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From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>, Marc Zyngier <maz@kernel.org>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Brown <broonie@kernel.org>,
	Anshuman Khandual <anshuman.khandual@arm.com>
Subject: [PATCH v6 3/9] arm64: kaslr: drop special case for ThunderX in kaslr_requires_kpti()
Date: Fri,  1 Jul 2022 15:04:38 +0200	[thread overview]
Message-ID: <20220701130444.2945106-4-ardb@kernel.org> (raw)
In-Reply-To: <20220701130444.2945106-1-ardb@kernel.org>

ThunderX is an obsolete platform that shipped without support for the
EFI_RNG_PROTOCOL in its firmware. Now that we no longer misidentify
small KASLR offsets as randomization being enabled, we can drop the
explicit check for ThunderX as well, given that KASLR is known to be
unavailable on these systems.

Note that we never enable KPTI on these systems, in spite of what this
function returns. The only penalty for getting it wrong (i.e., returning
true here on a ThunderX system) is that we will end up using non-global
mappings for the kernel pointlessly.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/cpufeature.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 22e3604aee02..af46ca0da994 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1550,18 +1550,6 @@ bool kaslr_requires_kpti(void)
 			return false;
 	}
 
-	/*
-	 * Systems affected by Cavium erratum 24756 are incompatible
-	 * with KPTI.
-	 */
-	if (IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456)) {
-		extern const struct midr_range cavium_erratum_27456_cpus[];
-
-		if (is_midr_in_range_list(read_cpuid_id(),
-					  cavium_erratum_27456_cpus))
-			return false;
-	}
-
 	return kaslr_enabled();
 }
 
-- 
2.35.1


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  parent reply	other threads:[~2022-07-01 13:06 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-01 13:04 [PATCH v6 0/9] arm64: add support for WXN Ard Biesheuvel
2022-07-01 13:04 ` [PATCH v6 1/9] arm64: kaslr: use an ordinary command line param for nokaslr Ard Biesheuvel
2022-07-01 14:07   ` Mark Brown
2022-07-01 13:04 ` [PATCH v6 2/9] arm64: kaslr: don't pretend KASLR is enabled if offset < MIN_KIMG_ALIGN Ard Biesheuvel
2022-07-01 14:12   ` Mark Brown
2022-07-01 13:04 ` Ard Biesheuvel [this message]
2022-07-01 13:04 ` [PATCH v6 4/9] arm64: head: allocate more pages for the kernel mapping Ard Biesheuvel
2022-07-01 13:04 ` [PATCH v6 5/9] arm64: head: move early kernel mapping and relocation code to C code Ard Biesheuvel
2022-07-01 13:04 ` [PATCH v6 6/9] arm64: mm: avoid fixmap for early swapper_pg_dir updates Ard Biesheuvel
2022-07-01 13:04 ` [PATCH v6 7/9] arm64: mm: omit redundant remap of kernel image Ard Biesheuvel
2022-07-01 13:04 ` [PATCH v6 8/9] mm: add arch hook to validate mmap() prot flags Ard Biesheuvel
2022-07-01 13:04 ` [PATCH v6 9/9] arm64: mm: add support for WXN memory translation attribute Ard Biesheuvel

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