parisc: Add KFENCE support

Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/Kconfig

@@ -48,6 +48,7 @@ config PARISC
 	select HAVE_ARCH_HASH
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_JUMP_LABEL_RELATIVE
+	select HAVE_ARCH_KFENCE
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_REGS_AND_STACK_ACCESS_API
@@ -254,11 +255,11 @@ config PARISC_PAGE_SIZE_4KB
 
 config PARISC_PAGE_SIZE_16KB
 	bool "16KB"
-	depends on PA8X00 && BROKEN
+	depends on PA8X00 && BROKEN && !KFENCE
 
 config PARISC_PAGE_SIZE_64KB
 	bool "64KB"
-	depends on PA8X00 && BROKEN
+	depends on PA8X00 && BROKEN && !KFENCE
 
 endchoice
 

arch/parisc/include/asm/kfence.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * PA-RISC KFENCE support.
+ *
+ * Copyright (C) 2021, Helge Deller <deller@gmx.de>
+ */
+
+#ifndef _ASM_PARISC_KFENCE_H
+#define _ASM_PARISC_KFENCE_H
+
+#include <linux/kfence.h>
+
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+static inline bool arch_kfence_init_pool(void)
+{
+	return true;
+}
+
+/* Protect the given page and flush TLB. */
+static inline bool kfence_protect_page(unsigned long addr, bool protect)
+{
+	pte_t *pte = virt_to_kpte(addr);
+
+	if (WARN_ON(!pte))
+		return false;
+
+	/*
+	 * We need to avoid IPIs, as we may get KFENCE allocations or faults
+	 * with interrupts disabled.
+	 */
+
+	if (protect)
+		set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT));
+	else
+		set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT));
+
+	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+
+	return true;
+}
+
+#endif /* _ASM_PARISC_KFENCE_H */

arch/parisc/kernel/traps.c

@@ -30,6 +30,7 @@
 #include <linux/ratelimit.h>
 #include <linux/uaccess.h>
 #include <linux/kdebug.h>
+#include <linux/kfence.h>
 
 #include <asm/assembly.h>
 #include <asm/io.h>
@@ -787,6 +788,10 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
 		/* Clean up and return if in exception table. */
 		if (fixup_exception(regs))
 			return;
+		/* Clean up and return if handled by kfence. */
+		if (kfence_handle_page_fault(fault_address,
+			parisc_acctyp(code, regs->iir) == VM_WRITE, regs))
+			return;
 		pdc_chassis_send_status(PDC_CHASSIS_DIRECT_PANIC);
 		parisc_terminate("Kernel Fault", regs, code, fault_address);
 	    }