[PATCH v7 0/5] kdump: Allow ELF header creation in new kernel

Michael Holzheu
2013-07-16T16:18:42Z

Hello Andrew,

Here a new kdump patch series that we have discussed with Vivek and
Hatayama during the last months.

Besides of the feature described below, this patch series also fixes a
regression on s390 that was introduced with the mmap patches for
/proc/vmcore (git commit 83086978c63afd7c73e1c).

See also:
http://lists.infradead.org/pipermail/kexec/2013-July/009287.html

Is it somehow possible to integrate this patch series into 3.11?

ChangeLog
=========
v6 => v7)

- Rebase to v3.11-rc1
- Return VM_FAULT_SIGBUS in fault handler for non s390
- Use __va() for buffer in fault handler

v5 => v6)

- Set elfcorehdr_addr to ELFCORE_ADDR_ERR after elfcorehdr_free()
- Fix OLDMEM_SIZE/ZFCPDUMP_HSA_SIZE confusion
- Remove return VM_FAULT_MAJOR/MINOR
- Use find_or_create_page() in mmap_vmcore_fault()
- Use kfree instead of vfree in elfcorehdr_free()

v4 => v5)

- Add weak function elfcorehdr_read_notes() to read ELF notes
- Rename weak functions for ELF header access and use "vmcorehdr_" prefix
- Generic vmcore code calls elfcorehdr_alloc() if elfcorehdr= is not specified
- Add vmcore fault handler for mmap of non-resident memory regions
- Add weak function remap_oldmem_pfn_range() to be used by zfcpdump for mmap

v3 => v4)

- Rebase to 3.10-rc2 + vmcore mmap patches v8

v2 => v3)

- Get rid of ELFCORE_ADDR_NEWMEM
- Make read_from_crash_header() only read from kernel
- Move read_from_crash_header() to weak function arch_read_from_crash_header()
- Implement read_from_crash_header() strong function for s390
- Set elfcorehdr_addr to address of new ELF header

v1 => v2)

- Rebase 3.10-rc2 + vmcore mmap patches
- Introduced arch_get/free_crash_header() and ELFCORE_ADDR_NEWMEM

Feature Description
===================
For s390 we want to use /proc/vmcore for our SCSI stand-alone
dump (zfcpdump). We have support where the first HSA_SIZE bytes are
saved into a hypervisor owned memory area (HSA) before the kdump
kernel is booted. When the kdump kernel starts, it is restricted
to use only HSA_SIZE bytes.

The advantages of this mechanism are:

* No crashkernel memory has to be defined in the old kernel.
* Early boot problems (before kexec_load has been done) can be dumped
* Non-Linux systems can be dumped.

We modify the s390 copy_oldmem_page() function to read from the HSA memory
if memory below HSA_SIZE bytes is requested.

Since we cannot use the kexec tool to load the kernel in this scenario,
we have to build the ELF header in the 2nd (kdump/new) kernel.

So with the following patch set we would like to introduce the new
function that the ELF header for /proc/vmcore can be created in the 2nd
kernel memory.

The following steps are done during zfcpdump execution:

1. Production system crashes
2. User boots a SCSI disk that has been prepared with the zfcpdump tool
3. Hypervisor saves CPU state of boot CPU and HSA_SIZE bytes of memory into HSA
4. Boot loader loads kernel into low memory area
5. Kernel boots and uses only HSA_SIZE bytes of memory
6. Kernel saves registers of non-boot CPUs
7. Kernel does memory detection for dump memory map
8. Kernel creates ELF header for /proc/vmcore
9. /proc/vmcore uses this header for initialization
10. The zfcpdump user space reads /proc/vmcore to write dump to SCSI disk
- copy_oldmem_page() copies from HSA for memory below HSA_SIZE
- copy_oldmem_page() copies from real memory for memory above HSA_SIZE
---
Jan Willeke (1):
s390/vmcore: Implement remap_oldmem_pfn_range for s390

Michael Holzheu (4):
vmcore: Introduce ELF header in new memory feature
s390/vmcore: Use ELF header in new memory feature
vmcore: Introduce remap_oldmem_pfn_range()
s390/vmcore: Use vmcore for zfcpdump

arch/s390/Kconfig | 3 +-
arch/s390/include/asm/sclp.h | 1 +
arch/s390/kernel/crash_dump.c | 228 ++++++++++++++++++++++++++++++++++--------
drivers/s390/char/zcore.c | 6 +-
fs/proc/vmcore.c | 152 ++++++++++++++++++++++++----
include/linux/crash_dump.h | 9 ++
6 files changed, 333 insertions(+), 66 deletions(-)

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