linux/arch/x86/mm
Thomas Gleixner 2a594d4ccf x86/exceptions: Split debug IST stack
The debug IST stack is actually two separate debug stacks to handle #DB
recursion. This is required because the CPU starts always at top of stack
on exception entry, which means on #DB recursion the second #DB would
overwrite the stack of the first.

The low level entry code therefore adjusts the top of stack on entry so a
secondary #DB starts from a different stack page. But the stack pages are
adjacent without a guard page between them.

Split the debug stack into 3 stacks which are separated by guard pages. The
3rd stack is never mapped into the cpu_entry_area and is only there to
catch triple #DB nesting:

      --- top of DB_stack	<- Initial stack
      --- end of DB_stack
      	  guard page

      --- top of DB1_stack	<- Top of stack after entering first #DB
      --- end of DB1_stack
      	  guard page

      --- top of DB2_stack	<- Top of stack after entering second #DB
      --- end of DB2_stack
      	  guard page

If DB2 would not act as the final guard hole, a second #DB would point the
top of #DB stack to the stack below #DB1 which would be valid and not catch
the not so desired triple nesting.

The backing store does not allocate any memory for DB2 and its guard page
as it is not going to be mapped into the cpu_entry_area.

 - Adjust the low level entry code so it adjusts top of #DB with the offset
   between the stacks instead of exception stack size.

 - Make the dumpstack code aware of the new stacks.

 - Adjust the in_debug_stack() implementation and move it into the NMI code
   where it belongs. As this is NMI hotpath code, it just checks the full
   area between top of DB_stack and bottom of DB1_stack without checking
   for the guard page. That's correct because the NMI cannot hit a
   stackpointer pointing to the guard page between DB and DB1 stack.  Even
   if it would, then the NMI operation still is unaffected, but the resume
   of the debug exception on the topmost DB stack will crash by touching
   the guard page.

  [ bp: Make exception_stack_names static const char * const ]

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Chang S. Bae" <chang.seok.bae@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: linux-doc@vger.kernel.org
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190414160145.439944544@linutronix.de
2019-04-17 15:14:28 +02:00
..
amdtopology.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
cpu_entry_area.c x86/exceptions: Split debug IST stack 2019-04-17 15:14:28 +02:00
debug_pagetables.c x86/mm/dump_pagetables: Use DEFINE_SHOW_ATTRIBUTE() 2018-12-18 13:05:54 +01:00
dump_pagetables.c x86/mm/dump_pagetables: Remove the unused prev_pud variable 2019-02-14 17:09:43 +01:00
extable.c x86-64: add warning for non-canonical user access address dereferences 2019-03-04 10:08:28 -08:00
fault.c x86/traps: Use cpu_entry_area instead of orig_ist 2019-04-17 13:01:59 +02:00
highmem_32.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
hugetlbpage.c x86/compat: Adjust in_compat_syscall() to generic code under !COMPAT 2018-11-01 12:59:25 +01:00
ident_map.c x86/mm: Stop pretending pgtable_l5_enabled is a variable 2018-05-19 11:56:57 +02:00
init_32.c mm, memory_hotplug: add nid parameter to arch_remove_memory 2018-12-28 12:11:49 -08:00
init_64.c mm, memory_hotplug: add nid parameter to arch_remove_memory 2018-12-28 12:11:49 -08:00
init.c mm: make free_reserved_area() return "const char *" 2018-12-28 12:11:48 -08:00
iomap_32.c x86/mm: Do not auto-massage page protections 2018-04-12 09:04:22 +02:00
ioremap.c x86: Make ARCH_USE_MEMREMAP_PROT a generic Kconfig symbol 2019-02-04 08:27:29 +01:00
kasan_init_64.c memblock: drop memblock_alloc_*_nopanic() variants 2019-03-12 10:04:02 -07:00
kaslr.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
kmmio.c x86/mm/kmmio: Make the tracer robust against L1TF 2018-08-08 22:28:34 +02:00
Makefile x86/mm/sme: Disable stack protection for mem_encrypt_identity.c 2018-02-28 15:24:12 +01:00
mem_encrypt_boot.S x86/mm/sme, objtool: Annotate indirect call in sme_encrypt_execute() 2018-02-21 09:05:04 +01:00
mem_encrypt_identity.c x86/mm/mem_encrypt: Fix erroneous sizeof() 2019-01-15 11:41:58 +01:00
mem_encrypt.c dma-direct: merge swiotlb_dma_ops into the dma_direct code 2018-12-13 21:06:17 +01:00
mm_internal.h x86/mm/cpa: Optimize cpa_flush_array() TLB invalidation 2018-12-17 18:54:26 +01:00
mmap.c x86/mm: Don't exceed the valid physical address space 2019-03-28 14:13:51 +01:00
mmio-mod.c x86: do not use print_symbol() 2018-01-05 15:23:01 +01:00
mpx.c x86/mpx: tweak header name 2019-02-18 17:49:30 +01:00
numa_32.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
numa_64.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
numa_emulation.c Merge branch 'core/urgent' into x86/urgent, to pick up objtool fix 2018-11-03 23:42:16 +01:00
numa_internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
numa.c memblock: drop __memblock_alloc_base() 2019-03-12 10:04:01 -07:00
pageattr-test.c x86/mm/cpa: Simplify the code after making cpa->vaddr invariant 2018-12-17 18:54:25 +01:00
pageattr.c x86/mm: Remove unused variable 'old_pte' 2019-03-06 23:24:53 +01:00
pat_internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pat_rbtree.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pat.c x86/mm: Fix decoy address handling vs 32-bit builds 2018-12-11 18:28:20 -08:00
pf_in.c x86/mm: Audit and remove any unnecessary uses of module.h 2016-07-14 13:04:20 +02:00
pf_in.h
pgtable_32.c x86/mm: Rename flush_tlb_single() and flush_tlb_one() to __flush_tlb_one_[user|kernel]() 2018-02-15 01:15:52 +01:00
pgtable.c mm: treewide: remove unused address argument from pte_alloc functions 2019-01-04 13:13:47 -08:00
physaddr.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
physaddr.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
pkeys.c x86/pkeys: Make init_pkru_value static 2018-12-03 19:10:18 +01:00
pti.c x86/mm/pti: Make local symbols static 2019-03-22 13:31:28 +01:00
setup_nx.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
srat.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
testmmiotrace.c Annotate hardware config module parameters in arch/x86/mm/ 2017-04-04 16:54:21 +01:00
tlb.c x86/mm: Remove unused variable 'cpu' 2019-03-06 23:24:52 +01:00