4 files changed, 61 insertions, 35 deletions

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index e8bb0d61ecdc..cd6d9a5a42f6 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -254,16 +254,18 @@ EXPORT_SYMBOL_GPL(kvm_read_and_reset_pf_reason);
 dotraplinkage void __kprobes
 do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
+        enum ctx_state prev_state;
+
         switch (kvm_read_and_reset_pf_reason()) {
         default:
                 do_page_fault(regs, error_code);
                 break;
         case KVM_PV_REASON_PAGE_NOT_PRESENT:
                 /* page is swapped out by the host. */
-                exception_enter(regs);
+                prev_state = exception_enter();
                 exit_idle();
                 kvm_async_pf_task_wait((u32)read_cr2());
-                exception_exit(regs);
+                exception_exit(prev_state);
                 break;
         case KVM_PV_REASON_PAGE_READY:
                 rcu_irq_enter();
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index ecc4ccbdd0cf..ff6d2271cbe2 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -175,34 +175,38 @@ do_trap(int trapnr, int signr, char *str, struct pt_regs *regs,
 #define DO_ERROR(trapnr, signr, str, name)                              \
 dotraplinkage void do_##name(struct pt_regs *regs, long error_code)     \
 {                                                                       \
-        exception_enter(regs);                                          \
+        enum ctx_state prev_state;                                      \
+                                                                        \
+        prev_state = exception_enter();                                 \
         if (notify_die(DIE_TRAP, str, regs, error_code,                 \
                         trapnr, signr) == NOTIFY_STOP) {                \
-                exception_exit(regs);                                   \
+                exception_exit(prev_state);                             \
                 return;                                                 \
         }                                                               \
         conditional_sti(regs);                                          \
         do_trap(trapnr, signr, str, regs, error_code, NULL);            \
-        exception_exit(regs);                                           \
+        exception_exit(prev_state);                                     \
 }
 
 #define DO_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr)         \
 dotraplinkage void do_##name(struct pt_regs *regs, long error_code)     \
 {                                                                       \
         siginfo_t info;                                                 \
+        enum ctx_state prev_state;                                      \
+                                                                        \
         info.si_signo = signr;                                          \
         info.si_errno = 0;                                              \
         info.si_code = sicode;                                          \
         info.si_addr = (void __user *)siaddr;                           \
-        exception_enter(regs);                                          \
+        prev_state = exception_enter();                                 \
         if (notify_die(DIE_TRAP, str, regs, error_code,                 \
                         trapnr, signr) == NOTIFY_STOP) {                \
-                exception_exit(regs);                                   \
+                exception_exit(prev_state);                             \
                 return;                                                 \
         }                                                               \
         conditional_sti(regs);                                          \
         do_trap(trapnr, signr, str, regs, error_code, &info);           \
-        exception_exit(regs);                                           \
+        exception_exit(prev_state);                                     \
 }
 
 DO_ERROR_INFO(X86_TRAP_DE, SIGFPE, "divide error", divide_error, FPE_INTDIV,
@@ -225,14 +229,16 @@ DO_ERROR_INFO(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check,
 /* Runs on IST stack */
 dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code)
 {
-        exception_enter(regs);
+        enum ctx_state prev_state;
+
+        prev_state = exception_enter();
         if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
                        X86_TRAP_SS, SIGBUS) != NOTIFY_STOP) {
                 preempt_conditional_sti(regs);
                 do_trap(X86_TRAP_SS, SIGBUS, "stack segment", regs, error_code, NULL);
                 preempt_conditional_cli(regs);
         }
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 
 dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
@@ -240,7 +246,7 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
         static const char str[] = "double fault";
         struct task_struct *tsk = current;
 
-        exception_enter(regs);
+        exception_enter();
         /* Return not checked because double check cannot be ignored */
         notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
 
@@ -260,8 +266,9 @@ dotraplinkage void __kprobes
 do_general_protection(struct pt_regs *regs, long error_code)
 {
         struct task_struct *tsk;
+        enum ctx_state prev_state;
 
-        exception_enter(regs);
+        prev_state = exception_enter();
         conditional_sti(regs);
 
 #ifdef CONFIG_X86_32
@@ -299,12 +306,14 @@ do_general_protection(struct pt_regs *regs, long error_code)
 
         force_sig(SIGSEGV, tsk);
 exit:
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 
 /* May run on IST stack. */
 dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_code)
 {
+        enum ctx_state prev_state;
+
 #ifdef CONFIG_DYNAMIC_FTRACE
         /*
          * ftrace must be first, everything else may cause a recursive crash.
@@ -314,7 +323,7 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
             ftrace_int3_handler(regs))
                 return;
 #endif
-        exception_enter(regs);
+        prev_state = exception_enter();
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
         if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
                                 SIGTRAP) == NOTIFY_STOP)
@@ -335,7 +344,7 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
         preempt_conditional_cli(regs);
         debug_stack_usage_dec();
 exit:
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 
 #ifdef CONFIG_X86_64
@@ -392,11 +401,12 @@ asmlinkage __kprobes struct pt_regs *sync_regs(struct pt_regs *eregs)
 dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
 {
         struct task_struct *tsk = current;
+        enum ctx_state prev_state;
         int user_icebp = 0;
         unsigned long dr6;
         int si_code;
 
