On Thu, Aug 14, 2025 at 03:27:01AM +0000, ChenMiao wrote: > From: chenmiao <chenmiao...@gmail.com> > > We need a text patching mechanism to ensure that in the subsequent > implementation of jump_label, the code can be modified to the correct > location. Therefore, FIX_TEXT_POKE0 has been added as a mapping area. > > Among these changes, we implement patch_map and support the > patch_insn_write API for single instruction writing.
I think the description here could be improved a bit. Something like: Add text patching api's to use in subsequent jump_label implementation. We use a new fixmap FIX_TEXT_POKE0 entry to temporarily override MMU mappings to allow read only text pages to be written to. A new function patch_insn_write is exposed to allow single instruction patching. > Link: https://lore.kernel.org/openrisc/aJIC8o1WmVHol9RY@antec/T/#t > > Signed-off-by: chenmiao <chenmiao...@gmail.com> > > --- > Changes in V3: > - Removed the unimplemented and unsupported is_exit_text, added > comments for the set_fixmap modification explaining why __init was > removed, and added new comments for patch_insn_write. > > Changes in V2: > - We modify the patch_insn_write(void *addr, const void *insn) API to > patch_insn_write(void *addr, u32 insn), derectly support a single u32 > instruction write to map memory. > - Create a new file named insn-def.h to define the or1k insn macro > size and more define in the future. > > Signed-off-by: chenmiao <chenmiao...@gmail.com> > --- > arch/openrisc/include/asm/Kbuild | 1 - > arch/openrisc/include/asm/fixmap.h | 1 + > arch/openrisc/include/asm/insn-def.h | 12 ++++ > arch/openrisc/include/asm/text-patching.h | 13 ++++ > arch/openrisc/kernel/Makefile | 1 + > arch/openrisc/kernel/patching.c | 78 +++++++++++++++++++++++ > arch/openrisc/mm/init.c | 10 ++- > 7 files changed, 114 insertions(+), 2 deletions(-) > create mode 100644 arch/openrisc/include/asm/insn-def.h > create mode 100644 arch/openrisc/include/asm/text-patching.h > create mode 100644 arch/openrisc/kernel/patching.c > > diff --git a/arch/openrisc/include/asm/Kbuild > b/arch/openrisc/include/asm/Kbuild > index 2b1a6b00cdac..cef49d60d74c 100644 > --- a/arch/openrisc/include/asm/Kbuild > +++ b/arch/openrisc/include/asm/Kbuild > @@ -9,4 +9,3 @@ generic-y += spinlock.h > generic-y += qrwlock_types.h > generic-y += qrwlock.h > generic-y += user.h > -generic-y += text-patching.h > diff --git a/arch/openrisc/include/asm/fixmap.h > b/arch/openrisc/include/asm/fixmap.h > index aaa6a26a3e92..74000215064d 100644 > --- a/arch/openrisc/include/asm/fixmap.h > +++ b/arch/openrisc/include/asm/fixmap.h > @@ -28,6 +28,7 @@ > > enum fixed_addresses { > FIX_EARLYCON_MEM_BASE, > + FIX_TEXT_POKE0, > __end_of_fixed_addresses > }; > > diff --git a/arch/openrisc/include/asm/insn-def.h > b/arch/openrisc/include/asm/insn-def.h > new file mode 100644 > index 000000000000..dc8d16db1579 > --- /dev/null > +++ b/arch/openrisc/include/asm/insn-def.h > @@ -0,0 +1,12 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2025 Chen Miao > + */ > + > +#ifndef __ASM_INSN_DEF_H > +#define __ASM_INSN_DEF_H > + > +/* or1k instructions are always 32 bits. */ > +#define OPENRISC_INSN_SIZE 4 > + > +#endif /* __ASM_INSN_DEF_H */ > diff --git a/arch/openrisc/include/asm/text-patching.h > b/arch/openrisc/include/asm/text-patching.h > new file mode 100644 > index 000000000000..bffe828288c3 > --- /dev/null > +++ b/arch/openrisc/include/asm/text-patching.h > @@ -0,0 +1,13 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2025 Chen Miao > + */ > + > +#ifndef _ASM_PATCHING_H_ > +#define _ASM_PATCHING_H_ > The ifdef here and above a incosistent. Can you try to use a consistent convention to what is already used in openrisc? Mostly we use: __ASM_OPENRISC_*_H > +#include <linux/types.h> > + > +int patch_insn_write(void *addr, u32 insn); > + > +#endif /* _ASM_PATCHING_H_ */ > diff --git a/arch/openrisc/kernel/Makefile b/arch/openrisc/kernel/Makefile > index 58e6a1b525b7..f0957ce16d6b 100644 > --- a/arch/openrisc/kernel/Makefile > +++ b/arch/openrisc/kernel/Makefile > @@ -13,5 +13,6 @@ obj-$(CONFIG_SMP) += smp.o sync-timer.o > obj-$(CONFIG_STACKTRACE) += stacktrace.o > obj-$(CONFIG_MODULES) += module.o > obj-$(CONFIG_OF) += prom.o > +obj-y += patching.o > > clean: > diff --git a/arch/openrisc/kernel/patching.c b/arch/openrisc/kernel/patching.c > new file mode 100644 > index 000000000000..73ae449c6c4e > --- /dev/null > +++ b/arch/openrisc/kernel/patching.c > @@ -0,0 +1,78 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* Copyright (C) 2020 SiFive > + * Copyright (C) 2025 Chen Miao > + */ > + > +#include <linux/mm.h> > +#include <linux/kernel.h> > +#include <linux/spinlock.h> > +#include <linux/uaccess.h> > + > +#include <asm/insn-def.h> > +#include <asm/cacheflush.h> > +#include <asm/page.h> > +#include <asm/fixmap.h> > +#include <asm/text-patching.h> > +#include <asm/sections.h> > + > +static DEFINE_RAW_SPINLOCK(patch_lock); > + > +static __always_inline void *patch_map(void *addr, int fixmap) > +{ > + uintptr_t uaddr = (uintptr_t) addr; > + phys_addr_t phys; > + > + if (core_kernel_text(uaddr)) { > + phys = __pa_symbol(addr); > + } else { > + struct page *page = vmalloc_to_page(addr); > + BUG_ON(!page); > + phys = page_to_phys(page) + offset_in_page(addr); > + } > + > + return (void *)set_fixmap_offset(fixmap, phys); > +} > + > +static void patch_unmap(int fixmap) > +{ > + clear_fixmap(fixmap); > +} > + > +static int __patch_insn_write(void *addr, u32 insn) > +{ > + void *waddr = addr; > + unsigned long flags = 0; > + int ret; > + > + raw_spin_lock_irqsave(&patch_lock, flags); > + > + waddr = patch_map(addr, FIX_TEXT_POKE0); > + > + ret = copy_to_kernel_nofault(waddr, &insn, OPENRISC_INSN_SIZE); > + local_icache_range_inv((unsigned long)waddr, > + (unsigned long)waddr + OPENRISC_INSN_SIZE); > + > + patch_unmap(FIX_TEXT_POKE0); > + > + raw_spin_unlock_irqrestore(&patch_lock, flags); > + > + return ret; > +} > + > +/* patch_insn_write - Write a single instruction to a specified memory > location > + * This API provides a single-instruction patching, primarily used for > runtime > + * code modification. > + * By the way, the insn size must be 4 bytes. > + */ The commit style is a bit off. In the kernel multi line comments usually start with a lone '/*'. e.g. /* * patch_insn_write - Write ... * ... */ > +int patch_insn_write(void *addr, u32 insn) > +{ > + u32 *tp = addr; > + int ret; > + > + if ((uintptr_t) tp & 0x3) > + return -EINVAL; > + > + ret = __patch_insn_write(tp, insn); > + > + return ret; > +} > diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c > index e4904ca6f0a0..ac256c3d9c7a 100644 > --- a/arch/openrisc/mm/init.c > +++ b/arch/openrisc/mm/init.c > @@ -226,7 +226,15 @@ static int __init map_page(unsigned long va, phys_addr_t > pa, pgprot_t prot) > return 0; > } > > -void __init __set_fixmap(enum fixed_addresses idx, > +/* Removing __init is necessary. Before supporting FIX_TEXT_POKE0, > + * __init here indicates that it is valid during the initialization phase > + * and is used for FIX_EARLYCON_MEM_BASE. However, attempting to support > + * FIX_TEXT_POKE0 would introduce a bug. FIX_TEXT_POKE0 is used after the > + * initialization phase, so __init would cause the function to become > invalid. > + * At that point, using set_fixmap would lead to accessing dirty data, > + * which is invalid. > + */ The comment about __init does not belong in the source here. Perhaps your comment could mention hwo the __set_fixmap function is used for both EARLYCON and TEXT_POKE mappings. Also, the comment style need to be updated. > +void __set_fixmap(enum fixed_addresses idx, > phys_addr_t phys, pgprot_t prot) > { > unsigned long address = __fix_to_virt(idx); > -- > 2.45.2 >
