Dear Dave,
At 07/09/2018 10:20 PM, Dave Anderson wrote:
[...]
Since the "__pgtable_l5_enabled" symbol is a static data symbol located
in the __START_KERNEL_map region, x86_64_VTOP() only needs the kernel's
"phys_base" value in order to translate the symbol value into a
physical address:
ulong x86_64_VTOP(ulong vaddr)
{
if (vaddr >= __START_KERNEL_map)
return ((vaddr) - (ulong)__START_KERNEL_map + machdep->machspec->phys_base);
else
return ((vaddr) - PAGE_OFFSET);
}
So if the contents of "__pgtable_l5_enabled" is all that is needed,
I think you can do something like:
case POST_RELOC:
+ if (!(machdep->flags & VM_5LEVEL) &&
+ kernel_symbol_exists("__pgtable_l5_enabled")) {
+ int l5_enabled;
+ readmem(symbol_value("__pgtable_l5_enabled"), KVADDR,
+ &l5_enabled, sizeof(int), "__pgtable_l5_enabled",
+ FAULT_ON_ERROR);
+
+ if (l5_enabled) {
+ ... execute the relevant section from PRE_GDB ...
+ }
which would be this section from PRE_GDB:
case VM_5LEVEL:
machdep->machspec->userspace_top = USERSPACE_TOP_5LEVEL;
machdep->machspec->page_offset = PAGE_OFFSET_5LEVEL;
machdep->machspec->vmalloc_start_addr = VMALLOC_START_ADDR_5LEVEL;
machdep->machspec->vmalloc_end = VMALLOC_END_5LEVEL;
machdep->machspec->modules_vaddr = MODULES_VADDR_5LEVEL;
machdep->machspec->modules_end = MODULES_END_5LEVEL;
machdep->machspec->vmemmap_vaddr = VMEMMAP_VADDR_5LEVEL;
machdep->machspec->vmemmap_end = VMEMMAP_END_5LEVEL;
if (symbol_exists("vmemmap_populate"))
machdep->flags |= VMEMMAP;
machdep->machspec->physical_mask_shift = __PHYSICAL_MASK_SHIFT_5LEVEL;
machdep->machspec->pgdir_shift = PGDIR_SHIFT_5LEVEL;
machdep->machspec->ptrs_per_pgd = PTRS_PER_PGD_5LEVEL;
if ((machdep->machspec->p4d = (char *)malloc(PAGESIZE())) == NULL)
error(FATAL, "cannot malloc p4d space.");
machdep->machspec->last_p4d_read = 0;
machdep->uvtop = x86_64_uvtop_level4; /* 5-level is optional per-task */
}
machdep->kvbase = (ulong)PAGE_OFFSET;
machdep->identity_map_base = (ulong)PAGE_OFFSET;
The only things that I can think of that might be a problem is the
readmem() of "__pgtable_l5_enabled" will need to get by this part
of x86_64_kvtop() in order to use x86_64_VTOP():
if (!IS_VMALLOC_ADDR(kvaddr)) {
*paddr = x86_64_VTOP(kvaddr);
if (!verbose)
return TRUE;
}
where IS_VMALLOC_ADDR() would still be using the 4-level addresses.
But that could be worked around some way.
AFAIC, It doesn't matter, here, due to the vt->vmalloc_start is 0 at
this time, we always use the x86_64_VTOP().
if (!vt->vmalloc_start) {
*paddr = x86_64_VTOP(kvaddr);
return TRUE;
}
if (!IS_VMALLOC_ADDR(kvaddr)) {
*paddr = x86_64_VTOP(kvaddr);
if (!verbose)
return TRUE;
}
Can you give that a test?
Yes, I have tested this both in KDump and virsh dump cases. It can work
well. I will send v2 patch for you.
Thanks,
dou.
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