-        exception_enter(regs);
+        prev_state = exception_enter();
 
         get_debugreg(dr6, 6);
 
@@ -466,7 +476,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
         debug_stack_usage_dec();
 
 exit:
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 
 /*
@@ -560,17 +570,21 @@ void math_error(struct pt_regs *regs, int error_code, int trapnr)
 
 dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code)
 {
-        exception_enter(regs);
+        enum ctx_state prev_state;
+
+        prev_state = exception_enter();
         math_error(regs, error_code, X86_TRAP_MF);
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 
 dotraplinkage void
 do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
 {
-        exception_enter(regs);
+        enum ctx_state prev_state;
+
+        prev_state = exception_enter();
         math_error(regs, error_code, X86_TRAP_XF);
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 
 dotraplinkage void
@@ -638,7 +652,9 @@ EXPORT_SYMBOL_GPL(math_state_restore);
 dotraplinkage void __kprobes
 do_device_not_available(struct pt_regs *regs, long error_code)
 {
-        exception_enter(regs);
+        enum ctx_state prev_state;
+
+        prev_state = exception_enter();
         BUG_ON(use_eager_fpu());
 
 #ifdef CONFIG_MATH_EMULATION
@@ -649,7 +665,7 @@ do_device_not_available(struct pt_regs *regs, long error_code)
 
                 info.regs = regs;
                 math_emulate(&info);
-                exception_exit(regs);
+                exception_exit(prev_state);
                 return;
         }
 #endif
@@ -657,15 +673,16 @@ do_device_not_available(struct pt_regs *regs, long error_code)
 #ifdef CONFIG_X86_32
         conditional_sti(regs);
 #endif
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 
 #ifdef CONFIG_X86_32
 dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
 {
         siginfo_t info;
+        enum ctx_state prev_state;
 
-        exception_enter(regs);
+        prev_state = exception_enter();
         local_irq_enable();
 
         info.si_signo = SIGILL;
@@ -677,7 +694,7 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
                 do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code,
                         &info);
         }
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
 #endif
 
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index f946e6ce3315..fa8c02de0d25 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1222,7 +1222,9 @@ good_area:
 dotraplinkage void __kprobes
 do_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
-        exception_enter(regs);
+        enum ctx_state prev_state;
+
+        prev_state = exception_enter();
         __do_page_fault(regs, error_code);
-        exception_exit(regs);
+        exception_exit(prev_state);
 }
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 5a69273e93e6..365f4a61bf04 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -5,7 +5,6 @@
 #include <linux/percpu.h>
 #include <asm/ptrace.h>
 
-#ifdef CONFIG_CONTEXT_TRACKING
 struct context_tracking {
         /*
          * When active is false, probes are unset in order
@@ -14,12 +13,13 @@ struct context_tracking {
          * may be further optimized using static keys.
          */
         bool active;
-        enum {
+        enum ctx_state {
                 IN_KERNEL = 0,
                 IN_USER,
         } state;
 };
 
+#ifdef CONFIG_CONTEXT_TRACKING
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
 
 static inline bool context_tracking_in_user(void)
@@ -35,14 +35,19 @@ static inline bool context_tracking_active(void)
 extern void user_enter(void);
 extern void user_exit(void);
 
-static inline void exception_enter(struct pt_regs *regs)
+static inline enum ctx_state exception_enter(void)
 {
+        enum ctx_state prev_ctx;
+
+        prev_ctx = this_cpu_read(context_tracking.state);
         user_exit();
+
+        return prev_ctx;
 }
 
-static inline void exception_exit(struct pt_regs *regs)
+static inline void exception_exit(enum ctx_state prev_ctx)
 {
-        if (user_mode(regs))
+        if (prev_ctx == IN_USER)
                 user_enter();
 }
 
@@ -52,8 +57,8 @@ extern void context_tracking_task_switch(struct task_struct *prev,
 static inline bool context_tracking_in_user(void) { return false; }
 static inline void user_enter(void) { }
 static inline void user_exit(void) { }
-static inline void exception_enter(struct pt_regs *regs) { }
-static inline void exception_exit(struct pt_regs *regs) { }
+static inline enum ctx_state exception_enter(void) { return 0; }
+static inline void exception_exit(enum ctx_state prev_ctx) { }
 static inline void context_tracking_task_switch(struct task_struct *prev,
                                                 struct task_struct *next) { }
 #endif /* !CONFIG_CONTEXT_TRACKING */