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

Pull x86 fixes from Thomas Gleixner:
 "A series of fixes for X86:

   - The final fix for the end-of-stack issue in the unwinder
   - Handle non PAT systems gracefully
   - Prevent access to uninitiliazed memory
   - Move early delay calaibration after basic init
   - Fix Kconfig help text
   - Fix a cross compile issue
   - Unbreak older make versions"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/timers: Move simple_udelay_calibration past init_hypervisor_platform
  x86/alternatives: Prevent uninitialized stack byte read in apply_alternatives()
  x86/PAT: Fix Xorg regression on CPUs that don't support PAT
  x86/watchdog: Fix Kconfig help text file path reference to lockup watchdog documentation
  x86/build: Permit building with old make versions
  x86/unwind: Add end-of-stack check for ftrace handlers
  Revert "x86/entry: Fix the end of the stack for newly forked tasks"
  x86/boot: Use CROSS_COMPILE prefix for readelf

2 files changed, 23 insertions, 18 deletions

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 50bc26949e9e..48ef7bb32c42 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -252,6 +252,23 @@ ENTRY(__switch_to_asm)
 END(__switch_to_asm)
 
 /*
+ * The unwinder expects the last frame on the stack to always be at the same
+ * offset from the end of the page, which allows it to validate the stack.
+ * Calling schedule_tail() directly would break that convention because its an
+ * asmlinkage function so its argument has to be pushed on the stack.  This
+ * wrapper creates a proper "end of stack" frame header before the call.
+ */
+ENTRY(schedule_tail_wrapper)
+	FRAME_BEGIN
+
+	pushl	%eax
+	call	schedule_tail
+	popl	%eax
+
+	FRAME_END
+	ret
+ENDPROC(schedule_tail_wrapper)
+/*
  * A newly forked process directly context switches into this address.
  *
  * eax: prev task we switched from
@@ -259,24 +276,15 @@ END(__switch_to_asm)
  * edi: kernel thread arg
  */
 ENTRY(ret_from_fork)
-	FRAME_BEGIN		/* help unwinder find end of stack */
-
-	/*
-	 * schedule_tail() is asmlinkage so we have to put its 'prev' argument
-	 * on the stack.
-	 */
-	pushl	%eax
-	call	schedule_tail
-	popl	%eax
+	call	schedule_tail_wrapper
 
 	testl	%ebx, %ebx
 	jnz	1f		/* kernel threads are uncommon */
 
 2:
 	/* When we fork, we trace the syscall return in the child, too. */
-	leal	FRAME_OFFSET(%esp), %eax
+	movl    %esp, %eax
 	call    syscall_return_slowpath
-	FRAME_END
 	jmp     restore_all
 
 	/* kernel thread */
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 607d72c4a485..4a4c0834f965 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -36,7 +36,6 @@
 #include <asm/smap.h>
 #include <asm/pgtable_types.h>
 #include <asm/export.h>
-#include <asm/frame.h>
 #include <linux/err.h>
 
 .code64
@@ -406,19 +405,17 @@ END(__switch_to_asm)
  * r12: kernel thread arg
  */
 ENTRY(ret_from_fork)
-	FRAME_BEGIN			/* help unwinder find end of stack */
 	movq	%rax, %rdi
-	call	schedule_tail		/* rdi: 'prev' task parameter */
+	call	schedule_tail			/* rdi: 'prev' task parameter */
 
-	testq	%rbx, %rbx		/* from kernel_thread? */
-	jnz	1f			/* kernel threads are uncommon */
+	testq	%rbx, %rbx			/* from kernel_thread? */
+	jnz	1f				/* kernel threads are uncommon */
 
 2:
-	leaq	FRAME_OFFSET(%rsp),%rdi	/* pt_regs pointer */
+	movq	%rsp, %rdi
 	call	syscall_return_slowpath	/* returns with IRQs disabled */
 	TRACE_IRQS_ON			/* user mode is traced as IRQS on */
 	SWAPGS
-	FRAME_END
 	jmp	restore_regs_and_iret
 
 1: