parisc: add set_fixmap()/clear_fixmap()

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

Signed-off-by: Sven Schnelle <[e-mail]>
Signed-off-by: Helge Deller <[e-mail]>

arch/parisc/include/asm/fixmap.h

···
  * from areas congruently mapped with user space.  It is 8MB large
  * and must be 16MB aligned */
 #define TMPALIAS_MAP_START	((__PAGE_OFFSET) - 16*1024*1024)
+
+#define FIXMAP_SIZE		(FIX_BITMAP_COUNT << PAGE_SHIFT)
+#define FIXMAP_START		(TMPALIAS_MAP_START - FIXMAP_SIZE)
 /* This is the kernel area for all maps (vmalloc, dma etc.)  most
  * usually, it extends up to TMPALIAS_MAP_START.  Virtual addresses
  * 0..GATEWAY_PAGE_SIZE are reserved for the gateway page */
 #define KERNEL_MAP_START	(GATEWAY_PAGE_SIZE)
-#define KERNEL_MAP_END		(TMPALIAS_MAP_START)
+#define KERNEL_MAP_END		(FIXMAP_START)
 
 #ifndef __ASSEMBLY__
+
+
+enum fixed_addresses {
+	/* Support writing RO kernel text via kprobes, jump labels, etc. */
+	FIX_TEXT_POKE0,
+	FIX_BITMAP_COUNT
+};
+
 extern void *parisc_vmalloc_start;
 #define PCXL_DMA_MAP_SIZE	(8*1024*1024)
 #define VMALLOC_START		((unsigned long)parisc_vmalloc_start)
 #define VMALLOC_END		(KERNEL_MAP_END)
+
+#define __fix_to_virt(_x) (FIXMAP_START + ((_x) << PAGE_SHIFT))
+
+void set_fixmap(enum fixed_addresses idx, phys_addr_t phys);
+void clear_fixmap(enum fixed_addresses idx);
+
 #endif /*__ASSEMBLY__*/
 
 #endif /*_ASM_FIXMAP_H*/

arch/parisc/mm/Makefile

···
 # Makefile for arch/parisc/mm
 #
 
-obj-y	 := init.o fault.o ioremap.o
+obj-y	 := init.o fault.o ioremap.o fixmap.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o

arch/parisc/mm/fixmap.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fixmaps for parisc
+ *
+ * Copyright (c) 2019 Sven Schnelle <[e-mail]>
+ */
+
+#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);
+}

arch/parisc/mm/init.c

···
 	 * But keep code for debugging purposes.
 	 */
 	printk("virtual kernel memory layout:\n"
-	       "    vmalloc : 0x%px - 0x%px   (%4ld MB)\n"
-	       "    memory  : 0x%px - 0x%px   (%4ld MB)\n"
-	       "      .init : 0x%px - 0x%px   (%4ld kB)\n"
-	       "      .data : 0x%px - 0x%px   (%4ld kB)\n"
-	       "      .text : 0x%px - 0x%px   (%4ld kB)\n",
+	       "     vmalloc : 0x%px - 0x%px   (%4ld MB)\n"
+	       "     fixmap  : 0x%px - 0x%px   (%4ld kB)\n"
+	       "     memory  : 0x%px - 0x%px   (%4ld MB)\n"
+	       "       .init : 0x%px - 0x%px   (%4ld kB)\n"
+	       "       .data : 0x%px - 0x%px   (%4ld kB)\n"
+	       "       .text : 0x%px - 0x%px   (%4ld kB)\n",
 
 	       (void*)VMALLOC_START, (void*)VMALLOC_END,
 	       (VMALLOC_END - VMALLOC_START) >> 20,
+
+	       (void *)FIXMAP_START, (void *)(FIXMAP_START + FIXMAP_SIZE),
+	       (unsigned long)(FIXMAP_SIZE / 1024),
 
 	       __va(0), high_memory,
 	       ((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,