x86: Exception hooks for userspace RCU extended QS

Add necessary hooks to x86 exception for userspace
RCU extended quiescent state support.

This includes traps, page fault, debug exceptions, etc...

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

3 files changed, 86 insertions, 28 deletions

diff --git a/arch/x86/include/asm/rcu.h b/arch/x86/include/asm/rcu.h
new file mode 100644
index 000000000000..439815b35ced
--- /dev/null
+++ b/arch/x86/include/asm/rcu.h
@@ -0,0 +1,20 @@
+#ifndef _ASM_X86_RCU_H
+#define _ASM_X86_RCU_H
+
+#include <linux/rcupdate.h>
+#include <asm/ptrace.h>
+
+static inline void exception_enter(struct pt_regs *regs)
+{
+        rcu_user_exit();
+}
+
+static inline void exception_exit(struct pt_regs *regs)
+{
+#ifdef CONFIG_RCU_USER_QS
+        if (user_mode(regs))
+                rcu_user_enter();
+#endif
+}
+
+#endif
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 74850e559449..378967578f22 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -55,6 +55,7 @@
 #include <asm/i387.h>
 #include <asm/fpu-internal.h>
 #include <asm/mce.h>
+#include <asm/rcu.h>
 
 #include <asm/mach_traps.h>
 
@@ -180,11 +181,15 @@ vm86_trap:
 #define DO_ERROR(trapnr, signr, str, name)                              \
 dotraplinkage void do_##name(struct pt_regs *regs, long error_code)     \
 {                                                                       \
-        if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr)  \
-                                                        == NOTIFY_STOP) \
+        exception_enter(regs);                                          \
+        if (notify_die(DIE_TRAP, str, regs, error_code,                 \
+                        trapnr, signr) == NOTIFY_STOP) {                \
+                exception_exit(regs);                                   \
                 return;                                                 \
+        }                                                               \
         conditional_sti(regs);                                          \
         do_trap(trapnr, signr, str, regs, error_code, NULL);            \
+        exception_exit(regs);                                           \
 }
 
 #define DO_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr)         \
@@ -195,11 +200,15 @@ dotraplinkage void do_##name(struct pt_regs *regs, long error_code)	\
         info.si_errno = 0;                                              \
         info.si_code = sicode;                                          \
         info.si_addr = (void __user *)siaddr;                           \
-        if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr)  \
-                                                        == NOTIFY_STOP) \
+        exception_enter(regs);                                          \
+        if (notify_die(DIE_TRAP, str, regs, error_code,                 \
+                        trapnr, signr) == NOTIFY_STOP) {                \
+                exception_exit(regs);                                   \
                 return;                                                 \
+        }                                                               \
         conditional_sti(regs);                                          \
         do_trap(trapnr, signr, str, regs, error_code, &info);           \
+        exception_exit(regs);                                           \
 }
 
 DO_ERROR_INFO(X86_TRAP_DE, SIGFPE, "divide error", divide_error, FPE_INTDIV,
@@ -222,12 +231,14 @@ 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);
         if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
-                        X86_TRAP_SS, SIGBUS) == NOTIFY_STOP)
-                return;
-        preempt_conditional_sti(regs);
-        do_trap(X86_TRAP_SS, SIGBUS, "stack segment", regs, error_code, NULL);
-        preempt_conditional_cli(regs);
+                       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);
 }
 
 dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
@@ -235,6 +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);
         /* Return not checked because double check cannot be ignored */
         notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
 
@@ -255,27 +267,28 @@ do_general_protection(struct pt_regs *regs, long error_code)
 {
         struct task_struct *tsk;
 
+        exception_enter(regs);
         conditional_sti(regs);
 
 #ifdef CONFIG_X86_32
         if (regs->flags & X86_VM_MASK) {
                 local_irq_enable();
                 handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);
-                return;
+                goto exit;
         }
 #endif
 
         tsk = current;
         if (!user_mode(regs)) {
                 if (fixup_exception(regs))
-                        return;
+                        goto exit;
 
                 tsk->thread.error_code = error_code;
                 tsk->thread.trap_nr = X86_TRAP_GP;
-                if (!notify_die(DIE_GPF, "general protection fault", regs, error_code,
-                               X86_TRAP_GP, SIGSEGV) == NOTIFY_STOP)
+                if (notify_die(DIE_GPF, "general protection fault", regs, error_code,
+                               X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP)
                         die("general protection fault", regs, error_code);
-                return;
+                goto exit;
         }
 
         tsk->thread.error_code = error_code;
@@ -291,7 +304,8 @@ do_general_protection(struct pt_regs *regs, long error_code)
         }
 
         force_sig(SIGSEGV, tsk);
-        return;
+exit:
+        exception_exit(regs);
 }
 
 /* May run on IST stack. */
@@ -306,15 +320,16 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
             ftrace_int3_handler(regs))
                 return;
 #endif
+        exception_enter(regs);
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
         if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
                                 SIGTRAP) == NOTIFY_STOP)
-                return;
+                goto exit;
 #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
 
         if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
                         SIGTRAP) == NOTIFY_STOP)
-                return;
+                goto exit;
 
