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From:   =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@gmail.com>
Date:   Thu, 9 Jul 2020 08:23:48 +0200
Message-ID: <CAJ+HfNiQgjW+GE4RLy3KufxyQm=6d34SPiUjvYWA3RukVX9URw@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] riscv: Add jump-label implementation
To:     Emil Renner Berthing <kernel@esmil.dk>
Cc:     linux-riscv <linux-riscv@lists.infradead.org>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, 8 Jul 2020 at 23:10, Emil Renner Berthing <kernel@esmil.dk> wrote:
>
> Add jump-label implementation based on the ARM64 version
> and add CONFIG_JUMP_LABEL=3Dy to the defconfigs.
>
> Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
> Reviewed-by: Bj=C3=B6rn T=C3=B6pel <bjorn.topel@gmail.com>

Tested-by: Bj=C3=B6rn T=C3=B6pel <bjorn.topel@gmail.com>

> ---
>
> Tested on the HiFive Unleashed board.
>
> Changes since v1:
> - WARN and give up gracefully if the jump offset cannot be
>   represented in a JAL instruction.
> - Add missing braces.
> - Add CONFIG_JUMP_LABEL=3Dy to defconfigs.
>
> All suggested by Bj=C3=B6rn T=C3=B6pel.
>
> Changes since RFC:
> - Use RISCV_PTR and RISCV_LGPTR macros to match struct jump_table
>   also in 32bit kernels.
> - Remove unneeded branch ? 1 : 0, thanks Bj=C3=B6rn
> - Fix \n\n instead of \n\t mistake
>
>  .../core/jump-labels/arch-support.txt         |  2 +-
>  arch/riscv/Kconfig                            |  2 +
>  arch/riscv/configs/defconfig                  |  1 +
>  arch/riscv/configs/nommu_k210_defconfig       |  1 +
>  arch/riscv/configs/nommu_virt_defconfig       |  1 +
>  arch/riscv/configs/rv32_defconfig             |  1 +
>  arch/riscv/include/asm/jump_label.h           | 59 +++++++++++++++++++
>  arch/riscv/kernel/Makefile                    |  2 +
>  arch/riscv/kernel/jump_label.c                | 49 +++++++++++++++
>  9 files changed, 117 insertions(+), 1 deletion(-)
>  create mode 100644 arch/riscv/include/asm/jump_label.h
>  create mode 100644 arch/riscv/kernel/jump_label.c
>
> diff --git a/Documentation/features/core/jump-labels/arch-support.txt b/D=
ocumentation/features/core/jump-labels/arch-support.txt
> index 632a1c7aefa2..760243d18ed7 100644
> --- a/Documentation/features/core/jump-labels/arch-support.txt
> +++ b/Documentation/features/core/jump-labels/arch-support.txt
> @@ -23,7 +23,7 @@
>      |    openrisc: | TODO |
>      |      parisc: |  ok  |
>      |     powerpc: |  ok  |
> -    |       riscv: | TODO |
> +    |       riscv: |  ok  |
>      |        s390: |  ok  |
>      |          sh: | TODO |
>      |       sparc: |  ok  |
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index fd639937e251..d2f5c53fdc19 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -46,6 +46,8 @@ config RISCV
>         select GENERIC_TIME_VSYSCALL if MMU && 64BIT
>         select HANDLE_DOMAIN_IRQ
>         select HAVE_ARCH_AUDITSYSCALL
> +       select HAVE_ARCH_JUMP_LABEL
> +       select HAVE_ARCH_JUMP_LABEL_RELATIVE
>         select HAVE_ARCH_KASAN if MMU && 64BIT
>         select HAVE_ARCH_KGDB
>         select HAVE_ARCH_KGDB_QXFER_PKT
> diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
> index 4da4886246a4..d58c93efb603 100644
> --- a/arch/riscv/configs/defconfig
