x86/dumpstack: When OOPSing, rewind the stack before do_exit()
If we call do_exit() with a clean stack, we greatly reduce the risk of
recursive oopses due to stack overflow in do_exit, and we allow
do_exit to work even if we OOPS from an IST stack. The latter gives
us a much better chance of surviving long enough after we detect a
stack overflow to write out our logs.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/32f73ceb372ec61889598da5e5b145889b9f2e19.1468527351.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 9ee0da1..b846875 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1423,3 +1423,14 @@
mov $-ENOSYS, %eax
sysret
END(ignore_sysret)
+
+ENTRY(rewind_stack_do_exit)
+ /* Prevent any naive code from trying to unwind to our caller. */
+ xorl %ebp, %ebp
+
+ movq PER_CPU_VAR(cpu_current_top_of_stack), %rax
+ leaq -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%rax), %rsp
+
+ call do_exit
+1: jmp 1b
+END(rewind_stack_do_exit)