         /*
          * Let others (NMI) know that the debug stack is in use
@@ -325,6 +340,8 @@ dotraplinkage void __kprobes notrace do_int3(struct pt_regs *regs, long error_co
         do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL);
         preempt_conditional_cli(regs);
         debug_stack_usage_dec();
+exit:
+        exception_exit(regs);
 }
 
 #ifdef CONFIG_X86_64
@@ -385,6 +402,8 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
         unsigned long dr6;
         int si_code;
 
+        exception_enter(regs);
+
         get_debugreg(dr6, 6);
 
         /* Filter out all the reserved bits which are preset to 1 */
@@ -400,7 +419,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
 
         /* Catch kmemcheck conditions first of all! */
         if ((dr6 & DR_STEP) && kmemcheck_trap(regs))
-                return;
+                goto exit;
 
         /* DR6 may or may not be cleared by the CPU */
         set_debugreg(0, 6);
@@ -415,7 +434,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
 
         if (notify_die(DIE_DEBUG, "debug", regs, PTR_ERR(&dr6), error_code,
                                                         SIGTRAP) == NOTIFY_STOP)
-                return;
+                goto exit;
 
         /*
          * Let others (NMI) know that the debug stack is in use
@@ -431,7 +450,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
                                         X86_TRAP_DB);
                 preempt_conditional_cli(regs);
                 debug_stack_usage_dec();
-                return;
+                goto exit;
         }
 
         /*
@@ -452,7 +471,8 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
         preempt_conditional_cli(regs);
         debug_stack_usage_dec();
 
-        return;
+exit:
+        exception_exit(regs);
 }
 
 /*
@@ -549,14 +569,17 @@ dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code)
 #ifdef CONFIG_X86_32
         ignore_fpu_irq = 1;
 #endif
-
+        exception_enter(regs);
         math_error(regs, error_code, X86_TRAP_MF);
+        exception_exit(regs);
 }
 
 dotraplinkage void
 do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
 {
+        exception_enter(regs);
         math_error(regs, error_code, X86_TRAP_XF);
+        exception_exit(regs);
 }
 
 dotraplinkage void
@@ -623,6 +646,7 @@ EXPORT_SYMBOL_GPL(math_state_restore);
 dotraplinkage void __kprobes
 do_device_not_available(struct pt_regs *regs, long error_code)
 {
+        exception_enter(regs);
 #ifdef CONFIG_MATH_EMULATION
         if (read_cr0() & X86_CR0_EM) {
                 struct math_emu_info info = { };
@@ -631,6 +655,7 @@ do_device_not_available(struct pt_regs *regs, long error_code)
 
                 info.regs = regs;
                 math_emulate(&info);
+                exception_exit(regs);
                 return;
         }
 #endif
@@ -638,12 +663,15 @@ do_device_not_available(struct pt_regs *regs, long error_code)
 #ifdef CONFIG_X86_32
         conditional_sti(regs);
 #endif
+        exception_exit(regs);
 }
 
 #ifdef CONFIG_X86_32
 dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
 {
         siginfo_t info;
+
+        exception_enter(regs);
         local_irq_enable();
 
         info.si_signo = SIGILL;
@@ -651,10 +679,11 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
         info.si_code = ILL_BADSTK;
         info.si_addr = NULL;
         if (notify_die(DIE_TRAP, "iret exception", regs, error_code,
-                        X86_TRAP_IRET, SIGILL) == NOTIFY_STOP)
-                return;
-        do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code,
-                &info);
+                        X86_TRAP_IRET, SIGILL) != NOTIFY_STOP) {
+                do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code,
+                        &info);
+        }
+        exception_exit(regs);
 }
 #endif
 
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 76dcd9d8e0bc..7dde46d68a25 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -18,6 +18,7 @@
 #include <asm/pgalloc.h>                /* pgd_*(), ...                 */
 #include <asm/kmemcheck.h>              /* kmemcheck_*(), ...           */
 #include <asm/fixmap.h>                 /* VSYSCALL_START               */
+#include <asm/rcu.h>                    /* exception_enter(), ...       */
 
 /*
  * Page fault error code bits:
@@ -1000,8 +1001,8 @@ static int fault_in_kernel_space(unsigned long address)
  * and the problem, and then passes it off to one of the appropriate
  * routines.
  */
-dotraplinkage void __kprobes
-do_page_fault(struct pt_regs *regs, unsigned long error_code)
+static void __kprobes
+__do_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
         struct vm_area_struct *vma;
         struct task_struct *tsk;
@@ -1209,3 +1210,11 @@ good_area:
 
         up_read(&mm->mmap_sem);
 }
+
+dotraplinkage void __kprobes
+do_page_fault(struct pt_regs *regs, unsigned long error_code)
+{
+        exception_enter(regs);
+        __do_page_fault(regs, error_code);
+        exception_exit(regs);
+}