linux-kernel - [PATCH 18/52] arm64: cpufeature: __this_cpu_has

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Date:   Mon, 26 Feb 2018 16:19:52 +0800
From:   Alex Shi <alex.shi@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>,
        Will Deacon <will.deacon@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        stable@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM64 PORT
        (AARCH64 ARCHITECTURE)), linux-kernel@...r.kernel.org (open list)
Cc:     James Morse <james.morse@....com>
Subject: [PATCH 18/52] arm64: cpufeature: __this_cpu_has_cap() shouldn't stop early

From: James Morse <james.morse@....com>

commit edf298cfce47 upstream.
Alex Shi rewrite this commit on func this_cpu_has_cap(). The following commit
log is still meaningful.

    this_cpu_has_cap() tests caps->desc not caps->matches, so it stops
    walking the list when it finds a 'silent' feature, instead of
    walking to the end of the list.

    Prior to v4.6's 644c2ae198412 ("arm64: cpufeature: Test 'matches' pointer
    to find the end of the list") we always tested desc to find the end of
    a capability list. This was changed for dubious things like PAN_NOT_UAO.
    v4.7's e3661b128e53e ("arm64: Allow a capability to be checked on
    single CPU") added this_cpu_has_cap() using the old desc style test.

    CC: Suzuki K Poulose <suzuki.poulose@....com>
    Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
    Acked-by: Marc Zyngier <marc.zyngier@....com>
    Signed-off-by: James Morse <james.morse@....com>
    Signed-off-by: Catalin Marinas <catalin.marinas@....com>
    Signed-off-by: Will Deacon <will.deacon@....com>

Signed-off-by: Alex Shi <alex.shi@...aro.org>
---
 arch/arm64/include/asm/futex.h | 1 +
 arch/arm64/kernel/cpufeature.c | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
index 1943cf6..718140a 100644
--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h
@@ -20,6 +20,7 @@
 
 #include <linux/futex.h>
 #include <linux/uaccess.h>
+#include <linux/compiler.h>
 
 #include <asm/errno.h>
 
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 3a129d4..fcb67e0 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1063,8 +1063,8 @@ bool this_cpu_has_cap(unsigned int cap)
 	if (WARN_ON(preemptible()))
 		return false;
 
-	for (caps = arm64_features; caps->desc; caps++)
-		if (caps->capability == cap && caps->matches)
+	for (caps = arm64_features; caps->matches; caps++)
+		if (caps->capability == cap)
 			return caps->matches(caps, SCOPE_LOCAL_CPU);
 
 	return false;
-- 
2.7.4