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

Pull x86 fixes from Ingo Molnar:
 "Misc fixes:
   - two fixes to make (very) old Intel CPUs boot reliably
   - fix the intel-mid driver and rename it
   - two KASAN false positive fixes
   - an FPU fix
   - two sysfb fixes
   - two build fixes related to new toolchain versions"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/platform/intel-mid: Rename platform_wdt to platform_mrfld_wdt
  x86/build: Build compressed x86 kernels as PIE when !CONFIG_RELOCATABLE as well
  x86/platform/intel-mid: Register watchdog device after SCU
  x86/fpu: Fix invalid FPU ptrace state after execve()
  x86/boot: Fail the boot if !M486 and CPUID is missing
  x86/traps: Ignore high word of regs->cs in early_fixup_exception()
  x86/dumpstack: Prevent KASAN false positive warnings
  x86/unwind: Prevent KASAN false positive warnings in guess unwinder
  x86/boot: Avoid warning for zero-filling .bss
  x86/sysfb: Fix lfb_size calculation
  x86/sysfb: Add support for 64bit EFI lfb_base

10 files changed, 95 insertions, 33 deletions

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 536ccfcc01c6..34d9e15857c3 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -40,8 +40,8 @@ GCOV_PROFILE := n
 UBSAN_SANITIZE :=n
 
 LDFLAGS := -m elf_$(UTS_MACHINE)
-ifeq ($(CONFIG_RELOCATABLE),y)
-# If kernel is relocatable, build compressed kernel as PIE.
+# Compressed kernel should be built as PIE since it may be loaded at any
+# address by the bootloader.
 ifeq ($(CONFIG_X86_32),y)
 LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
 else
@@ -51,7 +51,6 @@ else
 LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \
 	&& echo "-z noreloc-overflow -pie --no-dynamic-linker")
 endif
-endif
 LDFLAGS_vmlinux := -T
 
 hostprogs-y	:= mkpiggy
diff --git a/arch/x86/boot/cpu.c b/arch/x86/boot/cpu.c
index 26240dde081e..4224ede43b4e 100644
--- a/arch/x86/boot/cpu.c
+++ b/arch/x86/boot/cpu.c
@@ -87,6 +87,12 @@ int validate_cpu(void)
 		return -1;
 	}
 
+	if (CONFIG_X86_MINIMUM_CPU_FAMILY <= 4 && !IS_ENABLED(CONFIG_M486) &&
+	    !has_eflag(X86_EFLAGS_ID)) {
+		printf("This kernel requires a CPU with the CPUID instruction.  Build with CONFIG_M486=y to run on this CPU.\n");
+		return -1;
+	}
+
 	if (err_flags) {
 		puts("This kernel requires the following features "
 		     "not present on the CPU:\n");
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 9b7cf5c28f5f..85f854b98a9d 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -112,7 +112,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
 		for (; stack < stack_info.end; stack++) {
 			unsigned long real_addr;
 			int reliable = 0;
-			unsigned long addr = *stack;
+			unsigned long addr = READ_ONCE_NOCHECK(*stack);
 			unsigned long *ret_addr_p =
 				unwind_get_return_address_ptr(&state);
 
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 47004010ad5d..ebb4e95fbd74 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -521,14 +521,14 @@ void fpu__clear(struct fpu *fpu)
 {
 	WARN_ON_FPU(fpu != &current->thread.fpu); /* Almost certainly an anomaly */
 
-	if (!use_eager_fpu() || !static_cpu_has(X86_FEATURE_FPU)) {
-		/* FPU state will be reallocated lazily at the first use. */
-		fpu__drop(fpu);
-	} else {
-		if (!fpu->fpstate_active) {
-			fpu__activate_curr(fpu);
-			user_fpu_begin();
-		}
+	fpu__drop(fpu);
+
+	/*
+	 * Make sure fpstate is cleared and initialized.
+	 */
+	if (static_cpu_has(X86_FEATURE_FPU)) {
+		fpu__activate_curr(fpu);
+		user_fpu_begin();
 		copy_init_fpstate_to_fpregs();
 	}
 }
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index b6b2f0264af3..2dabea46f039 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -665,14 +665,17 @@ __PAGE_ALIGNED_BSS
 initial_pg_pmd:
 	.fill 1024*KPMDS,4,0
 #else
-ENTRY(initial_page_table)
+.globl initial_page_table
+initial_page_table:
 	.fill 1024,4,0
 #endif
 initial_pg_fixmap:
 	.fill 1024,4,0
-ENTRY(empty_zero_page)
+.globl empty_zero_page
+empty_zero_page:
 	.fill 4096,1,0
-ENTRY(swapper_pg_dir)
+.globl swapper_pg_dir
+swapper_pg_dir:
 	.fill 1024,4,0
 EXPORT_SYMBOL(empty_zero_page)
 
diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c
index 764a29f84de7..85195d447a92 100644
--- a/arch/x86/kernel/sysfb_simplefb.c
+++ b/arch/x86/kernel/sysfb_simplefb.c
@@ -66,13 +66,36 @@ __init int create_simplefb(const struct screen_info *si,
 {
 	struct platform_device *pd;
 	struct resource res;
-	unsigned long len;
+	u64 base, size;
+	u32 length;
 
-	/* don't use lfb_size as it may contain the whole VMEM instead of only
-	 * the part that is occupied by the framebuffer */
-	len = mode->height * mode->stride;
-	len = PAGE_ALIGN(len);
-	if (len > (u64)si->lfb_size << 16) {
+	/*
+	 * If the 64BIT_BASE capability is set, ext_lfb_base will contain the
+	 * upper half of the base address. Assemble the address, then make sure
+	 * it is valid and we can actually access it.
+	 */
+	base = si->lfb_base;
+	if (si->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
+		base |= (u64)si->ext_lfb_base << 32;
+	if (!base || (u64)(resource_size_t)base != base) {
+		printk(KERN_DEBUG "sysfb: inaccessible VRAM base\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Don't use lfb_size as IORESOURCE size, since it may contain the
+	 * entire VMEM, and thus require huge mappings. Use just the part we
+	 * need, that is, the part where the framebuffer is located. But verify
+	 * that it does not exceed the advertised VMEM.
+	 * Note that in case of VBE, the lfb_size is shifted by 16 bits for
+	 * historical reasons.
+	 */
+	size = si->lfb_size;
+	if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
+		size <<= 16;
+	length = mode->height * mode->stride;
+	length = PAGE_ALIGN(length);
+	if (length > size) {
 		printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
 		return -EINVAL;
 	}
@@ -81,8 +104,8 @@ __init int create_simplefb(const struct screen_info *si,
 	memset(&res, 0, sizeof(res));
 	res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 	res.name = simplefb_resname;
-	res.start = si->lfb_base;
-	res.end = si->lfb_base + len - 1;
+	res.start = base;
+	res.end = res.start + length - 1;
 	if (res.end <= res.start)
 		return -EINVAL;
 
diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c
index 2d721e533cf4..b80e8bf43cc6 100644
--- a/arch/x86/kernel/unwind_guess.c
+++ b/arch/x86/kernel/unwind_guess.c
@@ -7,11 +7,13 @@
 
 unsigned long unwind_get_return_address(struct unwind_state *state)
 {
+	unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
+
 	if (unwind_done(state))
 		return 0;
 
 	return ftrace_graph_ret_addr(state->task, &state->graph_idx,
-				     *state->sp, state->sp);
+				     addr, state->sp);
 }
 EXPORT_SYMBOL_GPL(unwind_get_return_address);
 
@@ -23,8 +25,10 @@ bool unwind_next_frame(struct unwind_state *state)
 		return false;
 
 	do {
+		unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
+
 		for (state->sp++; state->sp < info->end; state->sp++)
-			if (__kernel_text_address(*state->sp))
+			if (__kernel_text_address(addr))
 				return true;
 
 		state->sp = info->next_sp;
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 79ae939970d3..fcd06f7526de 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -135,7 +135,12 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
 	if (early_recursion_flag > 2)
 		goto halt_loop;
 
