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

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Message-ID: <5FC4A8D79744B238+97288be4-6c1a-4c0d-ae7d-be2029ec87f3@uniontech.com>
Date: Wed, 5 Nov 2025 11:41:09 +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 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.
>> +
>>   		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
>>
>