From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] ARM: Make the dumped instructions are consistent with the disassembled ones
Date: Mon, 10 Oct 2022 18:46:12 +0800 [thread overview]
Message-ID: <08054412-06de-3c3e-48b8-1a7eb327a2d0@huawei.com> (raw)
In-Reply-To: <CAMj1kXFHGPpoSvt3J2XN4tAf2QZ--Lp8KpsuyufSjx+HuRfz0A@mail.gmail.com>
On 2022/10/10 18:10, Ard Biesheuvel wrote:
> On Mon, 10 Oct 2022 at 11:56, Zhen Lei <thunder.leizhen@huawei.com> wrote:
>>
>> In ARM, the mapping of instruction memory is always little-endian, except
>> some BE-32 supported ARM architectures. Such as ARMv7-R, its instruction
>> endianness may be BE-32. Of course, its data endianness will also be BE-32
>> mode. Due to two negatives make a positive, the instruction stored in the
>> register after reading is in little-endian format. But for the case of
>> BE-8, the instruction endianness is LE, the instruction stored in the
>> register after reading is in big-endian format, which is inconsistent
>> with the disassembled one.
>>
>> For example:
>> The content of disassembly:
>> c0429ee8: e3500000 cmp r0, #0
>> c0429eec: 159f2044 ldrne r2, [pc, #68]
>> c0429ef0: 108f2002 addne r2, pc, r2
>> c0429ef4: 1882000a stmne r2, {r1, r3}
>> c0429ef8: e7f000f0 udf #0
>>
>> The output of undefined instruction exception:
>> Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
>> ... ...
>> Code: 000050e3 44209f15 02208f10 0a008218 (f000f0e7)
>>
>> This inconveniences the checking of instructions. What's worse is that,
>> for somebody who don't know about this, might think the instructions are
>> all broken.
>>
>> So, when CONFIG_CPU_ENDIAN_BE8=y, let's convert the instructions to
>> little-endian format before they are printed. The conversion result is
>> as follows:
>> Code: e3500000 159f2044 108f2002 1882000a (e7f000f0)
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>> arch/arm/kernel/traps.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
>> index 34aa80c09c508c1..50b00c9091f079d 100644
>> --- a/arch/arm/kernel/traps.c
>> +++ b/arch/arm/kernel/traps.c
>> @@ -193,6 +193,13 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
>> bad = get_user(val, &((u32 __user *)addr)[i]);
>> }
>>
>> + if (IS_ENABLED(CONFIG_CPU_ENDIAN_BE8)) {
>> + if (thumb)
>> + val = (__force unsigned int)cpu_to_le16(val);
>
> Better use swab16() here instead of the ugly __force cast, given that
> the swab is going to occur unconditionally here.
Good idea.
>
>
>> + else
>> + val = (__force unsigned int)cpu_to_le32(val);
>
> and swab32() here
OK
>
>
>> + }
>> +
>> if (!bad)
>> p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ",
>> width, val);
>> --
>> 2.25.1
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> .
>
--
Regards,
Zhen Lei
next prev parent reply other threads:[~2022-10-10 10:46 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-10 9:53 [PATCH v2 0/2] ARM: Make the dumped instructions are consistent with the disassembled ones Zhen Lei
2022-10-10 9:53 ` [PATCH v2 1/2] ARM: Fix some check warnings of tool sparse Zhen Lei
2022-10-10 10:20 ` Ard Biesheuvel
2022-10-10 10:58 ` Leizhen (ThunderTown)
2022-10-10 11:06 ` Ard Biesheuvel
2022-10-10 16:08 ` Russell King (Oracle)
2022-10-10 16:14 ` Ard Biesheuvel
2022-10-10 16:17 ` Russell King (Oracle)
2022-10-11 2:29 ` Leizhen (ThunderTown)
2022-10-13 10:51 ` Russell King (Oracle)
2022-10-13 11:34 ` Leizhen (ThunderTown)
2022-11-28 8:39 ` Leizhen (ThunderTown)
2022-10-10 16:05 ` Russell King (Oracle)
2022-10-11 2:13 ` Leizhen (ThunderTown)
2022-10-13 1:28 ` Leizhen (ThunderTown)
2022-10-10 9:53 ` [PATCH v2 2/2] ARM: Make the dumped instructions are consistent with the disassembled ones Zhen Lei
2022-10-10 10:10 ` Ard Biesheuvel
2022-10-10 10:46 ` Leizhen (ThunderTown) [this message]
2022-10-10 11:07 ` Ard Biesheuvel
2022-10-10 11:29 ` Leizhen (ThunderTown)
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