Messages in this thread | | | Date | Wed, 08 Mar 2023 19:09:34 +0300 | From | Evgeniy Baskov <> | Subject | Re: [PATCH v4 08/26] x86/boot: Map memory explicitly |
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On 2023-03-08 13:28, Ard Biesheuvel wrote: > On Wed, 8 Mar 2023 at 10:38, Ard Biesheuvel <ardb@kernel.org> wrote: >> >> On Thu, 15 Dec 2022 at 13:38, Evgeniy Baskov <baskov@ispras.ru> wrote: >> > >> > Implicit mappings hide possible memory errors, e.g. allocations for >> > ACPI tables were not included in boot page table size. >> > >> > Replace all implicit mappings from page fault handler with >> > explicit mappings. >> > >> >> I agree with the motivation but this patch seems to break the boot >> under SeaBIOS/QEMU, and I imagine other legacy BIOS boot scenarios as >> well. >> >> Naively, I would assume that there is simply a legacy BIOS region that >> we fail to map here, but I am fairly clueless when it comes to non-EFI >> x86 boot so take this with a grain of salt. >> > > The below seems to help - not sure why exactly, but apparently legacy > BIOS needs the bootparams struct to be mapped writable?
I think I got too eager adding mappings to everything. In the process_efi_entries() bootparams should already be mapped, so I will just remove the call. And AFAIK bootparams is indeed gets written to.
> > --- a/arch/x86/boot/compressed/kaslr.c > +++ b/arch/x86/boot/compressed/kaslr.c > @@ -31,6 +31,7 @@ > #include <linux/ctype.h> > #include <generated/utsversion.h> > #include <generated/utsrelease.h> > +#include <asm/shared/pgtable.h> > > #define _SETUP > #include <asm/setup.h> /* For COMMAND_LINE_SIZE */ > @@ -688,7 +689,7 @@ process_efi_entries(unsigned long minimum, > unsigned long image_size) > u32 nr_desc; > int i; > > - kernel_add_identity_map((unsigned long)e, (unsigned long)(e + > 1), 0); > + kernel_add_identity_map((unsigned long)e, (unsigned long)(e + > 1), MAP_WRITE); > > signature = (char *)&e->efi_loader_signature; > if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) &&
Thanks, Evgeniy Baskov
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