setup.o or32_ksyms.o process.o dma.o \
> traps.o time.o irq.o entry.o ptrace.o signal.o \
> sys_call_table.o unwinder.o cacheinfo.o
>
> +obj-$(CONFIG_JUMP_LABEL) += jump_label.o
> obj-$(CONFIG_SMP) += smp.o sync-timer.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
> obj-$(CONFIG_MODULES) += module.o
> diff --git a/arch/openrisc/kernel/jump_label.c b/arch/openrisc/kernel/jump_label.c
> new file mode 100644
> index 000000000000..071dacad885c
> --- /dev/null
> +++ b/arch/openrisc/kernel/jump_label.c
> @@ -0,0 +1,52 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2025 Chen Miao
> + *
> + * Based on arch/arm/kernel/jump_label.c
> + */
> +#include <linux/jump_label.h>
> +#include <linux/kernel.h>
> +#include <linux/memory.h>
> +#include <asm/bug.h>
> +#include <asm/cacheflush.h>
> +#include <asm/text-patching.h>
> +
> +bool arch_jump_label_transform_queue(struct jump_entry *entry,
> + enum jump_label_type type)
> +{
> + void *addr = (void *)jump_entry_code(entry);
> + u32 insn;
> +
> + if (type == JUMP_LABEL_JMP) {
> + long offset;
> +
> + offset = jump_entry_target(entry) - jump_entry_code(entry);
> + /*
> + * The actual maximum range of the l.j instruction's offset is -134,217,728
> + * ~ 134,217,724 (sign 26-bit imm).
> + * For the original jump range, we need to right-shift N by 2 to obtain the
> + * instruction's offset.
> + */
> + if (unlikely(offset < -134217728 || offset > 134217724)) {
> + WARN_ON_ONCE(true);
> + }
> + /* 26bit imm mask */
> + offset = (offset >> 2) & 0x03ffffff;
> +
> + insn = offset;
> + } else {
> + insn = OPENRISC_INSN_NOP;
> + }
> +
> + if (early_boot_irqs_disabled) {
> + copy_to_kernel_nofault(addr, &insn, sizeof(insn));
> + } else {
> + patch_insn_write(addr, insn);
> + }
> + return true;
> +}
> +
> +void arch_jump_label_transform_apply(void)
> +{
> + kick_all_cpus_sync();
> +}
> diff --git a/arch/openrisc/kernel/setup.c b/arch/openrisc/kernel/setup.c
> index a9fb9cc6779e..000a9cc10e6f 100644
> --- a/arch/openrisc/kernel/setup.c
> +++ b/arch/openrisc/kernel/setup.c
> @@ -249,6 +249,8 @@ void __init setup_arch(char **cmdline_p)
> initrd_below_start_ok = 1;
> }
> #endif
> + /* perform jump_table sorting before paging_init locks down read only memory */
> + jump_label_init();
>
> /* paging_init() sets up the MMU and marks all pages as reserved */
> paging_init();
> --
> 2.45.2
>
