linux-kernel - Re: [PATCH] arm64/mm: Reject invalid NUMA option

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Message-ID: <7e85ea83-de5f-c789-2e3c-e468a50ed4bd@redhat.com>
Date:   Tue, 28 Apr 2020 14:35:20 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Mark Rutland <mark.rutland@....com>, catalin.marinas@....com,
        linux-kernel@...r.kernel.org, shan.gavin@...il.com,
        will@...nel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64/mm: Reject invalid NUMA option

Hi Steven and Mark,

On 4/28/20 1:09 PM, Steven Rostedt wrote:

[...]

> 
> Could this be a bug in the implementation of strncmp() in
> arch/arm64/lib/strncmp.S. As I don't know arm64 assembly, I have no idea
> what it is trying to do.
> 
> But strncmp("o","off",3) returning zero *is* a bug.
> 

I think it's false alarm. The patch has been in my local repo for a while.
I checked out 5.7.rc3 and tried passing "numa=o" to the kernel, @numa_off
is unchanged and its value is false. I also check the return value from
strncmp() as below, it's correct. Nothing is broken. I should have retested
before posting it. Sorry for the noise. Please ignore the crap patch :)

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index 4decf1659700..a8e5c6f7ba25 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c
@@ -32,6 +32,13 @@ static __init int numa_parse_early_param(char *opt)
         if (str_has_prefix(opt, "off"))
                 numa_off = true;
  
+       pr_info("numa_off=%s\n", numa_off ? "true" : "false");
+       pr_info("opt=%s\n", opt);
+       pr_info("len=%d\n", (int)strlen("off"));
+       pr_info("\n");
+       pr_info("================================\n");
+       pr_info("strncmp(opt, 'off', 3)=%d\n", strncmp(opt, "off", 3));
+

[    0.000000] NUMA: numa_off=false
[    0.000000] NUMA: opt=o
[    0.000000] NUMA: len=3
[    0.000000] NUMA:
[    0.000000] NUMA: ================================
[    0.000000] NUMA: strncmp(opt, 'off', 3)=-102

Thanks,
Gavin