[PATCH v2] MIPS: KASLR: Avoid endless loop in sync_icache when synci_step is zero

[PATCH v2] MIPS: KASLR: Avoid endless loop in sync_icache when synci_step is zero

[Jinyang He]

Avoid endless loop if synci_step was zero read by rdhwr instruction.

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@loongson.cn>
---
 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 57bdd276..47aeb33 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -64,7 +64,7 @@ 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();
-- 
2.1.0

Re: [PATCH v2] MIPS: KASLR: Avoid endless loop in sync_icache when synci_step is zero

[Thomas Bogendoerfer]

On Fri, Dec 04, 2020 at 09:11:46AM +0800, Jinyang He wrote:
> Avoid endless loop if synci_step was zero read by rdhwr instruction.
> 
> 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@loongson.cn>
> ---
>  arch/mips/kernel/relocate.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

applied to mips-next.

Thomas.

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