Cleans up fork/exec's procinfo/data handling

[akaros.git] / kern / src / syscall.c

/* See COPYRIGHT for copyright information. */

#ifdef __SHARC__
#pragma nosharc
#endif

#include <ros/common.h>
#include <arch/types.h>
#include <arch/arch.h>
#include <arch/mmu.h>
#include <arch/console.h>
#include <ros/time.h>
#include <error.h>

#include <elf.h>
#include <string.h>
#include <assert.h>
#include <process.h>
#include <schedule.h>
#include <pmap.h>
#include <umem.h>
#include <mm.h>
#include <trap.h>
#include <syscall.h>
#include <kmalloc.h>
#include <stdio.h>
#include <resource.h>
#include <frontend.h>
#include <colored_caches.h>
#include <hashtable.h>
#include <bitmask.h>
#include <vfs.h>
#include <devfs.h>
#include <smp.h>
#include <arsc_server.h>
#include <event.h>


#ifdef __CONFIG_NETWORKING__
#include <arch/nic_common.h>
extern int (*send_frame)(const char *CT(len) data, size_t len);
extern unsigned char device_mac[6];
#endif

/* Tracing Globals */
int systrace_flags = 0;
struct systrace_record *systrace_buffer = 0;
uint32_t systrace_bufidx = 0;
size_t systrace_bufsize = 0;
struct proc *systrace_procs[MAX_NUM_TRACED] = {0};
spinlock_t systrace_lock = SPINLOCK_INITIALIZER;

/* Not enforcing the packing of systrace_procs yet, but don't rely on that */
static bool proc_is_traced(struct proc *p)
{
        for (int i = 0; i < MAX_NUM_TRACED; i++)
                if (systrace_procs[i] == p)
                        return true;
        return false;
}

/* Helper to finish a syscall, signalling if appropriate */
static void finish_sysc(struct syscall *sysc, struct proc *p)
{
        /* Atomically turn on the LOCK and SC_DONE flag.  The lock tells userspace
         * we're messing with the flags and to not proceed.  We use it instead of
         * CASing with userspace.  We need the atomics since we're racing with
         * userspace for the event_queue registration.  The 'lock' tells userspace
         * to not muck with the flags while we're signalling. */
        atomic_or(&sysc->flags, SC_K_LOCK | SC_DONE); 
        __signal_syscall(sysc, p);
        atomic_and(&sysc->flags, ~SC_K_LOCK); 
}

/* Helper that "finishes" the current async syscall.  This should be used when
 * we are calling a function in a syscall that might not return and won't be
 * able to use the normal syscall return path, such as proc_yield() and
 * resource_req().  Call this from within syscall.c (I don't want it global).
 *
 * It is possible for another user thread to see the syscall being done early -
 * they just need to be careful with the weird proc management calls (as in,
 * don't trust an async fork).
 *
 * *sysc is in user memory, and should be pinned (TODO: UMEM).  There may be
 * issues with unpinning this if we never return. */
static void finish_current_sysc(int retval)
{
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        assert(pcpui->cur_sysc);
        pcpui->cur_sysc->retval = retval;
        finish_sysc(pcpui->cur_sysc, pcpui->cur_proc);
}

/* Callable by any function while executing a syscall (or otherwise, actually).
 */
void set_errno(int errno)
{
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        if (pcpui->cur_sysc)
                pcpui->cur_sysc->err = errno;
}

/************** Utility Syscalls **************/

static int sys_null(void)
{
        return 0;
}

/* Diagnostic function: blocks the kthread/syscall, to help userspace test its
 * async I/O handling. */
static int sys_block(struct proc *p, unsigned int usec)
{
        struct timer_chain *tchain = &per_cpu_info[core_id()].tchain;
        struct alarm_waiter a_waiter;
        init_awaiter(&a_waiter, 0);
        /* Note printing takes a few ms, so your printds won't be perfect. */
        printd("[kernel] sys_block(), sleeping at %llu\n", read_tsc());
        set_awaiter_rel(&a_waiter, usec);
        set_alarm(tchain, &a_waiter);
        sleep_on_awaiter(&a_waiter);
        printd("[kernel] sys_block(), waking up at %llu\n", read_tsc());
        return 0;
}

// Writes 'val' to 'num_writes' entries of the well-known array in the kernel
// address space.  It's just #defined to be some random 4MB chunk (which ought
// to be boot_alloced or something).  Meant to grab exclusive access to cache
// lines, to simulate doing something useful.
static int sys_cache_buster(struct proc *p, uint32_t num_writes,
                             uint32_t num_pages, uint32_t flags)
{ TRUSTEDBLOCK /* zra: this is not really part of the kernel */
        #define BUSTER_ADDR             0xd0000000L  // around 512 MB deep
        #define MAX_WRITES              1048576*8
        #define MAX_PAGES               32
        #define INSERT_ADDR     (UINFO + 2*PGSIZE) // should be free for these tests
        uint32_t* buster = (uint32_t*)BUSTER_ADDR;
        static spinlock_t buster_lock = SPINLOCK_INITIALIZER;
        uint64_t ticks = -1;
        page_t* a_page[MAX_PAGES];

        /* Strided Accesses or Not (adjust to step by cachelines) */
        uint32_t stride = 1;
        if (flags & BUSTER_STRIDED) {
                stride = 16;
                num_writes *= 16;
        }

        /* Shared Accesses or Not (adjust to use per-core regions)
         * Careful, since this gives 8MB to each core, starting around 512MB.
         * Also, doesn't separate memory for core 0 if it's an async call.
         */
        if (!(flags & BUSTER_SHARED))
                buster = (uint32_t*)(BUSTER_ADDR + core_id() * 0x00800000);

        /* Start the timer, if we're asked to print this info*/
        if (flags & BUSTER_PRINT_TICKS)
                ticks = start_timing();

        /* Allocate num_pages (up to MAX_PAGES), to simulate doing some more
         * realistic work.  Note we don't write to these pages, even if we pick
         * unshared.  Mostly due to the inconvenience of having to match up the
         * number of pages with the number of writes.  And it's unnecessary.
         */
        if (num_pages) {
                spin_lock(&buster_lock);
                for (int i = 0; i < MIN(num_pages, MAX_PAGES); i++) {
                        upage_alloc(p, &a_page[i],1);
                        page_insert(p->env_pgdir, a_page[i], (void*)INSERT_ADDR + PGSIZE*i,
                                    PTE_USER_RW);
                        page_decref(a_page[i]);
                }
                spin_unlock(&buster_lock);
        }

        if (flags & BUSTER_LOCKED)
                spin_lock(&buster_lock);
        for (int i = 0; i < MIN(num_writes, MAX_WRITES); i=i+stride)
                buster[i] = 0xdeadbeef;
        if (flags & BUSTER_LOCKED)
                spin_unlock(&buster_lock);

        if (num_pages) {
                spin_lock(&buster_lock);
                for (int i = 0; i < MIN(num_pages, MAX_PAGES); i++) {
                        page_remove(p->env_pgdir, (void*)(INSERT_ADDR + PGSIZE * i));
                        page_decref(a_page[i]);
                }
                spin_unlock(&buster_lock);
        }