-	if (regs->cs != __KERNEL_CS)
+	/*
+	 * Old CPUs leave the high bits of CS on the stack
+	 * undefined.  I'm not sure which CPUs do this, but at least
+	 * the 486 DX works this way.
+	 */
+	if ((regs->cs & 0xFFFF) != __KERNEL_CS)
 		goto fail;
 
 	/*
diff --git a/arch/x86/platform/intel-mid/device_libs/Makefile b/arch/x86/platform/intel-mid/device_libs/Makefile
index 429d08be7848..dd6cfa4ad3ac 100644
--- a/arch/x86/platform/intel-mid/device_libs/Makefile
+++ b/arch/x86/platform/intel-mid/device_libs/Makefile
@@ -28,4 +28,4 @@ obj-$(subst m,y,$(CONFIG_GPIO_PCA953X)) += platform_pcal9555a.o
 obj-$(subst m,y,$(CONFIG_GPIO_PCA953X)) += platform_tca6416.o
 # MISC Devices
 obj-$(subst m,y,$(CONFIG_KEYBOARD_GPIO)) += platform_gpio_keys.o
-obj-$(subst m,y,$(CONFIG_INTEL_MID_WATCHDOG)) += platform_wdt.o
+obj-$(subst m,y,$(CONFIG_INTEL_MID_WATCHDOG)) += platform_mrfld_wdt.o
diff --git a/arch/x86/platform/intel-mid/device_libs/platform_wdt.c b/arch/x86/platform/intel-mid/device_libs/platform_mrfld_wdt.c
index de734134bc8d..3f1f1c77d090 100644
--- a/arch/x86/platform/intel-mid/device_libs/platform_wdt.c
+++ b/arch/x86/platform/intel-mid/device_libs/platform_mrfld_wdt.c
@@ -1,5 +1,5 @@
 /*
- * platform_wdt.c: Watchdog platform library file
+ * Intel Merrifield watchdog platform device library file
  *
  * (C) Copyright 2014 Intel Corporation
  * Author: David Cohen <david.a.cohen@linux.intel.com>
@@ -14,7 +14,9 @@
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>
 #include <linux/platform_data/intel-mid_wdt.h>
+
 #include <asm/intel-mid.h>
+#include <asm/intel_scu_ipc.h>
 #include <asm/io_apic.h>
 
 #define TANGIER_EXT_TIMER0_MSI 15
@@ -50,14 +52,34 @@ static struct intel_mid_wdt_pdata tangier_pdata = {
 	.probe = tangier_probe,
 };
 
-static int __init register_mid_wdt(void)
+static int wdt_scu_status_change(struct notifier_block *nb,
+				 unsigned long code, void *data)
 {
-	if (intel_mid_identify_cpu() == INTEL_MID_CPU_CHIP_TANGIER) {
-		wdt_dev.dev.platform_data = &tangier_pdata;
-		return platform_device_register(&wdt_dev);
+	if (code == SCU_DOWN) {
+		platform_device_unregister(&wdt_dev);
+		return 0;
 	}
 
-	return -ENODEV;
+	return platform_device_register(&wdt_dev);
 }
 
+static struct notifier_block wdt_scu_notifier = {
+	.notifier_call	= wdt_scu_status_change,
+};
+
+static int __init register_mid_wdt(void)
+{
+	if (intel_mid_identify_cpu() != INTEL_MID_CPU_CHIP_TANGIER)
+		return -ENODEV;
+
+	wdt_dev.dev.platform_data = &tangier_pdata;
+
+	/*
+	 * We need to be sure that the SCU IPC is ready before watchdog device
+	 * can be registered:
+	 */
+	intel_scu_notifier_add(&wdt_scu_notifier);
+
+	return 0;
+}
 rootfs_initcall(register_mid_wdt);