linux-kernel - [PATCH] arm64/traps: Avoid unnecessary kernel/user pointer conversion

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Date:   Tue, 14 Sep 2021 20:57:42 +0530
From:   Amit Daniel Kachhap <amit.kachhap@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        Vincenzo Frascino <Vincenzo.Frascino@....com>,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Subject: [PATCH] arm64/traps: Avoid unnecessary kernel/user pointer conversion

Annotating a pointer from kernel to __user and then back again might
confuse sparse. In call_undef_hook() it can be avoided by not using the
intermediate user pointer variable.

Note: This patch adds no functional changes to code.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
---
 arch/arm64/kernel/traps.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index b03e383d944a..357d10a8bbf5 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -404,7 +404,8 @@ static int call_undef_hook(struct pt_regs *regs)
 
 	if (!user_mode(regs)) {
 		__le32 instr_le;
-		if (get_kernel_nofault(instr_le, (__force __le32 *)pc))
+		if (get_kernel_nofault(instr_le,
+				       (__le32 *)instruction_pointer(regs)))
 			goto exit;
 		instr = le32_to_cpu(instr_le);
 	} else if (compat_thumb_mode(regs)) {
-- 
2.17.1