---

yaml
---
r: 3629
b: refs/heads/master
c: ffaa8bd
h: refs/heads/master
i:
  3627: 85411f3
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 6ae3db110e62b0846aae1b5c6e661484ee3a5ed1
+refs/heads/master: ffaa8bd6c904d1ab79b677905067349a5ff51d84

trunk/arch/i386/kernel/process.c

@@ -616,6 +616,33 @@ handle_io_bitmap(struct thread_struct *next, struct tss_struct *tss)
 	tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
 }
 
+/*
+ * This function selects if the context switch from prev to next
+ * has to tweak the TSC disable bit in the cr4.
+ */
+static inline void disable_tsc(struct task_struct *prev_p,
+			       struct task_struct *next_p)
+{
+	struct thread_info *prev, *next;
+
+	/*
+	 * gcc should eliminate the ->thread_info dereference if
+	 * has_secure_computing returns 0 at compile time (SECCOMP=n).
+	 */
+	prev = prev_p->thread_info;
+	next = next_p->thread_info;
+
+	if (has_secure_computing(prev) || has_secure_computing(next)) {
+		/* slow path here */
+		if (has_secure_computing(prev) &&
+		    !has_secure_computing(next)) {
+			write_cr4(read_cr4() & ~X86_CR4_TSD);
+		} else if (!has_secure_computing(prev) &&
+			   has_secure_computing(next))
+			write_cr4(read_cr4() | X86_CR4_TSD);
+	}
+}
+
 /*
  *	switch_to(x,yn) should switch tasks from x to y.
  *
@@ -695,6 +722,8 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
 	if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr))
 		handle_io_bitmap(next, tss);
 
+	disable_tsc(prev_p, next_p);
+
 	return prev_p;
 }
 

trunk/arch/x86_64/kernel/process.c

@@ -481,6 +481,33 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long rsp,
 	return err;
 }
 
+/*
+ * This function selects if the context switch from prev to next
+ * has to tweak the TSC disable bit in the cr4.
+ */
+static inline void disable_tsc(struct task_struct *prev_p,
+			       struct task_struct *next_p)
+{
+	struct thread_info *prev, *next;
+
+	/*
+	 * gcc should eliminate the ->thread_info dereference if
+	 * has_secure_computing returns 0 at compile time (SECCOMP=n).
+	 */
+	prev = prev_p->thread_info;
+	next = next_p->thread_info;
+
+	if (has_secure_computing(prev) || has_secure_computing(next)) {
+		/* slow path here */
+		if (has_secure_computing(prev) &&
+		    !has_secure_computing(next)) {
+			write_cr4(read_cr4() & ~X86_CR4_TSD);
+		} else if (!has_secure_computing(prev) &&
+			   has_secure_computing(next))
+			write_cr4(read_cr4() | X86_CR4_TSD);
+	}
+}
+
 /*
  * This special macro can be used to load a debugging register
  */
@@ -599,6 +626,8 @@ struct task_struct *__switch_to(struct task_struct *prev_p, struct task_struct *
 		}
 	}
 
+	disable_tsc(prev_p, next_p);
+
 	return prev_p;
 }
 

trunk/include/asm-i386/tlbflush.h

@@ -22,16 +22,18 @@
  */
 #define __flush_tlb_global()						\
 	do {								\
-		unsigned int tmpreg;					\
+		unsigned int tmpreg, cr4, cr4_orig;			\
 									\
 		__asm__ __volatile__(					\
-			"movl %1, %%cr4;  # turn off PGE     \n"	\
+			"movl %%cr4, %2;  # turn off PGE     \n"	\
+			"movl %2, %1;                        \n"	\
+			"andl %3, %1;                        \n"	\
+			"movl %1, %%cr4;                     \n"	\
 			"movl %%cr3, %0;                     \n"	\
 			"movl %0, %%cr3;  # flush TLB        \n"	\
 			"movl %2, %%cr4;  # turn PGE back on \n"	\
-			: "=&r" (tmpreg)				\
-			: "r" (mmu_cr4_features & ~X86_CR4_PGE),	\
-			  "r" (mmu_cr4_features)			\
+			: "=&r" (tmpreg), "=&r" (cr4), "=&r" (cr4_orig)	\
+			: "i" (~X86_CR4_PGE)				\
 			: "memory");					\
 	} while (0)
 

trunk/include/asm-x86_64/tlbflush.h

@@ -22,16 +22,18 @@
  */
 #define __flush_tlb_global()						\
 	do {								\
-		unsigned long tmpreg;					\
+		unsigned long tmpreg, cr4, cr4_orig;			\
 									\
 		__asm__ __volatile__(					\
-			"movq %1, %%cr4;  # turn off PGE     \n"	\
+			"movq %%cr4, %2;  # turn off PGE     \n"	\
+			"movq %2, %1;                        \n"	\
+			"andq %3, %1;                        \n"	\
+			"movq %1, %%cr4;                     \n"	\
 			"movq %%cr3, %0;  # flush TLB        \n"	\
 			"movq %0, %%cr3;                     \n"	\
 			"movq %2, %%cr4;  # turn PGE back on \n"	\
-			: "=&r" (tmpreg)				\
-			: "r" (mmu_cr4_features & ~X86_CR4_PGE),	\
-			  "r" (mmu_cr4_features)			\
+			: "=&r" (tmpreg), "=&r" (cr4), "=&r" (cr4_orig)	\
+			: "i" (~X86_CR4_PGE)				\
 			: "memory");					\
 	} while (0)
 

trunk/include/linux/seccomp.h

@@ -19,6 +19,11 @@ static inline void secure_computing(int this_syscall)
 		__secure_computing(this_syscall);
 }
 
+static inline int has_secure_computing(struct thread_info *ti)
+{
+	return unlikely(test_ti_thread_flag(ti, TIF_SECCOMP));
+}
+
 #else /* CONFIG_SECCOMP */
 
 #if (__GNUC__ > 2)
@@ -28,6 +33,11 @@ static inline void secure_computing(int this_syscall)
 #endif
 
 #define secure_computing(x) do { } while (0)
+/* static inline to preserve typechecking */
+static inline int has_secure_computing(struct thread_info *ti)
+{
+	return 0;
+}
 
 #endif /* CONFIG_SECCOMP */