linux-kernel - [PATCH] arm64: cpufeature: Don't expose ZFR0 to userspace when SVE is not enabled

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Message-Id: <20191014102113.16546-1-julien.grall@arm.com>
Date:   Mon, 14 Oct 2019 11:21:13 +0100
From:   Julien Grall <julien.grall@....com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     will@...nel.org, catalin.marinas@....com, suzuki.poulose@....com,
        Dave.Martin@....com, Julien Grall <julien.grall@....com>
Subject: [PATCH] arm64: cpufeature: Don't expose ZFR0 to userspace when SVE is not enabled

The kernel may not support SVE if CONFIG_ARM64_SVE is not set and
will hide the feature from the from userspace.

Unfortunately, the fields of ID_AA64ZFR0_EL1 are still exposed and could
lead to undefined behavior in userspace.

The kernel should not used the register when CONFIG_SVE is disabled.
Therefore, we only need to hidden them from the userspace.

Signed-off-by: Julien Grall <julien.grall@....com>
Fixes: 06a916feca2b ('arm64: Expose SVE2 features for userspace')
---
 arch/arm64/kernel/cpufeature.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index cabebf1a7976..80f459ad0190 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -176,11 +176,16 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64zfr0[] = {
-	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SM4_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SHA3_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_BITPERM_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_AES_SHIFT, 4, 0),
-	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SVEVER_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
+		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SM4_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
+		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SHA3_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
+		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_BITPERM_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
+		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_AES_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
+		       FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SVEVER_SHIFT, 4, 0),
 	ARM64_FTR_END,
 };
 
-- 
2.11.0