        /* Print info */
        if (flags & BUSTER_PRINT_TICKS) {
                ticks = stop_timing(ticks);
                printk("%llu,", ticks);
        }
        return 0;
}

static int sys_cache_invalidate(void)
{
        #ifdef __i386__
                wbinvd();
        #endif
        return 0;
}

/* sys_reboot(): called directly from dispatch table. */

/* Print a string to the system console. */
static ssize_t sys_cputs(struct proc *p, const char *DANGEROUS string,
                         size_t strlen)
{
        char *t_string;
        t_string = user_strdup_errno(p, string, strlen);
        if (!t_string)
                return -1;
        printk("%.*s", strlen, t_string);
        user_memdup_free(p, t_string);
        return (ssize_t)strlen;
}

// Read a character from the system console.
// Returns the character.
static uint16_t sys_cgetc(struct proc *p)
{
        uint16_t c;

        // The cons_getc() primitive doesn't wait for a character,
        // but the sys_cgetc() system call does.
        while ((c = cons_getc()) == 0)
                cpu_relax();

        return c;
}

/* Returns the id of the cpu this syscall is executed on. */
static uint32_t sys_getcpuid(void)
{
        return core_id();
}

// TODO: Temporary hack until thread-local storage is implemented on i386 and
// this is removed from the user interface
static size_t sys_getvcoreid(struct proc *p)
{
        return proc_get_vcoreid(p, core_id());
}

/************** Process management syscalls **************/

/* Returns the calling process's pid */
static pid_t sys_getpid(struct proc *p)
{
        return p->pid;
}

/* Creates a process from the file 'path'.  The process is not runnable by
 * default, so it needs it's status to be changed so that the next call to
 * schedule() will try to run it.  TODO: take args/envs from userspace. */
static int sys_proc_create(struct proc *p, char *path, size_t path_l,
                           struct procinfo *pi)
{
        int pid = 0;
        char *t_path;
        struct file *program;
        struct proc *new_p;

        /* Copy in the path.  Consider putting an upper bound on path_l. */
        t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        program = do_file_open(t_path, 0, 0);
        user_memdup_free(p, t_path);
        if (!program)
                return -1;                      /* presumably, errno is already set */
        /* TODO: need to split the proc creation, since you must load after setting
         * args/env, since auxp gets set up there. */
        //new_p = proc_create(program, 0, 0);
        if (proc_alloc(&new_p, current))
                goto mid_error;
        /* Set the argument stuff needed by glibc */
        if (memcpy_from_user_errno(p, new_p->procinfo->argp, pi->argp,
                                   sizeof(pi->argp)))
                goto late_error;
        if (memcpy_from_user_errno(p, new_p->procinfo->argbuf, pi->argbuf,
                                   sizeof(pi->argbuf)))
                goto late_error;
        if (load_elf(new_p, program))
                goto late_error;
        kref_put(&program->f_kref);
        /* Connect to stdin, stdout, stderr (part of proc_create()) */
        assert(insert_file(&new_p->open_files, dev_stdin,  0) == 0);
        assert(insert_file(&new_p->open_files, dev_stdout, 0) == 1);
        assert(insert_file(&new_p->open_files, dev_stderr, 0) == 2);
        __proc_ready(new_p);
        pid = new_p->pid;
        proc_decref(new_p);     /* give up the reference created in proc_create() */
        return pid;
late_error:
        proc_destroy(new_p);
mid_error:
        kref_put(&program->f_kref);
        return -1;
}

/* Makes process PID runnable.  Consider moving the functionality to process.c */
static error_t sys_proc_run(struct proc *p, unsigned pid)
{
        struct proc *target = pid2proc(pid);
        error_t retval = 0;

        if (!target)
                return -EBADPROC;
        // note we can get interrupted here. it's not bad.
        spin_lock(&p->proc_lock);
        // make sure we have access and it's in the right state to be activated
        if (!proc_controls(p, target)) {
                proc_decref(target);
                retval = -EPERM;
        } else if (target->state != PROC_CREATED) {
                proc_decref(target);
                retval = -EINVAL;
        } else {
                __proc_set_state(target, PROC_RUNNABLE_S);
                schedule_proc(target);
        }
        spin_unlock(&p->proc_lock);
        proc_decref(target);
        return retval;
}

/* Destroy proc pid.  If this is called by the dying process, it will never
 * return.  o/w it will return 0 on success, or an error.  Errors include:
 * - EBADPROC: if there is no such process with pid
 * - EPERM: if caller does not control pid */
static error_t sys_proc_destroy(struct proc *p, pid_t pid, int exitcode)
{
        error_t r;
        struct proc *p_to_die = pid2proc(pid);

        if (!p_to_die) {
                set_errno(ESRCH);
                return -1;
        }
        if (!proc_controls(p, p_to_die)) {
                proc_decref(p_to_die);
                set_errno(EPERM);
                return -1;
        }
        if (p_to_die == p) {
                p->exitcode = exitcode;
                printd("[PID %d] proc exiting gracefully (code %d)\n", p->pid,exitcode);
        } else {
                p_to_die->exitcode = exitcode;  /* so its parent has some clue */
                printd("[%d] destroying proc %d\n", p->pid, p_to_die->pid);
        }
        proc_destroy(p_to_die);
        /* we only get here if we weren't the one to die */
        proc_decref(p_to_die);
        return ESUCCESS;
}

static int sys_proc_yield(struct proc *p, bool being_nice)
{
        /* proc_yield() often doesn't return - we need to set the syscall retval
         * early.  If it doesn't return, it expects to eat our reference (for now).
         */
        finish_current_sysc(0);
        proc_incref(p, 1);
        proc_yield(p, being_nice);
        proc_decref(p);
        return 0;
}

static ssize_t sys_fork(env_t* e)
{
        // TODO: right now we only support fork for single-core processes
        if (e->state != PROC_RUNNING_S) {
                set_errno(EINVAL);
                return -1;
        }
        env_t* env;
        assert(!proc_alloc(&env, current));
        assert(env != NULL);

        env->heap_top = e->heap_top;
        env->ppid = e->pid;
        /* Can't really fork if we don't have a current_tf to fork */
        if (!current_tf) {
                set_errno(EINVAL);
                return -1;
        }
        env->env_tf = *current_tf;

        /* We need to speculatively say the syscall worked before copying the memory
         * out, since the 'forked' process's call never actually goes through the
         * syscall return path, and will never think it is done.  This violates a
         * few things.  Just be careful with fork. */
        finish_current_sysc(0);

        env->cache_colors_map = cache_colors_map_alloc();
        for(int i=0; i < llc_cache->num_colors; i++)
                if(GET_BITMASK_BIT(e->cache_colors_map,i))
                        cache_color_alloc(llc_cache, env->cache_colors_map);

        duplicate_vmrs(e, env);

        int copy_page(env_t* e, pte_t* pte, void* va, void* arg)
        {
                env_t* env = (env_t*)arg;

                if(PAGE_PRESENT(*pte))
                {
                        page_t* pp;
                        if(upage_alloc(env,&pp,0))
                                return -1;
                        if(page_insert(env->env_pgdir,pp,va,*pte & PTE_PERM))
                        {
                                page_decref(pp);
                                return -1;
                        }
                        pagecopy(page2kva(pp),ppn2kva(PTE2PPN(*pte)));
                        page_decref(pp);
                } else {
                        assert(PAGE_PAGED_OUT(*pte));
                        /* TODO: (SWAP) will need to either make a copy or CoW/refcnt the
                         * backend store.  For now, this PTE will be the same as the
                         * original PTE */
                        panic("Swapping not supported!");
                        pte_t* newpte = pgdir_walk(env->env_pgdir,va,1);
                        if(!newpte)
                                return -1;
                        *newpte = *pte;
                }
                return 0;
        }

