linux.git/arch/x86/boot, branch v4.12

x86/boot/KASLR: Fix kexec crash due to 'virt_addr' calculation bug

2017-06-30T06:53:14+00:00

Kernel text KASLR is separated into physical address and virtual
address randomization. And for virtual address randomization, we
only randomiza to get an offset between 16M and KERNEL_IMAGE_SIZE.
So the initial value of 'virt_addr' should be LOAD_PHYSICAL_ADDR,
but not the original kernel loading address 'output'.

The bug will cause kernel boot failure if kernel is loaded at a different
position than the address, 16M, which is decided at compiled time.
Kexec/kdump is such practical case.

To fix it, just assign LOAD_PHYSICAL_ADDR to virt_addr as initial
value.

Tested-by: Dave Young 
Signed-off-by: Baoquan He 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: 8391c73 ("x86/KASLR: Randomize virtual address separately")
Link: http://lkml.kernel.org/r/1498567146-11990-3-git-send-email-bhe@redhat.com
Signed-off-by: Ingo Molnar

x86/boot/KASLR: Add checking for the offset of kernel virtual address randomization

2017-06-30T06:53:14+00:00

For kernel text KASLR, the virtual address is confined to area of 1G,
[0xffffffff80000000, 0xffffffffc0000000). For the implemenataion of
virtual address randomization, we only randomize to get an offset
between 16M and 1G, then add this offset to the starting address,
0xffffffff80000000. Here 16M is the offset which is decided at linking
stage. So the amount of the local variable 'virt_addr' which respresents
the offset plus the kernel output size can not exceed KERNEL_IMAGE_SIZE.

Add a debug check for the offset. If out of bounds, print error
message and hang there.

Suggested-by: Ingo Molnar 
Signed-off-by: Baoquan He 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1498567146-11990-2-git-send-email-bhe@redhat.com
Signed-off-by: Ingo Molnar

x86/boot: Use CROSS_COMPILE prefix for readelf

2017-05-21T11:04:27+00:00

The boot code Makefile contains a straight 'readelf' invocation. This
causes build warnings in cross compile environments, when there is no
unprefixed readelf accessible via $PATH.

Add the missing $(CROSS_COMPILE) prefix.

[ tglx: Rewrote changelog ]

Fixes: 98f78525371b ("x86/boot: Refuse to build with data relocations")
Signed-off-by: Rob Landley 
Acked-by: Kees Cook 
Cc: Jiri Kosina 
Cc: Paul Bolle 
Cc: "H.J. Lu" 
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/ced18878-693a-9576-a024-113ef39a22c0@landley.net
Signed-off-by: Thomas Gleixner

x86/mm: Add support for gbpages to kernel_ident_mapping_init()

2017-05-08T06:28:40+00:00

Kernel identity mappings on x86-64 kernels are created in two
ways: by the early x86 boot code, or by kernel_ident_mapping_init().

Native kernels (which is the dominant usecase) use the former,
but the kexec and the hibernation code uses kernel_ident_mapping_init().

There's a subtle difference between these two ways of how identity
mappings are created, the current kernel_ident_mapping_init() code
creates identity mappings always using 2MB page(PMD level) - while
the native kernel boot path also utilizes gbpages where available.

This difference is suboptimal both for performance and for memory
usage: kernel_ident_mapping_init() needs to allocate pages for the
page tables when creating the new identity mappings.

This patch adds 1GB page(PUD level) support to kernel_ident_mapping_init()
to address these concerns.

The primary advantage would be better TLB coverage/performance,
because we'd utilize 1GB TLBs instead of 2MB ones.

It is also useful for machines with large number of memory to
save paging structure allocations(around 4MB/TB using 2MB page)
when setting identity mappings for all the memory, after using
1GB page it will consume only 8KB/TB.

( Note that this change alone does not activate gbpages in kexec,
  we are doing that in a separate patch. )

Signed-off-by: Xunlei Pang 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Young 
Cc: Denys Vlasenko 
Cc: Eric Biederman 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Yinghai Lu 
Cc: akpm@linux-foundation.org
Cc: kexec@lists.infradead.org
Link: http://lkml.kernel.org/r/1493862171-8799-1-git-send-email-xlpang@redhat.com
Signed-off-by: Ingo Molnar

x86/boot: Declare error() as noreturn

2017-05-07T08:59:05+00:00

The compressed boot function error() is used to halt execution, but it
wasn't marked with "noreturn". This fixes that in preparation for
supporting kernel FORTIFY_SOURCE, which uses the noreturn annotation
on panic, and calls error(). GCC would warn about a noreturn function
calling a non-noreturn function:

  arch/x86/boot/compressed/misc.c: In function ‘fortify_panic’:
  arch/x86/boot/compressed/misc.c:416:1: warning: ‘noreturn’ function does return
   }
 ^

Signed-off-by: Kees Cook 
Cc: Daniel Micay 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: H. Peter Anvin 
Link: http://lkml.kernel.org/r/20170506045116.GA2879@beast
Signed-off-by: Ingo Molnar

Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-05-02T06:54:56+00:00

Pull x86 mm updates from Ingo Molnar:
 "The main x86 MM changes in this cycle were:

