parisc: add set_fixmap()/clear_fixmap()

These functions will be used for adding code patching
functions later.

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

arch/parisc/mm/fixmap.c

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fixmaps for parisc
+ *
+ * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+ */
+
+#include <linux/kprobes.h>
+#include <linux/mm.h>
+#include <asm/cacheflush.h>
+#include <asm/fixmap.h>
+
+void set_fixmap(enum fixed_addresses idx, phys_addr_t phys)
+{
+	unsigned long vaddr = __fix_to_virt(idx);
+	pgd_t *pgd = pgd_offset_k(vaddr);
+	pmd_t *pmd = pmd_offset(pgd, vaddr);
+	pte_t *pte;
+
+	if (pmd_none(*pmd))
+		pmd = pmd_alloc(NULL, pgd, vaddr);
+
+	pte = pte_offset_kernel(pmd, vaddr);
+	if (pte_none(*pte))
+		pte = pte_alloc_kernel(pmd, vaddr);
+
+	set_pte_at(&init_mm, vaddr, pte, __mk_pte(phys, PAGE_KERNEL_RWX));
+	flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
+}
+
+void clear_fixmap(enum fixed_addresses idx)
+{
+	unsigned long vaddr = __fix_to_virt(idx);
+	pgd_t *pgd = pgd_offset_k(vaddr);
+	pmd_t *pmd = pmd_offset(pgd, vaddr);
+	pte_t *pte = pte_offset_kernel(pmd, vaddr);
+
+	pte_clear(&init_mm, vaddr, pte);
+
+	flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
+}