        /* In general, a forked process should be a fresh process, and we copy over
         * whatever stuff is needed between procinfo/procdata. */
        /* Copy over the procinfo argument stuff in case they don't exec */
        memcpy(env->procinfo->argp, e->procinfo->argp, sizeof(e->procinfo->argp));
        memcpy(env->procinfo->argbuf, e->procinfo->argbuf,
               sizeof(e->procinfo->argbuf));
        #ifdef __i386__
        /* new guy needs to know about ldt (everything else in procdata is fresh */
        env->procdata->ldt = e->procdata->ldt;
        #endif

        /* for now, just copy the contents of every present page in the entire
         * address space. */
        if (env_user_mem_walk(e, 0, UMAPTOP, &copy_page, env)) {
                proc_destroy(env);      /* this is prob what you want, not decref by 2 */
                set_errno(ENOMEM);
                return -1;
        }
        clone_files(&e->open_files, &env->open_files);
        __proc_ready(env);
        __proc_set_state(env, PROC_RUNNABLE_S);
        schedule_proc(env);

        // don't decref the new process.
        // that will happen when the parent waits for it.
        // TODO: if the parent doesn't wait, we need to change the child's parent
        // when the parent dies, or at least decref it

        printd("[PID %d] fork PID %d\n",e->pid,env->pid);
        return env->pid;
}

/* Load the binary "path" into the current process, and start executing it.
 * argv and envp are magically bundled in procinfo for now.  Keep in sync with
 * glibc's sysdeps/ros/execve.c.  Once past a certain point, this function won't
 * return.  It assumes (and checks) that it is current.  Don't give it an extra
 * refcnt'd *p (syscall won't do that). 
 * Note: if someone batched syscalls with this call, they could clobber their
 * old memory (and will likely PF and die).  Don't do it... */
static int sys_exec(struct proc *p, char *path, size_t path_l,
                    struct procinfo *pi)
{
        int ret = -1;
        char *t_path;
        struct file *program;
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
        struct trapframe *old_cur_tf = pcpui->cur_tf;

        /* We probably want it to never be allowed to exec if it ever was _M */
        if (p->state != PROC_RUNNING_S) {
                set_errno(EINVAL);
                return -1;
        }
        if (p != pcpui->cur_proc) {
                set_errno(EINVAL);
                return -1;
        }
        /* Can't exec if we don't have a current_tf to restart (if we fail).  This
         * isn't 100% true, but I'm okay with it. */
        if (!old_cur_tf) {
                set_errno(EINVAL);
                return -1;
        }
        /* Copy in the path.  Consider putting an upper bound on path_l. */
        t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        /* Clear the current_tf.  We won't be returning the 'normal' way.  Even if
         * we want to return with an error, we need to go back differently in case
         * we succeed.  This needs to be done before we could possibly block, but
         * unfortunately happens before the point of no return. */
        pcpui->cur_tf = 0;
        /* This could block: */
        program = do_file_open(t_path, 0, 0);
        user_memdup_free(p, t_path);
        if (!program)
                goto early_error;
        /* Set the argument stuff needed by glibc */
        if (memcpy_from_user_errno(p, p->procinfo->argp, pi->argp,
                                   sizeof(pi->argp)))
                goto mid_error;
        if (memcpy_from_user_errno(p, p->procinfo->argbuf, pi->argbuf,
                                   sizeof(pi->argbuf)))
                goto mid_error;
        /* This is the point of no return for the process. */
        #ifdef __i386__
        /* clear this, so the new program knows to get an LDT */
        p->procdata->ldt = 0;
        #endif
        destroy_vmrs(p);
        close_all_files(&p->open_files, TRUE);
        env_user_mem_free(p, 0, UMAPTOP);
        if (load_elf(p, program)) {
                kref_put(&program->f_kref);
                /* Need an edible reference for proc_destroy in case it doesn't return.
                 * sys_exec was given current's ref (counted once just for current) */
                proc_incref(p, 1);
                proc_destroy(p);
                proc_decref(p);
                /* We don't want to do anything else - we just need to not accidentally
                 * return to the user (hence the all_out) */
                goto all_out;
        }
        printd("[PID %d] exec %s\n", p->pid, file_name(program));
        kref_put(&program->f_kref);
        goto success;
        /* These error and out paths are so we can handle the async interface, both
         * for when we want to error/return to the proc, as well as when we succeed
         * and want to start the newly exec'd _S */
mid_error:
        /* These two error paths are for when we want to restart the process with an
         * error value (errno is already set). */
        kref_put(&program->f_kref);
early_error:
        p->env_tf = *old_cur_tf;
        finish_current_sysc(-1);
success:
        /* Here's how we'll restart the new (or old) process: */
        spin_lock(&p->proc_lock);
        __proc_set_state(p, PROC_RUNNABLE_S);
        schedule_proc(p);
        spin_unlock(&p->proc_lock);
all_out:
        /* we can't return, since we'd write retvals to the old location of the
         * sycall struct (which has been freed and is in the old userspace) (or has
         * already been written to).*/
        abandon_core();
        smp_idle();
        assert(0);
}

static ssize_t sys_trywait(env_t* e, pid_t pid, int* status)
{
        struct proc* p = pid2proc(pid);

        // TODO: this syscall is racy, so we only support for single-core procs
        if(e->state != PROC_RUNNING_S)
                return -1;

        // TODO: need to use errno properly.  sadly, ROS error codes conflict..

        if(p)
        {
                ssize_t ret;

                if(current->pid == p->ppid)
                {
                        if(p->state == PROC_DYING)
                        {
                                memcpy_to_user(e,status,&p->exitcode,sizeof(int));
                                printd("[PID %d] waited for PID %d (code %d)\n",
                                       e->pid,p->pid,p->exitcode);
                                ret = 0;
                        }
                        else // not dead yet
                        {
                                set_errno(ESUCCESS);
                                ret = -1;
                        }
                }
                else // not a child of the calling process
                {
                        set_errno(EPERM);
                        ret = -1;
                }

