From: Dave Hansen <dave.hansen@linux.intel.com>
Date: Mon, 4 Dec 2017 15:07:54 +0100
Subject: x86/mm: Move the CR3 construction functions to tlbflush.h
Git-commit: 50fb83a62cf472dc53ba23bd3f7bd6c1b2b3b53e
Patch-mainline: v4.15-rc5
References: bsc#1068032 CVE-2017-5754

For flushing the TLB, the ASID which has been programmed into the hardware
must be known.  That differs from what is in 'cpu_tlbstate'.

Add functions to transform the 'cpu_tlbstate' values into to the one
programmed into the hardware (CR3).

It's not easy to include mmu_context.h into tlbflush.h, so just move the
CR3 building over to tlbflush.h.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/mmu_context.h |   12 +-----------
 arch/x86/include/asm/tlbflush.h    |   26 ++++++++++++++++++++++++++
 arch/x86/mm/tlb.c                  |    8 ++++----
 3 files changed, 31 insertions(+), 15 deletions(-)

--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -301,16 +301,6 @@ static inline bool arch_vma_access_permi
 	return __pkru_allows_pkey(vma_pkey(vma), write);
 }
 
-static inline unsigned long build_cr3(struct mm_struct *mm, u16 asid)
-{
-	return __sme_pa(mm->pgd) | asid;
-}
-
-static inline unsigned long build_cr3_noflush(struct mm_struct *mm, u16 asid)
-{
-	return __sme_pa(mm->pgd) | asid | CR3_NOFLUSH;
-}
-
 /*
  * This can be used from process context to figure out what the value of
  * CR3 is without needing to do a (slow) read_cr3().
@@ -320,7 +310,7 @@ static inline unsigned long build_cr3_no
  */
 static inline unsigned long __get_current_cr3_fast(void)
 {
-	unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm),
+	unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
 		this_cpu_read(cpu_tlbstate.loaded_mm_asid));
 
 	/* For now, be very restrictive about when this can be called. */
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -68,6 +68,32 @@ static inline u64 inc_mm_tlb_gen(struct
 	return atomic64_inc_return(&mm->context.tlb_gen);
 }
 
+/*
+ * If PCID is on, ASID-aware code paths put the ASID+1 into the PCID bits.
+ * This serves two purposes.  It prevents a nasty situation in which
+ * PCID-unaware code saves CR3, loads some other value (with PCID == 0),
+ * and then restores CR3, thus corrupting the TLB for ASID 0 if the saved
+ * ASID was nonzero.  It also means that any bugs involving loading a
+ * PCID-enabled CR3 with CR4.PCIDE off will trigger deterministically.
+ */
+struct pgd_t;
+static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
+{
+	if (static_cpu_has(X86_FEATURE_PCID)) {
+		VM_WARN_ON_ONCE(asid > 4094);
+		return __sme_pa(pgd) | (asid + 1);
+	} else {
+		VM_WARN_ON_ONCE(asid != 0);
+		return __sme_pa(pgd);
+	}
+}
+
+static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
+{
+	VM_WARN_ON_ONCE(asid > 4094);
+	return __sme_pa(pgd) | (asid + 1) | CR3_NOFLUSH;
+}
+
 #ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
 #else
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -128,7 +128,7 @@ void switch_mm_irqs_off(struct mm_struct
 	 * isn't free.
 	 */
 #ifdef CONFIG_DEBUG_VM
-	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev, prev_asid))) {
+	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid))) {
 		/*
 		 * If we were to BUG here, we'd be very likely to kill
 		 * the system so hard that we don't see the call trace.
@@ -195,7 +195,7 @@ void switch_mm_irqs_off(struct mm_struct
 		if (need_flush) {
 			this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
 			this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
-			write_cr3(build_cr3(next, new_asid));
+			write_cr3(build_cr3(next->pgd, new_asid));
 
 			/*
 			 * NB: This gets called via leave_mm() in the idle path
@@ -208,7 +208,7 @@ void switch_mm_irqs_off(struct mm_struct
 			trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
 		} else {
 			/* The new ASID is already up to date. */
-			write_cr3(build_cr3_noflush(next, new_asid));
+			write_cr3(build_cr3_noflush(next->pgd, new_asid));
 
 			/* See above wrt _rcuidle. */
 			trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, 0);
@@ -324,7 +324,7 @@ void initialize_tlbstate_and_flush(void)
 		!(cr4_read_shadow() & X86_CR4_PCIDE));
 
 	/* Force ASID 0 and force a TLB flush. */
-	write_cr3(build_cr3(mm, 0));
+	write_cr3(build_cr3(mm->pgd, 0));
 
 	/* Reinitialize tlbstate. */
 	this_cpu_write(cpu_tlbstate.loaded_mm_asid, 0);
