1 files changed, 128 insertions, 0 deletions
diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
new file mode 100644
index 000000000..e9e828b6b
--- /dev/null
+++ b/arch/arm/kernel/patch.c
@@ -0,0 +1,128 @@
+// 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;
+};
+
+#ifdef CONFIG_MMU
+static DEFINE_RAW_SPINLOCK(patch_lock);
+
+static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
+{
+	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)
+		raw_spin_lock_irqsave(&patch_lock, *flags);
+
+	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)
+{
+	clear_fixmap(fixmap);
+
+	if (flags)
+		raw_spin_unlock_irqrestore(&patch_lock, *flags);
+}
+#else
+static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
+{
+	return addr;
+}
+static void __kprobes patch_unmap(int fixmap, unsigned long *flags) { }
+#endif
+
+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);
+
+	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);
+	}
+
+	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);
+}