arm64: mm: move fixmap code to its own file

Over time, arm64's mm/mmu.c has become increasingly large and painful to
navigate. Move the fixmap code to its own file where it can be understood in
isolation.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/r/20230406152759.4164229-3-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

5 files changed, 222 insertions, 195 deletions

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 508238f73ba8..42e21c6bc0dd 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -103,6 +103,7 @@ enum fixed_addresses {
 #define FIXMAP_PAGE_IO     __pgprot(PROT_DEVICE_nGnRE)
 
 void __init early_fixmap_init(void);
+void __init fixmap_copy(pgd_t *pgdir);
 
 #define __early_set_fixmap __set_fixmap
 
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 48f8466a4be9..4384eaa0aeb7 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -65,6 +65,8 @@ extern void paging_init(void);
 extern void bootmem_init(void);
 extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
 extern void init_mem_pgprot(void);
+extern void create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
+				   phys_addr_t size, pgprot_t prot);
 extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 			       unsigned long virt, phys_addr_t size,
 			       pgprot_t prot, bool page_mappings_only);
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index ff1e800ba7a1..dbd1bc95967d 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -2,7 +2,7 @@
 obj-y				:= dma-mapping.o extable.o fault.o init.o \
 				   cache.o copypage.o flush.o \
 				   ioremap.o mmap.o pgd.o mmu.o \
-				   context.o proc.o pageattr.o
+				   context.o proc.o pageattr.o fixmap.o
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
 obj-$(CONFIG_PTDUMP_CORE)	+= ptdump.o
 obj-$(CONFIG_PTDUMP_DEBUGFS)	+= ptdump_debugfs.o
diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
new file mode 100644
index 000000000000..7fbdd6faf500
--- /dev/null
+++ b/arch/arm64/mm/fixmap.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Fixmap manipulation code
+ */
+
+#include <linux/bug.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/libfdt.h>
+#include <linux/memory.h>
+#include <linux/mm.h>
+#include <linux/sizes.h>
+
+#include <asm/fixmap.h>
+#include <asm/kernel-pgtable.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+
+static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
+static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
+static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
+
+static inline pud_t *fixmap_pud(unsigned long addr)
+{
+	pgd_t *pgdp = pgd_offset_k(addr);
+	p4d_t *p4dp = p4d_offset(pgdp, addr);
+	p4d_t p4d = READ_ONCE(*p4dp);
+
+	BUG_ON(p4d_none(p4d) || p4d_bad(p4d));
+
+	return pud_offset_kimg(p4dp, addr);
+}
+
+static inline pmd_t *fixmap_pmd(unsigned long addr)
+{
+	pud_t *pudp = fixmap_pud(addr);
+	pud_t pud = READ_ONCE(*pudp);
+
+	BUG_ON(pud_none(pud) || pud_bad(pud));
+
+	return pmd_offset_kimg(pudp, addr);
+}
+
+static inline pte_t *fixmap_pte(unsigned long addr)
+{
+	return &bm_pte[pte_index(addr)];
+}
+
+/*
+ * The p*d_populate functions call virt_to_phys implicitly so they can't be used
+ * directly on kernel symbols (bm_p*d). This function is called too early to use
+ * lm_alias so __p*d_populate functions must be used to populate with the
+ * physical address from __pa_symbol.
+ */
+void __init early_fixmap_init(void)
+{
+	pgd_t *pgdp;
+	p4d_t *p4dp, p4d;
+	pud_t *pudp;
+	pmd_t *pmdp;
+	unsigned long addr = FIXADDR_TOT_START;
+
+	pgdp = pgd_offset_k(addr);
+	p4dp = p4d_offset(pgdp, addr);
+	p4d = READ_ONCE(*p4dp);
+	if (CONFIG_PGTABLE_LEVELS > 3 &&
+	    !(p4d_none(p4d) || p4d_page_paddr(p4d) == __pa_symbol(bm_pud))) {
+		/*
+		 * We only end up here if the kernel mapping and the fixmap
+		 * share the top level pgd entry, which should only happen on
+		 * 16k/4 levels configurations.
+		 */
+		BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
+		pudp = pud_offset_kimg(p4dp, addr);
+	} else {
+		if (p4d_none(p4d))
+			__p4d_populate(p4dp, __pa_symbol(bm_pud), P4D_TYPE_TABLE);
+		pudp = fixmap_pud(addr);
+	}
+	if (pud_none(READ_ONCE(*pudp)))
+		__pud_populate(pudp, __pa_symbol(bm_pmd), PUD_TYPE_TABLE);
+	pmdp = fixmap_pmd(addr);
+	__pmd_populate(pmdp, __pa_symbol(bm_pte), PMD_TYPE_TABLE);
+
+	/*
+	 * The boot-ioremap range spans multiple pmds, for which
+	 * we are not prepared:
+	 */
+	BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
