[RFC PATCH v2 04/18] arm64: head: cover entire kernel image in ID map

[Ard Biesheuvel]

As a first step towards avoiding the need to create, tear down and
recreate the kernel virtual mapping with MMU and caches disabled, start
by expanding the ID map so it covers the page tables as well as all
executable code. This will allow us to populate the page tables with the
MMU and caches on, and call KASLR init code before setting up the
virtual mapping.

Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
 arch/arm64/include/asm/kernel-pgtable.h |  2 +-
 arch/arm64/kernel/head.S                | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 96dc0f7da258..b62200a9456e 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -87,7 +87,7 @@
 			+ 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 IDMAP_DIR_SIZE		(IDMAP_PGTABLE_LEVELS * PAGE_SIZE)
+#define IDMAP_DIR_SIZE		INIT_DIR_SIZE
 
 /* Initial memory map size */
 #if ARM64_KERNEL_USES_PMD_MAPS
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 275cd14a70c2..727561972e4a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -287,7 +287,7 @@ SYM_FUNC_END(clear_page_tables)
 
 SYM_FUNC_START_LOCAL(create_idmap)
 	adrp	x0, idmap_pg_dir
-	adrp	x3, __idmap_text_start		// __pa(__idmap_text_start)
+	adrp	x3, _text			// __pa(_text)
 
 #ifdef CONFIG_ARM64_VA_BITS_52
 	mrs_s	x6, SYS_ID_AA64MMFR2_EL1
@@ -312,10 +312,10 @@ SYM_FUNC_START_LOCAL(create_idmap)
 	 * Calculate the maximum allowed value for TCR_EL1.T0SZ so that the
 	 * entire ID map region can be mapped. As T0SZ == (64 - #bits used),
 	 * this number conveniently equals the number of leading zeroes in
-	 * the physical address of __idmap_text_end.
+	 * the physical address of _end.
 	 */
 	mov	x4, PTRS_PER_PGD
-	adrp	x5, __idmap_text_end
+	adrp	x5, _end
 	clz	x5, x5
 	cmp	x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough?
 	b.ge	1f			// .. then skip VA range extension
@@ -351,7 +351,7 @@ SYM_FUNC_START_LOCAL(create_idmap)
 	mov	x4, #1 << (PHYS_MASK_SHIFT - PGDIR_SHIFT)
 #endif
 1:
-	adr_l	x6, __idmap_text_end		// __pa(__idmap_text_end)
+	adr_l	x6, _end			// __pa(_end)
 	mov	x7, SWAPPER_MM_MMUFLAGS
 
 	map_memory x0, x1, x3, x6, x7, x3, x4, x10, x11, x12, x13, x14
@@ -884,7 +884,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 	msr	sctlr_el1, x20			// disable the MMU
 	isb
 	bl	clear_page_tables
-	bl	create_kernel_mapping		// recreate kernel mapping
+	bl	create_kernel_mapping		// Recreate kernel mapping
 
 	tlbi	vmalle1				// Remove any stale TLB entries
 	dsb	nsh
-- 
2.30.2