diff --git a/src/dev.c b/src/dev.c
index 09d3fcb..e94a77d 100644
--- a/src/dev.c
+++ b/src/dev.c
@@ -1,8 +1,5 @@
 #include <dev.h>
 
-#include <driver.h>
-#include <errno.h>
-
 isize dev_read(dev_t dev, u8 *buf, usize size) {
     return dev.driver->read(dev.num, buf, size);
 }
diff --git a/src/dev_table.c b/src/dev_table.c
index f56ea13..12da046 100644
--- a/src/dev_table.c
+++ b/src/dev_table.c
@@ -3,8 +3,7 @@
 #include <init.h>
 #include <string.h>
 
-extern dev_init_t _dev_init_start;
-extern dev_init_t _dev_init_end;
+extern dev_init_t _dev_init_start, _dev_init_end;
 
 static i32 init(void) {
     for (usize i = 0; DEV_TABLE[i].name; i++) {
diff --git a/src/intr.c b/src/intr.c
index 532213a..c14cbf0 100644
--- a/src/intr.c
+++ b/src/intr.c
@@ -15,10 +15,10 @@ static u32 nr_isrs = 0;
 i32 intr_register_isr(irq_t irq, void (*isr)(void *data), void *data) {
     if (nr_isrs == INTR_ISR_CAPACITY)
         return -EAGAIN;
-    isrs[nr_isrs].irq = irq;
-    isrs[nr_isrs].isr = isr;
-    isrs[nr_isrs].data = data;
-    nr_isrs++;
+    u32 idx = nr_isrs++;
+    isrs[idx].irq = irq;
+    isrs[idx].isr = isr;
+    isrs[idx].data = data;
     return 0;
 }
 
diff --git a/src/kmain.c b/src/kmain.c
index 99ede6d..bd76209 100644
--- a/src/kmain.c
+++ b/src/kmain.c
@@ -11,7 +11,6 @@ void init(void);
     proc_init(init_proc, init, 0, nullptr, 0, nullptr);
 
     sched_update_state(init_proc, PROC_STATE_READY);
-
     sched_start();
 
     unreachable();
diff --git a/src/syscalls/exit.c b/src/syscalls/exit.c
index 00959b3..96e96db 100644
--- a/src/syscalls/exit.c
+++ b/src/syscalls/exit.c
@@ -4,30 +4,30 @@
 
 [[noreturn]] isize sys_exit(const trapframe_t *frame) {
     i32 status = frame->a0;
-    proc_t *proc = curr_proc;
 
-    proc->exit_status = status;
+    curr_proc->exit_status = status;
 
-    while (!list_empty(&proc->children)) {
-        proc_t *child = list_first_entry(&proc->children, proc_t, tree_node);
+    while (!list_empty(&curr_proc->children)) {
+        proc_t *child =
+            list_first_entry(&curr_proc->children, proc_t, tree_node);
         proc_adopt(proc_table[1], child);
     }
 
-    while (!list_empty(&proc->zombie_children)) {
+    while (!list_empty(&curr_proc->zombie_children)) {
         proc_t *child =
-            list_first_entry(&proc->zombie_children, proc_t, tree_node);
+            list_first_entry(&curr_proc->zombie_children, proc_t, tree_node);
         proc_adopt(proc_table[1], child);
     }
 
-    proc_t *parent = proc->parent;
-    list_remove(&proc->tree_node);
-    list_push_back(&parent->zombie_children, &proc->tree_node);
+    proc_t *parent = curr_proc->parent;
+    list_remove(&curr_proc->tree_node);
+    list_push_back(&parent->zombie_children, &curr_proc->tree_node);
 
     if (parent->state == PROC_STATE_WAIT_CHILD) {
-        parent->proc_waiting = proc;
+        parent->proc_waiting = curr_proc;
         sched_update_state(parent, PROC_STATE_READY);
     }
 
-    sched_update_state(proc, PROC_STATE_ZOMBIE);
+    sched_update_state(curr_proc, PROC_STATE_ZOMBIE);
     unreachable();
 }
diff --git a/src/syscalls/proc.c b/src/syscalls/proc.c
index d5eb36a..c5ab7d6 100644
--- a/src/syscalls/proc.c
+++ b/src/syscalls/proc.c
@@ -9,9 +9,11 @@ isize sys_proc(const trapframe_t *frame) {
     char **argv = (char **) frame->a1;
     if (!entry || !argv)
         return -EFAULT;
-    usize argc;
-    for (argc = 0; argv[argc]; argc++)
-        ;
+
+    usize argc = 0;
+    while (argv[argc]) {
+        argc++;
+    }
 
     proc_t *proc = (proc_t *) kmalloc(sizeof(proc_t));
     if (!proc)
diff --git a/src/syscalls/read.c b/src/syscalls/read.c
index 8f8e9e5..4da010f 100644
--- a/src/syscalls/read.c
+++ b/src/syscalls/read.c
@@ -7,10 +7,9 @@ isize sys_read(const trapframe_t *frame) {
     i32 fd = frame->a0;
     u8 *buf = (u8 *) frame->a1;
     usize size = frame->a2;
-    if (proc_is_bad_fd(curr_proc, fd))
+    if (proc_is_bad_fd(curr_proc, fd) &&
+        !(curr_proc->fds[fd].flags & FD_FLAG_READABLE))
         return -EBADF;
-    if (!(curr_proc->fds[fd].flags & FD_FLAG_READABLE))
-        return -EINVAL;
     if (!buf)
         return -EFAULT;
 
diff --git a/src/syscalls/wait.c b/src/syscalls/wait.c
index 3b7be09..d46603e 100644
--- a/src/syscalls/wait.c
+++ b/src/syscalls/wait.c
@@ -11,19 +11,16 @@ isize sys_wait(const trapframe_t *frame) {
         list_empty(&curr_proc->zombie_children))
         return -ECHILD;
 
+    proc_t *proc;
     if (!list_empty(&curr_proc->zombie_children)) {
-        proc_t *proc =
-            list_first_entry(&curr_proc->zombie_children, proc_t, tree_node);
-        if (status)
-            *status = proc->exit_status & 0xFF;
-        proc_deinit(proc);
-        kfree(proc);
-        return proc->pid;
+        proc = list_first_entry(&curr_proc->zombie_children, proc_t, tree_node);
+        goto quit;
     }
 
     sched_update_state(curr_proc, PROC_STATE_WAIT_CHILD);
+    proc = curr_proc->proc_waiting;
 
-    proc_t *proc = curr_proc->proc_waiting;
+quit:
     if (status)
         *status = proc->exit_status & 0xFF;
     proc_deinit(proc);
diff --git a/src/syscalls/write.c b/src/syscalls/write.c
index 2fddcff..945923a 100644
--- a/src/syscalls/write.c
+++ b/src/syscalls/write.c
@@ -7,10 +7,9 @@ isize sys_write(const trapframe_t *frame) {
     i32 fd = frame->a0;
     const u8 *buf = (const u8 *) frame->a1;
     usize size = frame->a2;
-    if (proc_is_bad_fd(curr_proc, fd))
+    if (proc_is_bad_fd(curr_proc, fd) &&
+        !(curr_proc->fds[fd].flags & FD_FLAG_WRITABLE))
         return -EBADF;
-    if (!(curr_proc->fds[fd].flags & FD_FLAG_WRITABLE))
-        return -EINVAL;
     if (!buf)
         return -EFAULT;
 
diff --git a/src/timer.c b/src/timer.c
index 495336b..149bdfa 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -1,9 +1,7 @@
 #include <timer.h>
 
 #include <csr.h>
-#include <errno.h>
 #include <init.h>
-#include <kalloc.h>
 #include <sbi.h>
 
 extern const u32 TIMER_FREQ;
diff --git a/src/trap.c b/src/trap.c
index 35bb129..90e6c5b 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -1,6 +1,5 @@
 #include <trap.h>
 
-#include <config.h>
 #include <csr.h>
 #include <errno.h>
 #include <init.h>
@@ -23,11 +22,10 @@ void trap_handler(trapframe_t *frame) {
         case CSR_SCAUSE_TIMER_INTR:
             timer_isr();
             break;
-        case CSR_SCAUSE_EXT_INTR: {
+        case CSR_SCAUSE_EXT_INTR:
             intr_isr();
             break;
         }
-        }
     } else {
         switch (frame->scause) {
         case CSR_SCAUSE_ECALL_U: