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| author | Jun Yao <yaojun8558363@gmail.com> | 2018-09-24 16:47:49 +0200 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2018-09-25 16:10:54 +0200 |
| commit | 2b5548b68199c17c1466d5798cf2c9cd806bdaa9 (patch) | |
| tree | 88c8b8710b472236e0724ba3d18e92b7eec341ba /arch/arm64/kernel | |
| parent | arm64/mm: Pass ttbr1 as a parameter to __enable_mmu() (diff) | |
| download | linux-2b5548b68199c17c1466d5798cf2c9cd806bdaa9.tar.xz linux-2b5548b68199c17c1466d5798cf2c9cd806bdaa9.zip | |
arm64/mm: Separate boot-time page tables from swapper_pg_dir
Since the address of swapper_pg_dir is fixed for a given kernel image,
it is an attractive target for manipulation via an arbitrary write. To
mitigate this we'd like to make it read-only by moving it into the
rodata section.
We require that swapper_pg_dir is at a fixed offset from tramp_pg_dir
and reserved_ttbr0, so these will also need to move into rodata.
However, swapper_pg_dir is allocated along with some transient page
tables used for boot which we do not want to move into rodata.
As a step towards this, this patch separates the boot-time page tables
into a new init_pg_dir, and reduces swapper_pg_dir to the single page it
needs to be. This allows us to retain the relationship between
swapper_pg_dir, tramp_pg_dir, and swapper_pg_dir, while cleanly
separating these from the boot-time page tables.
The init_pg_dir holds all of the pgd/pud/pmd/pte levels needed during
boot, and all of these levels will be freed when we switch to the
swapper_pg_dir, which is initialized by the existing code in
paging_init(). Since we start off on the init_pg_dir, we no longer need
to allocate a transient page table in paging_init() in order to ensure
that swapper_pg_dir isn't live while we initialize it.
There should be no functional change as a result of this patch.
Signed-off-by: Jun Yao <yaojun8558363@gmail.com>
Reviewed-by: James Morse <james.morse@arm.com>
[Mark: place init_pg_dir after BSS, fold mm changes, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel')
| -rw-r--r-- | arch/arm64/kernel/head.S | 10 | ||||
| -rw-r--r-- | arch/arm64/kernel/vmlinux.lds.S | 6 |
2 files changed, 10 insertions, 6 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 7983ddf0c0e9..7bf52ee0a805 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -291,7 +291,7 @@ __create_page_tables: * dirty cache lines being evicted. */ adrp x0, idmap_pg_dir - adrp x1, swapper_pg_end + adrp x1, init_pg_end sub x1, x1, x0 bl __inval_dcache_area @@ -299,7 +299,7 @@ __create_page_tables: * Clear the idmap and swapper page tables. */ adrp x0, idmap_pg_dir - adrp x1, swapper_pg_end + adrp x1, init_pg_end sub x1, x1, x0 1: stp xzr, xzr, [x0], #16 stp xzr, xzr, [x0], #16 @@ -373,7 +373,7 @@ __create_page_tables: /* * Map the kernel image (starting with PHYS_OFFSET). */ - adrp x0, swapper_pg_dir + adrp x0, init_pg_dir mov_q x5, KIMAGE_VADDR + TEXT_OFFSET // compile time __va(_text) add x5, x5, x23 // add KASLR displacement mov x4, PTRS_PER_PGD @@ -390,7 +390,7 @@ __create_page_tables: * tables again to remove any speculatively loaded cache lines. */ adrp x0, idmap_pg_dir - adrp x1, swapper_pg_end + adrp x1, init_pg_end sub x1, x1, x0 dmb sy bl __inval_dcache_area @@ -824,7 +824,7 @@ __primary_switch: mrs x20, sctlr_el1 // preserve old SCTLR_EL1 value #endif - adrp x1, swapper_pg_dir + adrp x1, init_pg_dir bl __enable_mmu #ifdef CONFIG_RELOCATABLE bl __relocate_kernel diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 605d1b60469c..ac4c10351b17 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -229,9 +229,13 @@ SECTIONS . += RESERVED_TTBR0_SIZE; #endif swapper_pg_dir = .; - . += SWAPPER_DIR_SIZE; + . += PAGE_SIZE; swapper_pg_end = .; + init_pg_dir = .; + . += INIT_DIR_SIZE; + init_pg_end = .; + __pecoff_data_size = ABSOLUTE(. - __initdata_begin); _end = .; |