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'vmcore-dmesg.c' already implements functionality to read
'vmcoreinfo' from vmcore file. The same can be used in other
features as well (one of which is reading the elf notes from
'kcore' file), so there is merit in moving this to the utility
libraries (util_lib).
Newer kernel versions (>= 4.19, with commit 23c85094fe1895caefdd
["proc/kcore: add vmcoreinfo note to /proc/kcore"], available),
have 'kcore' which now contains a new PT_NOTE which carries
the VMCOREINFO information.
If the same is available, we can benefit by using it in 'kexec-tools'.
This is especially useful for architectures like arm64 as we can
get kernel symbols like 'PHYS_OFFSET' from the '/proc/kcore' itself
and use it to calculate 'phys_offset' before we make a call to
'set_phys_offset()'.
For older kernels, we can try and determine the PHYS_OFFSET
value from PT_LOAD segments inside 'kcore' via some jugglery
of the correct virtual and physical address combinations.
Subsequent patch(es) in this series will use the same feature
to read the 'kcore' file.
This patch also makes some of the functions which were earlier
present in 'vmcore-dmesg.c' as non-static, so as to allow
future patches to use them as library functions.
Also we add the capability to read 'NUMBER(PHYS_OFFSET)' from
vmcoreinfo to the already present 'scan_vmcoreinfo()' code.
Future patches can look at reading more vmcoreinfo information
(for e.g. 'kaslr_offset()' for x86_64 and arm64) by using the
same framework.
Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
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