move init fully to proc. remove init pages prealloc. prepare for scheduling

27 files changed, 275 insertions, 57 deletions

diff --git a/api/error.h b/api/error.h
index de7d4b2..af85bd9 100644
--- a/api/error.h
+++ b/api/error.h
@@ -18,5 +18,8 @@
 #define EOVERFLOW 15
 #define EBADCALL 16
 #define EPERM 17
+#define EBADPROC 18
+#define ENOMAIL 19
+#define ETIMEOUT 20
 
 #endif
diff --git a/api/process.h b/api/process.h
new file mode 100644
index 0000000..080e001
--- /dev/null
+++ b/api/process.h
@@ -0,0 +1,8 @@
+#ifndef _JOVE_API_PROCESS_H
+#define _JOVE_API_PROCESS_H 1
+
+#include <stdint.h>
+
+typedef intmax_t pid_t;
+
+#endif
diff --git a/api/syscall.h b/api/syscall.h
index a116177..2502621 100644
--- a/api/syscall.h
+++ b/api/syscall.h
@@ -4,6 +4,7 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include "process.h"
 #include "obj.h"
 
 /* General syscall behavior:
@@ -123,6 +124,45 @@ struct syscall_pagedir_unmap
     objpath_part_t none_path[];
 };
 
+/**JOVE_OBJ_PCB syscalls.
+ * */
+
+enum
+{
+    _SYSCALL_PCB_NONE = 0,
+    SYSCALL_PCB_YIELD,
+    SYSCALL_PCB_SEND,
+    SYSCALL_PCB_RECV
+};
+
+#define SYSCALL_PERM_PCB_YIELD (JOVE_PERM_WRITE)
+#define SYSCALL_PERM_PCB_SEND (JOVE_PERM_MUTATE)
+#define SYSCALL_PERM_PCB_RECV (JOVE_PERM_MUTATE)
+
+#define SYSCALL_PERM_PCB_SEND_TGT (JOVE_PERM_MUTATE)
+#define SYSCALL_PERM_PCB_RECV_DST (JOVE_PERM_MUTATE)
+
+struct syscall_pcb_yield 
+{
+    pid_t yield_target;
+};
+
+struct syscall_pcb_send
+{
+    pid_t send_target;
+    uintmax_t send_timeout;
+    uint16_t send_path_length;
+    objpath_part_t send_path[];
+};
+
+struct syscall_pcb_recv
+{
+    pid_t recv_target;
+    uintmax_t recv_timeout;
+    uint16_t recv_path_length;
+    objpath_part_t recv_path[];
+};
+
 /**JOVE_OBJ_INITRD_FILE syscalls
  * */
 
diff --git a/arch/x86_64/hal/paging.c b/arch/x86_64/hal/paging.c
index 408b5d5..a0d6ca9 100644
--- a/arch/x86_64/hal/paging.c
+++ b/arch/x86_64/hal/paging.c
@@ -2,7 +2,7 @@
 #include "arch/x86_64/x86_64.h"
 #include "hal/memory.h"
 #include "jove.h"
-#include "init.h"
+#include "proc/init.h"
 #include "config.h"
 #include "hal/obj.h"
 #include "lib/string.h"
diff --git a/arch/x86_64/hal/serial_com.c b/arch/x86_64/hal/serial_com.c
index 8454c8a..343d2ae 100644
--- a/arch/x86_64/hal/serial_com.c
+++ b/arch/x86_64/hal/serial_com.c
@@ -2,7 +2,7 @@
 #include "port.h"
 #include "jove.h"
 #include "hal/obj.h"
-#include "init.h"
+#include "proc/init.h"
 #include "lib/printf.h"
 
 static int
diff --git a/arch/x86_64/hal/smp.c b/arch/x86_64/hal/smp.c
index 4c79d79..b894eb9 100644
--- a/arch/x86_64/hal/smp.c
+++ b/arch/x86_64/hal/smp.c
@@ -1,5 +1,5 @@
 #include "smp.h"
-#include "init.h"
+#include "proc/init.h"
 #include "config.h"
 #include "jove.h"
 #include "paging.h"
diff --git a/arch/x86_64/lib/printf.c b/arch/x86_64/lib/printf.c
index f60b943..794a592 100644
--- a/arch/x86_64/lib/printf.c
+++ b/arch/x86_64/lib/printf.c
@@ -1,7 +1,7 @@
 #include "../hal/serial_com.h"
 #include "lib/printf.h"
 #include "lib/virtterm.h"
-#include "init.h"
+#include "proc/init.h"
 
 int
 kvprintf(const char *fmt, va_list ap)
diff --git a/arch/x86_64/main.c b/arch/x86_64/main.c
index f5a9d39..92f9fe1 100644
--- a/arch/x86_64/main.c
+++ b/arch/x86_64/main.c
@@ -1,6 +1,6 @@
 #include "api/init.h"
 #include "jove.h"
-#include "init.h"
+#include "proc/init.h"
 #include "lib/string.h"
 #include "lib/printf.h"
 #include "lib/virtterm.h"
diff --git a/arch/x86_64/proc/init.c b/arch/x86_64/proc/init.c
index be1d556..3787c7b 100644
--- a/arch/x86_64/proc/init.c
+++ b/arch/x86_64/proc/init.c
@@ -1,4 +1,4 @@
-#include "init.h"
+#include "proc/init.h"
 #include "arch/x86_64/hal/msr.h"
 #include "config.h"
 #include "proc/process.h"
@@ -12,10 +12,6 @@
 #include "boot/cmdline.h"
 #include "boot/initrd.h"
 
-PAGEALIGN static uint8_t s_init_program_pages[INIT_PROGRAM_PAGES_MAX][0x1000];
-PAGEALIGN static uint8_t s_init_stack_pages[INIT_STACK_PAGES + 3][0x1000];
-PAGEALIGN static uint8_t s_init_message_page[0x1000];
-
 static int
 elf_is_valid(struct elf_header *ehdr)
 {
@@ -78,7 +74,6 @@ init_setup(void)
     size_t last_base = 0;
 
     //Load the init ELF
-    size_t last_page = 0;
     for(size_t i = 0; i < init_ehdr->e_phnum; i++) {
         struct elf_phdr *phdr = init_data + init_ehdr->e_phoff + i * init_ehdr->e_phentsize;
         if(phdr->p_type != PT_LOAD) continue;
@@ -93,18 +88,15 @@ init_setup(void)
 
         for(size_t i = 0; i < pages; i++) {
             uintptr_t page_virt = page_base + (i << 12);
-            if(last_page >= INIT_PROGRAM_PAGES_MAX) {
-                kpanic("Program exceeds size limit! (%i > %i)\n", last_page, INIT_PROGRAM_PAGES_MAX);
-            }
 
             int tblres = 0;
+            jove_owned_obj_t page_frame;
             do {
-                uintptr_t tbl_frame = KPTR_TOPHYS(&s_init_program_pages[last_page++]);
-                tblres = pagedir_map_table(pml4, tbl_frame, page_virt);
-                if(tblres == EHASMAP) last_page--;
-            }while(!tblres);
+                page_frame = init_pop_alloc();
+                tblres = pagedir_map_table(pml4, obj_getvalue(&page_frame), page_virt);
+            }while(tblres == 0);
 
-            pagedir_map_frame(pml4, KPTR_TOPHYS(&s_init_program_pages[last_page++]), page_virt,
+            pagedir_map_frame(pml4, obj_getvalue(&page_frame), page_virt,
                               PAGE_WRITEABLE | PAGE_USER);
         }
 
@@ -116,25 +108,24 @@ init_setup(void)
     size_t stack_base = 0x00007FFFFFFFF000;
     int stack_mapres = 0;
 
-    last_page = 0;
     for(size_t i = 0; i < INIT_STACK_PAGES; i++) {
         uintptr_t page_virt = stack_base - (i << 12);
         int tblres = 0;
 
+        jove_owned_obj_t page_frame;
         do {
-            uintptr_t tbl_frame = KPTR_TOPHYS(&s_init_stack_pages[last_page++]);
-            tblres = pagedir_map_table(pml4, tbl_frame, page_virt);
-            if(tblres == EHASMAP) last_page--;
+            page_frame = init_pop_alloc();
+            tblres = pagedir_map_table(pml4, obj_getvalue(&page_frame), page_virt);
         }while(!tblres);
 
-        pagedir_map_frame(pml4, KPTR_TOPHYS(&s_init_stack_pages[last_page++]), page_virt,
+        pagedir_map_frame(pml4, obj_getvalue(&page_frame), page_virt,
                           PAGE_WRITEABLE | PAGE_USER | PAGE_XD);
     }
 
     //Map the syscall message.
     last_base = (last_base + 0xFFF) & ~0xFFF;
-    uintptr_t message_pptr = KPTR_TOPHYS(s_init_message_page);
-    pagedir_map_frame(pml4, message_pptr, last_base,
+    jove_owned_obj_t message_frame = init_pop_alloc();
+    pagedir_map_frame(pml4, obj_getvalue(&message_frame), last_base,
                       PAGE_WRITEABLE | PAGE_USER | PAGE_XD);
 
     extern struct init_payload _init_payload;
diff --git a/arch/x86_64/proc/process.c b/arch/x86_64/proc/process.c
index 6165585..d5513bc 100644
--- a/arch/x86_64/proc/process.c
+++ b/arch/x86_64/proc/process.c
@@ -6,7 +6,7 @@
 #include "hal/obj.h"
 #include "hal/smp.h"
 #include "lib/string.h"
-#include "init.h"
+#include "proc/init.h"
 #include "jove.h"
 
 PAGEALIGN uint8_t s_init_iopb[0x2000];
@@ -28,6 +28,8 @@ processing_setup(void (*process_main))
     init_pcb->header.pagedir = obj_release(objdir_getlocal(_rootdir_obj, ROOTDIR_PAGEDIR_I));
 
     init_pcb->header.pid = 1;
+    init_pcb->header.state = PCB_STATE_RUNNING;
+
     init_pcb->ksp = (void*)ksp;
 
     jove_owned_obj_t *iopb_obj = objdir_getlocal(_rootdir_obj, ROOTDIR_IOPB_I);
diff --git a/arch/x86_64/proc/process.h b/arch/x86_64/proc/process.h
index 534c8d5..6a0aa96 100644
--- a/arch/x86_64/proc/process.h
+++ b/arch/x86_64/proc/process.h
@@ -8,13 +8,10 @@
 typedef struct process_control_block
 {
     struct pcb_expected_header header;
-    struct process_control_block *sched_next;
 
     jove_obj_t *iopb;
 
-    enum pcb_state state;
     int killed;
-    struct pcb_mailbox send, recv;
     
     struct cpu_context context;
     void *ksp;
diff --git a/boot/initrd.c b/boot/initrd.c
index e1a7ec3..f9bf47e 100644
--- a/boot/initrd.c
+++ b/boot/initrd.c
@@ -1,6 +1,6 @@
 #include "initrd.h"
 #include "arch/x86_64/hal/obj.h"
-#include "init.h"
+#include "proc/init.h"
 #include "jove.h"
 #include "lib/printf.h"
 #include "lib/tar.h"
diff --git a/boot/limine/framebuffer.c b/boot/limine/framebuffer.c
index 3758167..87b124a 100644
--- a/boot/limine/framebuffer.c
+++ b/boot/limine/framebuffer.c
@@ -2,7 +2,7 @@
 #include "jove.h"
 #include "lib/printf.h"
 #include "limine.h"
-#include "init.h"
+#include "proc/init.h"
 #include "hal/framebuffer.h"
 
 extern struct limine_framebuffer_response *_limine_framebuffers;
diff --git a/boot/limine/memorymap.c b/boot/limine/memorymap.c
index c6a9064..b90f176 100644
--- a/boot/limine/memorymap.c
+++ b/boot/limine/memorymap.c
@@ -4,7 +4,7 @@
 #include "hal/memory.h"
 #include "hal/obj.h"
 #include "panic/panic.h"
-#include "init.h"
+#include "proc/init.h"
 #include "lib/printf.h"
 
 extern struct limine_memmap_response *_limine_memmap_resp;
diff --git a/config.h b/config.h
index 498a842..c732d01 100644
--- a/config.h
+++ b/config.h
@@ -11,7 +11,6 @@
 #define FRAMEBUFFER_MAX_WIDTH 1920
 #define FRAMEBUFFER_MAX_HEIGHT 1080
 
-#define INIT_PROGRAM_PAGES_MAX 96
 #define INIT_STACK_PAGES 2
 
 #define LOCKSTACK_MAX 64
diff --git a/doc/syscall.md b/doc/syscall.md
index 4fd55ad..1e03425 100644
--- a/doc/syscall.md
+++ b/doc/syscall.md
@@ -95,9 +95,11 @@ If the untyped path does not point to a `JOVE_OBJ_NONE` object, the kernel will
 
 ### JOVE_OBJ_OBJDIR
 
-| Syscall                | Permissions Required |
-|------------------------|----------------------|
-| SYSCALL_OBJDIR_OBJTYPE | JOVE_PERM_READ       |
+| Syscall                | Target Permissions                   |
+|------------------------|--------------------------------------|
+| SYSCALL_OBJDIR_OBJTYPE | JOVE_PERM_READ                       |
+| SYSCALL_OBJDIR_UNTYPE  | JOVE_PERM_WRITE <br>JOVE_PERM_MUTATE |
+| SYSCALL_OBJDIR_SEND    | JOVE_PERM_MUTATE                     |
 
 #### SYSCALL_OBJDIR_OBJTYPE
 
@@ -111,6 +113,18 @@ If the message is too small to hold the payload, the kernel will return `-ETOOSM
 
 If the entry index exceeds `JOVE_OBJDIR_ENTRIES`, the kernel returns `-EOOB`.
 
+#### SYSCALL_OBJDIR_UNTYPE
+
+Converts the target object to an untyped object if possible.
+
+| Data         | Entry Index |
+|--------------|-------------|
+| Size (bytes) |      2      |
+
+If the target object does not have underlying memory, the kernel will replace the object with `JOVE_OBJ_NONE`.
+
+If the target object has underlying memory, the kernel will replace the object with `JOVE_OBJ_UNTYPED`.
+
 
 ### JOVE_OBJ_PAGEDIR
 
@@ -263,6 +277,76 @@ If the page frame pointed to by virtual address does not correspond to a shared
 
 Successful unmapping returns `0`.
 
+### JOVE_OBJ_PCB
+
+| Syscall           | Target Permissions | Subject Permissions |
+|-------------------|--------------------|---------------------|
+| SYSCALL_PCB_YIELD | JOVE_PERM_WRITE    |                     |
+| SYSCALL_PCB_SEND  | JOVE_PERM_MUTATE   | JOVE_PERM_MUTATE    |
+| SYSCALL_PCB_RECV  | JOVE_PERM_MUTATE   | JOVE_PERM_MUTATE    |
+
+#### SYSCALL_PCB_YIELD
+
+Yields control to the specified process.
+
+| Data         | Yield target  |
+|--------------|---------------|
+| Size (bytes) | sizeof(pid_t) |
+
+If the yield target = `0`, the scheduler will determine the next process.
+
+If the yield target does not exist, the kernel will return `-ENOPROC`.
+
+#### SYSCALL_PCB_SEND
+
+Attempts to send the target object to a process specified by destination process.
+
+If blocking timeout is zero, then the process will wait for the destination process to recieve the object forever.
+
+If the blocking timeout is non-zero, then the process will wait for the destination process to recieve the object for the specified number of scheduler ticks.
+
+| Data         | Destination Process | Blocking Timeout  | Send Path Length | Send Path            |
+|--------------|---------------------|-------------------|------------------|----------------------|
+| Size (bytes) |    sizeof(pid_t)    | sizeof(uintmax_t) |         2        | 2 * send_path_length |
+
+While the object is being sent, the kernel will lock the object and copy a pointer to it into the send mailbox.
+
+If the target path does not represent a valid object, the kernel will return `-EBADPATH`.
+
+If the target path represents a `JOVE_OBJ_NONE` object, the kernel will return `-EBADOBJ`.
+
+If the target object does not have the `JOVE_PERM_MUTATE` permission, the kernel will return `-EPERM`.
+
+If the destination process does not represent a valid process, the kernel will return `-EBADPROC`.
+
+If the blocking timeout expires and the message was not sent, the kernel will return `-ETIMEOUT`.
+
+If the send is successful, the sent object is replaced by a `JOVE_OBJ_NONE` object and the kernel will return 0.
+
+#### SYSCALL_PCB_RECV
+
+Recieves kernel objects from the PCB mailbox.
+
+If a sender is specified, then the mailbox will only accept mail from that specific sender.
+
+Blocks on recieve until blocking timeout expires or forever if blocking timeout was zero.
+
+Destination object is locked until the timeout expires or an object is placed in the destination path.
+
+| Data         | Sending Process | Blocking Timeout  | Dest Path Length | Dest path         |
+|--------------|-----------------|-------------------|------------------|-------------------|
+| Size (bytes) |  sizeof(pid_t)  | sizeof(uintmax_t) |         2        | 2 * dest_path_len |
+
+If the specified pid does not correspond to a process, the kernel will return `-ENOPROC`.
+
+If the destination path does not correspond to a `JOVE_OBJ_NONE` object, the kernel will return `-EFULL`.
+
+If the destination path does not have the `JOVE_PERM_MUTATE` permission, the kernel will return `-EPERM`.
+
+Recieved messages will be sent to the specified destination path.
+
+Successful retrieval returns `0`.
+
 ### JOVE_OBJ_INITRD_FILE
 
 | Syscall                  | Target Permissions |
diff --git a/hal/untyped.c b/hal/untyped.c
index 6957175..ca69228 100644
--- a/hal/untyped.c
+++ b/hal/untyped.c
@@ -18,7 +18,7 @@ int
 untyped_split(jove_owned_obj_t *tgt, jove_owned_obj_t *dst, size_t bytes)
 {
     jove_untyped_t *tgt_untyped = obj_deref(tgt);
-    if(tgt_untyped->limit - bytes < JOVE_UNTYPED_MINSIZE) return ETOOSMALL;
+    if(tgt_untyped->limit - bytes < JOVE_UNTYPED_MINSIZE) return -ETOOSMALL;
 
     tgt_untyped->limit -= bytes;
     obj_settype(dst, JOVE_OBJ_UNTYPED);
@@ -35,7 +35,7 @@ untyped_merge(jove_owned_obj_t *a, jove_owned_obj_t *b)
     jove_untyped_t *a_untyped = obj_deref(a);
     jove_untyped_t *b_untyped = obj_deref(b);
     if((uintptr_t)a_untyped + a_untyped->limit == (uintptr_t)b_untyped) {
-        return EBADARG;
+        return -EBADARG;
     }
     if((uintptr_t)b_untyped + b_untyped->limit == (uintptr_t)a_untyped) {
         return untyped_merge(b, a);
diff --git a/lib/errstr.c b/lib/errstr.c
index 6c4425d..d4aed8a 100644
--- a/lib/errstr.c
+++ b/lib/errstr.c
@@ -15,7 +15,15 @@ errstr(int err)
         [EHASMAP] = "HAS MAP",
         [EALIGN] = "ALIGNMENT ERROR",
         [EEXIST] = "ALREADY EXISTS",
-        [EBUSY] = "RESOURCE BUSY"
+        [EBUSY] = "RESOURCE BUSY",
+        [EEMPTY] = "EMPTY",
+        [EFULL] = "FULL",
+        [EOVERFLOW] = "OVERFLOW",
+        [EBADCALL] = "BAD CALL",
+        [EPERM] = "NO PERMISSION",
+        [EBADPROC] = "INVALID PROCESS",
+        [ENOMAIL] = "NO MAIL",
+        [ETIMEOUT] = "TIMEOUT"
     };
     if(err >= sizeof(errstrs) / sizeof(const char*)) {
         return "UNKNOWN ERROR";
diff --git a/lib/printf.c b/lib/printf.c
index 0a9cc15..7fa681e 100644
--- a/lib/printf.c
+++ b/lib/printf.c
@@ -1,6 +1,6 @@
 #include "printf.h"
 #include "string.h"
-#include "init.h"
+#include "proc/init.h"
 #include "hal/obj.h"
 #include <stdint.h>
 
