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

arch/x86/Kconfig

···
 	  Management" code will be disabled if you say Y here.
 
 	  See also <file:Documentation/x86/i386/IO-APIC.txt>,
-	  <file:Documentation/nmi_watchdog.txt> and the SMP-HOWTO available at
+	  <file:Documentation/lockup-watchdogs.txt> and the SMP-HOWTO available at
 	  <http://www.tldp.org/docs.html#howto>.
 
 	  If you don't know what to do here, say N.

arch/x86/Makefile

···
 	# If '-Os' is enabled, disable it and print a warning.
         ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
           undefine CONFIG_CC_OPTIMIZE_FOR_SIZE
-	  $(warning Disabling CONFIG_CC_OPTIMIZE_FOR_SIZE.  Your compiler does not have -mfentry so you cannot optimize for size with CONFIG_FUNCTION_GRAPH_TRACER.)
+          $(warning Disabling CONFIG_CC_OPTIMIZE_FOR_SIZE.  Your compiler does not have -mfentry so you cannot optimize for size with CONFIG_FUNCTION_GRAPH_TRACER.)
         endif
 
     endif

arch/x86/boot/compressed/Makefile

···
 quiet_cmd_check_data_rel = DATAREL $@
 define cmd_check_data_rel
 	for obj in $(filter %.o,$^); do \
-		readelf -S $$obj | grep -qF .rel.local && { \
+		${CROSS_COMPILE}readelf -S $$obj | grep -qF .rel.local && { \
 			echo "error: $$obj has data relocations!" >&2; \
 			exit 1; \
 		} || true; \

arch/x86/entry/entry_32.S

···
 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
···
  * 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 */

arch/x86/entry/entry_64.S

···
 #include <asm/smap.h>
 #include <asm/pgtable_types.h>
 #include <asm/export.h>
-#include <asm/frame.h>
 #include <linux/err.h>
 
 .code64
···
  * 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:

arch/x86/kernel/alternative.c

···
 		memcpy(insnbuf, replacement, a->replacementlen);
 		insnbuf_sz = a->replacementlen;
 
-		/* 0xe8 is a relative jump; fix the offset. */
-		if (*insnbuf == 0xe8 && a->replacementlen == 5) {
+		/*
+		 * 0xe8 is a relative jump; fix the offset.
+		 *
+		 * Instruction length is checked before the opcode to avoid
+		 * accessing uninitialized bytes for zero-length replacements.
+		 */
+		if (a->replacementlen == 5 && *insnbuf == 0xe8) {
 			*(s32 *)(insnbuf + 1) += replacement - instr;
 			DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",
 				*(s32 *)(insnbuf + 1),

arch/x86/kernel/setup.c

···
 	 */
 	x86_configure_nx();
 
-	simple_udelay_calibration();
-
 	parse_early_param();
 
 #ifdef CONFIG_MEMORY_HOTPLUG
···
 	 * needs to be done after dmi_scan_machine, for the BP.
 	 */
 	init_hypervisor_platform();
+
+	simple_udelay_calibration();
 
 	x86_init.resources.probe_roms();
 

arch/x86/kernel/unwind_frame.c

···
 	return (unsigned long *)task_pt_regs(state->task) - 2;
 }
 
+static bool is_last_frame(struct unwind_state *state)
+{
+	return state->bp == last_frame(state);
+}
+
 #ifdef CONFIG_X86_32
 #define GCC_REALIGN_WORDS 3
 #else
···
 	return last_frame(state) - GCC_REALIGN_WORDS;
 }
 
-static bool is_last_task_frame(struct unwind_state *state)
+static bool is_last_aligned_frame(struct unwind_state *state)
 {
 	unsigned long *last_bp = last_frame(state);
 	unsigned long *aligned_bp = last_aligned_frame(state);
 
 	/*
-	 * We have to check for the last task frame at two different locations
-	 * because gcc can occasionally decide to realign the stack pointer and
-	 * change the offset of the stack frame in the prologue of a function
-	 * called by head/entry code.  Examples:
+	 * GCC can occasionally decide to realign the stack pointer and change
+	 * the offset of the stack frame in the prologue of a function called
+	 * by head/entry code.  Examples:
 	 *
 	 * <start_secondary>:
 	 *      push   %edi
···
 	 *      push   %rbp
 	 *      mov    %rsp,%rbp
 	 *
-	 * Note that after aligning the stack, it pushes a duplicate copy of
-	 * the return address before pushing the frame pointer.
+	 * After aligning the stack, it pushes a duplicate copy of the return
+	 * address before pushing the frame pointer.
 	 */
-	return (state->bp == last_bp ||
-		(state->bp == aligned_bp && *(aligned_bp+1) == *(last_bp+1)));
+	return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1));
+}
+
+static bool is_last_ftrace_frame(struct unwind_state *state)
+{
+	unsigned long *last_bp = last_frame(state);
+	unsigned long *last_ftrace_bp = last_bp - 3;
+
+	/*
+	 * When unwinding from an ftrace handler of a function called by entry
+	 * code, the stack layout of the last frame is:
+	 *
+	 *   bp
+	 *   parent ret addr
+	 *   bp
+	 *   function ret addr
+	 *   parent ret addr
+	 *   pt_regs
+	 *   -----------------
+	 */
+	return (state->bp == last_ftrace_bp &&
+		*state->bp == *(state->bp + 2) &&
+		*(state->bp + 1) == *(state->bp + 4));
+}
+
+static bool is_last_task_frame(struct unwind_state *state)
+{
+	return is_last_frame(state) || is_last_aligned_frame(state) ||
+	       is_last_ftrace_frame(state);
 }
 
 /*

arch/x86/mm/pat.c

···
 }
 early_param("nopat", nopat);
 
+static bool __read_mostly __pat_initialized = false;
+
 bool pat_enabled(void)
 {
-	return !!__pat_enabled;
+	return __pat_initialized;
 }
 EXPORT_SYMBOL_GPL(pat_enabled);
 
···
 	}
 
 	wrmsrl(MSR_IA32_CR_PAT, pat);
+	__pat_initialized = true;
 
 	__init_cache_modes(pat);
 }
 
 static void pat_ap_init(u64 pat)
 {
-	if (!boot_cpu_has(X86_FEATURE_PAT)) {
+	if (!this_cpu_has(X86_FEATURE_PAT)) {
 		/*
 		 * If this happens we are on a secondary CPU, but switched to
 		 * PAT on the boot CPU. We have no way to undo PAT.
···
 	u64 pat;
 	struct cpuinfo_x86 *c = &boot_cpu_data;
 
-	if (!pat_enabled()) {
+	if (!__pat_enabled) {
 		init_cache_modes();
 		return;
 	}