x86/cpu: Uninline CR4 accessors

cpu_tlbstate is exported because various TLB-related functions need
access to it, but cpu_tlbstate is sensitive information which should
only be accessed by well-contained kernel functions and not be directly
exposed to modules.

The various CR4 accessors require cpu_tlbstate as the CR4 shadow cache
is located there.

In preparation for unexporting cpu_tlbstate, create a builtin function
for manipulating CR4 and rework the various helpers to use it.

No functional change.

 [ bp: push the export of native_write_cr4() only when CONFIG_LKTDM=m to
   the last patch in the series. ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200421092558.939985695@linutronix.de

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 6f66d84..d804030 100644 (file)
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -276,37 +276,25 @@ static inline bool nmi_uaccess_okay(void)
 
 #define nmi_uaccess_okay nmi_uaccess_okay
 
+void cr4_update_irqsoff(unsigned long set, unsigned long clear);
+unsigned long cr4_read_shadow(void);
+
 /* Initialize cr4 shadow for this CPU. */
 static inline void cr4_init_shadow(void)
 {
        this_cpu_write(cpu_tlbstate.cr4, __read_cr4());
 }
 
-static inline void __cr4_set(unsigned long cr4)
-{
-       lockdep_assert_irqs_disabled();
-       this_cpu_write(cpu_tlbstate.cr4, cr4);
-       __write_cr4(cr4);
-}
-
 /* Set in this cpu's CR4. */
 static inline void cr4_set_bits_irqsoff(unsigned long mask)
 {
-       unsigned long cr4;
-
-       cr4 = this_cpu_read(cpu_tlbstate.cr4);
-       if ((cr4 | mask) != cr4)
-               __cr4_set(cr4 | mask);
+       cr4_update_irqsoff(mask, 0);
 }
 
 /* Clear in this cpu's CR4. */
 static inline void cr4_clear_bits_irqsoff(unsigned long mask)
 {
-       unsigned long cr4;
-
-       cr4 = this_cpu_read(cpu_tlbstate.cr4);
-       if ((cr4 & ~mask) != cr4)
-               __cr4_set(cr4 & ~mask);
+       cr4_update_irqsoff(0, mask);
 }
 
 /* Set in this cpu's CR4. */
@@ -329,20 +317,6 @@ static inline void cr4_clear_bits(unsigned long mask)
        local_irq_restore(flags);
 }
 
-static inline void cr4_toggle_bits_irqsoff(unsigned long mask)
-{
-       unsigned long cr4;
-
-       cr4 = this_cpu_read(cpu_tlbstate.cr4);
-       __cr4_set(cr4 ^ mask);
-}
-
-/* Read the CR4 shadow. */
-static inline unsigned long cr4_read_shadow(void)
-{
-       return this_cpu_read(cpu_tlbstate.cr4);
-}
-
 /*
  * Mark all other ASIDs as invalid, preserves the current.
  */

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index bed0cb8..82042f4 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -387,7 +387,28 @@ set_register:
                          bits_missing);
        }
 }
-EXPORT_SYMBOL(native_write_cr4);
+EXPORT_SYMBOL_GPL(native_write_cr4);
+
+void cr4_update_irqsoff(unsigned long set, unsigned long clear)
+{
+       unsigned long newval, cr4 = this_cpu_read(cpu_tlbstate.cr4);
+
+       lockdep_assert_irqs_disabled();
+
+       newval = (cr4 & ~clear) | set;
+       if (newval != cr4) {
+               this_cpu_write(cpu_tlbstate.cr4, newval);
+               __write_cr4(newval);
+       }
+}
+EXPORT_SYMBOL(cr4_update_irqsoff);
+
+/* Read the CR4 shadow. */
+unsigned long cr4_read_shadow(void)
+{
+       return this_cpu_read(cpu_tlbstate.cr4);
+}
+EXPORT_SYMBOL_GPL(cr4_read_shadow);
 
 void cr4_init(void)
 {

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9da70b2..f2eab49 100644 (file)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -612,6 +612,17 @@ void speculation_ctrl_update_current(void)
        preempt_enable();
 }
 
+static inline void cr4_toggle_bits_irqsoff(unsigned long mask)
+{
+       unsigned long newval, cr4 = this_cpu_read(cpu_tlbstate.cr4);
+
+       newval = cr4 ^ mask;
+       if (newval != cr4) {
+               this_cpu_write(cpu_tlbstate.cr4, newval);
+               __write_cr4(newval);
+       }
+}
+
 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
 {
        unsigned long tifp, tifn;