                // if the wait succeeded, decref twice
                if (ret == 0)
                        proc_decref(p);
                proc_decref(p);
                return ret;
        }

        set_errno(EPERM);
        return -1;
}

/************** Memory Management Syscalls **************/

static void *sys_mmap(struct proc *p, uintptr_t addr, size_t len, int prot,
                      int flags, int fd, off_t offset)
{
        return mmap(p, addr, len, prot, flags, fd, offset);
}

static intreg_t sys_mprotect(struct proc *p, void *addr, size_t len, int prot)
{
        return mprotect(p, (uintptr_t)addr, len, prot);
}

static intreg_t sys_munmap(struct proc *p, void *addr, size_t len)
{
        return munmap(p, (uintptr_t)addr, len);
}

static ssize_t sys_shared_page_alloc(env_t* p1,
                                     void**DANGEROUS _addr, pid_t p2_id,
                                     int p1_flags, int p2_flags
                                    )
{
        printk("[kernel] shared page alloc is deprecated/unimplemented.\n");
        return -1;
}

static int sys_shared_page_free(env_t* p1, void*DANGEROUS addr, pid_t p2)
{
        return -1;
}


static int sys_resource_req(struct proc *p, int type, unsigned int amt_wanted,
                            unsigned int amt_wanted_min, int flags)
{
        int retval;
        finish_current_sysc(0);
        /* this might not return (if it's a _S -> _M transition) */
        proc_incref(p, 1);
        retval = resource_req(p, type, amt_wanted, amt_wanted_min, flags);
        proc_decref(p);
        return retval;
}

/* Untested.  Will notify the target on the given vcore, if the caller controls
 * the target.  Will honor the target's wanted/vcoreid.  u_ne can be NULL. */
static int sys_notify(struct proc *p, int target_pid, unsigned int ev_type,
                      struct event_msg *u_msg)
{
        struct event_msg local_msg = {0};
        struct proc *target = pid2proc(target_pid);
        if (!target) {
                set_errno(EBADPROC);
                return -1;
        }
        if (!proc_controls(p, target)) {
                proc_decref(target);
                set_errno(EPERM);
                return -1;
        }
        /* if the user provided an ev_msg, copy it in and use that */
        if (u_msg) {
                if (memcpy_from_user(p, &local_msg, u_msg, sizeof(struct event_msg))) {
                        proc_decref(target);
                        set_errno(EINVAL);
                        return -1;
                }
        }
        send_kernel_event(target, &local_msg, 0);
        proc_decref(target);
        return 0;
}

/* Will notify the calling process on the given vcore, independently of WANTED
 * or advertised vcoreid.  If you change the parameters, change pop_ros_tf() */
static int sys_self_notify(struct proc *p, uint32_t vcoreid,
                           unsigned int ev_type, struct event_msg *u_msg)
{
        struct event_msg local_msg = {0};

        printd("[kernel] received self notify for vcoreid %d, type %d, msg %08p\n",
               vcoreid, ev_type, u_msg);
        /* if the user provided an ev_msg, copy it in and use that */
        if (u_msg) {
                if (memcpy_from_user(p, &local_msg, u_msg, sizeof(struct event_msg))) {
                        set_errno(EINVAL);
                        return -1;
                }
        }
        /* this will post a message and IPI, regardless of wants/needs/debutantes.*/
        post_vcore_event(p, &local_msg, vcoreid);
        proc_notify(p, vcoreid);
        return 0;
}

/* This will set a local timer for usec, then shut down the core.  There's a
 * slight race between spinner and halt.  For now, the core will wake up for
 * other interrupts and service them, but will not process routine messages or
 * do anything other than halt until the alarm goes off.  We could just unset
 * the alarm and return early.  On hardware, there are a lot of interrupts that
 * come in.  If we ever use this, we can take a closer look.  */
static int sys_halt_core(struct proc *p, unsigned int usec)
{
        struct timer_chain *tchain = &per_cpu_info[core_id()].tchain;
        struct alarm_waiter a_waiter;
        bool spinner = TRUE;
        void unblock(struct alarm_waiter *waiter)
        {
                spinner = FALSE;
        }
        init_awaiter(&a_waiter, unblock);
        set_awaiter_rel(&a_waiter, MAX(usec, 100));
        set_alarm(tchain, &a_waiter);
        enable_irq();
        /* Could wake up due to another interrupt, but we want to sleep still. */
        while (spinner) {
                cpu_halt();     /* slight race between spinner and halt */
                cpu_relax();
        }
        printd("Returning from halting\n");
        return 0;
}

/************** Platform Specific Syscalls **************/

//Read a buffer over the serial port
static ssize_t sys_serial_read(env_t* e, char *DANGEROUS _buf, size_t len)
{
        printk("[kernel] serial reading is deprecated.\n");
        if (len == 0)
                return 0;

        #ifdef __CONFIG_SERIAL_IO__
            char *COUNT(len) buf = user_mem_assert(e, _buf, len, 1, PTE_USER_RO);
                size_t bytes_read = 0;
                int c;
                while((c = serial_read_byte()) != -1) {
                        buf[bytes_read++] = (uint8_t)c;
                        if(bytes_read == len) break;
                }
                return (ssize_t)bytes_read;
        #else
                return -EINVAL;
        #endif
}

//Write a buffer over the serial port
static ssize_t sys_serial_write(env_t* e, const char *DANGEROUS buf, size_t len)
{
        printk("[kernel] serial writing is deprecated.\n");
        if (len == 0)
                return 0;
        #ifdef __CONFIG_SERIAL_IO__
                char *COUNT(len) _buf = user_mem_assert(e, buf, len, 1, PTE_USER_RO);
                for(int i =0; i<len; i++)
                        serial_send_byte(buf[i]);
                return (ssize_t)len;
        #else
                return -EINVAL;
        #endif
}

#ifdef __CONFIG_NETWORKING__
// This is not a syscall we want. Its hacky. Here just for syscall stuff until get a stack.
static ssize_t sys_eth_read(env_t* e, char *DANGEROUS buf)
{
        if (eth_up) {

                uint32_t len;
                char *ptr;

                spin_lock(&packet_buffers_lock);

                if (num_packet_buffers == 0) {
                        spin_unlock(&packet_buffers_lock);
                        return 0;
                }

                ptr = packet_buffers[packet_buffers_head];
                len = packet_buffers_sizes[packet_buffers_head];

                num_packet_buffers--;
                packet_buffers_head = (packet_buffers_head + 1) % MAX_PACKET_BUFFERS;

                spin_unlock(&packet_buffers_lock);

                char* _buf = user_mem_assert(e, buf, len, 1, PTE_U);

                memcpy(_buf, ptr, len);

                kfree(ptr);

                return len;
        }
        else
                return -EINVAL;
}

// This is not a syscall we want. Its hacky. Here just for syscall stuff until get a stack.
static ssize_t sys_eth_write(env_t* e, const char *DANGEROUS buf, size_t len)
{
        if (eth_up) {

                if (len == 0)
                        return 0;

                // HACK TO BYPASS HACK
                int just_sent = send_frame(buf, len);

                if (just_sent < 0) {
                        printk("Packet send fail\n");
                        return 0;
                }

                return just_sent;

                // END OF RECURSIVE HACK
/*
                char *COUNT(len) _buf = user_mem_assert(e, buf, len, PTE_U);
                int total_sent = 0;
                int just_sent = 0;
                int cur_packet_len = 0;
                while (total_sent != len) {
                        cur_packet_len = ((len - total_sent) > MTU) ? MTU : (len - total_sent);
                        char dest_mac[6] = APPSERVER_MAC_ADDRESS;
                        char* wrap_buffer = eth_wrap(_buf + total_sent, cur_packet_len, device_mac, dest_mac, APPSERVER_PORT);
                        just_sent = send_frame(wrap_buffer, cur_packet_len + sizeof(struct ETH_Header));

                        if (just_sent < 0)
                                return 0; // This should be an error code of its own

                        if (wrap_buffer)
                                kfree(wrap_buffer);

                        total_sent += cur_packet_len;
                }

                return (ssize_t)len;
*/
        }
        else
                return -EINVAL;
}

static ssize_t sys_eth_get_mac_addr(env_t* e, char *DANGEROUS buf) 
{
        if (eth_up) {
                for (int i = 0; i < 6; i++)
                        buf[i] = device_mac[i];
                return 0;
        }
        else
                return -EINVAL;
}

static int sys_eth_recv_check(env_t* e) 
{
        if (num_packet_buffers != 0) 
                return 1;
        else
                return 0;
}

#endif // Network

static intreg_t sys_read(struct proc *p, int fd, void *buf, int len)
{
        ssize_t ret;
        struct file *file = get_file_from_fd(&p->open_files, fd);
        if (!file) {
                set_errno(EBADF);
                return -1;
        }
        if (!file->f_op->read) {
                kref_put(&file->f_kref);
                set_errno(EINVAL);
                return -1;
        }
        /* TODO: (UMEM) currently, read() handles user memcpy issues, but we
         * probably should user_mem_check and pin the region here, so read doesn't
         * worry about it */
        ret = file->f_op->read(file, buf, len, &file->f_pos);
        kref_put(&file->f_kref);
        return ret;
}

static intreg_t sys_write(struct proc *p, int fd, const void *buf, int len)
{
        ssize_t ret;
        struct file *file = get_file_from_fd(&p->open_files, fd);
        if (!file) {
                set_errno(EBADF);
                return -1;
        }
        if (!file->f_op->write) {
                kref_put(&file->f_kref);
                set_errno(EINVAL);
                return -1;
        }
        /* TODO: (UMEM) */
        ret = file->f_op->write(file, buf, len, &file->f_pos);
        kref_put(&file->f_kref);
        return ret;
}

/* Checks args/reads in the path, opens the file, and inserts it into the
 * process's open file list. 
 *
 * TODO: take the path length */
static intreg_t sys_open(struct proc *p, const char *path, size_t path_l,
                         int oflag, int mode)
{
        int fd = 0;
        struct file *file;

        printd("File %s Open attempt\n", path);
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        mode &= ~p->fs_env.umask;
        file = do_file_open(t_path, oflag, mode);
        user_memdup_free(p, t_path);
        if (!file)
                return -1;
        fd = insert_file(&p->open_files, file, 0);      /* stores the ref to file */
        kref_put(&file->f_kref);
        if (fd < 0) {
                warn("File insertion failed");
                return -1;
        }
        printd("File %s Open, res=%d\n", path, fd);
        return fd;
}

static intreg_t sys_close(struct proc *p, int fd)
{
        struct file *file = put_file_from_fd(&p->open_files, fd);
        if (!file) {
                set_errno(EBADF);
                return -1;
        }
        return 0;
}

/* kept around til we remove the last ufe */
#define ufe(which,a0,a1,a2,a3) \
        frontend_syscall_errno(p,APPSERVER_SYSCALL_##which,\
                           (int)(a0),(int)(a1),(int)(a2),(int)(a3))

static intreg_t sys_fstat(struct proc *p, int fd, struct kstat *u_stat)
{
        struct kstat *kbuf;
        struct file *file = get_file_from_fd(&p->open_files, fd);
        if (!file) {
                set_errno(EBADF);
                return -1;
        }
        kbuf = kmalloc(sizeof(struct kstat), 0);
        if (!kbuf) {
                kref_put(&file->f_kref);
                set_errno(ENOMEM);
                return -1;
        }
        stat_inode(file->f_dentry->d_inode, kbuf);
        kref_put(&file->f_kref);
        /* TODO: UMEM: pin the memory, copy directly, and skip the kernel buffer */
        if (memcpy_to_user_errno(p, u_stat, kbuf, sizeof(struct kstat))) {
                kfree(kbuf);
                set_errno(EINVAL);
                return -1;
        }
        kfree(kbuf);
        return 0;
}

/* sys_stat() and sys_lstat() do nearly the same thing, differing in how they
 * treat a symlink for the final item, which (probably) will be controlled by
 * the lookup flags */
static intreg_t stat_helper(struct proc *p, const char *path, size_t path_l,
                            struct kstat *u_stat, int flags)
{
        struct kstat *kbuf;
        struct dentry *path_d;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        path_d = lookup_dentry(t_path, flags);
        user_memdup_free(p, t_path);
        if (!path_d)
                return -1;
        kbuf = kmalloc(sizeof(struct kstat), 0);
        if (!kbuf) {
                set_errno(ENOMEM);
                kref_put(&path_d->d_kref);
                return -1;
        }
        stat_inode(path_d->d_inode, kbuf);
        kref_put(&path_d->d_kref);
        /* TODO: UMEM: pin the memory, copy directly, and skip the kernel buffer */
        if (memcpy_to_user_errno(p, u_stat, kbuf, sizeof(struct kstat))) {
                kfree(kbuf);
                set_errno(EINVAL);
                return -1;
        }
        kfree(kbuf);
        return 0;
}

/* Follow a final symlink */
static intreg_t sys_stat(struct proc *p, const char *path, size_t path_l,
                         struct kstat *u_stat)
{
        return stat_helper(p, path, path_l, u_stat, LOOKUP_FOLLOW);
}

/* Don't follow a final symlink */
static intreg_t sys_lstat(struct proc *p, const char *path, size_t path_l,
                          struct kstat *u_stat)
{
        return stat_helper(p, path, path_l, u_stat, 0);
}

intreg_t sys_fcntl(struct proc *p, int fd, int cmd, int arg)
{
        int retval = 0;
        struct file *file = get_file_from_fd(&p->open_files, fd);
        if (!file) {
                set_errno(EBADF);
                return -1;
        }
        switch (cmd) {
                case (F_DUPFD):
                        retval = insert_file(&p->open_files, file, arg);
                        if (retval < 0) {
                                set_errno(-retval);
                                retval = -1;
                        }
                        break;
                case (F_GETFD):
                        retval = p->open_files.fd[fd].fd_flags;
                        break;
                case (F_SETFD):
                        if (arg == FD_CLOEXEC)
                                file->f_flags |= O_CLOEXEC;
                        break;
                case (F_GETFL):
                        retval = file->f_flags;
                        break;
                case (F_SETFL):
                        /* only allowed to set certain flags. */
                        arg &= O_FCNTL_FLAGS;
                        file->f_flags = (file->f_flags & ~O_FCNTL_FLAGS) | arg;
                        break;
                default:
                        warn("Unsupported fcntl cmd %d\n", cmd);
        }
        kref_put(&file->f_kref);
        return retval;
}

