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

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Message-ID: <9362A6495165FCC0+d659800e-6751-4d26-a8b8-183705798e96@uniontech.com>
Date: Fri, 31 Oct 2025 10:40:07 +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
Subject: Re: [PATCH] kexec: print out debugging message if required for
 kexec_load


在 2025/10/30 21:58, Baoquan He 写道:
> On 10/30/25 at 07:41pm, Qiang Ma wrote:
>> 在 2025/10/30 17:42, Baoquan He 写道:
>>> On 10/30/25 at 03:33pm, 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.
>>> kexec_file_dbg_print setting when CONFIG_KEXEC_FILE is set. I doubt it
>>> doesn't work when you unset CONFIG_KEXEC_FILE.
>> Yes, I just actually tested it and it really doesn't work when unset
>> CONFIG_KEXEC_FILE.
>>
>> In the next version, I can add a KEXEC_DEBUG for the kernel and kexec-tools.
> Hold on please, it may not need that highweight change. I will reply to
> you tomorrow if I have other idea.
Ok. My current idea is to refer to kexec_file, define a kexec_dbg_print,
initialize it in the kimage_alloc_init(), modify KEXEC_FLAGS and 
kexec_dprintk,
and add the judgment of kexec_debug.
>>>> Signed-off-by: Qiang Ma <maqianga@...ontech.com>
>>>> ---
>>>>    kernel/kexec.c | 11 +++++++++++
>>>>    1 file changed, 11 insertions(+)
>>>>
>>>> diff --git a/kernel/kexec.c b/kernel/kexec.c
>>>> index 28008e3d462e..02845a7499e9 100644
>>>> --- a/kernel/kexec.c
>>>> +++ b/kernel/kexec.c
>>>> @@ -151,7 +151,15 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
>>>>    	if (ret)
>>>>    		goto out;
>>>> +	kexec_dprintk("nr_segments = %lu\n", image->nr_segments);
>>>>    	for (i = 0; i < nr_segments; i++) {
>>>> +		struct kexec_segment *ksegment;
>>>> +
>>>> +		ksegment = &image->segment[i];
>>>> +		kexec_dprintk("segment[%d]: buf=0x%p bufsz=0x%zx mem=0x%lx memsz=0x%zx\n",
>>>> +			      i, ksegment->buf, ksegment->bufsz, ksegment->mem,
>>>> +			      ksegment->memsz);
>>>> +
>>>>    		ret = kimage_load_segment(image, i);
>>>>    		if (ret)
>>>>    			goto out;
>>>> @@ -163,6 +171,9 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
>>>>    	if (ret)
>>>>    		goto out;
>>>> +	kexec_dprintk("kexec_file_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
>>>>
>>>>
>