diff --git a/lib/virtterm.c b/lib/virtterm.c
index 0daa921..8518530 100644
--- a/lib/virtterm.c
+++ b/lib/virtterm.c
@@ -2,7 +2,7 @@
 #include "boot/cmdline.h"
 #include "boot/initrd.h"
 #include "hal/obj.h"
-#include "init.h"
+#include "proc/init.h"
 #include "jove.h"
 #include "hal/framebuffer.h"
 #include "lib/printf.h"
diff --git a/proc/init.c b/proc/init.c
new file mode 100644
index 0000000..65299f4
--- /dev/null
+++ b/proc/init.c
@@ -0,0 +1,34 @@
+#include "init.h"
+#include "hal/memory.h"
+#include "panic/panic.h"
+
+objpath_part_t s_last_untyped = JOVE_OBJDIR_ENTRIES-1;
+
+jove_owned_obj_t
+init_pop_alloc(void)
+{
+    jove_owned_obj_t *untyped_dir = objdir_trygetlocal(_rootdir_obj, ROOTDIR_UNTYPED_I);
+    if(untyped_dir == 0) {
+        kpanic("Untyped directory is locked!\n");
+    }
+    int cycles = 0;
+
+    while(cycles++ < 512) {
+        if(objdir_peeklocal(untyped_dir, s_last_untyped).type != JOVE_OBJ_UNTYPED) {
+            s_last_untyped--;
+            continue;
+        }
+
+        jove_owned_obj_t frame = { 0 };
+        jove_owned_obj_t *untyped = objdir_getlocal(untyped_dir, s_last_untyped);
+
+        if(untyped_split(untyped, &frame, 0x1000) < 0) {
+            kpanic("%s: Failed to split last untyped.\n", __func__);
+        }
+
+        obj_release(untyped);
+        obj_release(untyped_dir);
+        return frame;
+    }
+    kpanic("%s: Kernel is out of memory!\n", __func__);
+}
diff --git a/init.h b/proc/init.h
index b80d1fa..910e2c9 100644
--- a/init.h
+++ b/proc/init.h
@@ -2,9 +2,13 @@
 #define _JOVE_INIT_H 1
 
 #include "api/init.h"
+#include "hal/obj.h"
 
 extern void *_rootdir_obj;
+extern struct init_payload _init_payload;
 
 void init_setup(void);
 
+jove_owned_obj_t init_pop_alloc(void);
+
 #endif
diff --git a/proc/process.c b/proc/process.c
index 55737f6..e811cb6 100644
--- a/proc/process.c
+++ b/proc/process.c
@@ -14,13 +14,25 @@ pcb_getpid(pcb_t *pcb)
 }
 
 jove_obj_t*
-pcb_rootdir(pcb_t *pcb)
+pcb_getrootdir(pcb_t *pcb)
 {
     return ((struct pcb_expected_header*)pcb)->rootdir;
 }
 
 jove_obj_t*
-pcb_pagedir(pcb_t *pcb)
+pcb_getpagedir(pcb_t *pcb)
 {
     return ((struct pcb_expected_header*)pcb)->pagedir;
 }
+
+enum pcb_state 
+pcb_getstate(pcb_t *pcb)
+{
+    return ((struct pcb_expected_header*)pcb)->state;
+}
+
+intmax_t 
+pcb_getstatecode(pcb_t *pcb)
+{
+    return ((struct pcb_expected_header*)pcb)->state_code;
+}
diff --git a/proc/process.h b/proc/process.h
index 2757f6f..ed40a4f 100644
--- a/proc/process.h
+++ b/proc/process.h
@@ -3,12 +3,16 @@
 
 #include "hal/obj.h"
 #include "lib/rbtree.h"
-
-typedef uintmax_t pid_t;
+#include "api/process.h"
 
 enum pcb_state
 {
-    PCB_DEAD, PCB_READY, PCB_RUNNING, PCB_BLOCKED
+    _PCB_STATE_INVALID = 0,
+    PCB_STATE_DEAD, 
+    PCB_STATE_READY, 
+    PCB_STATE_RUNNING, 
+    PCB_STATE_WAITING, 
+    PCB_STATE_BLOCKED_MAIL
 };
 
 struct pcb_mailbox
@@ -20,11 +24,16 @@ struct pcb_mailbox
 struct pcb_expected_header
 {
     struct rbtree_node tree_node;
-    struct process_control_block *sched_next;
+    struct pcb_expected_header *sched_next;
 
     pid_t pid;
     jove_obj_t *rootdir;
     jove_obj_t *pagedir;
+    
+    enum pcb_state state;
+    intmax_t state_code;
+
+    struct pcb_mailbox send, recv;
 };
 
 typedef struct process_control_block pcb_t;
@@ -32,12 +41,12 @@ typedef struct process_control_block pcb_t;
 jove_owned_obj_t *process_current(void);
 
 void pcb_new(pcb_t *pcb);
-/*Returns the process ID of the passed PCB. */
-pid_t pcb_getpid(pcb_t *pcb);
-/*Returns the root kernel object directory of this PCB. */
-jove_obj_t *pcb_rootdir(pcb_t *pcb);
 
