linux-kernel - [PATCH AUTOSEL 4.9 36/48] MIPS: KASLR: Avoid endless loop in sync_icache if synci

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Date:   Tue, 22 Dec 2020 21:24:04 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jinyang He <hejinyang@...ngson.cn>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Sasha Levin <sashal@...nel.org>, linux-mips@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 36/48] MIPS: KASLR: Avoid endless loop in sync_icache if synci_step is zero

From: Jinyang He <hejinyang@...ngson.cn>

[ Upstream commit c0aac3a51cb6364bed367ee3e1a96ed414f386b4 ]

Most platforms do not need to do synci instruction operations when
synci_step is 0. But for example, the synci implementation on Loongson64
platform has some changes. On the one hand, it ensures that the memory
access instructions have been completed. On the other hand, it guarantees
that all prefetch instructions need to be fetched again. And its address
information is useless. Thus, only one synci operation is required when
synci_step is 0 on Loongson64 platform. I guess that some other platforms
have similar implementations on synci, so add judgment conditions in
`while` to ensure that at least all platforms perform synci operations
once. For those platforms that do not need synci, they just do one more
operation similar to nop.

Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/mips/kernel/relocate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
index 1958910b75c07..f759aae1e1f3d 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -52,7 +52,7 @@ static void __init sync_icache(void *kbase, unsigned long kernel_length)
 			: "r" (kbase));

 		kbase += step;
-	} while (kbase < kend);
+	} while (step && kbase < kend);

 	/* Completion barrier */
 	__sync();
-- 
2.27.0