v4.19.13 snapshot.
diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
new file mode 100644
index 0000000..a50dc00
--- /dev/null
+++ b/arch/arm/kernel/patch.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/kprobes.h>
+#include <linux/mm.h>
+#include <linux/stop_machine.h>
+
+#include <asm/cacheflush.h>
+#include <asm/fixmap.h>
+#include <asm/smp_plat.h>
+#include <asm/opcodes.h>
+#include <asm/patch.h>
+
+struct patch {
+ void *addr;
+ unsigned int insn;
+};
+
+static DEFINE_SPINLOCK(patch_lock);
+
+static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
+ __acquires(&patch_lock)
+{
+ unsigned int uintaddr = (uintptr_t) addr;
+ bool module = !core_kernel_text(uintaddr);
+ struct page *page;
+
+ if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+ page = vmalloc_to_page(addr);
+ else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
+ page = virt_to_page(addr);
+ else
+ return addr;
+
+ if (flags)
+ spin_lock_irqsave(&patch_lock, *flags);
+ else
+ __acquire(&patch_lock);
+
+ set_fixmap(fixmap, page_to_phys(page));
+
+ return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
+}
+
+static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
+ __releases(&patch_lock)
+{
+ clear_fixmap(fixmap);
+
+ if (flags)
+ spin_unlock_irqrestore(&patch_lock, *flags);
+ else
+ __release(&patch_lock);
+}
+
+void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
+{
+ bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
+ unsigned int uintaddr = (uintptr_t) addr;
+ bool twopage = false;
+ unsigned long flags;
+ void *waddr = addr;
+ int size;
+
+ if (remap)
+ waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
+ else
+ __acquire(&patch_lock);
+
+ if (thumb2 && __opcode_is_thumb16(insn)) {
+ *(u16 *)waddr = __opcode_to_mem_thumb16(insn);
+ size = sizeof(u16);
+ } else if (thumb2 && (uintaddr & 2)) {
+ u16 first = __opcode_thumb32_first(insn);
+ u16 second = __opcode_thumb32_second(insn);
+ u16 *addrh0 = waddr;
+ u16 *addrh1 = waddr + 2;
+
+ twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2;
+ if (twopage && remap)
+ addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL);
+
+ *addrh0 = __opcode_to_mem_thumb16(first);
+ *addrh1 = __opcode_to_mem_thumb16(second);
+
+ if (twopage && addrh1 != addr + 2) {
+ flush_kernel_vmap_range(addrh1, 2);
+ patch_unmap(FIX_TEXT_POKE1, NULL);
+ }
+
+ size = sizeof(u32);
+ } else {
+ if (thumb2)
+ insn = __opcode_to_mem_thumb32(insn);
+ else
+ insn = __opcode_to_mem_arm(insn);
+
+ *(u32 *)waddr = insn;
+ size = sizeof(u32);
+ }
+
+ if (waddr != addr) {
+ flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
+ patch_unmap(FIX_TEXT_POKE0, &flags);
+ } else
+ __release(&patch_lock);
+
+ flush_icache_range((uintptr_t)(addr),
+ (uintptr_t)(addr) + size);
+}
+
+static int __kprobes patch_text_stop_machine(void *data)
+{
+ struct patch *patch = data;
+
+ __patch_text(patch->addr, patch->insn);
+
+ return 0;
+}
+
+void __kprobes patch_text(void *addr, unsigned int insn)
+{
+ struct patch patch = {
+ .addr = addr,
+ .insn = insn,
+ };
+
+ stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
+}