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@xxxxxxxxxxxxxx>
---
arch/parisc/include/asm/patch.h | 7 +++
arch/parisc/kernel/Makefile | 3 +-
arch/parisc/kernel/patch.c | 78 +++++++++++++++++++++++++++++++++
3 files changed, 87 insertions(+), 1 deletion(-)
create mode 100644 arch/parisc/include/asm/patch.h
create mode 100644 arch/parisc/kernel/patch.c
diff --git a/arch/parisc/include/asm/patch.h b/arch/parisc/include/asm/patch.h
new file mode 100644
index 000000000000..24ceb84519e4
--- /dev/null
+++ b/arch/parisc/include/asm/patch.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PARISC_KERNEL_PATCH_H
+#define _PARISC_KERNEL_PATCH_H
+
+void patch_text(void *addr, unsigned int insn);
+
+#endif
diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index 8e5f1ab65c68..d29bbd1a73b2 100644
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -9,7 +9,8 @@ obj-y := cache.o pacache.o setup.o pdt.o traps.o time.o irq.o \
pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \
ptrace.o hardware.o inventory.o drivers.o alternative.o \
signal.o hpmc.o real2.o parisc_ksyms.o unaligned.o \
- process.o processor.o pdc_cons.o pdc_chassis.o unwind.o
+ process.o processor.o pdc_cons.o pdc_chassis.o unwind.o \
+ patch.o
ifdef CONFIG_FUNCTION_TRACER
# Do not profile debug and lowlevel utilities
diff --git a/arch/parisc/kernel/patch.c b/arch/parisc/kernel/patch.c
new file mode 100644
index 000000000000..4a3bff87b177
--- /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@xxxxxxxxxxxxxx>
+ */
+
+#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 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;
+
+ 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);
+}
--
2.20.1