static intreg_t sys_access(struct proc *p, const char *path, size_t path_l,
                           int mode)
{
        int retval;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        retval = do_access(t_path, mode);
        user_memdup_free(p, t_path);
        printd("Access for path: %s retval: %d\n", path, retval);
        if (retval < 0) {
                set_errno(-retval);
                return -1;
        }
        return retval;
}

intreg_t sys_umask(struct proc *p, int mask)
{
        int old_mask = p->fs_env.umask;
        p->fs_env.umask = mask & S_PMASK;
        return old_mask;
}

intreg_t sys_chmod(struct proc *p, const char *path, size_t path_l, int mode)
{
        int retval;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        retval = do_chmod(t_path, mode);
        user_memdup_free(p, t_path);
        if (retval < 0) {
                set_errno(-retval);
                return -1;
        }
        return retval;
}

static intreg_t sys_lseek(struct proc *p, int fd, off_t offset, int whence)
{
        off_t ret;
        struct file *file = get_file_from_fd(&p->open_files, fd);
        if (!file) {
                set_errno(EBADF);
                return -1;
        }
        ret = file->f_op->llseek(file, offset, whence);
        kref_put(&file->f_kref);
        return ret;
}

intreg_t sys_link(struct proc *p, char *old_path, size_t old_l,
                  char *new_path, size_t new_l)
{
        int ret;
        char *t_oldpath = user_strdup_errno(p, old_path, old_l);
        if (t_oldpath == NULL)
                return -1;
        char *t_newpath = user_strdup_errno(p, new_path, new_l);
        if (t_newpath == NULL) {
                user_memdup_free(p, t_oldpath);
                return -1;
        }
        ret = do_link(t_oldpath, t_newpath);
        user_memdup_free(p, t_oldpath);
        user_memdup_free(p, t_newpath);
        return ret;
}

intreg_t sys_unlink(struct proc *p, const char *path, size_t path_l)
{
        int retval;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        retval = do_unlink(t_path);
        user_memdup_free(p, t_path);
        return retval;
}

intreg_t sys_symlink(struct proc *p, char *old_path, size_t old_l,
                     char *new_path, size_t new_l)
{
        int ret;
        char *t_oldpath = user_strdup_errno(p, old_path, old_l);
        if (t_oldpath == NULL)
                return -1;
        char *t_newpath = user_strdup_errno(p, new_path, new_l);
        if (t_newpath == NULL) {
                user_memdup_free(p, t_oldpath);
                return -1;
        }
        ret = do_symlink(new_path, old_path, S_IRWXU | S_IRWXG | S_IRWXO);
        user_memdup_free(p, t_oldpath);
        user_memdup_free(p, t_newpath);
        return ret;
}

intreg_t sys_readlink(struct proc *p, char *path, size_t path_l,
                      char *u_buf, size_t buf_l)
{
        char *symname;
        ssize_t copy_amt;
        struct dentry *path_d;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (t_path == NULL)
                return -1;
        path_d = lookup_dentry(t_path, 0);
        user_memdup_free(p, t_path);
        if (!path_d)
                return -1;
        symname = path_d->d_inode->i_op->readlink(path_d);
        copy_amt = strnlen(symname, buf_l - 1) + 1;
        if (memcpy_to_user_errno(p, u_buf, symname, copy_amt)) {
                kref_put(&path_d->d_kref);
                set_errno(EINVAL);
                return -1;
        }
        kref_put(&path_d->d_kref);
        printd("READLINK returning %s\n", u_buf);
        return copy_amt;
}

intreg_t sys_chdir(struct proc *p, const char *path, size_t path_l)
{
        int retval;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        retval = do_chdir(&p->fs_env, t_path);
        user_memdup_free(p, t_path);
        if (retval) {
                set_errno(-retval);
                return -1;
        }
        return 0;
}

/* Note cwd_l is not a strlen, it's an absolute size */
intreg_t sys_getcwd(struct proc *p, char *u_cwd, size_t cwd_l)
{
        int retval = 0;
        char *kfree_this;
        char *k_cwd = do_getcwd(&p->fs_env, &kfree_this, cwd_l);
        if (!k_cwd)
                return -1;              /* errno set by do_getcwd */
        if (memcpy_to_user_errno(p, u_cwd, k_cwd, strnlen(k_cwd, cwd_l - 1) + 1))
                retval = -1;
        kfree(kfree_this);
        return retval;
}

intreg_t sys_mkdir(struct proc *p, const char *path, size_t path_l, int mode)
{
        int retval;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        mode &= ~p->fs_env.umask;
        retval = do_mkdir(t_path, mode);
        user_memdup_free(p, t_path);
        return retval;
}

intreg_t sys_rmdir(struct proc *p, const char *path, size_t path_l)
{
        int retval;
        char *t_path = user_strdup_errno(p, path, path_l);
        if (!t_path)
                return -1;
        retval = do_rmdir(t_path);
        user_memdup_free(p, t_path);
        return retval;
}

intreg_t sys_gettimeofday(struct proc *p, int *buf)
{
        static spinlock_t gtod_lock = SPINLOCK_INITIALIZER;
        static int t0 = 0;

        spin_lock(&gtod_lock);
        if(t0 == 0)

#if (defined __CONFIG_APPSERVER__)
        t0 = ufe(time,0,0,0,0);
#else
        // Nanwan's birthday, bitches!!
        t0 = 1242129600;
#endif 
        spin_unlock(&gtod_lock);

        long long dt = read_tsc();
        /* TODO: This probably wants its own function, using a struct timeval */
        int kbuf[2] = {t0+dt/system_timing.tsc_freq,
            (dt%system_timing.tsc_freq)*1000000/system_timing.tsc_freq};

        return memcpy_to_user_errno(p,buf,kbuf,sizeof(kbuf));
}

#define SIZEOF_STRUCT_TERMIOS 60
intreg_t sys_tcgetattr(struct proc *p, int fd, void *termios_p)
{
        int* kbuf = kmalloc(SIZEOF_STRUCT_TERMIOS,0);
        int ret = ufe(tcgetattr,fd,PADDR(kbuf),0,0);
        if(ret != -1 && memcpy_to_user_errno(p,termios_p,kbuf,SIZEOF_STRUCT_TERMIOS))
                ret = -1;
        kfree(kbuf);
        return ret;
}

intreg_t sys_tcsetattr(struct proc *p, int fd, int optional_actions,
                       const void *termios_p)
{
        void* kbuf = user_memdup_errno(p,termios_p,SIZEOF_STRUCT_TERMIOS);
        if(kbuf == NULL)
                return -1;
        int ret = ufe(tcsetattr,fd,optional_actions,PADDR(kbuf),0);
        user_memdup_free(p,kbuf);
        return ret;
}

