From: chenmiao <[email protected]> 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.
Previously, __set_fix was marked with __init as it was only used during the EARLYCON stage. Now that TEXT_POKE mappings require post-init usage (e.g., FIX_TEXT_POKE0), keeping __init would cause runtime bugs whenset_fixmap accesses invalid memory. Thus, we remove the __init flag to ensure __set_fix remains valid beyond initialization. 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 <[email protected]> --- Changes in V4: - Fixed incorrect macro definitions and malformed comments. 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 <[email protected]> --- 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 | 79 +++++++++++++++++++++++ arch/openrisc/mm/init.c | 6 +- 7 files changed, 111 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..e28a9a9604fc --- /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_OPENRISC_INSN_DEF_H +#define __ASM_OPENRISC_INSN_DEF_H + +/* or1k instructions are always 32 bits. */ +#define OPENRISC_INSN_SIZE 4 + +#endif /* __ASM_OPENRISC_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..d19098dac0cc --- /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_OPENRISC_PATCHING_H +#define _ASM_OPENRISC_PATCHING_H + +#include <linux/types.h> + +int patch_insn_write(void *addr, u32 insn); + +#endif /* _ASM_OPENRISC_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..d186172beb33 --- /dev/null +++ b/arch/openrisc/kernel/patching.c @@ -0,0 +1,79 @@ +// 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. + */ +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..9382d9a0ec78 100644 --- a/arch/openrisc/mm/init.c +++ b/arch/openrisc/mm/init.c @@ -226,7 +226,11 @@ 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, +/* + * __set_fix must now support both EARLYCON and TEXT_POKE mappings, + * which are used at different stages of kernel execution. + */ +void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) { unsigned long address = __fix_to_virt(idx); -- 2.45.2
