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authorMark Rutland <mark.rutland@arm.com>2016-01-25 12:45:12 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2016-02-16 16:10:46 +0100
commit068a17a5805dfbca4bbf03e664ca6b19709cc7a8 (patch)
tree01a868d7db697bedc1b4a52af9b93ee27a4fab4d /arch/arm64/mm/kasan_init.c
parentarm64: ensure _stext and _etext are page-aligned (diff)
downloadlinux-068a17a5805dfbca4bbf03e664ca6b19709cc7a8.tar.xz
linux-068a17a5805dfbca4bbf03e664ca6b19709cc7a8.zip
arm64: mm: create new fine-grained mappings at boot
At boot we may change the granularity of the tables mapping the kernel (by splitting or making sections). This may happen when we create the linear mapping (in __map_memblock), or at any point we try to apply fine-grained permissions to the kernel (e.g. fixup_executable, mark_rodata_ro, fixup_init). Changing the active page tables in this manner may result in multiple entries for the same address being allocated into TLBs, risking problems such as TLB conflict aborts or issues derived from the amalgamation of TLB entries. Generally, a break-before-make (BBM) approach is necessary to avoid conflicts, but we cannot do this for the kernel tables as it risks unmapping text or data being used to do so. Instead, we can create a new set of tables from scratch in the safety of the existing mappings, and subsequently migrate over to these using the new cpu_replace_ttbr1 helper, which avoids the two sets of tables being active simultaneously. To avoid issues when we later modify permissions of the page tables (e.g. in fixup_init), we must create the page tables at a granularity such that later modification does not result in splitting of tables. This patch applies this strategy, creating a new set of fine-grained page tables from scratch, and safely migrating to them. The existing fixmap and kasan shadow page tables are reused in the new fine-grained tables. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Tested-by: Jeremy Linton <jeremy.linton@arm.com> Cc: Laura Abbott <labbott@fedoraproject.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/mm/kasan_init.c')
-rw-r--r--arch/arm64/mm/kasan_init.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 263b59020500..cc569a38bc76 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -97,6 +97,21 @@ asmlinkage void __init kasan_early_init(void)
kasan_map_early_shadow();
}
+/*
+ * Copy the current shadow region into a new pgdir.
+ */
+void __init kasan_copy_shadow(pgd_t *pgdir)
+{
+ pgd_t *pgd, *pgd_new, *pgd_end;
+
+ pgd = pgd_offset_k(KASAN_SHADOW_START);
+ pgd_end = pgd_offset_k(KASAN_SHADOW_END);
+ pgd_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
+ do {
+ set_pgd(pgd_new, *pgd);
+ } while (pgd++, pgd_new++, pgd != pgd_end);
+}
+
static void __init clear_pgds(unsigned long start,
unsigned long end)
{