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arm64/mm: move runtime pgds to rodata 

Now that deliberate writes to swapper_pg_dir are made via the fixmap, we
can defend against errant writes by moving it into the rodata section.
Since tramp_pg_dir and reserved_ttbr0 must be at a fixed offset from
swapper_pg_dir, and are not modified at runtime, these are also moved
into the rodata section. Likewise, idmap_pg_dir is not modified at
runtime, and is moved into rodata.

Signed-off-by: Jun Yao <yaojun8558363@gmail.com>
Reviewed-by: James Morse <james.morse@arm.com>
[Mark: simplify linker script, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Jun Yao 2018-09-24 17:56:18 +01:00 committed by Catalin Marinas
parent 2330b7ca78
commit 8eb7e28d4c
2 changed files with 24 additions and 21 deletions
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12
arch/arm64/kernel/head.S
View File

@ -287,18 +287,20 @@ __create_page_tables:
mov x28, lr
/*
* Invalidate the idmap and swapper page tables to avoid potential
* dirty cache lines being evicted.
* Invalidate the init page tables to avoid potential dirty cache lines
* being evicted. Other page tables are allocated in rodata as part of
* the kernel image, and thus are clean to the PoC per the boot
* protocol.
*/
adrp x0, idmap_pg_dir
adrp x0, init_pg_dir
adrp x1, init_pg_end
sub x1, x1, x0
bl __inval_dcache_area
/*
* Clear the idmap and swapper page tables.
* Clear the init page tables.
*/
adrp x0, idmap_pg_dir
adrp x0, init_pg_dir
adrp x1, init_pg_end
sub x1, x1, x0
1: stp xzr, xzr, [x0], #16

33
arch/arm64/kernel/vmlinux.lds.S
View File

@ -138,6 +138,23 @@ SECTIONS
EXCEPTION_TABLE(8) /* __init_begin will be marked RO NX */
NOTES
. = ALIGN(PAGE_SIZE);
idmap_pg_dir = .;
. += IDMAP_DIR_SIZE;
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
tramp_pg_dir = .;
. += PAGE_SIZE;
#endif
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
reserved_ttbr0 = .;
. += RESERVED_TTBR0_SIZE;
#endif
swapper_pg_dir = .;
. += PAGE_SIZE;
swapper_pg_end = .;
. = ALIGN(SEGMENT_ALIGN);
__init_begin = .;
__inittext_begin = .;
@ -216,22 +233,6 @@ SECTIONS
BSS_SECTION(0, 0, 0)
. = ALIGN(PAGE_SIZE);
idmap_pg_dir = .;
. += IDMAP_DIR_SIZE;
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
tramp_pg_dir = .;
. += PAGE_SIZE;
#endif
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
reserved_ttbr0 = .;
. += RESERVED_TTBR0_SIZE;
#endif
swapper_pg_dir = .;
. += PAGE_SIZE;
swapper_pg_end = .;
init_pg_dir = .;
. += INIT_DIR_SIZE;
init_pg_end = .;