kern: Add SYS_read system call for file I/O

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

5 files changed, 87 insertions, 1 deletions

diff --git a/src/sys/compat/unix/os/os_filedesc.c b/src/sys/compat/unix/os/os_filedesc.c
index 48ea6be..673701f 100644
--- a/src/sys/compat/unix/os/os_filedesc.c
+++ b/src/sys/compat/unix/os/os_filedesc.c
@@ -33,6 +33,7 @@
 #include <sys/mount.h>
 #include <sys/errno.h>
 #include <sys/types.h>
+#include <os/kalloc.h>
 #include <os/systm.h>
 #include <os/filedesc.h>
 #include <compat/unix/syscall.h>
@@ -105,3 +106,35 @@ sys_mount(struct syscall_args *scargs)
     args.fstype = fstype;
     return kmount(&args, u_mountflags);
 }
+
+/*
+ * ARG0: fd
+ * ARG1: buf[]
+ * ARG2: count
+ */
+scret_t
+sys_read(struct syscall_args *scargs)
+{
+    int fd = SCARG(scargs, int, 0);
+    char *u_buf = SCARG(scargs, char *, 1);
+    size_t count = SCARG(scargs, size_t, 2);
+    char *kbuf;
+    ssize_t retval;
+    int error;
+
+    /* Do we have enough memory to fulfill this */
+    kbuf = kalloc(count);
+    if (kbuf == NULL) {
+        return -ENOMEM;
+    }
+
+    retval = read(fd, kbuf, count);
+    if (retval < 0) {
+        kfree(kbuf);
+        return retval;
+    }
+
+    error = copyout(kbuf, u_buf, count);
+    kfree(kbuf);
+    return (error == 0) ? retval : error;
+}
diff --git a/src/sys/include/compat/unix/syscall.h b/src/sys/include/compat/unix/syscall.h
index 8b7e7d7..be351e8 100644
--- a/src/sys/include/compat/unix/syscall.h
+++ b/src/sys/include/compat/unix/syscall.h
@@ -63,6 +63,11 @@ scret_t sys_query(struct syscall_args *scargs);
  */
 scret_t sys_open(struct syscall_args *scargs);
 
+/*
+ * Read a file
+ */
+scret_t sys_read(struct syscall_args *scargs);
+
 #ifdef _NEED_UNIX_SCTAB
 scret_t(*g_unix_sctab[])(struct syscall_args *) = {
     [SYS_none]   = NULL,
@@ -77,7 +82,8 @@ scret_t(*g_unix_sctab[])(struct syscall_args *) = {
     [SYS_getargv] = sys_getargv,
     [SYS_reboot]  = sys_reboot,
     [SYS_waitpid] = sys_waitpid,
-    [SYS_dmsio] = sys_dmsio
+    [SYS_dmsio] = sys_dmsio,
+    [SYS_read] = sys_read
 };
 
 #endif  /* !_NEED_UNIX_SCTAB */
diff --git a/src/sys/include/os/filedesc.h b/src/sys/include/os/filedesc.h
index 0023526..8cdf161 100644
--- a/src/sys/include/os/filedesc.h
+++ b/src/sys/include/os/filedesc.h
@@ -93,4 +93,16 @@ int fd_open(const char *path, mode_t mode);
  */
 ssize_t write(int fd, const void *buf, size_t count);
 
+/*
+ * Read a file descriptor
+ *
+ * @fd: File descriptor to read from
+ * @buf: Buffer to read into
+ * @count: Number of bytes to read
+ *
+ * Returns the number of bytes read on success, otherwise a less
+ * than zero value on error.
+ */
+ssize_t read(int fd, void *buf, size_t count);
+
 #endif  /* !_OS_FILEDESC_H_ */
diff --git a/src/sys/include/sys/syscall.h b/src/sys/include/sys/syscall.h
index 2ff6087..1138029 100644
--- a/src/sys/include/sys/syscall.h
+++ b/src/sys/include/sys/syscall.h
@@ -56,6 +56,7 @@
 #define SYS_reboot      0x0B    /* reboot the system */
 #define SYS_waitpid     0x0C    /* wait for child to exit */
 #define SYS_dmsio       0x0D    /* DMS I/O */
+#define SYS_read        0x0E    /* read a file descriptor */
 
 typedef __ssize_t scret_t;
 typedef __ssize_t scarg_t;
diff --git a/src/sys/os/os_filedes.c b/src/sys/os/os_filedes.c
index 5789427..9ba0c63 100644
--- a/src/sys/os/os_filedes.c
+++ b/src/sys/os/os_filedes.c
@@ -273,6 +273,40 @@ write(int fd, const void *buf, size_t count)
     return count;
 }
 
+ssize_t
+read(int fd, void *buf, size_t count)
+{
+    struct proc *self = proc_self();
+    struct filedesc *fdp;
+    int error;
+
+    if (buf == NULL) {
+        return -EINVAL;
+    }
+
+    /* Must be valid */
+    error = proc_check_addr(self, (uintptr_t)buf, count);
+    if (error < 0) {
+        return error;
+    }
+
+    /* We need the actual descriptor */
+    if ((fdp = fd_get(self, fd)) == NULL) {
+        return -EBADF;
+    }
+
+    /* Can we read from it? */
+    if (fdp->mode == O_WRONLY) {
+        return -EPERM;
+    }
+
+    if (fdp->vp == NULL) {
+        return -EIO;
+    }
+
+    return vop_read(fdp->vp, buf, count);
+}
+
 /*
  * ARG0: Path
  * ARG1: Mode