mutex: add initial mutex support

We'll later use this to peg __sched, which will be our
first example subsection to test with linker tables.
Before we do the work to pget mutext to __sched we'll
add a bit more kernel interface support to make things
a bit more interesting and useful to test.

This a simple mutex implementation which just wraps around
the pthread pthread_mutex_t.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>

3 files changed, 43 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index d69aa28..8282f3e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 CFLAGS += -O2 -g
 CFLAGS += -std=gnu99 -Wall -Werror
+CFLAGS += -pthread
 CFLAGS += -DCONFIG_KPROBES
 INCLUDES = -I include/ -I arch/x86/include/
 CFLAGS += $(INCLUDES)
@@ -43,6 +44,7 @@ OBJS =  arch/x86/kernel/sort-init.o \
 	memory.o \
 	kasan.o\
 	arch/x86/kernel/init.o \
+	kernel/locking/mutex.o \
 	kprobes.o \
 	pci.o \
 	pci-quirks.o \
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
new file mode 100644
index 0000000..f8134ec
--- /dev/null
+++ b/include/linux/mutex.h
@@ -0,0 +1,15 @@
+#ifndef __LINUX_MUTEX_H
+#define __LINUX_MUTEX_H
+
+#include <pthread.h>
+
+struct mutex {
+	pthread_mutex_t lock;
+};
+
+void mutex_init(struct mutex *lock);
+void mutex_destroy(struct mutex *lock);
+void mutex_lock(struct mutex *lock);
+void mutex_unlock(struct mutex *lock);
+
+#endif /* __LINUX_MUTEX_H */
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
new file mode 100644
index 0000000..21e6212
--- /dev/null
+++ b/kernel/locking/mutex.c
@@ -0,0 +1,26 @@
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+
+void mutex_init(struct mutex *lock)
+{
+	int r;
+
+	r = pthread_mutex_init(&lock->lock, NULL);
+	if (r)
+		BUG_ON(r);
+}
+
+void mutex_destroy(struct mutex *lock)
+{
+	pthread_mutex_destroy(&lock->lock);
+}
+
+void mutex_lock(struct mutex *lock)
+{
+	pthread_mutex_lock(&lock->lock);
+}
+
+void mutex_unlock(struct mutex *lock)
+{
+	pthread_mutex_unlock(&lock->lock);
+}