1 files changed, 325 insertions, 0 deletions
diff --git a/user/libthread/thread.c b/user/libthread/thread.c
new file mode 100644
index 0000000..56f6ac0
--- /dev/null
+++ b/user/libthread/thread.c
@@ -0,0 +1,325 @@
+/**
+ * @file thread.c
+ * @author Hanjie Wu (hanjiew)
+ * @author Devang Acharya (devanga)
+ * @brief Implementation of main thread functions
+ * @date 2023-02-22
+ *
+ */
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <mutex.h>
+#include <simics.h>
+#include <syscall.h>
+#include <thr_internals.h>
+#include <thread.h>
+#include <ureg.h>
+
+/* return value for thread swexn */
+#define THREAD_EXIT_SWEXN -2
+
+/**
+ * @brief stack size requested
+ */
+static uintptr_t thr_stack_size;
+/**
+ * @brief stack size aligned
+ */
+static uintptr_t thr_stack_alloc_size;
+/**
+ * @brief highest address of thread stacks
+ */
+static uintptr_t thr_stack_begin;
+/**
+ * @brief lowest address of thread stacks
+ */
+static uintptr_t thr_stack_end;
+
+/**
+ * @brief tcb for main thread
+ */
+tcb_t main_tcb;
+
+/**
+ * @brief global lock for tcb operations
+ */
+mutex_t tcb_lock;
+
+/**
+ * @brief list of unused tcbs
+ */
+tcb_t* free_tcbs = NULL;
+
+/**
+ * @brief get esp register
+ */
+uintptr_t get_esp();
+/**
+ * @brief swexn handler for multithread programs
+ */
+static void thr_swexn_handler(void* arg, ureg_t* reg);
+/**
+ * @brief wrapper function for thread_fork syscall
+ * @param tcb tcb for new thread
+ * @param f user thread entry point
+ * @param args user arg for f
+ */
+int thread_fork(tcb_t* tcb, void* (*f)(void*), void* args);
+
+/**
+ * @brief Get the tcb of the thread this function is called form
+ *
+ * @return tcb_t*   pointer to current thread's TCB
+ */
+tcb_t* get_self_tcb() {
+    uintptr_t esp = get_esp();
+
+    /* check esp in main thread area */
+    if (esp > main_tcb.stack_lo) {
+        return &main_tcb;
+    }
+
+    /* calculate stack area from esp */
+    uintptr_t stack_end = esp + (thr_stack_begin - esp) % thr_stack_alloc_size;
+    /* pointer to tcb is at highest address in current thread stack */
+    return *(tcb_t**)(stack_end - sizeof(tcb_t*));
+}
+
+/**
+ * @brief Initialize thread library. Must be called once before using any thread
+ *        functions.
+ *
+ * Thread stack structure:
+ * +-------------------------+-----+---------------+
+ * | thread stack                  |address of tcb |
+ * +-------------------------+-----+---------------+
+ *
+ *
+ * @param size  the amount of stack space available for each thread
+ *
+ * @return int  0 on success, -1 on faliure
+ */
+int thr_init(uintptr_t size) {
+    /* set globals */
+    thr_stack_size = size;
+    thr_stack_alloc_size = ((size + PAGE_SIZE - 1) & PAGE_ALIGN_MASK);
+    thr_stack_begin = ((main_tcb.stack_lo) & PAGE_ALIGN_MASK);
+    thr_stack_end = thr_stack_begin;
+
+    /* initialize global lock - will never fail */
+    mutex_init(&tcb_lock);
+
+    if (swexn(ex_stack_end, thr_swexn_handler, NULL, NULL) < 0)
+        return -1;
+
+    return 0;
+}
+
+/**
+ * @brief Create a new thread with the entry point 'func', and arguments 'args'
+ *
+ * @param func  thread entry point
+ * @param args  thread entry function arguments
+ *
+ * @return -1 on failure, 0 on success
+ */
+int thr_create(void* (*func)(void*), void* args) {
+    /* holds return values for error checking and the TID to be returned */
+    int result;
+
+    /* holds pointer tcb for new thread */
+    tcb_t* thread_tcb;
+
+    mutex_lock(&tcb_lock);
+
+    /* find tcb from free list */
+    if (free_tcbs != NULL) {
+        thread_tcb = free_tcbs;
+        /* reuse stack area */
+        result = new_pages((void*)thread_tcb->stack_lo, thr_stack_alloc_size);
+
+        if (result != 0) {
+            mutex_unlock(&tcb_lock);
+            return -1;
+        }
+
+        /* remove from list (use tcb->right as link list) */
+        free_tcbs = free_tcbs->right;
+    }
+
+    else {
+        /* allocate new tcb */
+        thread_tcb = malloc(sizeof(tcb_t));
+
+        if (thread_tcb == NULL) {
+            mutex_unlock(&tcb_lock);
+            return -1;
+        }
+
+        thr_stack_end -= thr_stack_alloc_size;
+        result = new_pages((void*)thr_stack_end, thr_stack_alloc_size);
+
+        /* if new_pages unsuccessful */
+        if (result != 0) {
+            thr_stack_end += thr_stack_alloc_size;
+            free(thread_tcb);
+            mutex_unlock(&tcb_lock);
+            return -1;
+        }
+
+        /* set tcb stack boundaries */
+        thread_tcb->stack_lo = thr_stack_end;
+        thread_tcb->stack_hi =
+            thr_stack_end + thr_stack_alloc_size - sizeof(tcb_t*);
+    }
+
+    /* put pointer to tcb at the top of stack for get_self_tcb() use */
+    *(tcb_t**)(thread_tcb->stack_lo + thr_stack_alloc_size - sizeof(tcb_t*)) =
+        thread_tcb;
+
+    thread_tcb->waiter = 0;
+    thread_tcb->exited = 0;
+    thread_tcb->is_main = 0;
+
+    cond_init(&thread_tcb->wait_cv);
+
+    thread_tcb->mutex_next = NULL;
+    thread_tcb->mutex_resume = 0;
+
+    /* create new thread */
+    result = thread_fork(thread_tcb, func, args);
+
+    /* if thread_fork failed */
+    if (result < 0) {
+        cond_destroy(&thread_tcb->wait_cv);
+        remove_pages((void*)thread_tcb->stack_lo);
+
+        thread_tcb->right = free_tcbs;
+        free_tcbs = thread_tcb;
+
+        mutex_unlock(&tcb_lock);
+
+        return -1;
+    }
+
+    /* thread successfully created, return tid */
+
+    thread_tcb->tid = result;
+    rb_insert_tcb(thread_tcb);
+
+    mutex_unlock(&tcb_lock);
+
+    return result;
+}
+
+/**
+ * @brief wait thread tid to exit and get exit status
+ *
+ * @param tid thread to wait
+ * @param statusp output pointer for exit status
+ * @return int      0 on success, -1 on error
+ */
+int thr_join(int tid, void** statusp) {
+    mutex_lock(&tcb_lock);
+
+    tcb_t* tcb = rb_find_tcb(tid);
+
+    if (tcb == NULL) {
+        mutex_unlock(&tcb_lock);
+        return -1;
+    }
+
+    /* other thread is waiting for the thread */
+    if (tcb->waiter != 0) {
+        mutex_unlock(&tcb_lock);
+        return -1;
+    }
+
+    /* make sure others will not wait on this thread */
+    tcb->waiter = 1;
+
+    /* wait until thread exits */
+    if (tcb->exited != 1) {
+        cond_wait(&tcb->wait_cv, &tcb_lock);
+    }
+
+    /* return exited thread status if user wants it */
+    if (statusp != NULL) {
+        *statusp = tcb->exit_value;
+    }
+
+    /* cleanup and return */
+    rb_delete_tcb(tcb);
+    cond_destroy(&tcb->wait_cv);
+
+    if (tcb->is_main == 0) {
+        remove_pages((void*)tcb->stack_lo);
+        tcb->right = free_tcbs;
+        free_tcbs = tcb;
+    }
+
+    mutex_unlock(&tcb_lock);
+    return 0;
+}
+
+/**
+ * @brief exit from thread with given status
+ *
+ * @param status
+ */
+void thr_exit(void* status) {
+    tcb_t* tcb = get_self_tcb();
+    mutex_lock(&tcb_lock);
+
+    tcb->exit_value = (void*)status;
+    tcb->exited = 1;
+
+    cond_signal(&tcb->wait_cv);
+    /* call vanish after unlock and do not use stack becuase the stack may have
+     * been freed by other threads */
+    mutex_unlock_vanish(&tcb_lock);
+}
+
+/**
+ * @brief return the ID of the current thread
+ *
+ * @return int  - ID of the current thread
+ */
+int thr_getid(void) {
+    return get_self_tcb()->tid;
+}
+
+/**
+ * @brief Defers execution of involing thread
+ *
+ * @param tid
+ * @return int
+ */
+int thr_yield(int tid) {
+    return yield(tid);
+}
+
+/**
+ * @brief thread entrypoint wrapper
+ * @param f user func
+ * @param arg user argument
+ */
+void thr_begin(void* (*f)(void*), void* arg) {
+    mutex_lock(&tcb_lock);
+    mutex_unlock(&tcb_lock);
+    thr_exit(f(arg));
+}
+
+/**
+ * @brief swexn handler
+ *
+ * @param arg
+ * @param reg
+ */
+static void thr_swexn_handler(void* arg, ureg_t* reg) {
+    task_vanish(THREAD_EXIT_SWEXN);
+}