From 7a1be318f5795cb66fa0dc86b3ace427fe68057f Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Sun, 11 Oct 2020 10:21:37 +0100 Subject: ARM: 9012/1: move device tree mapping out of linear region On ARM, setting up the linear region is tricky, given the constraints around placement and alignment of the memblocks, and how the kernel itself as well as the DT are placed in physical memory. Let's simplify matters a bit, by moving the device tree mapping to the top of the address space, right between the end of the vmalloc region and the start of the the fixmap region, and create a read-only mapping for it that is independent of the size of the linear region, and how it is organized. Since this region was formerly used as a guard region, which will now be populated fully on LPAE builds by this read-only mapping (which will still be able to function as a guard region for stray writes), bump the start of the [underutilized] fixmap region by 512 KB as well, to ensure that there is always a proper guard region here. Doing so still leaves ample room for the fixmap space, even with NR_CPUS set to its maximum value of 32. Tested-by: Linus Walleij Reviewed-by: Linus Walleij Reviewed-by: Nicolas Pitre Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King --- arch/arm/kernel/head.S | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'arch/arm/kernel/head.S') diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S index f8904227e7fd..9b18d8c66129 100644 --- a/arch/arm/kernel/head.S +++ b/arch/arm/kernel/head.S @@ -275,9 +275,8 @@ __create_page_tables: */ mov r0, r2, lsr #SECTION_SHIFT movs r0, r0, lsl #SECTION_SHIFT - subne r3, r0, r8 - addne r3, r3, #PAGE_OFFSET - addne r3, r4, r3, lsr #(SECTION_SHIFT - PMD_ORDER) + ldrne r3, =FDT_FIXED_BASE >> (SECTION_SHIFT - PMD_ORDER) + addne r3, r3, r4 orrne r6, r7, r0 strne r6, [r3], #1 << PMD_ORDER addne r6, r6, #1 << SECTION_SHIFT -- cgit v1.2.3