kern: proc: Add getargv system call

Introduce a getargv system call that allows one to fetch an argument
string using an index into the argument vector.

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

4 files changed, 34 insertions, 2 deletions

diff --git a/src/sys/include/compat/unix/syscall.h b/src/sys/include/compat/unix/syscall.h
index 743e50c..2cca0bc 100644
--- a/src/sys/include/compat/unix/syscall.h
+++ b/src/sys/include/compat/unix/syscall.h
@@ -71,7 +71,8 @@ scret_t(*g_unix_sctab[])(struct syscall_args *) = {
     [SYS_spawn]  = sys_spawn,
     [SYS_mount]  = sys_mount,
     [SYS_open]   = sys_open,
-    [SYS_muxtap] = sys_muxtap
+    [SYS_muxtap] = sys_muxtap,
+    [SYS_getargv] = sys_getargv
 };
 
 #endif  /* !_NEED_UNIX_SCTAB */
diff --git a/src/sys/include/sys/proc.h b/src/sys/include/sys/proc.h
index 5bffc3e..dcf6108 100644
--- a/src/sys/include/sys/proc.h
+++ b/src/sys/include/sys/proc.h
@@ -218,5 +218,10 @@ __dead void md_proc_kick(struct proc *procp);
  */
 scret_t sys_spawn(struct syscall_args *scargs);
 
+/*
+ * Get argument number n
+ */
+scret_t sys_getargv(struct syscall_args *scargs);
+
 #endif  /* !_KERNEL */
 #endif  /* !_SYS_PROC_H_ */
diff --git a/src/sys/include/sys/syscall.h b/src/sys/include/sys/syscall.h
index 09996ae..8353eda 100644
--- a/src/sys/include/sys/syscall.h
+++ b/src/sys/include/sys/syscall.h
@@ -51,7 +51,8 @@
 #define SYS_spawn       0x06    /* spawn a process */
 #define SYS_mount       0x07    /* mount a filesystem */
 #define SYS_open        0x08    /* open a file */
-#define SYS_muxtap      0x09 /* mux an I/O tap */
+#define SYS_muxtap      0x09    /* mux an I/O tap */
+#define SYS_getargv     0x0A    /* get process argv */
 
 typedef __ssize_t scret_t;
 typedef __ssize_t scarg_t;
diff --git a/src/sys/os/os_proc.c b/src/sys/os/os_proc.c
index 27ffac8..4af45a0 100644
--- a/src/sys/os/os_proc.c
+++ b/src/sys/os/os_proc.c
@@ -320,3 +320,28 @@ sys_spawn(struct syscall_args *scargs)
     envblk = penv_blk_cpy(proc_self(), u_blk);
     return proc_spawn(buf, envblk);
 }
+
+/*
+ * Get argument number number
+ *
+ * ARG0: Argument number
+ * ARG1: Buffer result
+ * ARG2: Max length
+ */
+scret_t
+sys_getargv(struct syscall_args *scargs)
+{
+    uint16_t argno = SCARG(scargs, uint16_t, 0);
+    char *u_buf = SCARG(scargs, char *, 1);
+    size_t maxlen = SCARG(scargs, size_t, 2);
+    struct proc *self = proc_self();
+    struct penv_blk *envblk = self->envblk;
+    char *arg;
+
+    if (argno >= envblk->argc) {
+        return -EINVAL;
+    }
+
+    arg = envblk->argv[argno];
+    return copyoutstr(arg, u_buf, maxlen);
+}