[Makedumpfile PATCH v3 1/2] makedumpfile: add runtime kaslr offset if it exists

[Pratyush Anand]

write_vmcoreinfo_data(void)
{
/*
+ * write 1st kernel's KERNELOFFSET
+ */
+ if (info->kaslr_offset)
+ fprintf(info->file_vmcoreinfo, "%s%lx\n", STR_KERNELOFFSET,
+ info->kaslr_offset);

When will this data written to VMCOREINFO file be used ?
info->kaslr_offset is necessary for vmlinux but -x and -i are exclusive.

Lets says we have got a vmcore1 after re-filtering original vmcore. Now, if we
would like to re-filter vmcore1 then we will need kaslr_offset again. So,
should we not right kaslr_offset in vmcoreinfo of vmcore1 as well?

write_vmcoreinfo_data() is called only for -g option, it makes a
VMCOREINFO file as a separate file, it doesn't overwrite VMCOREINFO in vmcore.

OK..got it.

Will remove this function and send v4.


Thanks

~Pratyush

[Pratyush Anand]

we do not call get_elf_info() in case of refiltering and sadump.
Therefore, we will not have any pt_load in that case, and so we get:

get_page_offset_x86_64: Can't get any pt_load to calculate page offset.

However, we will have vmcoreinfo and vmlinux information in case of
re-filtering. So, we are able to find kaslr offset and we can get
page_offset_base address. Thus we can read the page offset as well.

If kaslr is not enabled and also we do not have valid PT_LOAD to
calculate page offset then use old method to find fixed page
offset.

In case of virsh dump virtual addresses in PT_LOAD are 0. Ignore such
addresses for the page_offset calculation.

Suggested-by: HATAYAMA Daisuke <***@jp.fujitsu.com>
Signed-off-by: Pratyush Anand <***@redhat.com>
---
arch/x86_64.c | 36 +++++++++++++++++++++++++++++-------
1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/arch/x86_64.c b/arch/x86_64.c
index fd2e8ac154d6..18384a8dd684 100644
--- a/arch/x86_64.c
+++ b/arch/x86_64.c
@@ -75,17 +75,39 @@ get_page_offset_x86_64(void)
int i;
unsigned long long phys_start;
unsigned long long virt_start;
+ unsigned long page_offset_base;
+
+ if (info->kaslr_offset) {
+ page_offset_base = get_symbol_addr("page_offset_base");
+ page_offset_base += info->kaslr_offset;
+ if (!readmem(VADDR, page_offset_base, &info->page_offset,
+ sizeof(info->page_offset))) {
+ ERRMSG("Can't read page_offset_base.\n");
+ return FALSE;
+ }
+ return TRUE;
+ }

- for (i = 0; get_pt_load(i, &phys_start, NULL, &virt_start, NULL); i++) {
- if (virt_start < __START_KERNEL_map
- && phys_start != NOT_PADDR) {
- info->page_offset = virt_start - phys_start;
- return TRUE;
+ if (get_num_pt_loads()) {
+ for (i = 0;
+ get_pt_load(i, &phys_start, NULL, &virt_start, NULL);
+ i++) {
+ if (virt_start != NOT_KV_ADDR
+ && virt_start < __START_KERNEL_map
+ && phys_start != NOT_PADDR) {
+ info->page_offset = virt_start - phys_start;
+ return TRUE;
+ }
}
}

- ERRMSG("Can't get any pt_load to calculate page offset.\n");
- return FALSE;
+ if (info->kernel_version < KERNEL_VERSION(2, 6, 27)) {
+ info->page_offset = __PAGE_OFFSET_ORIG;
+ } else {
+ info->page_offset = __PAGE_OFFSET_2_6_27;
+ }
+
+ return TRUE;
}

int