linux-kernel - [PATCH v3 02/60] arm64: mm: Take potential load offset into account when KASLR is off

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Date:   Tue,  7 Mar 2023 15:04:24 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ryan Roberts <ryan.roberts@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH v3 02/60] arm64: mm: Take potential load offset into account when KASLR is off

We enable CONFIG_RELOCATABLE even when CONFIG_RANDOMIZE_BASE is
disabled, and this permits the loader (i.e., EFI) to place the kernel
anywhere in physical memory as long as the base address is 64k aligned.

This means that the 'KASLR' case described in the header that defines
the size of the statically allocated page tables could take effect even
when CONFIG_RANDMIZE_BASE=n. So check for CONFIG_RELOCATABLE instead.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/arm64/include/asm/kernel-pgtable.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index fcd14197756f0619..4d13c73171e1e360 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -53,7 +53,7 @@
  * address is just pushed over a boundary and the start address isn't).
  */
 
-#ifdef CONFIG_RANDOMIZE_BASE
+#ifdef CONFIG_RELOCATABLE
 #define EARLY_KASLR	(1)
 #else
 #define EARLY_KASLR	(0)
-- 
2.39.2