[PATCH v2 0/2] kexec-tools/arm64: Add support to read PHYS_OFFSET from kcore

[Bhupesh Sharma <bhsharma@redhat.com>]

Changes from v1:
---------------
 - Added the support for older kernels, where we determine the
   PHYS_OFFSET value from PT_LOAD segments inside 'kcore'.
 - Improved commit logs since v1.

On certain arm64 platforms, it has been noticed that due
to a hole at the start of physical ram exposed to kernel
(i.e. it doesn't start from address 0), the kernel still
calculates the 'memstart_addr' kernel variable as 0.

Whereas the SYSTEM_RAM or IOMEM_RESERVED range in '/proc/iomem'
would carry a first entry whose start address is non-zero
(as the physical ram exposed to the kernel starts from a
non-zero address).

In such cases, if we rely on '/proc/iomem' entries to
calculate the phys_offset, then we will have mismatch
between the user-space and kernel space 'PHYS_OFFSET'
value. The present 'kexec-tools' code does the same
in 'get_memory_ranges_iomem_cb()' function when it makes
a call to 'set_phys_offset()'. This can cause the vmcore
generated via 'kexec-tools' to miss the last few bytes as
the first '/proc/iomem' starts from a non-zero address.

Please see [0] for the original bug-report from Yanjiang Jin.

This patchset tries to fix the same.

Details about the patches in this series:
----------------------------------------
PATCH 1/2 ->

- Tries to move the elf read functionality from 'vmcore-dmesg.c' to
  a new utility library named 'elf_info.c', so that subsequent patches
  can use the same.
- See the patch log for more details.

PATCH 2/2 ->
- Implements the actual functionality of reading the PHYS_OFFSET for arm64
  platforms from the kcore (either VMCOREINFO PT_NOTE inside 'kcore'
  or from the PT_LOAD segments inside 'kcore').
- See the patch log for more details.

[0] https://www.spinics.net/lists/kexec/msg20618.html

Bhupesh Sharma (2):
  util_lib: Add functionality to read elf notes
  arm64: Add support to read PHYS_OFFSET from 'kcore' - pt_note or
    pt_load (if available)

 kexec/arch/arm64/kexec-arm64.c                     | 194 +++++-
 kexec/arch/arm64/kexec-arm64.h                     |  15 +-
 util_lib/Makefile                                  |   4 +-
 vmcore-dmesg/vmcore-dmesg.c => util_lib/elf_info.c | 193 ++++--
 util_lib/include/elf_info.h                        |  35 +
 vmcore-dmesg/Makefile                              |   4 +-
 vmcore-dmesg/vmcore-dmesg.c                        | 742 +--------------------
 7 files changed, 386 insertions(+), 801 deletions(-)
 copy vmcore-dmesg/vmcore-dmesg.c => util_lib/elf_info.c (86%)
 create mode 100644 util_lib/include/elf_info.h

-- 
2.7.4


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