efi/fdt: Avoid FDT manipulation after ExitBootServices()

Some AArch64 UEFI implementations disable the MMU in ExitBootServices(),
after which unaligned accesses to RAM are no longer supported.

Commit:

  abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel")

fixed an issue in the memory map handling of the stub FDT code, but
inadvertently created an issue with such firmware, by moving some
of the FDT manipulation to after the invocation of ExitBootServices().

Given that the stub's libfdt implementation uses the ordinary, accelerated
string functions, which rely on hardware handling of unaligned accesses,
manipulating the FDT with the MMU off may result in alignment faults.

So fix the situation by moving the update_fdt_memmap() call into the
callback function invoked by efi_exit_boot_services() right before it
calls the ExitBootServices() UEFI service (which is arguably a better
place for it anyway)

Note that disabling the MMU in ExitBootServices() is not compliant with
the UEFI spec, and carries great risk due to the fact that switching from
cached to uncached memory accesses halfway through compiler generated code
(i.e., involving a stack) can never be done in a way that is architecturally
safe.

Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Riku Voipio <riku.voipio@linaro.org>
Cc: <stable@vger.kernel.org>
Cc: mark.rutland@arm.com
Cc: linux-efi@vger.kernel.org
Cc: matt@codeblueprint.co.uk
Cc: leif.lindholm@linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1485971102-23330-2-git-send-email-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

path: root/include/net/netns/mib.h

#ifndef __NETNS_MIB_H__
#define __NETNS_MIB_H__

#include <net/snmp.h>

struct netns_mib {
	DEFINE_SNMP_STAT(struct tcp_mib, tcp_statistics);
	DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics);
	DEFINE_SNMP_STAT(struct linux_mib, net_statistics);
	DEFINE_SNMP_STAT(struct udp_mib, udp_statistics);
	DEFINE_SNMP_STAT(struct udp_mib, udplite_statistics);
	DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics);
	DEFINE_SNMP_STAT_ATOMIC(struct icmpmsg_mib, icmpmsg_statistics);

#if IS_ENABLED(CONFIG_IPV6)
	struct proc_dir_entry *proc_net_devsnmp6;
	DEFINE_SNMP_STAT(struct udp_mib, udp_stats_in6);
	DEFINE_SNMP_STAT(struct udp_mib, udplite_stats_in6);
	DEFINE_SNMP_STAT(struct ipstats_mib, ipv6_statistics);
	DEFINE_SNMP_STAT(struct icmpv6_mib, icmpv6_statistics);
	DEFINE_SNMP_STAT_ATOMIC(struct icmpv6msg_mib, icmpv6msg_statistics);
#endif
#ifdef CONFIG_XFRM_STATISTICS
	DEFINE_SNMP_STAT(struct linux_xfrm_mib, xfrm_statistics);
#endif
};

#endif