> +++ b/arch/riscv/configs/defconfig
> @@ -17,6 +17,7 @@ CONFIG_BPF_SYSCALL=3Dy
>  CONFIG_SOC_SIFIVE=3Dy
>  CONFIG_SOC_VIRT=3Dy
>  CONFIG_SMP=3Dy
> +CONFIG_JUMP_LABEL=3Dy
>  CONFIG_MODULES=3Dy
>  CONFIG_MODULE_UNLOAD=3Dy
>  CONFIG_NET=3Dy
> diff --git a/arch/riscv/configs/nommu_k210_defconfig b/arch/riscv/configs=
/nommu_k210_defconfig
> index b48138e329ea..cd1df62b13c7 100644
> --- a/arch/riscv/configs/nommu_k210_defconfig
> +++ b/arch/riscv/configs/nommu_k210_defconfig
> @@ -33,6 +33,7 @@ CONFIG_SMP=3Dy
>  CONFIG_NR_CPUS=3D2
>  CONFIG_CMDLINE=3D"earlycon console=3DttySIF0"
>  CONFIG_CMDLINE_FORCE=3Dy
> +CONFIG_JUMP_LABEL=3Dy
>  # CONFIG_BLOCK is not set
>  CONFIG_BINFMT_FLAT=3Dy
>  # CONFIG_COREDUMP is not set
> diff --git a/arch/riscv/configs/nommu_virt_defconfig b/arch/riscv/configs=
/nommu_virt_defconfig
> index cf74e179bf90..f27596e9663e 100644
> --- a/arch/riscv/configs/nommu_virt_defconfig
> +++ b/arch/riscv/configs/nommu_virt_defconfig
> @@ -30,6 +30,7 @@ CONFIG_MAXPHYSMEM_2GB=3Dy
>  CONFIG_SMP=3Dy
>  CONFIG_CMDLINE=3D"root=3D/dev/vda rw earlycon=3Duart8250,mmio,0x10000000=
,115200n8 console=3DttyS0"
>  CONFIG_CMDLINE_FORCE=3Dy
> +CONFIG_JUMP_LABEL=3Dy
>  # CONFIG_BLK_DEV_BSG is not set
>  CONFIG_PARTITION_ADVANCED=3Dy
>  # CONFIG_MSDOS_PARTITION is not set
> diff --git a/arch/riscv/configs/rv32_defconfig b/arch/riscv/configs/rv32_=
defconfig
> index 05bbf5240569..3a55f0e00d6c 100644
> --- a/arch/riscv/configs/rv32_defconfig
> +++ b/arch/riscv/configs/rv32_defconfig
> @@ -17,6 +17,7 @@ CONFIG_BPF_SYSCALL=3Dy
>  CONFIG_SOC_VIRT=3Dy
>  CONFIG_ARCH_RV32I=3Dy
>  CONFIG_SMP=3Dy
> +CONFIG_JUMP_LABEL=3Dy
>  CONFIG_MODULES=3Dy
>  CONFIG_MODULE_UNLOAD=3Dy
>  CONFIG_NET=3Dy
> diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm=
/jump_label.h
> new file mode 100644
> index 000000000000..d5fb342bfccf
> --- /dev/null
> +++ b/arch/riscv/include/asm/jump_label.h
> @@ -0,0 +1,59 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020 Emil Renner Berthing
> + *
> + * 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
> +
> +static __always_inline bool arch_static_branch(struct static_key *key,
> +                                              bool branch)
> +{
> +       asm_volatile_goto(
> +               "       .option push                            \n\t"
> +               "       .option norelax                         \n\t"
> +               "       .option norvc                           \n\t"
> +               "1:     nop                                     \n\t"
> +               "       .option pop                             \n\t"
> +               "       .pushsection    __jump_table, \"aw\"    \n\t"
> +               "       .align          " RISCV_LGPTR "         \n\t"
> +               "       .long           1b - ., %l[label] - .   \n\t"
> +               "       " RISCV_PTR "   %0 - .                  \n\t"
> +               "       .popsection                             \n\t"
> +               :  :  "i"(&((char *)key)[branch]) :  : label);
> +
> +       return false;
> +label:
> +       return true;
> +}
> +
> +static __always_inline bool arch_static_branch_jump(struct static_key *k=
ey,
> +                                                   bool branch)
> +{