+		     != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));
+
+	if ((pmdp != fixmap_pmd(__fix_to_virt(FIX_BTMAP_BEGIN)))
+	     || pmdp != fixmap_pmd(__fix_to_virt(FIX_BTMAP_END))) {
+		WARN_ON(1);
+		pr_warn("pmdp %p != %p, %p\n",
+			pmdp, fixmap_pmd(__fix_to_virt(FIX_BTMAP_BEGIN)),
+			fixmap_pmd(__fix_to_virt(FIX_BTMAP_END)));
+		pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
+			__fix_to_virt(FIX_BTMAP_BEGIN));
+		pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
+			__fix_to_virt(FIX_BTMAP_END));
+
+		pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
+		pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
+	}
+}
+
+/*
+ * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
+ * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
+ */
+void __set_fixmap(enum fixed_addresses idx,
+			       phys_addr_t phys, pgprot_t flags)
+{
+	unsigned long addr = __fix_to_virt(idx);
+	pte_t *ptep;
+
+	BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
+
+	ptep = fixmap_pte(addr);
+
+	if (pgprot_val(flags)) {
+		set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
+	} else {
+		pte_clear(&init_mm, addr, ptep);
+		flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
+	}
+}
+
+void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
+{
+	const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
+	int offset;
+	void *dt_virt;
+
+	/*
+	 * Check whether the physical FDT address is set and meets the minimum
+	 * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
+	 * at least 8 bytes so that we can always access the magic and size
+	 * fields of the FDT header after mapping the first chunk, double check
+	 * here if that is indeed the case.
+	 */
+	BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
+	if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
+		return NULL;
+
+	/*
+	 * Make sure that the FDT region can be mapped without the need to
+	 * allocate additional translation table pages, so that it is safe
+	 * to call create_mapping_noalloc() this early.
+	 *
+	 * On 64k pages, the FDT will be mapped using PTEs, so we need to
+	 * be in the same PMD as the rest of the fixmap.
+	 * On 4k pages, we'll use section mappings for the FDT so we only
+	 * have to be in the same PUD.
+	 */
+	BUILD_BUG_ON(dt_virt_base % SZ_2M);
+
+	BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
+		     __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
+
+	offset = dt_phys % SWAPPER_BLOCK_SIZE;
+	dt_virt = (void *)dt_virt_base + offset;
+
+	/* map the first chunk so we can read the size from the header */
+	create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE),
+			dt_virt_base, SWAPPER_BLOCK_SIZE, prot);
+
+	if (fdt_magic(dt_virt) != FDT_MAGIC)
+		return NULL;
+
+	*size = fdt_totalsize(dt_virt);
+	if (*size > MAX_FDT_SIZE)
+		return NULL;
+
+	if (offset + *size > SWAPPER_BLOCK_SIZE)
+		create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
+			       round_up(offset + *size, SWAPPER_BLOCK_SIZE), prot);
+
+	return dt_virt;
+}
+
+/*
+ * Copy the fixmap region into a new pgdir.
+ */
+void __init fixmap_copy(pgd_t *pgdir)
+{
+	if (!READ_ONCE(pgd_val(*pgd_offset_pgd(pgdir, FIXADDR_TOT_START)))) {
+		/*
+		 * The fixmap falls in a separate pgd to the kernel, and doesn't
+		 * live in the carveout for the swapper_pg_dir. We can simply
+		 * re-use the existing dir for the fixmap.
+		 */
+		set_pgd(pgd_offset_pgd(pgdir, FIXADDR_TOT_START),
+			READ_ONCE(*pgd_offset_k(FIXADDR_TOT_START)));
+	} else if (CONFIG_PGTABLE_LEVELS > 3) {
+		pgd_t *bm_pgdp;
+		p4d_t *bm_p4dp;
+		pud_t *bm_pudp;
+		/*
+		 * The fixmap shares its top level pgd entry with the kernel
+		 * mapping. This can really only occur when we are running
+		 * with 16k/4 levels, so we can simply reuse the pud level
+		 * entry instead.
+		 */
+		BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
+		bm_pgdp = pgd_offset_pgd(pgdir, FIXADDR_TOT_START);
+		bm_p4dp = p4d_offset(bm_pgdp, FIXADDR_TOT_START);
+		bm_pudp = pud_set_fixmap_offset(bm_p4dp, FIXADDR_TOT_START);
+		pud_populate(&init_mm, bm_pudp, lm_alias(bm_pmd));
+		pud_clear_fixmap();
+	} else {
+		BUG();
+	}
+}
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 44954251e14d..ef59c18fbf8c 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -73,10 +73,6 @@ long __section(".mmuoff.data.write") __early_cpu_boot_status;
 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
 EXPORT_SYMBOL(empty_zero_page);
 
