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Message-ID: <230722113014.M0204460@vega.pgw.jp>
Date: Sat, 22 Jul 2023 11:30:14 +0900
From: <kabe@...a.pgw.jp>
To: rostedt@...dmis.org
Cc: regressions@...ts.linux.dev, bagasdotme@...il.com,
alexander.deucher@....com, christian.koenig@....com,
Xinhui.Pan@....com, tglx@...utronix.de, mingo@...hat.com,
bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
kkabe@...a.pgw.jp
Subject: Re: radeon.ko/i586: BUG: kernel NULL pointer dereference,address:00000004
rostedt@...dmis.org sed in <20230717113623.41878887@...dalf.local.home>
>> On Fri, 14 Jul 2023 14:34:04 +0900
>> <kkabe@...a.pgw.jp> wrote:
>>
>> > Patch in
>> > https://bugzilla.kernel.org/show_bug.cgi?id=217669#c4
>> > fixed the problem in freedesktop.org kernel 5.18.0-rc2 .
>> > This may explain that in kernel.org tree, the said commit is in kernel-5.19.
>>
>> You mean the patch that adds:
>>
>> #if defined(FTRACE_MCOUNT_MAX_OFFSET) && (FTRACE_MCOUNT_MAX_OFFSET)
>>
>> ?
>>
>> Nothing should be setting FTRACE_MCOUNT_MAX_OFFSET to anything but non
>> zero. But doing a grep, I now see:
>>
>> # define FTRACE_MCOUNT_MAX_OFFSET ENDBR_INSN_SIZE
>>
>> Where it breaks that assumption if ENDBR_INSN_SIZE == 0 :-p
>> (and that's my code!)
>>
>> OK, does this fix it? (I haven't tested nor compiled this)
>>
>> -- Steve
>>
>> diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
>> index 897cf02c20b1..801f4414da3e 100644
>> --- a/arch/x86/include/asm/ftrace.h
>> +++ b/arch/x86/include/asm/ftrace.h
>> @@ -13,7 +13,7 @@
>> #ifdef CONFIG_HAVE_FENTRY
>> # include <asm/ibt.h>
>> /* Add offset for endbr64 if IBT enabled */
>> -# define FTRACE_MCOUNT_MAX_OFFSET ENDBR_INSN_SIZE
>> +# define FTRACE_MCOUNT_MAX_OFFSET (ENDBR_INSN_SIZE + MCOUNT_INSN_SIZE)
>> #endif
>>
>> #ifdef CONFIG_DYNAMIC_FTRACE
>>
Above patch didn't work, but
Does it matter that I am compiling with "gcc -fcf-protection=none"
to not emit endbr32 instructions for i586?
--
kabe
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