arm64: mm: Reserve enough pages for the initial ID map

The logic that conditionally allocates one additional page at each
swapper page table level if KASLR is enabled is also applied to the
initial ID map, now that we have started using the same set of macros
to allocate the space for it.

However, the placement of the kernel in physical memory might result in
additional pages being needed at any level, even if KASLR is disabled in
the build. So account for this in the computation.

Fixes: c3cee924 ("arm64: head: cover entire kernel image in initial ID map")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220826164800.2059148-1-ardb@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/kernel-pgtable.h

@@ -64,28 +64,28 @@
 #define EARLY_KASLR	(0)
 #endif
 
-#define EARLY_ENTRIES(vstart, vend, shift) \
-	((((vend) - 1) >> (shift)) - ((vstart) >> (shift)) + 1 + EARLY_KASLR)
+#define EARLY_ENTRIES(vstart, vend, shift, add) \
+	((((vend) - 1) >> (shift)) - ((vstart) >> (shift)) + 1 + add)
 
-#define EARLY_PGDS(vstart, vend) (EARLY_ENTRIES(vstart, vend, PGDIR_SHIFT))
+#define EARLY_PGDS(vstart, vend, add) (EARLY_ENTRIES(vstart, vend, PGDIR_SHIFT, add))
 
 #if SWAPPER_PGTABLE_LEVELS > 3
-#define EARLY_PUDS(vstart, vend) (EARLY_ENTRIES(vstart, vend, PUD_SHIFT))
+#define EARLY_PUDS(vstart, vend, add) (EARLY_ENTRIES(vstart, vend, PUD_SHIFT, add))
 #else
-#define EARLY_PUDS(vstart, vend) (0)
+#define EARLY_PUDS(vstart, vend, add) (0)
 #endif
 
 #if SWAPPER_PGTABLE_LEVELS > 2
-#define EARLY_PMDS(vstart, vend) (EARLY_ENTRIES(vstart, vend, SWAPPER_TABLE_SHIFT))
+#define EARLY_PMDS(vstart, vend, add) (EARLY_ENTRIES(vstart, vend, SWAPPER_TABLE_SHIFT, add))
 #else
-#define EARLY_PMDS(vstart, vend) (0)
+#define EARLY_PMDS(vstart, vend, add) (0)
 #endif
 
-#define EARLY_PAGES(vstart, vend) ( 1 			/* PGDIR page */				\
-			+ EARLY_PGDS((vstart), (vend)) 	/* each PGDIR needs a next level page table */	\
-			+ EARLY_PUDS((vstart), (vend))	/* each PUD needs a next level page table */	\
-			+ EARLY_PMDS((vstart), (vend)))	/* each PMD needs a next level page table */
-#define INIT_DIR_SIZE (PAGE_SIZE * EARLY_PAGES(KIMAGE_VADDR, _end))
+#define EARLY_PAGES(vstart, vend, add) ( 1 			/* PGDIR page */				\
+			+ EARLY_PGDS((vstart), (vend), add) 	/* each PGDIR needs a next level page table */	\
+			+ EARLY_PUDS((vstart), (vend), add)	/* each PUD needs a next level page table */	\
+			+ EARLY_PMDS((vstart), (vend), add))	/* each PMD needs a next level page table */
+#define INIT_DIR_SIZE (PAGE_SIZE * EARLY_PAGES(KIMAGE_VADDR, _end, EARLY_KASLR))
 
 /* the initial ID map may need two extra pages if it needs to be extended */
 #if VA_BITS < 48
@@ -93,7 +93,7 @@
 #else
 #define INIT_IDMAP_DIR_SIZE	(INIT_IDMAP_DIR_PAGES * PAGE_SIZE)
 #endif
-#define INIT_IDMAP_DIR_PAGES	EARLY_PAGES(KIMAGE_VADDR, _end + MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE)
+#define INIT_IDMAP_DIR_PAGES	EARLY_PAGES(KIMAGE_VADDR, _end + MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE, 1)
 
 /* Initial memory map size */
 #if ARM64_KERNEL_USES_PMD_MAPS