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-rw-r--r--arch/Kconfig10
-rw-r--r--arch/x86/Kconfig1
-rw-r--r--arch/x86/include/asm/thread_info.h7
-rw-r--r--arch/x86/kernel/process.c2
-rw-r--r--arch/x86/kernel/signal.c3
-rw-r--r--include/linux/user-return-notifier.h49
-rw-r--r--kernel/Makefile1
-rw-r--r--kernel/fork.c2
-rw-r--r--kernel/user-return-notifier.c46
9 files changed, 119 insertions, 2 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 7f418bbc261a..4e312fffbfd7 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -83,6 +83,13 @@ config KRETPROBES
def_bool y
depends on KPROBES && HAVE_KRETPROBES
+config USER_RETURN_NOTIFIER
+ bool
+ depends on HAVE_USER_RETURN_NOTIFIER
+ help
+ Provide a kernel-internal notification when a cpu is about to
+ switch to user mode.
+
config HAVE_IOREMAP_PROT
bool
@@ -126,4 +133,7 @@ config HAVE_DMA_API_DEBUG
config HAVE_DEFAULT_NO_SPIN_MUTEXES
bool
+config HAVE_USER_RETURN_NOTIFIER
+ bool
+
source "kernel/gcov/Kconfig"
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 72ace9515a07..8b54096e6d73 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -50,6 +50,7 @@ config X86
select HAVE_KERNEL_BZIP2
select HAVE_KERNEL_LZMA
select HAVE_ARCH_KMEMCHECK
+ select HAVE_USER_RETURN_NOTIFIER
config OUTPUT_FORMAT
string
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index d27d0a2fec4c..375c917c37d2 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -83,6 +83,7 @@ struct thread_info {
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
+#define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */
#define TIF_NOTSC 16 /* TSC is not accessible in userland */
#define TIF_IA32 17 /* 32bit process */
#define TIF_FORK 18 /* ret_from_fork */
@@ -107,6 +108,7 @@ struct thread_info {
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#define _TIF_MCE_NOTIFY (1 << TIF_MCE_NOTIFY)
+#define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
#define _TIF_NOTSC (1 << TIF_NOTSC)
#define _TIF_IA32 (1 << TIF_IA32)
#define _TIF_FORK (1 << TIF_FORK)
@@ -142,13 +144,14 @@ struct thread_info {
/* Only used for 64 bit */
#define _TIF_DO_NOTIFY_MASK \
- (_TIF_SIGPENDING|_TIF_MCE_NOTIFY|_TIF_NOTIFY_RESUME)
+ (_TIF_SIGPENDING | _TIF_MCE_NOTIFY | _TIF_NOTIFY_RESUME | \
+ _TIF_USER_RETURN_NOTIFY)
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW \
(_TIF_IO_BITMAP|_TIF_DEBUGCTLMSR|_TIF_DS_AREA_MSR|_TIF_NOTSC)
-#define _TIF_WORK_CTXSW_PREV _TIF_WORK_CTXSW
+#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW|_TIF_DEBUG)
#define PREEMPT_ACTIVE 0x10000000
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 5284cd2b5776..e51b056fc88f 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -9,6 +9,7 @@
#include <linux/pm.h>
#include <linux/clockchips.h>
#include <linux/random.h>
+#include <linux/user-return-notifier.h>
#include <trace/events/power.h>
#include <asm/system.h>
#include <asm/apic.h>
@@ -224,6 +225,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
*/
memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
}
+ propagate_user_return_notify(prev_p, next_p);
}
int sys_fork(struct pt_regs *regs)
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 6a44a76055ad..c49f90f7957a 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -19,6 +19,7 @@
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/uaccess.h>
+#include <linux/user-return-notifier.h>
#include <asm/processor.h>
#include <asm/ucontext.h>
@@ -872,6 +873,8 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
if (current->replacement_session_keyring)
key_replace_session_keyring();
}
+ if (thread_info_flags & _TIF_USER_RETURN_NOTIFY)
+ fire_user_return_notifiers();
#ifdef CONFIG_X86_32
clear_thread_flag(TIF_IRET);
diff --git a/include/linux/user-return-notifier.h b/include/linux/user-return-notifier.h
new file mode 100644
