Matt Fleming a5caa209ba x86/efi: Fix boot crash by mapping EFI memmap entries bottom-up at runtime, instead of top-down ... Beginning with UEFI v2.5 EFI_PROPERTIES_TABLE was introduced that signals that the firmware PE/COFF loader supports splitting code and data sections of PE/COFF images into separate EFI memory map entries. This allows the kernel to map those regions with strict memory protections, e.g. EFI_MEMORY_RO for code, EFI_MEMORY_XP for data, etc. Unfortunately, an unwritten requirement of this new feature is that the regions need to be mapped with the same offsets relative to each other as observed in the EFI memory map. If this is not done crashes like this may occur, BUG: unable to handle kernel paging request at fffffffefe6086dd IP: [<fffffffefe6086dd>] 0xfffffffefe6086dd Call Trace: [<ffffffff8104c90e>] efi_call+0x7e/0x100 [<ffffffff81602091>] ? virt_efi_set_variable+0x61/0x90 [<ffffffff8104c583>] efi_delete_dummy_variable+0x63/0x70 [<ffffffff81f4e4aa>] efi_enter_virtual_mode+0x383/0x392 [<ffffffff81f37e1b>] start_kernel+0x38a/0x417 [<ffffffff81f37495>] x86_64_start_reservations+0x2a/0x2c [<ffffffff81f37582>] x86_64_start_kernel+0xeb/0xef Here 0xfffffffefe6086dd refers to an address the firmware expects to be mapped but which the OS never claimed was mapped. The issue is that included in these regions are relative addresses to other regions which were emitted by the firmware toolchain before the "splitting" of sections occurred at runtime. Needless to say, we don't satisfy this unwritten requirement on x86_64 and instead map the EFI memory map entries in reverse order. The above crash is almost certainly triggerable with any kernel newer than v3.13 because that's when we rewrote the EFI runtime region mapping code, in commit d2f7cbe7b2 ("x86/efi: Runtime services virtual mapping"). For kernel versions before v3.13 things may work by pure luck depending on the fragmentation of the kernel virtual address space at the time we map the EFI regions. Instead of mapping the EFI memory map entries in reverse order, where entry N has a higher virtual address than entry N+1, map them in the same order as they appear in the EFI memory map to preserve this relative offset between regions. This patch has been kept as small as possible with the intention that it should be applied aggressively to stable and distribution kernels. It is very much a bugfix rather than support for a new feature, since when EFI_PROPERTIES_TABLE is enabled we must map things as outlined above to even boot - we have no way of asking the firmware not to split the code/data regions. In fact, this patch doesn't even make use of the more strict memory protections available in UEFI v2.5. That will come later. Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Matt Fleming <matt.fleming@intel.com> Cc: <stable@vger.kernel.org> Cc: Borislav Petkov <bp@suse.de> Cc: Chun-Yi <jlee@suse.com> Cc: Dave Young <dyoung@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: James Bottomley <JBottomley@Odin.com> Cc: Lee, Chun-Yi <jlee@suse.com> Cc: Leif Lindholm <leif.lindholm@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matthew Garrett <mjg59@srcf.ucam.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Jones <pjones@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1443218539-7610-2-git-send-email-matt@codeblueprint.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org>		2015-10-01 12:51:28 +02:00
..
atom	x86/platform: Make atom/pmc_atom.c explicitly non-modular	2015-08-25 09:47:50 +02:00
ce4100	x86: ce4100, irq: Do not set legacy_pic to null_legacy_pic	2014-06-21 23:05:42 +02:00
efi	x86/efi: Fix boot crash by mapping EFI memmap entries bottom-up at runtime, instead of top-down	2015-10-01 12:51:28 +02:00
geode	x86/geode: Fix incorrect placement of __initdata tag	2013-10-01 13:21:27 +02:00
goldfish	goldfish: platform device for x86	2013-01-21 12:09:19 -08:00
intel	x86/platform/iosf_mbi: Add Intel Tangier PCI id	2015-07-16 17:48:48 +02:00
intel-mid	Replace module_init with equivalent device_initcall in non modules.	2015-07-02 10:30:48 -07:00
intel-quark	x86/intel/quark: Run IMR self-test on IMR capble hw only	2015-04-02 12:47:50 +02:00
iris	x86: platform: iris: drop owner assignment from platform_drivers	2014-10-20 16:20:15 +02:00
olpc	x86/olpc/xo15/sci: Use newly added power_supply_put API	2015-03-13 23:15:53 +01:00
scx200	X86: drivers: remove __dev* attributes.	2013-01-03 15:57:04 -08:00
sfi	x86: Cleanup irq_domain ops	2015-04-24 15:36:55 +02:00
ts5500	x86/platform/ts5500: Add support for TS-5400 boards	2014-07-16 21:17:42 +02:00
uv	kexec: split kexec_load syscall from kexec core code	2015-09-10 13:29:01 -07:00
Makefile	x86/platform/iosf_mbi: Move to dedicated folder	2015-07-16 17:48:47 +02:00