x86/kexec: fix potential cmem->ranges out of memory

In memmap_exclude_ranges(), elfheader will be excluded from crashk_res. 
In the current x86 architecture code, the elfheader is always allocated at
crashk_res.start.  It seems that there won't be a new split range.  But it
depends on the allocation position of elfheader in crashk_res.  To avoid
potential out of memory in future, add a extra slot.  Otherwise loading
the kdump kernel will fail because crash_exclude_mem_range will return
-ENOMEM.  random kexec_buf for passing dm crypt keys may cause a range
split too, add another extra slot here.

The similar issue also exists in fill_up_crash_elf_data().  The range to
be excluded is [0, 1M], start (0) is special and will not appear in the
middle of existing cmem->ranges[].  But in cast the low 1M could be
changed in the future, add a extra slot too.

Previous discussions:
[1] https://lore.kernel.org/kexec/ZXk2oBf%2FT1Ul6o0c@MiWiFi-R3L-srv/
[2] https://lore.kernel.org/kexec/273284e8-7680-4f5f-8065-c5d780987e59@easystack.cn/
[3] https://lore.kernel.org/kexec/ZYQ6O%2F57sHAPxTHm@MiWiFi-R3L-srv/

Link: https://lkml.kernel.org/r/20250904093855.1180154-1-coxu@redhat.com
Signed-off-by: fuqiang wang <fuqiang.wang@easystack.cn>
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions