diff --git a/arch/at91sam3x8e/atomic.c b/arch/at91sam3x8e/atomic.c
index 6bab9cb..f80da00 100644
--- a/arch/at91sam3x8e/atomic.c
+++ b/arch/at91sam3x8e/atomic.c
@@ -3,7 +3,7 @@
 #include <ardix/atomic.h>
 #include <ardix/atom.h>
 
-static ATOM_DEFINE(atomic_context);
+static ATOM(atomic_context);
 
 void atomic_enter(void)
 {
diff --git a/include/arch-generic/entry.h b/include/arch-generic/entry.h
index 2d81f1d..920ac00 100644
--- a/include/arch-generic/entry.h
+++ b/include/arch-generic/entry.h
@@ -3,15 +3,18 @@
 #pragma once
 
 /**
- * Perform a syscall.
+ * @brief Perform a syscall.
  *
- * This is the first and only method called by the irq handler for system calls.
- * It is responsible for finishing the context switch, obtaining the syscall
- * number and arguments, and invoking the respective system call.
+ * This is called by the syscall exception handler.  It is responsible for
+ * finishing the context switch, obtaining the syscall number and arguments,
+ * and invoking the respective system call.  If the return value of this
+ * function is nonzero, the scheduler is invoked after the call and before
+ * returning to userspace.
  *
- * @param sp: The current stack pointer.
+ * @param sp current stack pointer
+ * @returns Whether rescheduling is required
  */
-void arch_enter(void *sp);
+int arch_enter(void *sp);
 
 /*
  * This file is part of Ardix.
diff --git a/include/arch-generic/syscall.h b/include/arch-generic/syscall.h
index 3d9e707..60536c9 100644
--- a/include/arch-generic/syscall.h
+++ b/include/arch-generic/syscall.h
@@ -2,8 +2,8 @@
 
 #pragma once
 
-#define ARCH_SYSCALL_READ	0
-#define ARCH_SYSCALL_WRITE	1
+#define ARCH_SYS_read		0
+#define ARCH_SYS_write		1
 
 /*
  * This file is part of Ardix.
diff --git a/include/ardix/atom.h b/include/ardix/atom.h
index 756fca0..a8d6d3f 100644
--- a/include/ardix/atom.h
+++ b/include/ardix/atom.h
@@ -5,7 +5,7 @@
 #include <ardix/types.h>
 #include <toolchain.h>
 
-#define ATOM_DEFINE(name) atom_t name = { .count = 0, }
+#define ATOM(name) atom_t name = { .count = 0, }
 
 void atom_init(atom_t *atom);
 
diff --git a/include/ardix/syscall.h b/include/ardix/syscall.h
index 4d8640c..658697c 100644
--- a/include/ardix/syscall.h
+++ b/include/ardix/syscall.h
@@ -10,8 +10,8 @@
 #include <toolchain.h>
 
 enum syscall {
-	SYSCALL_READ		= ARCH_SYSCALL_READ,
-	SYSCALL_WRITE		= ARCH_SYSCALL_WRITE,
+	SYS_read		= ARCH_SYS_read,
+	SYS_write		= ARCH_SYS_write,
 	NSYSCALLS
 };
 
diff --git a/kernel/syscall.c b/kernel/syscall.c
index 871cf40..e59d499 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -10,8 +10,8 @@
 __rodata
 int (*const sys_table[NSYSCALLS])(sysarg_t arg1, sysarg_t arg2, sysarg_t arg3,
 				  sysarg_t arg4, sysarg_t arg5, sysarg_t arg6) = {
-	sys_table_entry(SYSCALL_READ, &sys_read),
-	sys_table_entry(SYSCALL_WRITE, &sys_write),
+	sys_table_entry(SYS_read,		sys_read),
+	sys_table_entry(SYS_write,		sys_write),
 };
 
 int sys_stub(void)
diff --git a/lib/unistd.c b/lib/unistd.c
index 5a0eb2e..77f7fc6 100644
--- a/lib/unistd.c
+++ b/lib/unistd.c
@@ -6,12 +6,12 @@
 
 ssize_t read(int fildes, void *buf, size_t nbyte)
 {
-	return syscall(SYSCALL_READ, (sysarg_t)fildes, (sysarg_t)buf, (sysarg_t)nbyte);
+	return syscall(SYS_read, (sysarg_t)fildes, (sysarg_t)buf, (sysarg_t)nbyte);
 }
 
 ssize_t write(int fildes, const void *buf, size_t nbyte)
 {
-	return syscall(SYSCALL_WRITE, (sysarg_t)fildes, (sysarg_t)buf, (sysarg_t)nbyte);
+	return syscall(SYS_write, (sysarg_t)fildes, (sysarg_t)buf, (sysarg_t)nbyte);
 }
 
 /*