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

Pull x86 fixes from Thomas Gleixner:
 "The final fixes for 4.11:

   - prevent a triple fault with function graph tracing triggered via
     suspend to ram

   - prevent optimizing for size when function graph tracing is enabled
     and the compiler does not support -mfentry

   - prevent mwaitx() being called with a zero timeout as mwaitx() might
     never return. Observed on the new Ryzen CPUs"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Prevent timer value 0 for MWAITX
  x86/build: convert function graph '-Os' error to warning
  ftrace/x86: Fix triple fault with graph tracing and suspend-to-ram

1 files changed, 12 insertions, 6 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index cbd73eb42170..5b7153540727 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -29,12 +29,6 @@
 #include <asm/ftrace.h>
 #include <asm/nops.h>
 
-#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && \
-	!defined(CC_USING_FENTRY) && \
-	!defined(CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE)
-# error The following combination is not supported: ((compiler missing -mfentry) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE)) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE
-#endif
-
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 int ftrace_arch_code_modify_prepare(void)
@@ -989,6 +983,18 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
 	unsigned long return_hooker = (unsigned long)
 				&return_to_handler;
 
+	/*
+	 * When resuming from suspend-to-ram, this function can be indirectly
+	 * called from early CPU startup code while the CPU is in real mode,
+	 * which would fail miserably.  Make sure the stack pointer is a
+	 * virtual address.
+	 *
+	 * This check isn't as accurate as virt_addr_valid(), but it should be
+	 * good enough for this purpose, and it's fast.
+	 */
+	if (unlikely((long)__builtin_frame_address(0) >= 0))
+		return;
+
 	if (unlikely(ftrace_graph_is_dead()))
 		return;