parisc: add parisc code patching

Instead of re-mapping the whole kernel text with RWX rights
add a patch_text() which can be used to replace instructions
in the kernel .text section. Based on the ARM implementation.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 78 insertions, 0 deletions

diff --git a/arch/parisc/kernel/patch.c b/arch/parisc/kernel/patch.c
new file mode 100644
index 000000000000..8c5ee684cb16
--- /dev/null
+++ b/arch/parisc/kernel/patch.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+ /*
+  * functions to patch RO kernel text during runtime
+  *
+  * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+  */
+
+#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/patch.h>
+
+struct patch {
+	void *addr;
+	unsigned int insn;
+};
+
+static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
+{
+	unsigned long 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;
+
+	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);
+}
+
+void __kprobes __patch_text(void *addr, unsigned int insn)
+{
+	unsigned long flags;
+	void *waddr = addr;
+	int size;
+
+	waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
+	*(u32 *)waddr = insn;
+	size = sizeof(u32);
+	flush_kernel_vmap_range(waddr, 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);
+}