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

   mds_user_clear.

   The mitigation is invoked in prepare_exit_to_usermode() which covers

   most of the kernel to user space transitions. There are a few exceptions

   which are not invoking prepare_exit_to_usermode() on return to user

   space. These exceptions use the paranoid exit code.

   all but one of the kernel to user space transitions.  The exception

   is when we return from a Non Maskable Interrupt (NMI), which is

   handled directly in do_nmi().

   - Non Maskable Interrupt (NMI):

     Access to sensible data like keys, credentials in the NMI context is

     mostly theoretical: The CPU can do prefetching or execute a

     misspeculated code path and thereby fetching data which might end up

     leaking through a buffer.

     But for mounting other attacks the kernel stack address of the task is

     already valuable information. So in full mitigation mode, the NMI is

     mitigated on the return from do_nmi() to provide almost complete

     coverage.

   - Double fault (#DF):

     A double fault is usually fatal, but the ESPFIX workaround, which can

     be triggered from user space through modify_ldt(2) is a recoverable

     double fault. #DF uses the paranoid exit path, so explicit mitigation

     in the double fault handler is required.

   - Machine Check Exception (#MC):

     Another corner case is a #MC which hits between the CPU buffer clear

     invocation and the actual return to user. As this still is in kernel

     space it takes the paranoid exit path which does not clear the CPU

     buffers. So the #MC handler repopulates the buffers to some

     extent. Machine checks are not reliably controllable and the window is

     extremly small so mitigation would just tick a checkbox that this

     theoretical corner case is covered. To keep the amount of special

     cases small, ignore #MC.

   - Debug Exception (#DB):

     This takes the paranoid exit path only when the INT1 breakpoint is in

     kernel space. #DB on a user space address takes the regular exit path,

     so no extra mitigation required.

   (The reason that NMI is special is that prepare_exit_to_usermode() can

    enable IRQs.  In NMI context, NMIs are blocked, and we don't want to

    enable IRQs with NMIs blocked.)

2. C-State transition

config GENERIC_BUG_RELATIVE_POINTERS

	bool

config GENERIC_HWEIGHT

	def_bool y

config ARCH_MAY_HAVE_PC_FDC

	def_bool y

	depends on ISA_DMA_API

enum {

	sym_vvar_start,

	sym_vvar_page,

	sym_hpet_page,

	sym_pvclock_page,

	sym_hvclock_page,

};

const int special_pages[] = {

	sym_vvar_page,

	sym_hpet_page,

	sym_pvclock_page,

	sym_hvclock_page,

};

struct vdso_sym required_syms[] = {

	[sym_vvar_start] = {"vvar_start", true},

	[sym_vvar_page] = {"vvar_page", true},

	[sym_hpet_page] = {"hpet_page", true},

	[sym_pvclock_page] = {"pvclock_page", true},

	[sym_hvclock_page] = {"hvclock_page", true},

	{"VDSO32_NOTE_MASK", true},

#define REG_OUT "a"

#endif

#define __HAVE_ARCH_SW_HWEIGHT

static __always_inline unsigned int __arch_hweight32(unsigned int w)

{

	unsigned int res;

	long sym_vvar_start;  /* Negative offset to the vvar area */

	long sym_vvar_page;

	long sym_hpet_page;

	long sym_pvclock_page;

	long sym_hvclock_page;

	long sym_VDSO32_NOTE_MASK;