x86/dumpstack: Handle stack overflow on all stacks

We currently special-case stack overflow on the task stack.  We're
going to start putting special stacks in the fixmap with a custom
layout, so they'll have guard pages, too.  Teach the unwinder to be
able to unwind an overflow of any of the stacks.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Link: https://lkml.kernel.org/r/20171204150605.802057305@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 14 insertions, 10 deletions

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index a33a1373a252..64f8ed2a4827 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -112,24 +112,28 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
          * - task stack
          * - interrupt stack
          * - HW exception stacks (double fault, nmi, debug, mce)
+         * - SYSENTER stack
          *
-         * x86-32 can have up to three stacks:
+         * x86-32 can have up to four stacks:
          * - task stack
          * - softirq stack
          * - hardirq stack
+         * - SYSENTER stack
          */
         for (regs = NULL; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
                 const char *stack_name;
 
-                /*
-                 * If we overflowed the task stack into a guard page, jump back
-                 * to the bottom of the usable stack.
-                 */
-                if (task_stack_page(task) - (void *)stack < PAGE_SIZE)
-                        stack = task_stack_page(task);
-
-                if (get_stack_info(stack, task, &stack_info, &visit_mask))
-                        break;
+                if (get_stack_info(stack, task, &stack_info, &visit_mask)) {
+                        /*
+                         * We weren't on a valid stack.  It's possible that
+                         * we overflowed a valid stack into a guard page.
+                         * See if the next page up is valid so that we can
+                         * generate some kind of backtrace if this happens.
+                         */
+                        stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack);
+                        if (get_stack_info(stack, task, &stack_info, &visit_mask))
+                                break;
+                }
 
                 stack_name = stack_type_name(stack_info.type);
                 if (stack_name)