Message-ID: <aJcI1pr9RMTvfcTj@antec>
Date: Sat, 9 Aug 2025 09:37:42 +0100
From: Stafford Horne <shorne@...il.com>
To: ChenMiao <chenmiao.ku@...il.com>
Cc: Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux OpenRISC <linux-openrisc@...r.kernel.org>,
	Jonathan Corbet <corbet@....net>, Jonas Bonn <jonas@...thpole.se>,
	Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Jason Baron <jbaron@...mai.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Sahil Siddiq <sahilcdq0@...il.com>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	Johannes Berg <johannes@...solutions.net>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 2/2] openrisc: Add jump label support

On Wed, Aug 06, 2025 at 02:05:04AM +0000, ChenMiao wrote:
> From: chenmiao <chenmiao.ku@...il.com>
> 
> Implemented the full functionality of jump_label, of course,
> with text patching supported by just one API.
> 
> By the way, add new macro OPENRISC_INSN_NOP in insn-def.h to use.
> 
> - V2: using the patch_insn_write(void *addr, u32 insn) not the
> const void *insn.
> 
> Link: https://lore.kernel.org/openrisc/aJIC8o1WmVHol9RY@antec/T/#t
> 
> Signed-off-by: chenmiao <chenmiao.ku@...il.com>
> ---
>  .../core/jump-labels/arch-support.txt         |  2 +-
>  arch/openrisc/Kconfig                         |  2 +
>  arch/openrisc/configs/or1ksim_defconfig       | 19 ++----
>  arch/openrisc/configs/virt_defconfig          |  1 +
>  arch/openrisc/include/asm/insn-def.h          |  3 +
>  arch/openrisc/include/asm/jump_label.h        | 68 +++++++++++++++++++
>  arch/openrisc/kernel/Makefile                 |  1 +
>  arch/openrisc/kernel/jump_label.c             | 53 +++++++++++++++
>  arch/openrisc/kernel/setup.c                  |  2 +
>  9 files changed, 138 insertions(+), 13 deletions(-)
>  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 59fe33cefba2..769705ac24d5 100644
> --- a/arch/openrisc/configs/or1ksim_defconfig
> +++ b/arch/openrisc/configs/or1ksim_defconfig
> @@ -3,26 +3,23 @@ CONFIG_LOG_BUF_SHIFT=14
>  CONFIG_BLK_DEV_INITRD=y
>  # CONFIG_RD_GZIP is not set
>  CONFIG_EXPERT=y
> -# CONFIG_KALLSYMS is not set
>  # CONFIG_EPOLL is not set
>  # CONFIG_TIMERFD is not set
>  # CONFIG_EVENTFD is not set
>  # CONFIG_AIO is not set
> -# CONFIG_VM_EVENT_COUNTERS is not set
> -# CONFIG_COMPAT_BRK is not set
> -CONFIG_SLUB=y
> -CONFIG_SLUB_TINY=y
> -CONFIG_MODULES=y
> -# CONFIG_BLOCK is not set
> +# 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
> +# CONFIG_COMPAT_BRK is not set
> +# CONFIG_VM_EVENT_COUNTERS is not set
>  CONFIG_NET=y
>  CONFIG_PACKET=y
>  CONFIG_UNIX=y
>  CONFIG_INET=y
> -# CONFIG_INET_XFRM_MODE_TRANSPORT is not set
> -# CONFIG_INET_XFRM_MODE_TUNNEL is not set
> -# CONFIG_INET_XFRM_MODE_BEET is not set
>  # CONFIG_INET_DIAG is not set
>  CONFIG_TCP_CONG_ADVANCED=y
>  # CONFIG_TCP_CONG_BIC is not set
> @@ -35,7 +32,6 @@ CONFIG_DEVTMPFS=y
>  CONFIG_DEVTMPFS_MOUNT=y
>  # CONFIG_PREVENT_FIRMWARE_BUILD is not set
>  # CONFIG_FW_LOADER is not set
> -CONFIG_PROC_DEVICETREE=y
>  CONFIG_NETDEVICES=y
>  CONFIG_ETHOC=y
>  CONFIG_MICREL_PHY=y
> @@ -53,4 +49,3 @@ CONFIG_SERIAL_OF_PLATFORM=y
>  # CONFIG_DNOTIFY is not set
>  CONFIG_TMPFS=y
>  CONFIG_NFS_FS=y
> -# CONFIG_ENABLE_MUST_CHECK is not set
> diff --git a/arch/openrisc/configs/virt_defconfig b/arch/openrisc/configs/virt_defconfig
> index c1b69166c500..4a80c5794877 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

The defconfig updates look quite different.  Did you use savedefconfig for both
of them?

> diff --git a/arch/openrisc/include/asm/insn-def.h b/arch/openrisc/include/asm/insn-def.h
> index dc8d16db1579..2ccdbb37c27c 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

I see you use this header again here, note that in
arch/openrisc/kernel/signal.c.  We write instructions to memory too for the
sigreturn trampoline.

Also, you use OPENRISC_INSN_SIZE below.  Could you move this header to this
patch completely?  I don't think its needed in the patching patch.

>  #endif /* __ASM_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..03afca9c3a1f
> --- /dev/null
> +++ b/arch/openrisc/include/asm/jump_label.h
> @@ -0,0 +1,68 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2025 Chen Miao
> + *
> + * Based on arch/arm/include/asm/jump_label.h
> + */
> +#ifndef __ASM_JUMP_LABEL_H
> +#define __ASM_JUMP_LABEL_H

Can this be __ASM_OPENRISC_JUMP_LABEL_H?

> +#ifndef __ASSEMBLY__

Note upstream this is now __ASSEMBLER__.

> +#include <linux/types.h>
> +#include <asm/insn-def.h>
> +
> +#define HAVE_JUMP_LABEL_BATCH
> +
> +#define JUMP_LABEL_NOP_SIZE OPENRISC_INSN_SIZE
> +
> +/*
> + * should aligned 4
> + * for jump_label relative
> + * entry.code   = nop.addr - . -> return false
> + * entry.target = l_yes - .    -> return true
> + * entry.key	= 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 /* __ASSEMBLY__ */
> +#endif /* __ASM_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..ce259ba30258
> --- /dev/null
> +++ b/arch/openrisc/kernel/jump_label.c
> @@ -0,0 +1,53 @@
> +// 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)
> +{
> +	// flush

Could you use the /* */ comment style?  Is this really flushing?

> +	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
> 

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