Messages in this thread | | | Date | Thu, 26 Jul 2018 17:50:08 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: 4.17.x won't boot due to "x86/boot/compressed/64: Handle 5-level paging boot if kernel is above 4G" |
| |
On Thu, Jul 26, 2018 at 08:10:42AM +0000, Dmitry Malkin wrote: > > > On 07/25/2018 11:21 PM, Kirill A. Shutemov wrote: > > On Wed, Jul 25, 2018 at 05:26:02PM +0000, Dmitry Malkin wrote: > > > there may be some other reasons which may cause undefined behavior (reboot > > > for example): > > > > > > in arch/x86/boot/compressed/pgtable_64.c in function paging_prepare(): > > > > > > 1. structure "paging_config" allocated on stack without setting default > > > value for flag "l5_required": > > > > > struct paging_config paging_config = {}; > > > l5_required is set only if CONFIG_X86_5LEVEL is defined > > Hm? C99 initializer zeros the structure. > https://elixir.bootlin.com/linux/latest/source/Makefile#L366 > Here I only see std=gnu89.
gnu89 support C99-style initializers. The syntax above would clear fields that not initialized explicitly, in this case all of them.
> > > 2. reading from memory which may be reserved in case of EFI systems: > > > > > ebda_start = *(unsigned short *)0x40e << 4; > > > > > bios_start = *(unsigned short *)0x413 << 10; > > > Also, on EFI system without CSM it will results in all zeros. Which will > > > place trampoline_start to 0x9d000. And it also may be reserved memory. In > > > fact I have such system and it is causes instant reboot (when code starts > > > copying to "trampoline_start"). > > Could you show dmesg from such system? > Sure, here it is (please note than not both pages are reserved but only > second one: 0x9e000-0x9ffff):
Well. That's bad.
I don't see much options but parse e820 in decompression code. I hoped to avoid this.
Let me see what I can do there.
-- Kirill A. Shutemov
| |