x86/efi: Always map the first physical page into the EFI pagetables

Commit:

  129766708 ("x86/efi: Only map RAM into EFI page tables if in mixed-mode")

stopped creating 1:1 mappings for all RAM, when running in native 64-bit mode.

It turns out though that there are 64-bit EFI implementations in the wild
(this particular problem has been reported on a Lenovo Yoga 710-11IKB),
which still make use of the first physical page for their own private use,
even though they explicitly mark it EFI_CONVENTIONAL_MEMORY in the memory
map.

In case there is no mapping for this particular frame in the EFI pagetables,
as soon as firmware tries to make use of it, a triple fault occurs and the
system reboots (in case of the Yoga 710-11IKB this is very early during bootup).

Fix that by always mapping the first page of physical memory into the EFI
pagetables. We're free to hand this page to the BIOS, as trim_bios_range()
will reserve the first page and isolate it away from memory allocators anyway.

Note that just reverting 129766708 alone is not enough on v4.9-rc1+ to fix the
regression on affected hardware, as this commit:

   ab72a27da ("x86/efi: Consolidate region mapping logic")

later made the first physical frame not to be mapped anyway.

Reported-by: Hanka Pavlikova <hanka@ucw.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vojtech Pavlik <vojtech@ucw.cz>
Cc: Waiman Long <waiman.long@hpe.com>
Cc: linux-efi@vger.kernel.org
Cc: stable@kernel.org # v4.8+
Fixes: 129766708 ("x86/efi: Only map RAM into EFI page tables if in mixed-mode")
Link: http://lkml.kernel.org/r/20170127222552.22336-1-matt@codeblueprint.co.uk
[ Tidied up the changelog and the comment. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

path: root/protos.h

#ifndef PROTOS_H
#define PROTOS_H

struct protocol;

extern struct protocol arp_ops;
extern struct protocol ethernet_ops;
extern struct protocol icmpv4_ops;
extern struct protocol icmpv6_ops;
extern struct protocol igmp_ops;
extern struct protocol ip_auth_ops;
extern struct protocol ip_esp_ops;
extern struct protocol ipv4_ops;
extern struct protocol ipv6_ops;
extern struct protocol ipv6_dest_opts_ops;
extern struct protocol ipv6_fragm_ops;
extern struct protocol ipv6_hop_by_hop_ops;
extern struct protocol ipv6_in_ipv4_ops;
extern struct protocol ipv6_mobility_ops;
extern struct protocol ipv6_no_next_header_ops;
extern struct protocol ipv6_routing_ops;
extern struct protocol lldp_ops;
extern struct protocol none_ops;
extern struct protocol tcp_ops;
extern struct protocol udp_ops;
extern struct protocol dccp_ops;
extern struct protocol vlan_ops;
extern struct protocol ieee80211_ops;
extern struct protocol QinQ_ops;
extern struct protocol mpls_uc_ops;
extern struct protocol nlmsg_ops;

#endif /* PROTOS_H */