index 000000000000..9c4a445bb43c
--- /dev/null
+++ b/include/linux/user-return-notifier.h
@@ -0,0 +1,49 @@
+#ifndef _LINUX_USER_RETURN_NOTIFIER_H
+#define _LINUX_USER_RETURN_NOTIFIER_H
+
+#ifdef CONFIG_USER_RETURN_NOTIFIER
+
+#include <linux/list.h>
+#include <linux/sched.h>
+
+struct user_return_notifier {
+ void (*on_user_return)(struct user_return_notifier *urn);
+ struct hlist_node link;
+};
+
+
+void user_return_notifier_register(struct user_return_notifier *urn);
+void user_return_notifier_unregister(struct user_return_notifier *urn);
+
+static inline void propagate_user_return_notify(struct task_struct *prev,
+ struct task_struct *next)
+{
+ if (test_tsk_thread_flag(prev, TIF_USER_RETURN_NOTIFY)) {
+ clear_tsk_thread_flag(prev, TIF_USER_RETURN_NOTIFY);
+ set_tsk_thread_flag(next, TIF_USER_RETURN_NOTIFY);
+ }
+}
+
+void fire_user_return_notifiers(void);
+
+static inline void clear_user_return_notifier(struct task_struct *p)
+{
+ clear_tsk_thread_flag(p, TIF_USER_RETURN_NOTIFY);
+}
+
+#else
+
+struct user_return_notifier {};
+
+static inline void propagate_user_return_notify(struct task_struct *prev,
+ struct task_struct *next)
+{
+}
+
+static inline void fire_user_return_notifiers(void) {}
+
+static inline void clear_user_return_notifier(struct task_struct *p) {}
+
+#endif
+
+#endif
diff --git a/kernel/Makefile b/kernel/Makefile
index d7c13d249b2d..6c5112844980 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -96,6 +96,7 @@ obj-$(CONFIG_SMP) += sched_cpupri.o
obj-$(CONFIG_SLOW_WORK) += slow-work.o
obj-$(CONFIG_SLOW_WORK_DEBUG) += slow-work-debugfs.o
obj-$(CONFIG_PERF_EVENTS) += perf_event.o
+obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/fork.c b/kernel/fork.c
index 166b8c49257c..7d4a348ea4f4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -64,6 +64,7 @@
#include <linux/magic.h>
#include <linux/perf_event.h>
#include <linux/posix-timers.h>
+#include <linux/user-return-notifier.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -249,6 +250,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
goto out;
setup_thread_stack(tsk, orig);
+ clear_user_return_notifier(tsk);
stackend = end_of_stack(tsk);
*stackend = STACK_END_MAGIC; /* for overflow detection */
diff --git a/kernel/user-return-notifier.c b/kernel/user-return-notifier.c
new file mode 100644
index 000000000000..03e2d6fd9b18
--- /dev/null
+++ b/kernel/user-return-notifier.c
@@ -0,0 +1,46 @@
+
+#include <linux/user-return-notifier.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+
+static DEFINE_PER_CPU(struct hlist_head, return_notifier_list);
+
+#define URN_LIST_HEAD per_cpu(return_notifier_list, raw_smp_processor_id())
+
+/*
+ * Request a notification when the current cpu returns to userspace. Must be
+ * called in atomic context. The notifier will also be called in atomic
+ * context.
+ */
+void user_return_notifier_register(struct user_return_notifier *urn)
+{
+ set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
+ hlist_add_head(&urn->link, &URN_LIST_HEAD);
+}
+EXPORT_SYMBOL_GPL(user_return_notifier_register);
+
+/*
+ * Removes a registered user return notifier. Must be called from atomic
+ * context, and from the same cpu registration occured in.
+ */
+void user_return_notifier_unregister(struct user_return_notifier *urn)
+{
+ hlist_del(&urn->link);
+ if (hlist_empty(&URN_LIST_HEAD))
+ clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
+}
+EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
+
+/* Calls registered user return notifiers */
+void fire_user_return_notifiers(void)
+{
+ struct user_return_notifier *urn;
+ struct hlist_node *tmp1, *tmp2;
+ struct hlist_head *head;
+
+ head = &get_cpu_var(return_notifier_list);
+ hlist_for_each_entry_safe(urn, tmp1, tmp2, head, link)
+ urn->on_user_return(urn);
+ put_cpu_var(return_notifier_list);
+}