[PATCH RFC 08/17] arm64: text replication: add node text patching

[Russell King (Oracle)]

Add support for text patching on our replicated texts.

Signed-off-by: Russell King (Oracle) <rmk+kernel at armlinux.org.uk>
---
 arch/arm64/include/asm/ktext.h  | 12 +++++++
 arch/arm64/kernel/alternative.c |  2 ++
 arch/arm64/kernel/patching.c    |  7 +++-
 arch/arm64/mm/ktext.c           | 58 +++++++++++++++++++++++++++++++++
 4 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/ktext.h b/arch/arm64/include/asm/ktext.h
index 1a5f7452a3bf..289e11289c06 100644
--- a/arch/arm64/include/asm/ktext.h
+++ b/arch/arm64/include/asm/ktext.h
@@ -5,9 +5,13 @@
 #ifndef ASM_KTEXT_H
 #define ASM_KTEXT_H
 
+#include <linux/kprobes.h>
+
 #ifdef CONFIG_REPLICATE_KTEXT
 
 void ktext_replication_init(void);
+void __kprobes ktext_replication_patch(u32 *tp,  __le32 insn);
+void ktext_replication_patch_alternative(__le32 *src, int nr_inst);
 
 #else
 
@@ -15,6 +19,14 @@ static inline void ktext_replication_init(void)
 {
 }
 
+static inline void __kprobes ktext_replication_patch(u32 *tp,  __le32 insn)
+{
+}
+
+static inline void ktext_replication_patch_alternative(__le32 *src, int nr_inst)
+{
+}
+
 #endif
 
 #endif
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index df9a73458a85..6a897d1dda76 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -15,6 +15,7 @@
 #include <asm/alternative.h>
 #include <asm/cpufeature.h>
 #include <asm/insn.h>
+#include <asm/ktext.h>
 #include <asm/module.h>
 #include <asm/sections.h>
 #include <asm/vdso.h>
@@ -174,6 +175,7 @@ static void __apply_alternatives(const struct alt_region *region,
 		alt_cb(alt, origptr, updptr, nr_inst);
 
 		if (!is_module) {
+			ktext_replication_patch_alternative(updptr, nr_inst);
 			clean_dcache_range_nopatch((u64)origptr,
 						   (u64)(origptr + nr_inst));
 		}
diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c
index b4835f6d594b..627fff6ddda2 100644
--- a/arch/arm64/kernel/patching.c
+++ b/arch/arm64/kernel/patching.c
@@ -10,6 +10,7 @@
 #include <asm/fixmap.h>
 #include <asm/insn.h>
 #include <asm/kprobes.h>
+#include <asm/ktext.h>
 #include <asm/patching.h>
 #include <asm/sections.h>
 
@@ -115,9 +116,13 @@ int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
 		return -EINVAL;
 
 	ret = aarch64_insn_write(tp, insn);
-	if (ret == 0)
+	if (ret == 0) {
+		/* Also patch the other nodes */
+		ktext_replication_patch(tp, cpu_to_le32(insn));
+
 		caches_clean_inval_pou((uintptr_t)tp,
 				     (uintptr_t)tp + AARCH64_INSN_SIZE);
+	}
 
 	return ret;
 }
diff --git a/arch/arm64/mm/ktext.c b/arch/arm64/mm/ktext.c
index 4c803b89fcfe..80120b5fd29f 100644
--- a/arch/arm64/mm/ktext.c
+++ b/arch/arm64/mm/ktext.c
@@ -3,8 +3,10 @@
  * Copyright (C) 2022, Oracle and/or its affiliates.
  */
 
+#include <linux/kallsyms.h>
 #include <linux/kernel.h>
 #include <linux/memblock.h>
+#include <linux/mm.h>
 #include <linux/numa.h>
 #include <linux/pgtable.h>
 #include <linux/string.h>
@@ -15,6 +17,62 @@
 
 static void *kernel_texts[MAX_NUMNODES];
 
+void __kprobes ktext_replication_patch(u32 *tp, __le32 insn)
+{
+	unsigned long offset;
+	int nid, this_nid;
+	__le32 *p;
+
+	if (!is_kernel_text((unsigned long)tp))
+		return;
+
+	offset = (unsigned long)tp - (unsigned long)_stext;
+
+	this_nid = numa_node_id();
+	if (this_nid) {
+		/* The cache maintenance by aarch64_insn_patch_text_nosync()
+		 * will occur on this node. We need it to occur on node 0.
+		 */
+		p = (void *)lm_alias(_stext) + offset;
+		caches_clean_inval_pou((u64)p, (u64)p + AARCH64_INSN_SIZE);
+	}
+
+	for_each_node(nid) {
+		if (!kernel_texts[nid])
+			continue;
+
+		p = kernel_texts[nid] + offset;
+		WRITE_ONCE(*p, insn);
+		caches_clean_inval_pou((u64)p, (u64)p + AARCH64_INSN_SIZE);
+	}
+}
+
+/* Copy the patched alternative from the node0 image to the other
+ * modes. src is the node 0 linear-mapping address.
+ */
+void ktext_replication_patch_alternative(__le32 *src, int nr_inst)
+{
+	unsigned long offset;
+	size_t size;
+	int nid;
+	__le32 *p;
+
+	offset = (unsigned long)src - (unsigned long)lm_alias(_stext);
+	if (WARN_ON_ONCE(offset >= _etext - _stext))
+		return;
+
+	size = AARCH64_INSN_SIZE * nr_inst;
+
+	for_each_node(nid) {
+		if (!kernel_texts[nid])
+			continue;
+
+		p = kernel_texts[nid] + offset;
+		memcpy(p, src, size);
+		clean_dcache_range_nopatch((u64)p, (u64)p + size);
+	}
+}
+
 /* Allocate memory for the replicated kernel texts. */
 void __init ktext_replication_init(void)
 {
-- 
2.30.2