-static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
-static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
-static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
-
 static DEFINE_SPINLOCK(swapper_pgdir_lock);
 static DEFINE_MUTEX(fixmap_lock);
 
@@ -452,8 +448,8 @@ static phys_addr_t pgd_pgtable_alloc(int shift)
  * without allocating new levels of table. Note that this permits the
  * creation of new section or page entries.
  */
-static void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
-				  phys_addr_t size, pgprot_t prot)
+void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
+				   phys_addr_t size, pgprot_t prot)
 {
 	if ((virt >= PAGE_END) && (virt < VMALLOC_START)) {
 		pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
@@ -795,34 +791,7 @@ static void __init map_kernel(pgd_t *pgdp)
 			   &vmlinux_initdata, 0, VM_NO_GUARD);
 	map_kernel_segment(pgdp, _data, _end, PAGE_KERNEL, &vmlinux_data, 0, 0);
 
-	if (!READ_ONCE(pgd_val(*pgd_offset_pgd(pgdp, FIXADDR_TOT_START)))) {
-		/*
-		 * The fixmap falls in a separate pgd to the kernel, and doesn't
-		 * live in the carveout for the swapper_pg_dir. We can simply
-		 * re-use the existing dir for the fixmap.
-		 */
-		set_pgd(pgd_offset_pgd(pgdp, FIXADDR_TOT_START),
-			READ_ONCE(*pgd_offset_k(FIXADDR_TOT_START)));
-	} else if (CONFIG_PGTABLE_LEVELS > 3) {
-		pgd_t *bm_pgdp;
-		p4d_t *bm_p4dp;
-		pud_t *bm_pudp;
-		/*
-		 * The fixmap shares its top level pgd entry with the kernel
-		 * mapping. This can really only occur when we are running
-		 * with 16k/4 levels, so we can simply reuse the pud level
-		 * entry instead.
-		 */
-		BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
-		bm_pgdp = pgd_offset_pgd(pgdp, FIXADDR_TOT_START);
-		bm_p4dp = p4d_offset(bm_pgdp, FIXADDR_TOT_START);
-		bm_pudp = pud_set_fixmap_offset(bm_p4dp, FIXADDR_TOT_START);
-		pud_populate(&init_mm, bm_pudp, lm_alias(bm_pmd));
-		pud_clear_fixmap();
-	} else {
-		BUG();
-	}
-
+	fixmap_copy(pgdp);
 	kasan_copy_shadow(pgdp);
 }
 