> +       asm_volatile_goto(
> +               "       .option push                            \n\t"
> +               "       .option norelax                         \n\t"
> +               "       .option norvc                           \n\t"
> +               "1:     jal             zero, %l[label]         \n\t"
> +               "       .option pop                             \n\t"
> +               "       .pushsection    __jump_table, \"aw\"    \n\t"
> +               "       .align          " RISCV_LGPTR "         \n\t"
> +               "       .long           1b - ., %l[label] - .   \n\t"
> +               "       " RISCV_PTR "   %0 - .                  \n\t"
> +               "       .popsection                             \n\t"
> +               :  :  "i"(&((char *)key)[branch]) :  : label);
> +
> +       return false;
> +label:
> +       return true;
> +}
> +
> +#endif  /* __ASSEMBLY__ */
> +#endif /* __ASM_JUMP_LABEL_H */
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index b355cf485671..a5287ab9f7f2 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -53,4 +53,6 @@ endif
>  obj-$(CONFIG_HOTPLUG_CPU)      +=3D cpu-hotplug.o
>  obj-$(CONFIG_KGDB)             +=3D kgdb.o
>
> +obj-$(CONFIG_JUMP_LABEL)       +=3D jump_label.o
> +
>  clean:
> diff --git a/arch/riscv/kernel/jump_label.c b/arch/riscv/kernel/jump_labe=
l.c
> new file mode 100644
> index 000000000000..1bab1abc1aa5
> --- /dev/null
> +++ b/arch/riscv/kernel/jump_label.c
> @@ -0,0 +1,49 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2020 Emil Renner Berthing
> + *
> + * Based on arch/arm64/kernel/jump_label.c
> + */
> +#include <linux/kernel.h>
> +#include <linux/jump_label.h>
> +#include <asm/bug.h>
> +#include <asm/patch.h>
> +
> +#define RISCV_INSN_NOP 0x00000013U
> +#define RISCV_INSN_JAL 0x0000006fU
> +
> +void arch_jump_label_transform(struct jump_entry *entry,
> +                              enum jump_label_type type)
> +{
> +       void *addr =3D (void *)jump_entry_code(entry);
> +       u32 insn;
> +
> +       if (type =3D=3D JUMP_LABEL_JMP) {
> +               long offset =3D jump_entry_target(entry) - jump_entry_cod=
e(entry);
> +
> +               if (WARN_ON(offset & 1 || offset < -524288 || offset >=3D=
 524288))
> +                       return;
> +
> +               insn =3D RISCV_INSN_JAL |
> +                       (((u32)offset & GENMASK(19, 12)) << (12 - 12)) |
> +                       (((u32)offset & GENMASK(11, 11)) << (20 - 11)) |
> +                       (((u32)offset & GENMASK(10,  1)) << (21 -  1)) |
> +                       (((u32)offset & GENMASK(20, 20)) << (31 - 20));
> +       } else {
> +               insn =3D RISCV_INSN_NOP;
> +       }
> +
> +       patch_text_nosync(addr, &insn, sizeof(insn));
> +}
> +
> +void arch_jump_label_transform_static(struct jump_entry *entry,
> +                                     enum jump_label_type type)
> +{
> +       /*
> +        * We use the same instructions in the arch_static_branch and
> +        * arch_static_branch_jump inline functions, so there's no
> +        * need to patch them up here.
> +        * The core will call arch_jump_label_transform  when those
> +        * instructions need to be replaced.
> +        */
> +}
> --
> 2.27.0
>