linux-kernel - Re: [PATCH v2 3/4] kexec: print out debugging message if required for kexec

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Message-ID: <44308A6B6D8BEB61+c143d52e-03dd-48bf-aadd-8a0d9196b280@uniontech.com>
Date: Wed, 5 Nov 2025 19:28:10 +0800
From: Qiang Ma <maqianga@...ontech.com>
To: Baoquan He <bhe@...hat.com>
Cc: akpm@...ux-foundation.org, kexec@...ts.infradead.org,
 linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 3/4] kexec: print out debugging message if required for
 kexec_load


在 2025/11/5 16:55, Baoquan He 写道:
> On 11/05/25 at 04:35pm, Qiang Ma wrote:
>> 在 2025/11/5 15:53, Baoquan He 写道:
>>> On 11/05/25 at 11:41am, Qiang Ma wrote:
>>>> 在 2025/11/5 11:01, Baoquan He 写道:
>>>>> On 11/03/25 at 02:34pm, Qiang Ma wrote:
>>>>>> The commit a85ee18c7900 ("kexec_file: print out debugging message
>>>>>> if required") has added general code printing in kexec_file_load(),
>>>>>> but not in kexec_load().
>>>>>>
>>>>>> Especially in the RISC-V architecture, kexec_image_info() has been
>>>>>> removed(commit eb7622d908a0 ("kexec_file, riscv: print out debugging
>>>>>> message if required")). As a result, when using '-d' for the kexec_load
>>>>>> interface, print nothing in the kernel space. This might be helpful for
>>>>>> verifying the accuracy of the data passed to the kernel. Therefore,
>>>>>> refer to this commit a85ee18c7900 ("kexec_file: print out debugging
>>>>>> message if required"), debug print information has been added.
>>>>>>
>>>>>> Signed-off-by: Qiang Ma <maqianga@...ontech.com>
>>>>>> Reported-by: kernel test robot <lkp@...el.com>
>>>>>> Closes: https://lore.kernel.org/oe-kbuild-all/202510310332.6XrLe70K-lkp@intel.com/
>>>>>> ---
>>>>>>     kernel/kexec.c | 11 +++++++++++
>>>>>>     1 file changed, 11 insertions(+)
>>>>>>
>>>>>> diff --git a/kernel/kexec.c b/kernel/kexec.c
>>>>>> index c7a869d32f87..9b433b972cc1 100644
>>>>>> --- a/kernel/kexec.c
>>>>>> +++ b/kernel/kexec.c
>>>>>> @@ -154,7 +154,15 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
>>>>>>     	if (ret)
>>>>>>     		goto out;
>>>>>> +	kexec_dprintk("nr_segments = %lu\n", nr_segments);
>>>>>>     	for (i = 0; i < nr_segments; i++) {
>>>>>> +		struct kexec_segment *ksegment;
>>>>>> +
>>>>>> +		ksegment = &image->segment[i];
>>>>>> +		kexec_dprintk("segment[%lu]: buf=0x%p bufsz=0x%zx mem=0x%lx memsz=0x%zx\n",
>>>>>> +			      i, ksegment->buf, ksegment->bufsz, ksegment->mem,
>>>>>> +			      ksegment->memsz);
>>>>> There has already been a print_segments() in kexec-tools/kexec/kexec.c,
>>>>> you will get duplicated printing. That sounds not good. Have you tested
>>>>> this?
>>>> I have tested it, kexec-tools is the debug message printed
>>>> in user space, while kexec_dprintk is printed
>>>> in kernel space.
>>>>
>>>> This might be helpful for verifying the accuracy of
>>>> the data passed to the kernel.
>>> Hmm, that's not necessary with a debug printing to verify value passed
>>> in kernel. We should only add debug pringing when we need but lack it.
>>> I didn't check it carefully, if you add the debug printing only for
>>> verifying accuracy, that doesn't justify the code change.
>> It's not entirely because of it.
>>
>> Another reason is that for RISC-V, for kexec_file_load interface,
>> kexec_image_info() was deleted at that time because the content
>> has been printed out in generic code.
>>
>> However, these contents were not printed in kexec_load because
>> kexec_image_info was deleted. So now it has been added.
> print_segments() in kexec-tools/kexec/kexec.c is a generic function,
> shouldn't you make it called in kexec-tools for risc-v? I am confused by
> the purpose of this patchset.
There is a problem with what I expressed.
I don't want to add print_segments to riscv.
I want to add some debugging message(ksegment,kimage,flag) for kexec_load.

Although ksegment debugging message has been printed in kexec-tools,
it is still helpful for debugging the kernel space function.
>
>>>>>> +
>>>>>>     		ret = kimage_load_segment(image, i);
>>>>>>     		if (ret)
>>>>>>     			goto out;
>>>>>> @@ -166,6 +174,9 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
>>>>>>     	if (ret)
>>>>>>     		goto out;
>>>>>> +	kexec_dprintk("kexec_load: type:%u, start:0x%lx head:0x%lx flags:0x%lx\n",
>>>>>> +		      image->type, image->start, image->head, flags);
>>>>>> +
>>>>>>     	/* Install the new kernel and uninstall the old */
>>>>>>     	image = xchg(dest_image, image);
>>>>>> -- 
>>>>>> 2.20.1
>>>>>>
>