Message-ID: <1E51DC0D8C72320F+8ad85e3e-1f03-4ca9-ba29-f2ff8a4cb831@uniontech.com>
Date: Wed, 5 Nov 2025 23:05:01 +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


On 2025/11/5 下午9:01, Baoquan He wrote:
> On 11/05/25 at 07:28pm, Qiang Ma wrote:
>> 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.
> Sorry, I can't support that. We all prepare the loading segments for the
> future jumping in kexec_tools if it's kexec_load interface. And calling
> print_segments() to print those loading information is natural. Why do we
> need print them two times for verifying if the printing is accuracy?
Is it necessary to verify the user-space data after it is passed to the 
kernel space?

> Could you explain why risc-v is special?
At first, when I saw that in the RISC-V architecture,
after kexec_image_info was removed from this commit eb7622d908a0
("kexec_file, riscv: print out debugging message if required"),
I thought only kexec_file_load was taken into consideration.
However, without considering that kexec_load would call
kexec_image_info to print segment and other debugging message,
I think that since it has been deleted.

Then, I referred to kexec_file_load and added these debugging message
to the general code of kexec_load. In this way, all architectures can
print these general debugging message.

Then I can add these debugging message to the general code,
so that all architectures can print these general debugging message.
>>>>>>>> +
>>>>>>>>      		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
>>>>>>>>
>

Powered by blists - more mailing lists