/* TODO: we don't have any notion of UIDs or GIDs yet, but don't let that stop a
 * process from thinking it can do these.  The other alternative is to have
 * glibc return 0 right away, though someone might want to do something with
 * these calls.  Someday. */
intreg_t sys_setuid(struct proc *p, uid_t uid)
{
        return 0;
}

intreg_t sys_setgid(struct proc *p, gid_t gid)
{
        return 0;
}

/************** Syscall Invokation **************/

const static struct sys_table_entry syscall_table[] = {
        [SYS_null] = {(syscall_t)sys_null, "null"},
        [SYS_block] = {(syscall_t)sys_block, "block"},
        [SYS_cache_buster] = {(syscall_t)sys_cache_buster, "buster"},
        [SYS_cache_invalidate] = {(syscall_t)sys_cache_invalidate, "wbinv"},
        [SYS_reboot] = {(syscall_t)reboot, "reboot!"},
        [SYS_cputs] = {(syscall_t)sys_cputs, "cputs"},
        [SYS_cgetc] = {(syscall_t)sys_cgetc, "cgetc"},
        [SYS_getcpuid] = {(syscall_t)sys_getcpuid, "getcpuid"},
        [SYS_getvcoreid] = {(syscall_t)sys_getvcoreid, "getvcoreid"},
        [SYS_getpid] = {(syscall_t)sys_getpid, "getpid"},
        [SYS_proc_create] = {(syscall_t)sys_proc_create, "proc_create"},
        [SYS_proc_run] = {(syscall_t)sys_proc_run, "proc_run"},
        [SYS_proc_destroy] = {(syscall_t)sys_proc_destroy, "proc_destroy"},
        [SYS_yield] = {(syscall_t)sys_proc_yield, "proc_yield"},
        [SYS_fork] = {(syscall_t)sys_fork, "fork"},
        [SYS_exec] = {(syscall_t)sys_exec, "exec"},
        [SYS_trywait] = {(syscall_t)sys_trywait, "trywait"},
        [SYS_mmap] = {(syscall_t)sys_mmap, "mmap"},
        [SYS_munmap] = {(syscall_t)sys_munmap, "munmap"},
        [SYS_mprotect] = {(syscall_t)sys_mprotect, "mprotect"},
        [SYS_shared_page_alloc] = {(syscall_t)sys_shared_page_alloc, "pa"},
        [SYS_shared_page_free] = {(syscall_t)sys_shared_page_free, "pf"},
        [SYS_resource_req] = {(syscall_t)sys_resource_req, "resource_req"},
        [SYS_notify] = {(syscall_t)sys_notify, "notify"},
        [SYS_self_notify] = {(syscall_t)sys_self_notify, "self_notify"},
        [SYS_halt_core] = {(syscall_t)sys_halt_core, "halt_core"},
#ifdef __CONFIG_SERIAL_IO__
        [SYS_serial_read] = {(syscall_t)sys_serial_read, "ser_read"},
        [SYS_serial_write] = {(syscall_t)sys_serial_write, "ser_write"},
#endif
#ifdef __CONFIG_NETWORKING__
        [SYS_eth_read] = {(syscall_t)sys_eth_read, "eth_read"},
        [SYS_eth_write] = {(syscall_t)sys_eth_write, "eth_write"},
        [SYS_eth_get_mac_addr] = {(syscall_t)sys_eth_get_mac_addr, "get_mac"},
        [SYS_eth_recv_check] = {(syscall_t)sys_eth_recv_check, "recv_check"},
#endif
#ifdef __CONFIG_ARSC_SERVER__
        [SYS_init_arsc] = {(syscall_t)sys_init_arsc, "init_arsc"},
#endif
        [SYS_read] = {(syscall_t)sys_read, "read"},
        [SYS_write] = {(syscall_t)sys_write, "write"},
        [SYS_open] = {(syscall_t)sys_open, "open"},
        [SYS_close] = {(syscall_t)sys_close, "close"},
        [SYS_fstat] = {(syscall_t)sys_fstat, "fstat"},
        [SYS_stat] = {(syscall_t)sys_stat, "stat"},
        [SYS_lstat] = {(syscall_t)sys_lstat, "lstat"},
        [SYS_fcntl] = {(syscall_t)sys_fcntl, "fcntl"},
        [SYS_access] = {(syscall_t)sys_access, "access"},
        [SYS_umask] = {(syscall_t)sys_umask, "umask"},
        [SYS_chmod] = {(syscall_t)sys_chmod, "chmod"},
        [SYS_lseek] = {(syscall_t)sys_lseek, "lseek"},
        [SYS_link] = {(syscall_t)sys_link, "link"},
        [SYS_unlink] = {(syscall_t)sys_unlink, "unlink"},
        [SYS_symlink] = {(syscall_t)sys_symlink, "symlink"},
        [SYS_readlink] = {(syscall_t)sys_readlink, "readlink"},
        [SYS_chdir] = {(syscall_t)sys_chdir, "chdir"},
        [SYS_getcwd] = {(syscall_t)sys_getcwd, "getcwd"},
        [SYS_mkdir] = {(syscall_t)sys_mkdir, "mkdri"},
        [SYS_rmdir] = {(syscall_t)sys_rmdir, "rmdir"},
        [SYS_gettimeofday] = {(syscall_t)sys_gettimeofday, "gettime"},
        [SYS_tcgetattr] = {(syscall_t)sys_tcgetattr, "tcgetattr"},
        [SYS_tcsetattr] = {(syscall_t)sys_tcsetattr, "tcsetattr"},
        [SYS_setuid] = {(syscall_t)sys_setuid, "setuid"},
        [SYS_setgid] = {(syscall_t)sys_setgid, "setgid"}
};

/* Executes the given syscall.
 *
 * Note tf is passed in, which points to the tf of the context on the kernel
 * stack.  If any syscall needs to block, it needs to save this info, as well as
 * any silly state.
 * 
 * This syscall function is used by both local syscall and arsc, and should
 * remain oblivious of the caller. */
intreg_t syscall(struct proc *p, uintreg_t sc_num, uintreg_t a0, uintreg_t a1,
                 uintreg_t a2, uintreg_t a3, uintreg_t a4, uintreg_t a5)
{
        const int max_syscall = sizeof(syscall_table)/sizeof(syscall_table[0]);

        uint32_t coreid, vcoreid;
        if (systrace_flags & SYSTRACE_ON) {
                if ((systrace_flags & SYSTRACE_ALLPROC) || (proc_is_traced(p))) {
                        coreid = core_id();
                        vcoreid = proc_get_vcoreid(p, coreid);
                        if (systrace_flags & SYSTRACE_LOUD) {
                                printk("[%16llu] Syscall %3d (%12s):(%08p, %08p, %08p, %08p, "
                                       "%08p, %08p) proc: %d core: %d vcore: %d\n", read_tsc(),
                                       sc_num, syscall_table[sc_num].name, a0, a1, a2, a3,
                                       a4, a5, p->pid, coreid, vcoreid);
                        } else {
                                struct systrace_record *trace;
                                uintptr_t idx, new_idx;
                                do {
                                        idx = systrace_bufidx;
                                        new_idx = (idx + 1) % systrace_bufsize;
                                } while (!atomic_cas_u32(&systrace_bufidx, idx, new_idx));
                                trace = &systrace_buffer[idx];
                                trace->timestamp = read_tsc();
                                trace->syscallno = sc_num;
                                trace->arg0 = a0;
                                trace->arg1 = a1;
                                trace->arg2 = a2;
                                trace->arg3 = a3;
                                trace->arg4 = a4;
                                trace->arg5 = a5;
                                trace->pid = p->pid;
                                trace->coreid = coreid;
                                trace->vcoreid = vcoreid;
                        }
                }
        }
        if (sc_num > max_syscall || syscall_table[sc_num].call == NULL)
                panic("Invalid syscall number %d for proc %x!", sc_num, p);

        return syscall_table[sc_num].call(p, a0, a1, a2, a3, a4, a5);
}

/* Execute the syscall on the local core */
void run_local_syscall(struct syscall *sysc)
{
        struct per_cpu_info *pcpui = &per_cpu_info[core_id()];

