kern: proc: Add address checking routine

Add routine to check if an address is valid within a process's address
space. More work will need to be done with this but this introduces a
great starting point

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

2 files changed, 36 insertions, 0 deletions

diff --git a/src/sys/include/sys/proc.h b/src/sys/include/sys/proc.h
index 2ff2876..6a356ef 100644
--- a/src/sys/include/sys/proc.h
+++ b/src/sys/include/sys/proc.h
@@ -147,6 +147,19 @@ int md_proc_kill(struct proc *procp, int flags);
 int md_set_ip(struct proc *procp, uintptr_t ip);
 
 /*
+ * Check that a virtual address is within the bounds of
+ * a process.
+ *
+ * @proc: Process the address should be within
+ * @addr: Virtual address to check
+ * @len: Length of memory referenced by 'addr'
+ *
+ * Returns zero if the address is within the process bounds,
+ * otherwise a less than zero value on failure.
+ */
+int proc_check_addr(struct proc *proc, uintptr_t addr, size_t len);
+
+/*
  * Put the current process into a halt loop
  * until the next one runs.
  */
diff --git a/src/sys/os/os_proc.c b/src/sys/os/os_proc.c
index 3a42496..f21fc69 100644
--- a/src/sys/os/os_proc.c
+++ b/src/sys/os/os_proc.c
@@ -139,3 +139,26 @@ proc_kill(struct proc *procp, int status)
     proc_clear_ranges(procp);
     return md_proc_kill(procp, 0);
 }
+
+
+/*
+ * Check that an address is within the bounds of a
+ * process.
+ */
+int
+proc_check_addr(struct proc *proc, uintptr_t addr, size_t len)
+{
+    uintptr_t stack_base;
+    uintptr_t stack_end;
+
+    /* Within the bounds of the stack? */
+    stack_base = STACK_TOP - STACK_LEN;
+    if (addr >= stack_base && addr <= STACK_TOP) {
+        return 0;
+    }
+    if ((stack_base + len) < stack_end) {
+        return 0;
+    }
+
+    return -EFAULT;
+}