@@ -1237,166 +1206,6 @@ void vmemmap_free(unsigned long start, unsigned long end,
 }
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
-static inline pud_t *fixmap_pud(unsigned long addr)
-{
-	pgd_t *pgdp = pgd_offset_k(addr);
-	p4d_t *p4dp = p4d_offset(pgdp, addr);
-	p4d_t p4d = READ_ONCE(*p4dp);
-
-	BUG_ON(p4d_none(p4d) || p4d_bad(p4d));
-
-	return pud_offset_kimg(p4dp, addr);
-}
-
-static inline pmd_t *fixmap_pmd(unsigned long addr)
-{
-	pud_t *pudp = fixmap_pud(addr);
-	pud_t pud = READ_ONCE(*pudp);
-
-	BUG_ON(pud_none(pud) || pud_bad(pud));
-
-	return pmd_offset_kimg(pudp, addr);
-}
-
-static inline pte_t *fixmap_pte(unsigned long addr)
-{
-	return &bm_pte[pte_index(addr)];
-}
-
-/*
- * The p*d_populate functions call virt_to_phys implicitly so they can't be used
- * directly on kernel symbols (bm_p*d). This function is called too early to use
- * lm_alias so __p*d_populate functions must be used to populate with the
- * physical address from __pa_symbol.
- */
-void __init early_fixmap_init(void)
-{
-	pgd_t *pgdp;
-	p4d_t *p4dp, p4d;
-	pud_t *pudp;
-	pmd_t *pmdp;
-	unsigned long addr = FIXADDR_TOT_START;
-
-	pgdp = pgd_offset_k(addr);
-	p4dp = p4d_offset(pgdp, addr);
-	p4d = READ_ONCE(*p4dp);
-	if (CONFIG_PGTABLE_LEVELS > 3 &&
-	    !(p4d_none(p4d) || p4d_page_paddr(p4d) == __pa_symbol(bm_pud))) {
-		/*
-		 * We only end up here if the kernel mapping and the fixmap
-		 * share the top level pgd entry, which should only happen on
-		 * 16k/4 levels configurations.
-		 */
-		BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
-		pudp = pud_offset_kimg(p4dp, addr);
-	} else {
-		if (p4d_none(p4d))
-			__p4d_populate(p4dp, __pa_symbol(bm_pud), P4D_TYPE_TABLE);
-		pudp = fixmap_pud(addr);
-	}
-	if (pud_none(READ_ONCE(*pudp)))
-		__pud_populate(pudp, __pa_symbol(bm_pmd), PUD_TYPE_TABLE);
-	pmdp = fixmap_pmd(addr);
-	__pmd_populate(pmdp, __pa_symbol(bm_pte), PMD_TYPE_TABLE);
-
-	/*
-	 * The boot-ioremap range spans multiple pmds, for which
-	 * we are not prepared:
-	 */
-	BUILD_BUG_ON((__fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT)
-		     != (__fix_to_virt(FIX_BTMAP_END) >> PMD_SHIFT));
-
-	if ((pmdp != fixmap_pmd(__fix_to_virt(FIX_BTMAP_BEGIN)))
-	     || pmdp != fixmap_pmd(__fix_to_virt(FIX_BTMAP_END))) {
-		WARN_ON(1);
-		pr_warn("pmdp %p != %p, %p\n",
-			pmdp, fixmap_pmd(__fix_to_virt(FIX_BTMAP_BEGIN)),
-			fixmap_pmd(__fix_to_virt(FIX_BTMAP_END)));
-		pr_warn("fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
-			__fix_to_virt(FIX_BTMAP_BEGIN));
-		pr_warn("fix_to_virt(FIX_BTMAP_END):   %08lx\n",
-			__fix_to_virt(FIX_BTMAP_END));
-
-		pr_warn("FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);
-		pr_warn("FIX_BTMAP_BEGIN:     %d\n", FIX_BTMAP_BEGIN);
-	}
-}
-
-/*
- * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
- * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
- */
-void __set_fixmap(enum fixed_addresses idx,
-			       phys_addr_t phys, pgprot_t flags)
-{
-	unsigned long addr = __fix_to_virt(idx);
-	pte_t *ptep;
-
-	BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
-
-	ptep = fixmap_pte(addr);
-
-	if (pgprot_val(flags)) {
-		set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
-	} else {
-		pte_clear(&init_mm, addr, ptep);
-		flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
-	}
-}
-
-void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
-{
-	const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
-	int offset;
-	void *dt_virt;
-
-	/*
-	 * Check whether the physical FDT address is set and meets the minimum
-	 * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
-	 * at least 8 bytes so that we can always access the magic and size
-	 * fields of the FDT header after mapping the first chunk, double check
-	 * here if that is indeed the case.
-	 */
-	BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
-	if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
-		return NULL;
-
-	/*
-	 * Make sure that the FDT region can be mapped without the need to
-	 * allocate additional translation table pages, so that it is safe
-	 * to call create_mapping_noalloc() this early.
-	 *
-	 * On 64k pages, the FDT will be mapped using PTEs, so we need to
-	 * be in the same PMD as the rest of the fixmap.
-	 * On 4k pages, we'll use section mappings for the FDT so we only
-	 * have to be in the same PUD.
-	 */
-	BUILD_BUG_ON(dt_virt_base % SZ_2M);
-
-	BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
-		     __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
-
-	offset = dt_phys % SWAPPER_BLOCK_SIZE;
-	dt_virt = (void *)dt_virt_base + offset;
-
-	/* map the first chunk so we can read the size from the header */
-	create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE),
-			dt_virt_base, SWAPPER_BLOCK_SIZE, prot);
-
-	if (fdt_magic(dt_virt) != FDT_MAGIC)
-		return NULL;
-
-	*size = fdt_totalsize(dt_virt);
-	if (*size > MAX_FDT_SIZE)
-		return NULL;
-
-	if (offset + *size > SWAPPER_BLOCK_SIZE)
-		create_mapping_noalloc(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
-			       round_up(offset + *size, SWAPPER_BLOCK_SIZE), prot);
-
-	return dt_virt;
-}
-
 int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
 {
 	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), mk_pud_sect_prot(prot));