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 collection of assorted fixes:

   - Fix for the pinned cr0/4 fallout which escaped all testing efforts
     because the kvm-intel module was never loaded when the kernel was
     compiled with CONFIG_PARAVIRT=n. The cr0/4 accessors are moved out
     of line and static key is now solely used in the core code and
     therefore can stay in the RO after init section. So the kvm-intel
     and other modules do not longer reference the (read only) static
     key which the module loader tried to update.

   - Prevent an infinite loop in arch_stack_walk_user() by breaking out
     of the loop once the return address is detected to be 0.

   - Prevent the int3_emulate_call() selftest from corrupting the stack
     when KASAN is enabled. KASASN clobbers more registers than covered
     by the emulated call implementation. Convert the int3_magic()
     selftest to a ASM function so the compiler cannot KASANify it.

   - Unbreak the build with old GCC versions and with the Gold linker by
     reverting the 'Move of _etext to the actual end of .text'. In both
     cases the build fails with 'Invalid absolute R_X86_64_32S
     relocation: _etext'

   - Initialize the context lock for init_mm, which was never an issue
     until the alternatives code started to use a temporary mm for
     patching.

   - Fix a build warning vs. the LOWMEM_PAGES constant where clang
     complains rightfully about a signed integer overflow in the shift
     operation by converting the operand to an ULL.

   - Adjust the misnamed ENDPROC() of common_spurious in the 32bit entry
     code"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/stacktrace: Prevent infinite loop in arch_stack_walk_user()
  x86/asm: Move native_write_cr0/4() out of line
  x86/pgtable/32: Fix LOWMEM_PAGES constant
  x86/alternatives: Fix int3_emulate_call() selftest stack corruption
  x86/entry/32: Fix ENDPROC of common_spurious
  Revert "x86/build: Move _etext to actual end of .text"
  x86/ldt: Initialize the context lock for init_mm

arch/x86/include/asm/mmu.h

@@ -59,6 +59,7 @@ typedef struct {
 #define INIT_MM_CONTEXT(mm)						\
 	.context = {							\
 		.ctx_id = 1,						\
+		.lock = __MUTEX_INITIALIZER(mm.context.lock),		\
 	}
 
 void leave_mm(int cpu);

arch/x86/include/asm/pgtable_32.h

@@ -106,6 +106,6 @@ do {						\
  * with only a host target support using a 32-bit type for internal
  * representation.
  */
-#define LOWMEM_PAGES ((((2<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
+#define LOWMEM_PAGES ((((_ULL(2)<<31) - __PAGE_OFFSET) >> PAGE_SHIFT))
 
 #endif /* _ASM_X86_PGTABLE_32_H */

arch/x86/include/asm/processor.h

@@ -741,6 +741,7 @@ extern void load_direct_gdt(int);
 extern void load_fixmap_gdt(int);
 extern void load_percpu_segment(int);
 extern void cpu_init(void);
+extern void cr4_init(void);
 
 static inline unsigned long get_debugctlmsr(void)
 {

arch/x86/include/asm/special_insns.h

@@ -18,9 +18,7 @@
  */
 extern unsigned long __force_order;
 
-/* Starts false and gets enabled once CPU feature detection is done. */
-DECLARE_STATIC_KEY_FALSE(cr_pinning);
-extern unsigned long cr4_pinned_bits;
+void native_write_cr0(unsigned long val);
 
 static inline unsigned long native_read_cr0(void)
 {
@@ -29,24 +27,6 @@ static inline unsigned long native_read_cr0(void)
 	return val;
 }
 
-static inline void native_write_cr0(unsigned long val)
-{
-	unsigned long bits_missing = 0;
-
-set_register:
-	asm volatile("mov %0,%%cr0": "+r" (val), "+m" (__force_order));
-
-	if (static_branch_likely(&cr_pinning)) {
-		if (unlikely((val & X86_CR0_WP) != X86_CR0_WP)) {
-			bits_missing = X86_CR0_WP;
-			val |= bits_missing;
-			goto set_register;
-		}
-		/* Warn after we've set the missing bits. */
-		WARN_ONCE(bits_missing, "CR0 WP bit went missing!?\n");
-	}
-}
-
 static inline unsigned long native_read_cr2(void)
 {
 	unsigned long val;
@@ -91,24 +71,7 @@ static inline unsigned long native_read_cr4(void)
 	return val;
 }
 
-static inline void native_write_cr4(unsigned long val)
-{
-	unsigned long bits_missing = 0;
-
-set_register:
-	asm volatile("mov %0,%%cr4": "+r" (val), "+m" (cr4_pinned_bits));
-
-	if (static_branch_likely(&cr_pinning)) {
-		if (unlikely((val & cr4_pinned_bits) != cr4_pinned_bits)) {
-			bits_missing = ~val & cr4_pinned_bits;
-			val |= bits_missing;
-			goto set_register;
-		}
-		/* Warn after we've set the missing bits. */
-		WARN_ONCE(bits_missing, "CR4 bits went missing: %lx!?\n",
-			  bits_missing);
-	}
-}
+void native_write_cr4(unsigned long val);
 
 #ifdef CONFIG_X86_64
 static inline unsigned long native_read_cr8(void)