Overview:
=========
The commit cbc2fe9d9cb2 ("kexec_file: add kexec_file flag to control
debug printing") added the kexec_file flag to control debug printing.
However, for arm64, after commit 6f8c1da071a4 ("kexec_file, arm64: print
out debugging message if required"), when using the kexec_load interface,
the kexec_image_info function is called to print debug message, but
it uses kexec_dprintk, which is only available under kexec_file,
then when specifying 'kexec -d', kexec_load interface will print nothing.

For riscv, commit eb7622d908a09 ("kexec_file, riscv: print out debugging
message if required") remove kexec_image_info(), because the content has
been printed out in generic code in kexec_file_load, but not in kexec_load.

Therefore, in order to solve the two problems mentioned above, for this
patchset, several things need to be done:

1. Enabling kexec_dprintk is available for kexec_load.
2. Add some debugging message of the deleted kexec_image_info
   to generic code.
3. Remove duplicate debugging prints for arm64.

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.

In this way, kexec_dprintk is available for kexec_load and kexec_file_load.

Then when specifying 'kexec -d', the debugging message using kexec_dprintk in
kexec_image_info can be printed normally.

The following are the key points of the specific changes:

1. rename kexec_file_dbg_print to kexec_dbg_print
2. Add KEXEC_DEBUG
3. Initialize kexec_dbg_print for kexec
4. 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:
[   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

On aarch64, the printed messages look like below:

Set CONFIG_KEXEC_FILE
[   39.033203] kexec_file: kernel: 0000000073414684 kernel_size: 0x3123a00
[   39.047010] kexec_file: Loaded initrd at 0x43cf0000 bufsz=0x17e0e19 memsz=0x17e1000
[   39.047054] kexec_file: Loaded dtb at 0x23ec00000 bufsz=0x386 memsz=0x1000
[   39.047056] kexec_file(Image): Loaded kernel at 0x40000000 bufsz=0x3123a00 memsz=0x3cf0000
[   39.047063] kexec_file: nr_segments = 3
[   39.047064] kexec_file: segment[0]: buf=0x0000000073414684 bufsz=0x3123a00 mem=0x40000000 memsz=0x3cf0000
[   39.073612] kexec_file: segment[1]: buf=0x000000005cd5746b bufsz=0x17e0e19 mem=0x43cf0000 memsz=0x17e1000
[   39.085309] kexec_file: segment[2]: buf=0x0000000084c4a0f1 bufsz=0x386 mem=0x23ec00000 memsz=0x1000
[   39.085459] machine_kexec_post_load:155:
[   39.085463]   kexec kimage info:
[   39.085467]     kern_reloc: 0x00000001620e2000
[   39.085468]     el2_vectors: 0x0000000000000000
[   39.085470] kexec_file: kexec_file_load: type:0, start:0x40000000 head:0x1620e4002 flags:0x8

Unset CONFIG_KEXEC_FILE:

With this patch:
[   35.156088] machine_kexec_post_load:155:
[   35.156097]   kexec kimage info:
[   35.156101]     kern_reloc: 0x000000011c134000
[   35.156102]     el2_vectors: 0x0000000000000000
[   35.156104] kexec: kexec_load: type:0, start:0x454d26b0 head:0x105c14002 flags:0xb70010

Without this patch:
There is no kexec print in dmesg.

Previous posts:
Link: https://lore.kernel.org/all/aTdxEvqY6Bcy7Wa1@MiWiFi-R3L-srv/

Qiang Ma (3):
  kexec: add kexec flag to control debug printing
  kexec: print out debugging message if required for kexec_load
  arm64: kexec: Adjust the debug print of kexec_image_info

 arch/arm64/kernel/machine_kexec.c | 2 --
 include/linux/kexec.h             | 9 +++++----
 include/uapi/linux/kexec.h        | 1 +
 kernel/kexec.c                    | 4 ++++
 kernel/kexec_core.c               | 4 +++-
 kernel/kexec_file.c               | 4 +---
 6 files changed, 14 insertions(+), 10 deletions(-)

-- 
2.20.1