kern: proc: Add initialization code for ring 3

This commit introduces several new functions for switching the processor
into a ring three context along with its task's respective process
descriptors to be implemented correctly.

- Add md_set_ip() to update proc instruction pointer
- Add stack definitions
- Add stack mapping logic
...

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/sys/include/sys/proc.h b/src/sys/include/sys/proc.h
index deed09b..d09e459 100644
--- a/src/sys/include/sys/proc.h
+++ b/src/sys/include/sys/proc.h
@@ -35,6 +35,12 @@
 #include <machine/pcb.h>    /* standard */
 
 /*
+ * The stack starts here and grows down
+ */
+#define STACK_TOP   0xBFFFFFFF
+#define STACK_LEN   4096
+
+/*
  * A process describes a running program image
  * on the system.
  *
@@ -69,4 +75,16 @@ int proc_init(struct proc *procp, int flags);
  */
 int md_proc_init(struct proc *procp, int flags);
 
+/*
+ * Set the instruction pointer field of a specific
+ * process
+ *
+ * @procp: Process to update
+ * @ip: Instruction pointer to write
+ *
+ * Returns zero on success, otherwise a less than
+ * zero value to indicate failure.
+ */
+int md_set_ip(struct proc *procp, uintptr_t ip);
+
 #endif  /* !_SYS_PROC_H_ */