   - continued native kernel PCID support preparation patches to the TLB
     flushing code (Andy Lutomirski)

   - various fixes related to 32-bit compat syscall returning address
     over 4Gb in applications, launched from 64-bit binaries - motivated
     by C/R frameworks such as Virtuozzo. (Dmitry Safonov)

   - continued Intel 5-level paging enablement: in particular the
     conversion of x86 GUP to the generic GUP code. (Kirill A. Shutemov)

   - x86/mpx ABI corner case fixes/enhancements (Joerg Roedel)

   - ... plus misc updates, fixes and cleanups"

* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (62 commits)
  mm, zone_device: Replace {get, put}_zone_device_page() with a single reference to fix pmem crash
  x86/mm: Fix flush_tlb_page() on Xen
  x86/mm: Make flush_tlb_mm_range() more predictable
  x86/mm: Remove flush_tlb() and flush_tlb_current_task()
  x86/vm86/32: Switch to flush_tlb_mm_range() in mark_screen_rdonly()
  x86/mm/64: Fix crash in remove_pagetable()
  Revert "x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation"
  x86/boot/e820: Remove a redundant self assignment
  x86/mm: Fix dump pagetables for 4 levels of page tables
  x86/mpx, selftests: Only check bounds-vs-shadow when we keep shadow
  x86/mpx: Correctly report do_mpx_bt_fault() failures to user-space
  Revert "x86/mm/numa: Remove numa_nodemask_from_meminfo()"
  x86/espfix: Add support for 5-level paging
  x86/kasan: Extend KASAN to support 5-level paging
  x86/mm: Add basic defines/helpers for CONFIG_X86_5LEVEL=y
  x86/paravirt: Add 5-level support to the paravirt code
  x86/mm: Define virtual memory map for 5-level paging
  x86/asm: Remove __VIRTUAL_MASK_SHIFT==47 assert
  x86/boot: Detect 5-level paging support
  x86/mm/numa: Remove numa_nodemask_from_meminfo()
  ...

x86/KASLR: Fix kexec kernel boot crash when KASLR randomization fails

2017-04-28T06:31:15+00:00

Dave found that a kdump kernel with KASLR enabled will reset to the BIOS
immediately if physical randomization failed to find a new position for
the kernel. A kernel with the 'nokaslr' option works in this case.

The reason is that KASLR will install a new page table for the identity
mapping, while it missed building it for the original kernel location
if KASLR physical randomization fails.

This only happens in the kexec/kdump kernel, because the identity mapping
has been built for kexec/kdump in the 1st kernel for the whole memory by
calling init_pgtable(). Here if physical randomizaiton fails, it won't build
the identity mapping for the original area of the kernel but change to a
new page table '_pgtable'. Then the kernel will triple fault immediately
caused by no identity mappings.

The normal kernel won't see this bug, because it comes here via startup_32()
and CR3 will be set to _pgtable already. In startup_32() the identity
mapping is built for the 0~4G area. In KASLR we just append to the existing
area instead of entirely overwriting it for on-demand identity mapping
building. So the identity mapping for the original area of kernel is still
there.

To fix it we just switch to the new identity mapping page table when physical
KASLR succeeds. Otherwise we keep the old page table unchanged just like
"nokaslr" does.

Signed-off-by: Baoquan He 
Signed-off-by: Dave Young 
Acked-by: Kees Cook 
Cc: Borislav Petkov 
Cc: Dave Jiang 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Garnier 
Cc: Thomas Gleixner 
Cc: Yinghai Lu 
Link: http://lkml.kernel.org/r/1493278940-5885-1-git-send-email-bhe@redhat.com
Signed-off-by: Ingo Molnar

x86/boot: Fix BSS corruption/overwrite bug in early x86 kernel startup

2017-04-20T08:05:23+00:00

The minimum size for a new stack (512 bytes) setup for arch/x86/boot components
when the bootloader does not setup/provide a stack for the early boot components
is not "enough".

The setup code executing as part of early kernel startup code, uses the stack
beyond 512 bytes and accidentally overwrites and corrupts part of the BSS
section. This is exposed mostly in the early video setup code, where
it was corrupting BSS variables like force_x, force_y, which in-turn affected
kernel parameters such as screen_info (screen_info.orig_video_cols) and
later caused an exception/panic in console_init().

Most recent boot loaders setup the stack for early boot components, so this
stack overwriting into BSS section issue has not been exposed.

Signed-off-by: Ashish Kalra 
Cc: 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/20170419152015.10011-1-ashishkalra@Ashishs-MacBook-Pro.local
Signed-off-by: Ingo Molnar

Merge branch 'x86/boot' into x86/mm, to avoid conflict

2017-04-11T06:56:05+00:00

There's a conflict between ongoing level-5 paging support and
the E820 rewrite. Since the E820 rewrite is essentially ready,
merge it into x86/mm to reduce tree conflicts.

Signed-off-by: Ingo Molnar

Merge branch 'WIP.x86/boot' into x86/boot, to pick up ready branch

2017-04-11T06:49:31+00:00

The E820 rework in WIP.x86/boot has gone through a couple of weeks
of exposure in -tip, merge it in a wider fashion.

Signed-off-by: Ingo Molnar