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

Pull x86 mm updates from Ingo Molnar:
 "Various x86 low level modifications:

   - preparatory work to support virtually mapped kernel stacks (Andy
     Lutomirski)

   - support for 64-bit __get_user() on 32-bit kernels (Benjamin
     LaHaise)

   - (involved) workaround for Knights Landing CPU erratum (Dave Hansen)

   - MPX enhancements (Dave Hansen)

   - mremap() extension to allow remapping of the special VDSO vma, for
     purposes of user level context save/restore (Dmitry Safonov)

   - hweight and entry code cleanups (Borislav Petkov)

   - bitops code generation optimizations and cleanups with modern GCC
     (H. Peter Anvin)

   - syscall entry code optimizations (Paolo Bonzini)"

* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (43 commits)
  x86/mm/cpa: Add missing comment in populate_pdg()
  x86/mm/cpa: Fix populate_pgd(): Stop trying to deallocate failed PUDs
  x86/syscalls: Add compat_sys_preadv64v2/compat_sys_pwritev64v2
  x86/smp: Remove unnecessary initialization of thread_info::cpu
  x86/smp: Remove stack_smp_processor_id()
  x86/uaccess: Move thread_info::addr_limit to thread_struct
  x86/dumpstack: Rename thread_struct::sig_on_uaccess_error to sig_on_uaccess_err
  x86/uaccess: Move thread_info::uaccess_err and thread_info::sig_on_uaccess_err to thread_struct
  x86/dumpstack: When OOPSing, rewind the stack before do_exit()
  x86/mm/64: In vmalloc_fault(), use CR3 instead of current->active_mm
  x86/dumpstack/64: Handle faults when printing the "Stack: " part of an OOPS
  x86/dumpstack: Try harder to get a call trace on stack overflow
  x86/mm: Remove kernel_unmap_pages_in_pgd() and efi_cleanup_page_tables()
  x86/mm/cpa: In populate_pgd(), don't set the PGD entry until it's populated
  x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()
  x86/mm: Use pte_none() to test for empty PTE
  x86/mm: Disallow running with 32-bit PTEs to work around erratum
  x86/mm: Ignore A/D bits in pte/pmd/pud_none()
  x86/mm: Move swap offset/type up in PTE to work around erratum
  x86/entry: Inline enter_from_user_mode()
  ...

1 files changed, 18 insertions, 2 deletions

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index ef8017ca5ba9..de8242d8bb61 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -87,7 +87,7 @@ static inline int valid_stack_ptr(struct task_struct *task,
 		else
 			return 0;
 	}
-	return p > t && p < t + THREAD_SIZE - size;
+	return p >= t && p < t + THREAD_SIZE - size;
 }
 
 unsigned long
@@ -98,6 +98,14 @@ print_context_stack(struct task_struct *task,
 {
 	struct stack_frame *frame = (struct stack_frame *)bp;
 
+	/*
+	 * If we overflowed the stack into a guard page, jump back to the
+	 * bottom of the usable stack.
+	 */
+	if ((unsigned long)task_stack_page(task) - (unsigned long)stack <
+	    PAGE_SIZE)
+		stack = (unsigned long *)task_stack_page(task);
+
 	while (valid_stack_ptr(task, stack, sizeof(*stack), end)) {
 		unsigned long addr;
 
@@ -226,6 +234,8 @@ unsigned long oops_begin(void)
 EXPORT_SYMBOL_GPL(oops_begin);
 NOKPROBE_SYMBOL(oops_begin);
 
+void __noreturn rewind_stack_do_exit(int signr);
+
 void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 {
 	if (regs && kexec_should_crash(current))
@@ -247,7 +257,13 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 		panic("Fatal exception in interrupt");
 	if (panic_on_oops)
 		panic("Fatal exception");
-	do_exit(signr);
+
+	/*
+	 * We're not going to return, but we might be on an IST stack or
+	 * have very little stack space left.  Rewind the stack and kill
+	 * the task.
+	 */
+	rewind_stack_do_exit(signr);
 }
 NOKPROBE_SYMBOL(oops_end);