From f0764c5fa6a4d12733cf207daea6e4dabfb56453 Mon Sep 17 00:00:00 2001
From: hinus <hinus@163.com>
Date: Thu, 29 Jul 2021 10:53:49 +0800
Subject: [PATCH] Title: System call 'close' Issue:
 https://gitee.com/hinus/linux_kernel_011/issues/I42Q8A Description: To close
 a file.

---
 fs/exec.c           |  7 +++++++
 fs/open.c           | 16 ++++++++++++++++
 include/linux/sys.h |  4 ++--
 include/unistd.h    |  5 +++--
 lib/Makefile        |  5 ++++-
 lib/close.c         |  5 +++++
 6 files changed, 37 insertions(+), 5 deletions(-)
 create mode 100644 lib/close.c

diff --git a/fs/exec.c b/fs/exec.c
index 1ed1682..f839b67 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -11,6 +11,8 @@
 
 #define MAX_ARG_PAGES 32
 
+extern int sys_close(int fd);
+
 static unsigned long * create_tables(char * p,int argc,int envc) {
     unsigned long *argv,*envp;
     unsigned long * sp;
@@ -199,6 +201,11 @@ int do_execve(unsigned long * eip,long tmp,char * filename,
         iput(current->executable);
     current->executable = inode;
 
+    for (i=0 ; i<NR_OPEN ; i++)
+        if ((current->close_on_exec>>i)&1)
+            sys_close(i);
+    current->close_on_exec = 0;
+
     free_page_tables(get_base(current->ldt[1]),get_limit(0x0f));
     free_page_tables(get_base(current->ldt[2]),get_limit(0x17));
 
diff --git a/fs/open.c b/fs/open.c
index 0199bc2..999d441 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -102,3 +102,19 @@ int sys_fstat() {
     return 0;
 }
 
+int sys_close(unsigned int fd) {
+    struct file * filp;
+    if (fd >= NR_OPEN)
+        return -EINVAL;
+    current->close_on_exec &= ~(1<<fd);
+    if (!(filp = current->filp[fd]))
+        return -EINVAL;
+    current->filp[fd] = NULL;
+    if (filp->f_count == 0)
+        panic("Close: file count is 0");
+    if (--filp->f_count)
+        return 0;
+    iput(filp->f_inode);
+    return 0;
+}
+
diff --git a/include/linux/sys.h b/include/linux/sys.h
index 13846cf..5d66342 100644
--- a/include/linux/sys.h
+++ b/include/linux/sys.h
@@ -4,7 +4,7 @@ extern int sys_fork();
 extern int sys_read();
 extern int sys_write();
 extern int sys_open();
-//extern int sys_close();
+extern int sys_close();
 //extern int sys_waitpid();
 //extern int sys_creat();
 //extern int sys_link();
@@ -93,7 +93,7 @@ fn_ptr sys_call_table[] = {
     sys_read,
     sys_write,
     sys_open,
-    0, /*sys_close,*/
+    sys_close,
     0, //sys_waitpid,
     0, //sys_creat,
     0, //sys_link,
diff --git a/include/unistd.h b/include/unistd.h
index a202200..a805ffd 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -151,7 +151,10 @@ __asm__ volatile("int $0x80\n\r"\
 
 extern int errno;
 
+int chdir(const char* pathname);
+int close(int fildes);
 int dup(int fildes);
+int execve(const char * filename, char ** argv, char ** envp);
 int fork();
 int fstat();
 int setup(void *BIOS);
@@ -159,10 +162,8 @@ 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 execve(const char * filename, char ** argv, char ** envp);
 
 int rmdir(const char* pathname);
-int chdir(const char* pathname);
 
 time_t time(time_t * tloc);
 
diff --git a/lib/Makefile b/lib/Makefile
index 331f5a5..9618874 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -2,7 +2,7 @@ AR  := ar
 LD  := ld
 GCC := gcc
 CCFLAG := -m32 -I../include -nostdinc -ffreestanding -fno-pic -Wall -fomit-frame-pointer -fno-stack-protector -c
-OBJS   := ctype.o write.o string.o open.o dup.o execve.o
+OBJS   := ctype.o write.o string.o open.o dup.o execve.o close.o
 
 lib.a : $(OBJS)
 		$(AR) rcs $@ $^
@@ -26,6 +26,9 @@ dup.o : dup.c
 execve.o : execve.c
 		$(GCC) $(CCFLAG) -o $@ $<
 
+close.o : close.c
+		$(GCC) $(CCFLAG) -o $@ $<
+
 clean : 
 		-rm *.o
 		-rm lib.a
diff --git a/lib/close.c b/lib/close.c
new file mode 100644
index 0000000..0ba4677
--- /dev/null
+++ b/lib/close.c
@@ -0,0 +1,5 @@
+#define __LIBRARY__
+#include <unistd.h>
+
+_syscall1(int,close,int,fd)
+
-- 
Gitee