-jove_obj_t *pcb_pagedir(pcb_t *pcb);
+pid_t pcb_getpid(pcb_t *pcb);
+jove_obj_t *pcb_getrootdir(pcb_t *pcb);
+jove_obj_t *pcb_getpagedir(pcb_t *pcb);
+enum pcb_state pcb_getstate(pcb_t *pcb);
+intmax_t pcb_getstatecode(pcb_t *pcb);
 
 extern pcb_t *pcb_tree;
 
diff --git a/sys/syscall.c b/sys/syscall.c
index 7207708..54d5468 100644
--- a/sys/syscall.c
+++ b/sys/syscall.c
@@ -38,7 +38,7 @@ static const syscall_handle_t s_syscall_handles[128] = {
     [JOVE_OBJ_PAGEDIR] = _syscall_handle_pagedir,
     [JOVE_OBJ_PROCESSOR] = _syscall_handle_generic,
     [JOVE_OBJ_SHMEMORY] = _syscall_handle_generic,
-    [JOVE_OBJ_PCB] = _syscall_handle_generic,
+    [JOVE_OBJ_PCB] = _syscall_handle_pcb,
     [JOVE_OBJ_INT_HANDLE] = _syscall_handle_generic,
     [JOVE_OBJ_INITRD_FILE] = _syscall_handle_initrd_file,
     [JOVE_OBJ_FRAMEBUFFER] = _syscall_handle_generic,
@@ -86,7 +86,7 @@ syscall_handler(uintmax_t message_path_raw, uint16_t message_pathlen)
 
     ctx.pcb = process_current();
     pcb_t *pcb = obj_deref(ctx.pcb);
-    ctx.objdir = lockstack_push(&ctx.lockstack, obj_take(pcb_rootdir(pcb)));
+    ctx.objdir = lockstack_push(&ctx.lockstack, obj_take(pcb_getrootdir(pcb)));
 
     ctx.message = link_try_traverse_objdir(
             ctx.objdir, &ctx.lockstack, message_pathlen, message_path);
@@ -113,7 +113,7 @@ syscall_handler(uintmax_t message_path_raw, uint16_t message_pathlen)
     }
 
     uintptr_t message_vptr = message_unmap(ctx.message.obj,
-            (jove_owned_obj_t*)pcb_pagedir(pcb));
+            (jove_owned_obj_t*)pcb_getpagedir(pcb));
 
     size_t messagelen = 0x1000;
     void *messagedata = (void*)message_getdata(ctx.message.obj);
@@ -154,7 +154,7 @@ syscall_handler(uintmax_t message_path_raw, uint16_t message_pathlen)
     }
 
 remap_return:
-    message_remap(ctx.message.obj, (jove_owned_obj_t*)pcb_pagedir(pcb), message_vptr);
+    message_remap(ctx.message.obj, (jove_owned_obj_t*)pcb_getpagedir(pcb), message_vptr);
 
 release_return:
     lockstack_popall(&ctx.lockstack);
diff --git a/sys/syscall.h b/sys/syscall.h
index 461b104..082fe29 100644
--- a/sys/syscall.h
+++ b/sys/syscall.h
@@ -57,6 +57,7 @@ int _syscall_handle_vtt(syscall_context_t *ctx);
 int _syscall_handle_objdir(syscall_context_t *ctx);
 int _syscall_handle_untyped(syscall_context_t *ctx);
 int _syscall_handle_pagedir(syscall_context_t *ctx);
+int _syscall_handle_pcb(syscall_context_t *ctx);
 int _syscall_handle_initrd_file(syscall_context_t *ctx);
 int _syscall_handle_message(syscall_context_t *ctx);
 
diff --git a/sys/syscall_pcb.c b/sys/syscall_pcb.c
new file mode 100644
index 0000000..b77be95
--- /dev/null
+++ b/sys/syscall_pcb.c
@@ -0,0 +1,26 @@
+#include "api/error.h"
+#include "lib/printf.h"
+#include "syscall.h"
+
+int
+s_syscall_pcb_yield(jove_owned_obj_t *pcb_obj,
+        size_t bytes_left,
+        void *payload_data)
+{
+    kprintf("%s: Stub!\n", __func__);
+    return 0;
+}
+
+int
+_syscall_handle_pcb(syscall_context_t *ctx)
+{
+    switch(ctx->header->callid) {
+        case SYSCALL_PCB_YIELD:
+            if(ctx->target.permissions & SYSCALL_PERM_PCB_YIELD)
+                return s_syscall_pcb_yield(ctx->target.obj, ctx->bytes_left, ctx->payload);
+            return -EPERM;
+
+        default:
+            return -EBADCALL;
+    }
+}