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authorMark Rutland <mark.rutland@arm.com>2016-05-31 15:58:00 +0100
committerWill Deacon <will.deacon@arm.com>2016-06-03 10:57:18 +0100
commitaed7eb8367939244ba19445292ffdfc398e0d66a (patch)
treeef1dd844179bf42f5c068b4db58488ecf9f65cc3
parent030c4d24447cbf2bd612baea5695952e5f62c042 (diff)
downloadlinux-aed7eb8367939244ba19445292ffdfc398e0d66a.tar.gz
arm64: fix alignment when RANDOMIZE_TEXT_OFFSET is enabled
With ARM64_64K_PAGES and RANDOMIZE_TEXT_OFFSET enabled, we hit the following issue on the boot: kernel BUG at arch/arm64/mm/mmu.c:480! Internal error: Oops - BUG: 0 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 4.6.0 #310 Hardware name: ARM Juno development board (r2) (DT) task: ffff000008d58a80 ti: ffff000008d30000 task.ti: ffff000008d30000 PC is at map_kernel_segment+0x44/0xb0 LR is at paging_init+0x84/0x5b0 pc : [<ffff000008c450b4>] lr : [<ffff000008c451a4>] pstate: 600002c5 Call trace: [<ffff000008c450b4>] map_kernel_segment+0x44/0xb0 [<ffff000008c451a4>] paging_init+0x84/0x5b0 [<ffff000008c42728>] setup_arch+0x198/0x534 [<ffff000008c40848>] start_kernel+0x70/0x388 [<ffff000008c401bc>] __primary_switched+0x30/0x74 Commit 7eb90f2ff7e3 ("arm64: cover the .head.text section in the .text segment mapping") removed the alignment between the .head.text and .text sections, and used the _text rather than the _stext interval for mapping the .text segment. Prior to this commit _stext was always section aligned and didn't cause any issue even when RANDOMIZE_TEXT_OFFSET was enabled. Since that alignment has been removed and _text is used to map the .text segment, we need ensure _text is always page aligned when RANDOMIZE_TEXT_OFFSET is enabled. This patch adds logic to TEXT_OFFSET fuzzing to ensure that the offset is always aligned to the kernel page size. To ensure this, we rely on the PAGE_SHIFT being available via Kconfig. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reported-by: Sudeep Holla <sudeep.holla@arm.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Fixes: 7eb90f2ff7e3 ("arm64: cover the .head.text section in the .text segment mapping") Signed-off-by: Will Deacon <will.deacon@arm.com>
-rw-r--r--arch/arm64/Makefile4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 354d75402ace..7085e322dc42 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -60,7 +60,9 @@ head-y := arch/arm64/kernel/head.o
# The byte offset of the kernel image in RAM from the start of RAM.
ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y)
-TEXT_OFFSET := $(shell awk 'BEGIN {srand(); printf "0x%03x000\n", int(512 * rand())}')
+TEXT_OFFSET := $(shell awk "BEGIN {srand(); printf \"0x%06x\n\", \
+ int(2 * 1024 * 1024 / (2 ^ $(CONFIG_ARM64_PAGE_SHIFT)) * \
+ rand()) * (2 ^ $(CONFIG_ARM64_PAGE_SHIFT))}")
else
TEXT_OFFSET := 0x00080000
endif