[RFC] efi/tpm: add efi.tpm_log as a reserved region in 820_table_firmware

[Dave Young]

On Thu, 12 Sept 2024 at 22:15, Ard Biesheuvel <ardb at kernel.org> wrote:
>
> (cc Dave)

Thanks for ccing me.

>
> Full thread here:
> https://lore.kernel.org/all/CAMj1kXG1hbiafKRyC5qM1Vj5X7x-dmLndqqo2AYnHMRxDz-80w@mail.gmail.com/T/#u
>
> On Thu, 12 Sept 2024 at 16:05, Ard Biesheuvel <ardb at kernel.org> wrote:
> >
> > On Thu, 12 Sept 2024 at 15:55, Usama Arif <usamaarif642 at gmail.com> wrote:
> > >
> > >
> > >
> > > On 12/09/2024 14:10, Ard Biesheuvel wrote:
> > > > Does the below help at all?
> > > >
> > > > --- a/drivers/firmware/efi/tpm.c
> > > > +++ b/drivers/firmware/efi/tpm.c
> > > > @@ -60,7 +60,7 @@ int __init efi_tpm_eventlog_init(void)
> > > >         }
> > > >
> > > >         tbl_size = sizeof(*log_tbl) + log_tbl->size;
> > > > -       memblock_reserve(efi.tpm_log, tbl_size);
> > > > +       efi_mem_reserve(efi.tpm_log, tbl_size);
> > > >
> > > >         if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR) {
> > > >                 pr_info("TPM Final Events table not present\n");
> > >
> > > Unfortunately not. efi_mem_reserve updates e820_table, while kexec looks at /sys/firmware/memmap
> > > which is e820_table_firmware.
> > >
> > > arch_update_firmware_area introduced in the RFC patch does the same thing as efi_mem_reserve does at
> > > its end, just with e820_table_firmware instead of e820_table.
> > > i.e. efi_mem_reserve does:
> > >         e820__range_update(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED);
> > >         e820__update_table(e820_table);
> > >
> > > while arch_update_firmware_area does:
> > >         e820__range_update_firmware(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED);
> > >         e820__update_table(e820_table_firmware);
> > >
> >
> > Shame.
> >
> > Using efi_mem_reserve() is appropriate here in any case, but I guess
> > kexec on x86 needs to be fixed to juggle the EFI memory map, memblock
> > table, and 3 (!) versions of the E820 table in the correct way
> > (e820_table, e820_table_kexec and e820_table_firmware)
> >
> > Perhaps we can put this additional logic in x86's implementation of
> > efi_arch_mem_reserve()? AFAICT, all callers of efi_mem_reserve() deal
> > with configuration tables produced by the firmware that may not be
> > reserved correctly if kexec looks at e820_table_firmware[] only.
>

I have not read all the conversations,  let me have a look and response later.

The first glance about the patch is that I think the kexec_file_load
syscall (default of latest kexec-tools) will not use
e820_table_firmware AFAIK.  it will only use e820_table_kexec.

Usama, can you confirm how you tested this?
kexec -c -l  will use kexec_load syscall
kexec [-s] -l will use kexec_file_load syscall

Thanks
Dave