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

Pull spectre/meltdown updates from Thomas Gleixner:
 "The next round of updates related to melted spectrum:

   - The initial set of spectre V1 mitigations:

       - Array index speculation blocker and its usage for syscall,
         fdtable and the n180211 driver.

       - Speculation barrier and its usage in user access functions

   - Make indirect calls in KVM speculation safe

   - Blacklisting of known to be broken microcodes so IPBP/IBSR are not
     touched.

   - The initial IBPB support and its usage in context switch

   - The exposure of the new speculation MSRs to KVM guests.

   - A fix for a regression in x86/32 related to the cpu entry area

   - Proper whitelisting for known to be safe CPUs from the mitigations.

   - objtool fixes to deal proper with retpolines and alternatives

   - Exclude __init functions from retpolines which speeds up the boot
     process.

   - Removal of the syscall64 fast path and related cleanups and
     simplifications

   - Removal of the unpatched paravirt mode which is yet another source
     of indirect unproteced calls.

   - A new and undisputed version of the module mismatch warning

   - A couple of cleanup and correctness fixes all over the place

  Yet another step towards full mitigation. There are a few things still
  missing like the RBS underflow mitigation for Skylake and other small
  details, but that's being worked on.

  That said, I'm taking a belated christmas vacation for a week and hope
  that everything is magically solved when I'm back on Feb 12th"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
  KVM/SVM: Allow direct access to MSR_IA32_SPEC_CTRL
  KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL
  KVM/VMX: Emulate MSR_IA32_ARCH_CAPABILITIES
  KVM/x86: Add IBPB support
  KVM/x86: Update the reverse_cpuid list to include CPUID_7_EDX
  x86/speculation: Fix typo IBRS_ATT, which should be IBRS_ALL
  x86/pti: Mark constant arrays as __initconst
  x86/spectre: Simplify spectre_v2 command line parsing
  x86/retpoline: Avoid retpolines for built-in __init functions
  x86/kvm: Update spectre-v1 mitigation
  KVM: VMX: make MSR bitmaps per-VCPU
  x86/paravirt: Remove 'noreplace-paravirt' cmdline option
  x86/speculation: Use Indirect Branch Prediction Barrier in context switch
  x86/cpuid: Fix up "virtual" IBRS/IBPB/STIBP feature bits on Intel
  x86/spectre: Fix spelling mistake: "vunerable"-> "vulnerable"
  x86/spectre: Report get_user mitigation for spectre_v1
  nl80211: Sanitize array index in parse_txq_params
  vfs, fdtable: Prevent bounds-check bypass via speculative execution
  x86/syscall: Sanitize syscall table de-references under speculation
  x86/get_user: Use pointer masking to limit speculation
  ...

3 files changed, 15 insertions, 128 deletions

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 1e3883e45687..74f6eee15179 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -21,6 +21,7 @@
 #include <linux/export.h>
 #include <linux/context_tracking.h>
 #include <linux/user-return-notifier.h>
+#include <linux/nospec.h>
 #include <linux/uprobes.h>
 #include <linux/livepatch.h>
 #include <linux/syscalls.h>
@@ -206,7 +207,7 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
 	 * special case only applies after poking regs and before the
 	 * very next return to user mode.
 	 */
-	current->thread.status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
+	ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
 #endif
 
 	user_enter_irqoff();
@@ -282,7 +283,8 @@ __visible void do_syscall_64(struct pt_regs *regs)
 	 * regs->orig_ax, which changes the behavior of some syscalls.
 	 */
 	if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) {
-		regs->ax = sys_call_table[nr & __SYSCALL_MASK](
+		nr = array_index_nospec(nr & __SYSCALL_MASK, NR_syscalls);
+		regs->ax = sys_call_table[nr](
 			regs->di, regs->si, regs->dx,
 			regs->r10, regs->r8, regs->r9);
 	}
@@ -304,7 +306,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
 	unsigned int nr = (unsigned int)regs->orig_ax;
 
