From: David Given <dg@cowlark.com>
Date: Thu, 21 Jan 2016 20:37:35 +0000 (+0100)
Subject: Move struct _uzistat into its own structure, shared between the kernel and
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=9ad0ca8733067d80828d8f235ef732c3b0caceda;p=FUZIX.git

Move struct _uzistat into its own structure, shared between the kernel and
userspace. stcpy() now copies this safely (avoiding compiler packing gotchas).
---

diff --git a/Kernel/include/kernel.h b/Kernel/include/kernel.h
index 84af6d41..7804828d 100644
--- a/Kernel/include/kernel.h
+++ b/Kernel/include/kernel.h
@@ -174,21 +174,6 @@ typedef struct dinode {
     blkno_t  i_addr[20];
 } dinode;               /* Exactly 64 bytes long! */
 
-struct  stat    /* Really only used by libc */
-{
-	int16_t   st_dev;
-	uint16_t  st_ino;
-	uint16_t  st_mode;
-	uint16_t  st_nlink;
-	uint16_t  st_uid;
-	uint16_t  st_gid;
-	uint16_t  st_rdev;
-	off_t   st_size;
-	uint32_t  st_atime;	/* Break in 2038 */
-	uint32_t  st_mtime;
-	uint32_t  st_ctime;
-};
-
 /* We use the Linux one for compatibility. There's no real Unix 'standard'
    for such things */
 
diff --git a/Kernel/include/userstructs.h b/Kernel/include/userstructs.h
new file mode 100644
index 00000000..6401de97
--- /dev/null
+++ b/Kernel/include/userstructs.h
@@ -0,0 +1,29 @@
+#ifndef _USERSTRUCTURES_H
+#define _USERSTRUCTURES_H
+
+/* Structures shared between kernel and user space.
+ *
+ * Only use explicitly sized types here --- otherwise differing compiler
+ * flags between kernel code and user code can pack them differently.
+ */
+
+struct _uzistat
+{
+	/* Do not change this without also changing stcpy() in syscall_fs.c. */
+
+	int16_t  st_dev;
+	uint16_t st_ino;
+	uint16_t st_mode;
+	uint16_t st_nlink;
+	uint16_t st_uid;
+	uint16_t st_gid;
+	uint16_t st_rdev;
+	uint32_t st_size;
+	uint32_t st_atime;  /* Breaks in 2038 */
+	uint32_t st_mtime;
+	uint32_t st_ctime;
+	uint32_t st_timeh;	/* Time high bytes */
+};
+
+#endif
+
diff --git a/Kernel/syscall_fs.c b/Kernel/syscall_fs.c
index 2c8056a7..c4dd91a7 100644
--- a/Kernel/syscall_fs.c
+++ b/Kernel/syscall_fs.c
@@ -2,6 +2,7 @@
 #include <version.h>
 #include <kdata.h>
 #include <printf.h>
+#include <userstructs.h>
 
 void updoff(void)
 {
@@ -134,9 +135,17 @@ arg_t _fstat(void)
 /* Utility for stat and fstat */
 int stcpy(inoptr ino, char *buf)
 {
-	int err = uput((char *) &(ino->c_dev), buf, 12);
-	err |= uput((char *) &(ino->c_node.i_addr[0]), buf + 12, 2);
-	err |= uput((char *) &(ino->c_node.i_size), buf + 14, 16);
+	/* Copying the structure a member at a time is too expensive.  Instead we
+	 * copy sequential runs of identical types (the only members which the
+	 * compiler guarantees are next to each other). */
+
+	uint32_t zero = 0;
+	struct _uzistat* st = (struct _uzistat*) buf;
+	int err = uput(&ino->c_dev,            &st->st_dev,   2 * sizeof(uint16_t));
+	err |=    uput(&ino->c_node.i_mode,    &st->st_mode,  4 * sizeof(uint16_t));
+	err |=    uput(&ino->c_node.i_addr[0], &st->st_rdev,  1 * sizeof(uint16_t));
+	err |=    uput(&ino->c_node.i_size,    &st->st_size,  4 * sizeof(uint32_t));
+	err |=    uput(&zero,                  &st->st_timeh, 1 * sizeof(uint32_t));
 	return err;
 }
 
diff --git a/Library/include/syscalls.h b/Library/include/syscalls.h
index 3adde780..96f56a8e 100644
--- a/Library/include/syscalls.h
+++ b/Library/include/syscalls.h
@@ -10,25 +10,12 @@
 #endif
 #include <sys/stat.h>
 
+/* TODO: make this less nasty. */
+#include "../../Kernel/include/userstructs.h"
+
 extern int errno;
 extern int syscall(int callno, ...);
 
-struct  _uzistat
-{
-	int16_t    st_dev;
-	uint16_t   st_ino;
-	uint16_t   st_mode;
-	uint16_t   st_nlink;
-	uint16_t   st_uid;
-	uint16_t   st_gid;
-	uint16_t   st_rdev;
-	uint32_t   st_size;
-	uint32_t   st_atime;
-	uint32_t   st_mtime;
-	uint32_t   st_ctime;
-	uint32_t   st_timeh;	/* Time high bytes */
-};
-
 struct _uzisysinfoblk {
   uint8_t infosize;		/* For expandability */
   uint8_t banks;		/* Banks in our 64K (and thus pagesize) */