linux-kernel - Re: [PATCH v3 0/3] kexec: print out debugging message if required for kexec

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Message-ID: <7aadda55-d2a4-40f9-95ef-d284ec358646@linux.ibm.com>
Date: Thu, 27 Nov 2025 17:31:13 +0530
From: Sourabh Jain <sourabhjain@...ux.ibm.com>
To: Qiang Ma <maqianga@...ontech.com>, akpm@...ux-foundation.org,
        bhe@...hat.com
Cc: kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        shivang upadhyay <shivangu@...ux.ibm.com>
Subject: Re: [PATCH v3 0/3] kexec: print out debugging message if required for
 kexec_load

Hello All,

Do we have plan to support KEXEC_DEBUG flag?

Because upstream kexec-tools already added support for KEXEC_DEBUG flag
and that breaks the kexec_load with -d option.

- kexec: add kexec flag to support debug printing
   https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git/commit/?id=71d6fd99af7e


Thanks,
Sourabh Jain


On 26/11/25 14:14, Qiang Ma wrote:
> Overview:
> =========
> 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().
>      
> Since kexec_load and kexec_file_load are not triggered simultaneously,
> we can unify the debug flag of kexec and kexec_file as kexec_dbg_print.
>      
> Next, we need to do some things in this patchset:
>      
> 1. rename kexec_file_dbg_print to kexec_dbg_print
> 2. Add KEXEC_DEBUG
> 3. Initialize kexec_dbg_print for kexec
> 4. Fix uninitialized struct kimage *image pointer
> 5. Set the reset of kexec_dbg_print to kimage_free
>
> Testing:
> =========
> I did testing on x86_64, arm64 and loongarch. On x86_64, the printed messages
> look like below:
>
> unset CONFIG_KEXEC_FILE:
> [   81.502374] kexec: kexec_load: type:0, start:0x23fff7700 head:0x10a4b9002 flags:0x3e0010
>
> set CONFIG_KEXEC_FILE
> [   36.774228] kexec_file: kernel: 0000000066c386c8 kernel_size: 0xd78400
> [   36.821814] kexec-bzImage64: Loaded purgatory at 0x23fffb000
> [   36.821826] kexec-bzImage64: Loaded boot_param, command line and misc at 0x23fff9000 bufsz=0x12d0 memsz=0x2000
> [   36.821829] kexec-bzImage64: Loaded 64bit kernel at 0x23d400000 bufsz=0xd73400 memsz=0x2ab7000
> [   36.821918] kexec-bzImage64: Loaded initrd at 0x23bd0b000 bufsz=0x16f40a8 memsz=0x16f40a8
> [   36.821920] kexec-bzImage64: Final command line is: root=/dev/mapper/test-root crashkernel=auto rd.lvm.lv=test/root
> [   36.821925] kexec-bzImage64: E820 memmap:
> [   36.821926] kexec-bzImage64: 0000000000000000-000000000009ffff (1)
> [   36.821928] kexec-bzImage64: 0000000000100000-0000000000811fff (1)
> [   36.821930] kexec-bzImage64: 0000000000812000-0000000000812fff (2)
> [   36.821931] kexec-bzImage64: 0000000000813000-00000000bee38fff (1)
> [   36.821933] kexec-bzImage64: 00000000bee39000-00000000beec2fff (2)
> [   36.821934] kexec-bzImage64: 00000000beec3000-00000000bf8ecfff (1)
> [   36.821935] kexec-bzImage64: 00000000bf8ed000-00000000bfb6cfff (2)
> [   36.821936] kexec-bzImage64: 00000000bfb6d000-00000000bfb7efff (3)
> [   36.821937] kexec-bzImage64: 00000000bfb7f000-00000000bfbfefff (4)
> [   36.821938] kexec-bzImage64: 00000000bfbff000-00000000bff7bfff (1)
> [   36.821939] kexec-bzImage64: 00000000bff7c000-00000000bfffffff (2)
> [   36.821940] kexec-bzImage64: 00000000feffc000-00000000feffffff (2)
> [   36.821941] kexec-bzImage64: 00000000ffc00000-00000000ffffffff (2)
> [   36.821942] kexec-bzImage64: 0000000100000000-000000023fffffff (1)
> [   36.872348] kexec_file: nr_segments = 4
> [   36.872356] kexec_file: segment[0]: buf=0x000000005314ece7 bufsz=0x4000 mem=0x23fffb000 memsz=0x5000
> [   36.872370] kexec_file: segment[1]: buf=0x000000006e59b143 bufsz=0x12d0 mem=0x23fff9000 memsz=0x2000
> [   36.872374] kexec_file: segment[2]: buf=0x00000000eb7b1fc3 bufsz=0xd73400 mem=0x23d400000 memsz=0x2ab7000
> [   36.882172] kexec_file: segment[3]: buf=0x000000006af76441 bufsz=0x16f40a8 mem=0x23bd0b000 memsz=0x16f5000
> [   36.889113] kexec_file: kexec_file_load: type:0, start:0x23fffb150 head:0x101a2e002 flags:0x8
>
> Changes in v3:
> ==========
> - Rename kexec_core_dbg_print to kexec_dbg_print
> - Remove unnecessary segments prints
> - Remove patch "kexec_file: Fix the issue of mismatch between loop variable types"
>
> Qiang Ma (3):
>    kexec: Fix uninitialized struct kimage *image pointer
>    kexec: add kexec flag to control debug printing
>    kexec: print out debugging message if required for kexec_load
>
>   include/linux/kexec.h      | 9 +++++----
>   include/uapi/linux/kexec.h | 1 +
>   kernel/kexec.c             | 8 +++++++-
>   kernel/kexec_core.c        | 4 +++-
>   kernel/kexec_file.c        | 4 +---
>   5 files changed, 17 insertions(+), 9 deletions(-)
>