 #ifdef CONFIG_IA32_EMULATION
-	current->thread.status |= TS_COMPAT;
+	ti->status |= TS_COMPAT;
 #endif
 
 	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
@@ -318,6 +320,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
 	}
 
 	if (likely(nr < IA32_NR_syscalls)) {
+		nr = array_index_nospec(nr, IA32_NR_syscalls);
 		/*
 		 * It's possible that a 32-bit syscall implementation
 		 * takes a 64-bit parameter but nonetheless assumes that
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index a83570495162..c752abe89d80 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -236,91 +236,20 @@ GLOBAL(entry_SYSCALL_64_after_hwframe)
 	pushq	%r9				/* pt_regs->r9 */
 	pushq	%r10				/* pt_regs->r10 */
 	pushq	%r11				/* pt_regs->r11 */
-	sub	$(6*8), %rsp			/* pt_regs->bp, bx, r12-15 not saved */
-	UNWIND_HINT_REGS extra=0
-
-	TRACE_IRQS_OFF
-
-	/*
-	 * If we need to do entry work or if we guess we'll need to do
-	 * exit work, go straight to the slow path.
-	 */
-	movq	PER_CPU_VAR(current_task), %r11
-	testl	$_TIF_WORK_SYSCALL_ENTRY|_TIF_ALLWORK_MASK, TASK_TI_flags(%r11)
-	jnz	entry_SYSCALL64_slow_path
-
-entry_SYSCALL_64_fastpath:
-	/*
-	 * Easy case: enable interrupts and issue the syscall.  If the syscall
-	 * needs pt_regs, we'll call a stub that disables interrupts again
-	 * and jumps to the slow path.
-	 */
-	TRACE_IRQS_ON
-	ENABLE_INTERRUPTS(CLBR_NONE)
-#if __SYSCALL_MASK == ~0
-	cmpq	$__NR_syscall_max, %rax
-#else
-	andl	$__SYSCALL_MASK, %eax
-	cmpl	$__NR_syscall_max, %eax
-#endif
-	ja	1f				/* return -ENOSYS (already in pt_regs->ax) */
-	movq	%r10, %rcx
-
-	/*
-	 * This call instruction is handled specially in stub_ptregs_64.
-	 * It might end up jumping to the slow path.  If it jumps, RAX
-	 * and all argument registers are clobbered.
-	 */
-#ifdef CONFIG_RETPOLINE
-	movq	sys_call_table(, %rax, 8), %rax
-	call	__x86_indirect_thunk_rax
-#else
-	call	*sys_call_table(, %rax, 8)
-#endif
-.Lentry_SYSCALL_64_after_fastpath_call:
-
-	movq	%rax, RAX(%rsp)
-1:
+	pushq	%rbx				/* pt_regs->rbx */
+	pushq	%rbp				/* pt_regs->rbp */
+	pushq	%r12				/* pt_regs->r12 */
+	pushq	%r13				/* pt_regs->r13 */
+	pushq	%r14				/* pt_regs->r14 */
+	pushq	%r15				/* pt_regs->r15 */
+	UNWIND_HINT_REGS
 
-	/*
-	 * If we get here, then we know that pt_regs is clean for SYSRET64.
-	 * If we see that no exit work is required (which we are required
-	 * to check with IRQs off), then we can go straight to SYSRET64.
-	 */
-	DISABLE_INTERRUPTS(CLBR_ANY)
 	TRACE_IRQS_OFF
-	movq	PER_CPU_VAR(current_task), %r11
-	testl	$_TIF_ALLWORK_MASK, TASK_TI_flags(%r11)
-	jnz	1f
-
-	LOCKDEP_SYS_EXIT
-	TRACE_IRQS_ON		/* user mode is traced as IRQs on */
-	movq	RIP(%rsp), %rcx
-	movq	EFLAGS(%rsp), %r11
-	addq	$6*8, %rsp	/* skip extra regs -- they were preserved */
-	UNWIND_HINT_EMPTY
-	jmp	.Lpop_c_regs_except_rcx_r11_and_sysret
 
