Hi Atsushi and Simon,
I find a problem about VMSPLIT on arm plarform, related to kexec and
makedumpfile.
When CONFIG_VMSPLIT_1G/2G is selected by kernel, PAGE_OFFSET is actually
0x40000000 or 0x80000000. However, kexec hard codes PAGE_OFFSET to
0xc0000000 (in kexec/arch/arm/crashdump-arm.h), which is incorrect in
these situations. For example, on realview-pbx board with 1G/3G VMSPLIT,
PHDRs in generated /proc/vmcore is as follow:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
NOTE 0x001000 0x00000000 0x00000000 0x00690 0x00690 0
LOAD 0x002000 0xc0000000 0x00000000 0x10000000 0x10000000 RWE 0
LOAD 0x10002000 0xe0000000 0x20000000 0x8000000 0x8000000 RWE 0
LOAD 0x18002000 0xf0000000 0x30000000 0x10000000 0x10000000 RWE 0
LOAD 0x28002000 0x40000000 0x80000000 0x10000000 0x10000000 RWE 0
Which should be:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
...
LOAD ... 0x40000000 0x00000000 0x10000000 0x10000000 RWE 0
LOAD ... 0x60000000 0x20000000 0x8000000 0x8000000 RWE 0
LOAD ... 0x70000000 0x30000000 0x10000000 0x10000000 RWE 0
LOAD ... 0xc0000000 0x80000000 0x10000000 0x10000000 RWE 0
I don't know why crash utility can deal with it without problem, but in
makedumpfile such VMSPLIT setting causes segfault:
$ ./makedumpfile -c -d 31 /proc/vmcore ./out -f
The kernel version is not supported.
The created dumpfile may be incomplete.
Excluding unnecessary pages : [ 0.0 %] /Segmentation fault
There are many ways to deal with it, I want discuss them in the maillist and
make a decision:
1. Kexec changes, detect PAGE_OFFSET dynamically. However, I don't know
whether there is a reliably way for this purpose, here I suggest
kernel to export PAGE_OFFSET through sysfs, such as
/sys/kernel/page_offset.
2. Or, kexec accepts PAGE_OFFSET as a command line arguments, let user
provide correct information.
3. Or, makedumpfile changes, don't trust EHDR anymore. Kernel should
export PAGE_OFFSET through VMCOREINFO.
How do you feel?
Thank you!
