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arm64: consistently use reserved_pg_dir

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Depending on configuration options and specific code paths, we either
use the empty_zero_page or the configuration-dependent reserved_ttbr0
as a reserved value for TTBR{0,1}_EL1.

To simplify this code, let's always allocate and use the same
reserved_pg_dir, replacing reserved_ttbr0. Note that this is allocated
(and hence pre-zeroed), and is also marked as read-only in the kernel
Image mapping.

Keeping this separate from the empty_zero_page potentially helps with
robustness as the empty_zero_page is used in a number of cases where a
failure to map it read-only could allow it to become corrupted.

The (presently unused) swapper_pg_end symbol is also removed, and
comments are added wherever we rely on the offsets between the
pre-allocated pg_dirs to keep these cases easily identifiable.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201103102229.8542-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Rutland
2020-11-03 10:22:29 +00:00
committed by Catalin Marinas
parent ba090f9caf
commit 833be850f1
9 changed files with 17 additions and 22 deletions
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8
arch/arm64/kernel/vmlinux.lds.S
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@@ -164,13 +164,11 @@ SECTIONS
. += PAGE_SIZE;
#endif
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
reserved_ttbr0 = .;
. += RESERVED_TTBR0_SIZE;
#endif
reserved_pg_dir = .;
. += PAGE_SIZE;
swapper_pg_dir = .;
. += PAGE_SIZE;
swapper_pg_end = .;
. = ALIGN(SEGMENT_ALIGN);
__init_begin = .;