parisc: Add KFENCE support

[Helge Deller <deller@gmx.de>]

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

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index afc3b8d03572..e4a6ae388eb3 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -47,6 +47,7 @@ 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
@@ -257,11 +258,11 @@ 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

diff --git a/arch/parisc/include/asm/kfence.h b/arch/parisc/include/asm/kfence.h
new file mode 100644
index 000000000000..41982ed5617b
--- /dev/null
+++ b/arch/parisc/include/asm/kfence.h
@@ -0,0 +1,45 @@
+/* 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));
+		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+	}
+	else
+		set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT));
+
+
+	return true;
+}
+
+#endif /* _ASM_PARISC_KFENCE_H */
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 716960f5d92e..ae4398ba0b7d 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -19,6 +19,7 @@
 #include <linux/uaccess.h>
 #include <linux/hugetlb.h>
 #include <linux/perf_event.h>
+#include <linux/kfence.h>

 #include <asm/traps.h>

@@ -416,6 +417,10 @@ void do_page_fault(struct pt_regs *regs, unsigned long code,
 		return;
 	}

+	if (!user_mode(regs) &&
+	    kfence_handle_page_fault(address, flags & FAULT_FLAG_WRITE, regs))
+		return;
+
 	parisc_terminate("Bad Address (null pointer deref?)", regs, code, address);

   out_of_memory: