From d959b68e09b636cd56f0e96bb3b771f76ab66171 Mon Sep 17 00:00:00 2001
From: hinus <hinus@163.com>
Date: Wed, 11 Aug 2021 16:39:19 +0800
Subject: [PATCH] Title: System call 'lseek' Issue:
 https://gitee.com/hinus/linux_kernel_011/issues/I44ZBN Description: System
 call 'lseek'

---
 fs/read_write.c     | 29 +++++++++++++++++++++++++++++
 include/linux/fs.h  |  2 ++
 include/linux/sys.h |  4 ++--
 include/unistd.h    |  2 ++
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 7c61f34..cf2c111 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -9,6 +9,35 @@ extern int rw_char(int rw,int dev, char * buf, int count, off_t * pos);
 extern int file_read(struct m_inode * inode, struct file * filp,
         char * buf, int count);
 
+int sys_lseek(unsigned int fd,off_t offset, int origin) {
+    struct file * file;
+    int tmp;
+
+    if (fd >= NR_OPEN || !(file=current->filp[fd]) || !(file->f_inode)
+            || !IS_SEEKABLE(MAJOR(file->f_inode->i_dev)))
+        return -EBADF;
+    if (file->f_inode->i_pipe)
+        return -ESPIPE;
+
+    switch (origin) {
+        case 0:
+            if (offset<0) return -EINVAL;
+            file->f_pos=offset;
+            break;
+        case 1:
+            if (file->f_pos+offset<0) return -EINVAL;
+            file->f_pos += offset;
+            break;
+        case 2:
+            if ((tmp=file->f_inode->i_size+offset) < 0)
+                file->f_pos = tmp;
+            break;
+        default:
+            return -EINVAL;
+    }
+    return file->f_pos;
+}
+
 int sys_read(unsigned int fd,char * buf,int count) {
     struct file * file;
     struct m_inode * inode;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7f9044f..808ad32 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3,6 +3,8 @@
 
 #include <sys/types.h>
 
+#define IS_SEEKABLE(x) ((x)>=1 && (x)<=3)
+
 #define READ 0
 #define WRITE 1
 #define READA 2
diff --git a/include/linux/sys.h b/include/linux/sys.h
index 1643a18..8ae4fc4 100644
--- a/include/linux/sys.h
+++ b/include/linux/sys.h
@@ -17,7 +17,7 @@ extern int sys_chmod();
 extern int sys_chown();
 extern int sys_break();
 //extern int sys_stat();
-//extern int sys_lseek();
+extern int sys_lseek();
 extern int sys_getpid();
 //extern int sys_mount();
 //extern int sys_umount();
@@ -108,7 +108,7 @@ fn_ptr sys_call_table[] = {
     sys_chown,
     sys_break,
     0, //sys_stat,
-    0, //sys_lseek,
+    sys_lseek,
     sys_getpid,
     0, //sys_mount,
 
diff --git a/include/unistd.h b/include/unistd.h
index a805ffd..6d3027d 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -162,9 +162,11 @@ int sync();
 int open(const char * filename, int flag, ...);
 int write(int fildes, const char * buf, off_t count);
 int read(int fildes, const char * buf, off_t count);
+int lseek(int fildes, off_t offset, int origin);
 
 int rmdir(const char* pathname);
 
 time_t time(time_t * tloc);
+int uname(struct utsname * name);
 
 #endif
-- 
Gitee