path: root/arch/arm64/kernel/head.S
diff options
authorMark Rutland <mark.rutland@arm.com>2014-06-24 16:51:35 +0100
committerMark Brown <broonie@linaro.org>2014-07-23 13:07:14 +0100
commitde06786c493930f7e82e90c77fa71af64166623d (patch)
treeb73f69baf8240cfe504bdf25253f5b29be2baa0c /arch/arm64/kernel/head.S
parent266d252b81d597b42cb86551ff2085285908d9b2 (diff)
arm64: place initial page tables above the kernel
Currently we place swapper_pg_dir and idmap_pg_dir below the kernel image, between PHYS_OFFSET and (PHYS_OFFSET + TEXT_OFFSET). However, bootloaders may use portions of this memory below the kernel and we do not parse the memory reservation list until after the MMU has been enabled. As such we may clobber some memory a bootloader wishes to have preserved. To enable the use of all of this memory by bootloaders (when the required memory reservations are communicated to the kernel) it is necessary to move our initial page tables elsewhere. As we currently have an effectively unbound requirement for memory at the end of the kernel image for .bss, we can place the page tables here. This patch moves the initial page table to the end of the kernel image, after the BSS. As they do not consist of any initialised data they will be stripped from the kernel Image as with the BSS. The BSS clearing routine is updated to stop at __bss_stop rather than _end so as to not clobber the page tables, and memory reservations made redundant by the new organisation are removed. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Laura Abbott <lauraa@codeaurora.org> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> (cherry picked from commit bd00cd5f8c8c3c282bb1e1eac6a6679a4f808091) Signed-off-by: Mark Brown <broonie@linaro.org> Conflicts: arch/arm64/mm/init.c
Diffstat (limited to 'arch/arm64/kernel/head.S')
1 files changed, 8 insertions, 20 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 9c41466060dd..05a104c59510 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -35,29 +35,17 @@
#include <asm/page.h>
#include <asm/virt.h>
- * swapper_pg_dir is the virtual address of the initial page table. We place
- * the page tables 3 * PAGE_SIZE below KERNEL_RAM_VADDR. The idmap_pg_dir has
- * 2 pages and is placed below swapper_pg_dir.
- */
#if (KERNEL_RAM_VADDR & 0xfffff) != 0x80000
#error KERNEL_RAM_VADDR must start at 0xXXX80000
- .globl swapper_pg_dir
- .equ swapper_pg_dir, KERNEL_RAM_VADDR - SWAPPER_DIR_SIZE
- .globl idmap_pg_dir
- .equ idmap_pg_dir, swapper_pg_dir - IDMAP_DIR_SIZE
- .macro pgtbl, ttb0, ttb1, phys
- add \ttb1, \phys, #TEXT_OFFSET - SWAPPER_DIR_SIZE
- sub \ttb0, \ttb1, #IDMAP_DIR_SIZE
+ .macro pgtbl, ttb0, ttb1, virt_to_phys
+ ldr \ttb1, =swapper_pg_dir
+ ldr \ttb0, =idmap_pg_dir
+ add \ttb1, \ttb1, \virt_to_phys
+ add \ttb0, \ttb0, \virt_to_phys
@@ -304,7 +292,7 @@ ENTRY(secondary_startup)
mov x23, x0 // x23=current cpu_table
cbz x23, __error_p // invalid processor (x23=0)?
- pgtbl x25, x26, x24 // x25=TTBR0, x26=TTBR1
+ pgtbl x25, x26, x28 // x25=TTBR0, x26=TTBR1
ldr x12, [x23, #CPU_INFO_SETUP]
add x12, x12, x28 // __virt_to_phys
blr x12 // initialise processor
@@ -418,7 +406,7 @@ ENDPROC(__calc_phys_offset)
* - UART mapping if CONFIG_EARLY_PRINTK is enabled (TTBR1)
- pgtbl x25, x26, x24 // idmap_pg_dir and swapper_pg_dir addresses
+ pgtbl x25, x26, x28 // idmap_pg_dir and swapper_pg_dir addresses
mov x27, lr
@@ -510,7 +498,7 @@ ENDPROC(__create_page_tables)
.quad __mmap_switched
.quad __bss_start // x6
- .quad _end // x7
+ .quad __bss_stop // x7
.quad processor_id // x4
.quad __fdt_pointer // x5
.quad memstart_addr // x6