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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2016-03-21 18:35:11 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2016-03-24 16:19:24 +0000
commitd5e5743797adc26e09db262e7a4b6b81d8c0f45c (patch)
tree3fc356370af64a6e2dd81e84bd70dca2f0a62701 /arch
parentf09f1bacfe2b1e64a5d94bc2711f73b654c95514 (diff)
arm64: kaslr: use callee saved register to preserve SCTLR across C call
The KASLR code incorrectly expects the contents of x18 to be preserved across a call into C code, and uses it to stash the contents of SCTLR_EL1 before enabling the MMU. If the MMU needs to be disabled again to create the randomized kernel mapping, x18 is written back to SCTLR_EL1, which is likely to crash the system if x18 has been clobbered by kasan_early_init() or kaslr_early_init(). So use x22 instead, which is not in use so far in head.S Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kernel/head.S4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 1672ca9e963b..a2cf0e3aa1ce 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -732,7 +732,7 @@ ENTRY(__early_cpu_boot_status)
*/
.section ".idmap.text", "ax"
__enable_mmu:
- mrs x18, sctlr_el1 // preserve old SCTLR_EL1 value
+ mrs x22, sctlr_el1 // preserve old SCTLR_EL1 value
mrs x1, ID_AA64MMFR0_EL1
ubfx x2, x1, #ID_AA64MMFR0_TGRAN_SHIFT, 4
cmp x2, #ID_AA64MMFR0_TGRAN_SUPPORTED
@@ -760,7 +760,7 @@ __enable_mmu:
* to take into account by discarding the current kernel mapping and
* creating a new one.
*/
- msr sctlr_el1, x18 // disable the MMU
+ msr sctlr_el1, x22 // disable the MMU
isb
bl __create_page_tables // recreate kernel mapping

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