From b901a125510486e190dd841dfa616cafff0c9242 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Tue, 22 May 2007 23:27:46 -0700
Subject: [PATCH] Make it safe to call close_file on an already closed file.

The SYSLINUX internal API closes a file automatically upon reading
to block EOF (not necessarily file EOF!)  Thus, it's fairly likely
we'll get SI == 0 (closed file) passed to close_file at some point
or another.

Just plain admit it, and make close_file accept SI == 0 by spec.
---
 comboot.inc  | 3 ---
 extlinux.asm | 4 +++-
 getc.inc     | 3 ---
 isolinux.asm | 4 +++-
 ldlinux.asm  | 4 +++-
 pxelinux.asm | 4 +++-
 6 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/comboot.inc b/comboot.inc
index 4896e39..034f924 100644
--- a/comboot.inc
+++ b/comboot.inc
@@ -434,10 +434,7 @@ comapi_read:
 ;
 comapi_close:
 		mov si,P_SI
-		and si,si
-		jz .nothing
 		call close_file
-.nothing:
 		clc
 		ret
 
diff --git a/extlinux.asm b/extlinux.asm
index 7d73507..a590a36 100644
--- a/extlinux.asm
+++ b/extlinux.asm
@@ -1039,8 +1039,10 @@ ThisInode	resb EXT2_GOOD_OLD_INODE_SIZE	; The most recently opened inode
 ;	     Assumes CS == DS.
 ;
 close_file:
+		and si,si
+		jz .closed
 		mov dword [si],0		; First dword == file_left
-		ret
+.closed:	ret
 
 ;
 ; searchdir:
diff --git a/getc.inc b/getc.inc
index 610d01b..5c8dc86 100644
--- a/getc.inc
+++ b/getc.inc
@@ -162,9 +162,6 @@ close:
 		push si
 		mov bx,[CurrentGetC]
 		mov si,[bx+gc_file]
-		and si,si
-		jz .closed
-.closed:
 		call close_file
 		add bx,getc_file_size
 		mov [CurrentGetC],bx
diff --git a/isolinux.asm b/isolinux.asm
index de4f164..f9e8741 100644
--- a/isolinux.asm
+++ b/isolinux.asm
@@ -1143,8 +1143,10 @@ local_boot:
 ;	     Assumes CS == DS.
 ;
 close_file:
+		and si,si
+		jz .closed
 		mov dword [si],0		; First dword == file_left
-		ret
+.closed:	ret
 
 ;
 ; searchdir:
diff --git a/ldlinux.asm b/ldlinux.asm
index 7d7b8f2..eed2951 100644
--- a/ldlinux.asm
+++ b/ldlinux.asm
@@ -1065,8 +1065,10 @@ search_dos_dir:
 ;	     Assumes CS == DS.
 ;
 close_file:
+		and si,si
+		jz .closed
 		mov dword [si],0		; First dword == file_left
-		ret
+.closed:	ret
 
 ;
 ; searchdir:
diff --git a/pxelinux.asm b/pxelinux.asm
index 253aa0f..3e50245 100644
--- a/pxelinux.asm
+++ b/pxelinux.asm
@@ -1078,8 +1078,10 @@ memory_scan_for_pxenv_struct:
 ; side and send a courtesy ERROR packet to the server.
 ;
 close_file:
+		and si,si
+		jz .closed
 		mov word [si],0		; Not in use
-		ret
+.closed:	ret
 
 ;
 ; searchdir:
-- 
2.7.4