Hi Juergen,
It helps to actually Cc the person who broke it ;-)
On Thu, Jun 23, 2022 at 11:46:07AM +0200, Juergen Gross wrote:
> Commit e32683c6f7d2 ("x86/mm: Fix RESERVE_BRK() for older binutils")
> put the brk area into the .bss..brk section (placed directly behind
> .bss),
Hm? It didn't actually do that.
For individual translation units, it did rename the section from
".brk_reservation" to ".bss..brk". But then during linking it's still
placed in .brk in vmlinux, just like before.
> causing it not to be cleared initially. As the brk area is used
> to allocate early page tables, these might contain garbage in not
> explicitly written entries.
>
> This is especially a problem for Xen PV guests, as the hypervisor will
> validate page tables (check for writable page tables and hypervisor
> private bits) before accepting them to be used. There have been reports
> of early crashes of PV guests due to illegal page table contents.
>
> Fix that by letting clear_bss() clear the brk area, too.
While it does make sense to clear the brk area, I don't understand how
my patch broke this. How was it getting cleared before?
--
Josh