        /* TODO: (UMEM) assert / pin the memory for the sysc */
        user_mem_assert(pcpui->cur_proc, sysc, sizeof(struct syscall),
                        sizeof(uintptr_t), PTE_USER_RW);
        pcpui->cur_sysc = sysc;                 /* let the core know which sysc it is */
        sysc->retval = syscall(pcpui->cur_proc, sysc->num, sysc->arg0, sysc->arg1,
                               sysc->arg2, sysc->arg3, sysc->arg4, sysc->arg5);
        /* Need to re-load pcpui, in case we migrated */
        pcpui = &per_cpu_info[core_id()];
        finish_sysc(sysc, pcpui->cur_proc);
        /* Can unpin (UMEM) at this point */
        pcpui->cur_sysc = 0;    /* no longer working on sysc */
}

/* A process can trap and call this function, which will set up the core to
 * handle all the syscalls.  a.k.a. "sys_debutante(needs, wants)".  If there is
 * at least one, it will run it directly. */
void prep_syscalls(struct proc *p, struct syscall *sysc, unsigned int nr_syscs)
{
        int retval;
        /* Careful with pcpui here, we could have migrated */
        if (!nr_syscs)
                return;
        /* For all after the first call, send ourselves a KMSG (TODO). */
        if (nr_syscs != 1)
                warn("Only one supported (Debutante calls: %d)\n", nr_syscs);
        /* Call the first one directly.  (we already checked to make sure there is
         * 1) */
        run_local_syscall(sysc);
}

/* Call this when something happens on the syscall where userspace might want to
 * get signaled.  Passing p, since the caller should know who the syscall
 * belongs to (probably is current). 
 *
 * You need to have SC_K_LOCK set when you call this. */
void __signal_syscall(struct syscall *sysc, struct proc *p)
{
        struct event_queue *ev_q;
        struct event_msg local_msg;
        /* User sets the ev_q then atomically sets the flag (races with SC_DONE) */
        if (atomic_read(&sysc->flags) & SC_UEVENT) {
                rmb();
                ev_q = sysc->ev_q;
                if (ev_q) {
                        memset(&local_msg, 0, sizeof(struct event_msg));
                        local_msg.ev_type = EV_SYSCALL;
                        local_msg.ev_arg3 = sysc;
                        send_event(p, ev_q, &local_msg, 0);
                }
        }
}

/* Syscall tracing */
static void __init_systrace(void)
{
        systrace_buffer = kmalloc(MAX_SYSTRACES*sizeof(struct systrace_record), 0);
        if (!systrace_buffer)
                panic("Unable to alloc a trace buffer\n");
        systrace_bufidx = 0;
        systrace_bufsize = MAX_SYSTRACES;
        /* Note we never free the buffer - it's around forever.  Feel free to change
         * this if you want to change the size or something dynamically. */
}

/* If you call this while it is running, it will change the mode */
void systrace_start(bool silent)
{
        static bool init = FALSE;
        spin_lock_irqsave(&systrace_lock);
        if (!init) {
                __init_systrace();
                init = TRUE;
        }
        systrace_flags = silent ? SYSTRACE_ON : SYSTRACE_ON | SYSTRACE_LOUD; 
        spin_unlock_irqsave(&systrace_lock);
}

int systrace_reg(bool all, struct proc *p)
{
        int retval = 0;
        spin_lock_irqsave(&systrace_lock);
        if (all) {
                printk("Tracing syscalls for all processes\n");
                systrace_flags |= SYSTRACE_ALLPROC;
                retval = 0;
        } else {
                for (int i = 0; i < MAX_NUM_TRACED; i++) {
                        if (!systrace_procs[i]) {
                                printk("Tracing syscalls for process %d\n", p->pid);
                                systrace_procs[i] = p;
                                retval = 0;
                                break;
                        }
                }
        }
        spin_unlock_irqsave(&systrace_lock);
        return retval;
}

void systrace_stop(void)
{
        spin_lock_irqsave(&systrace_lock);
        systrace_flags = 0;
        for (int i = 0; i < MAX_NUM_TRACED; i++)
                systrace_procs[i] = 0;
        spin_unlock_irqsave(&systrace_lock);
}

/* If you registered a process specifically, then you need to dereg it
 * specifically.  Or just fully stop, which will do it for all. */
int systrace_dereg(bool all, struct proc *p)
{
        spin_lock_irqsave(&systrace_lock);
        if (all) {
                printk("No longer tracing syscalls for all processes.\n");
                systrace_flags &= ~SYSTRACE_ALLPROC;
        } else {
                for (int i = 0; i < MAX_NUM_TRACED; i++) {
                        if (systrace_procs[i] == p) {
                                systrace_procs[i] = 0;
                                printk("No longer tracing syscalls for process %d\n", p->pid);
                        }
                }
        }
        spin_unlock_irqsave(&systrace_lock);
        return 0;
}

/* Regardless of locking, someone could be writing into the buffer */
void systrace_print(bool all, struct proc *p)
{
        spin_lock_irqsave(&systrace_lock);
        /* if you want to be clever, you could make this start from the earliest
         * timestamp and loop around.  Careful of concurrent writes. */
        for (int i = 0; i < systrace_bufsize; i++)
                if (systrace_buffer[i].timestamp)
                        printk("[%16llu] Syscall %3d (%12s):(%08p, %08p, %08p, %08p, %08p,"
                               "%08p) proc: %d core: %d vcore: %d\n",
                               systrace_buffer[i].timestamp,
                               systrace_buffer[i].syscallno,
                               syscall_table[systrace_buffer[i].syscallno].name,
                               systrace_buffer[i].arg0,
                               systrace_buffer[i].arg1,
                               systrace_buffer[i].arg2,
                               systrace_buffer[i].arg3,
                               systrace_buffer[i].arg4,
                               systrace_buffer[i].arg5,
                               systrace_buffer[i].pid,
                               systrace_buffer[i].coreid,
                               systrace_buffer[i].vcoreid);
        spin_unlock_irqsave(&systrace_lock);
}

void systrace_clear_buffer(void)
{
        spin_lock_irqsave(&systrace_lock);
        memset(systrace_buffer, 0, sizeof(struct systrace_record) * MAX_SYSTRACES);
        spin_unlock_irqsave(&systrace_lock);
}