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Message-ID: <20250904100109.688033-2-chenmiao.ku@gmail.com>
Date: Thu, 4 Sep 2025 10:00:49 +0000
From: ChenMiao <chenmiao.ku@...il.com>
To: Linux Kernel <linux-kernel@...r.kernel.org>,
Linux OpenRISC <linux-openrisc@...r.kernel.org>
Cc: chenmiao <chenmiao.ku@...il.com>,
Jonas Bonn <jonas@...thpole.se>,
Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
Stafford Horne <shorne@...il.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"Mike Rapoport (Microsoft)" <rppt@...nel.org>,
Luis Chamberlain <mcgrof@...nel.org>,
Johannes Berg <johannes@...solutions.net>,
Nicolas Schier <nicolas.schier@...ux.dev>,
Sahil Siddiq <sahilcdq0@...il.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [PATCH v4 1/4] openrisc: Add text patching API support
From: chenmiao <chenmiao.ku@...il.com>
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 <chenmiao.ku@...il.com>
---
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 <chenmiao.ku@...il.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 | 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
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