[syslinux:master] PXELINUX: Fix timer bug

[syslinux-bot for Gene Cumm]

Commit-ID:  d8402d0e3919ff5318c4bbad690be32bf715936e
Gitweb:     http://syslinux.zytor.com/commit/d8402d0e3919ff5318c4bbad690be32bf715936e
Author:     Gene Cumm <gene.cumm at gmail.com>
AuthorDate: Fri, 5 Nov 2010 13:32:52 -0400
Committer:  Gene Cumm <gene.cumm at gmail.com>
CommitDate: Fri, 5 Nov 2010 13:32:52 -0400

PXELINUX: Fix timer bug

Certain calls to the PXE stack could potentially remove us from
memory.  Revert the INT 1Ch timer to its previous state.


---
 core/pxelinux.asm |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/core/pxelinux.asm b/core/pxelinux.asm
index a46b3da..165472d 100644
--- a/core/pxelinux.asm
+++ b/core/pxelinux.asm
@@ -365,6 +365,15 @@ pxenv:
 		pushfd
 		pushad
 
+		; We may be removing ourselves from memory
+		cmp bx,0073h
+		jz .disable_timer
+		jmp .store_stack
+
+.disable_timer:
+		call timer_cleanup
+
+.store_stack:
 		mov [cs:PXEStack],sp
 		mov [cs:PXEStack+2],ss
 		lss sp,[cs:InitStack]
@@ -391,6 +400,16 @@ pxenv:
 		; This clobbers the AX return, but we already saved it into
 		; the PXEStatus variable.
 		popad
+
+		; If the TFTP failed, it could return.
+		cmp bx,0073h
+		jz .enable_timer
+		jmp .pop_flags
+
+.enable_timer:
+		call timer_init
+
+.pop_flags:
 		popfd				; Restore flags (incl. IF, DF)
 		ret