-1:
-	/*
-	 * The fast path looked good when we started, but something changed
-	 * along the way and we need to switch to the slow path.  Calling
-	 * raise(3) will trigger this, for example.  IRQs are off.
-	 */
-	TRACE_IRQS_ON
-	ENABLE_INTERRUPTS(CLBR_ANY)
-	SAVE_EXTRA_REGS
-	movq	%rsp, %rdi
-	call	syscall_return_slowpath	/* returns with IRQs disabled */
-	jmp	return_from_SYSCALL_64
-
-entry_SYSCALL64_slow_path:
 	/* IRQs are off. */
-	SAVE_EXTRA_REGS
 	movq	%rsp, %rdi
 	call	do_syscall_64		/* returns with IRQs disabled */
 
-return_from_SYSCALL_64:
 	TRACE_IRQS_IRETQ		/* we're about to change IF */
 
 	/*
@@ -393,7 +322,6 @@ syscall_return_via_sysret:
 	/* rcx and r11 are already restored (see code above) */
 	UNWIND_HINT_EMPTY
 	POP_EXTRA_REGS
-.Lpop_c_regs_except_rcx_r11_and_sysret:
 	popq	%rsi	/* skip r11 */
 	popq	%r10
 	popq	%r9
@@ -424,47 +352,6 @@ syscall_return_via_sysret:
 	USERGS_SYSRET64
 END(entry_SYSCALL_64)
 
-ENTRY(stub_ptregs_64)
-	/*
-	 * Syscalls marked as needing ptregs land here.
-	 * If we are on the fast path, we need to save the extra regs,
-	 * which we achieve by trying again on the slow path.  If we are on
-	 * the slow path, the extra regs are already saved.
-	 *
-	 * RAX stores a pointer to the C function implementing the syscall.
-	 * IRQs are on.
-	 */
-	cmpq	$.Lentry_SYSCALL_64_after_fastpath_call, (%rsp)
-	jne	1f
-
-	/*
-	 * Called from fast path -- disable IRQs again, pop return address
-	 * and jump to slow path
-	 */
-	DISABLE_INTERRUPTS(CLBR_ANY)
-	TRACE_IRQS_OFF
-	popq	%rax
-	UNWIND_HINT_REGS extra=0
-	jmp	entry_SYSCALL64_slow_path
-
-1:
-	JMP_NOSPEC %rax				/* Called from C */
-END(stub_ptregs_64)
-
-.macro ptregs_stub func
-ENTRY(ptregs_\func)
-	UNWIND_HINT_FUNC
-	leaq	\func(%rip), %rax
-	jmp	stub_ptregs_64
-END(ptregs_\func)
-.endm
-
-/* Instantiate ptregs_stub for each ptregs-using syscall */
-#define __SYSCALL_64_QUAL_(sym)
-#define __SYSCALL_64_QUAL_ptregs(sym) ptregs_stub sym
-#define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym)
-#include <asm/syscalls_64.h>
-
 /*
  * %rdi: prev task
  * %rsi: next task
diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c
index 9c09775e589d..c176d2fab1da 100644
--- a/arch/x86/entry/syscall_64.c
+++ b/arch/x86/entry/syscall_64.c
@@ -7,14 +7,11 @@
 #include <asm/asm-offsets.h>
 #include <asm/syscall.h>
 
-#define __SYSCALL_64_QUAL_(sym) sym
-#define __SYSCALL_64_QUAL_ptregs(sym) ptregs_##sym
-
-#define __SYSCALL_64(nr, sym, qual) extern asmlinkage long __SYSCALL_64_QUAL_##qual(sym)(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
+#define __SYSCALL_64(nr, sym, qual) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 #include <asm/syscalls_64.h>
 #undef __SYSCALL_64
 
-#define __SYSCALL_64(nr, sym, qual) [nr] = __SYSCALL_64_QUAL_##qual(sym),
+#define __SYSCALL_64(nr, sym, qual) [nr] = sym,
 
 extern long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);