Recently a patch by HPA was added to the elflink branch, "isolinux: Clear upper half of EDX before using..." http://git.zytor.com/?p=syslinux/syslinux.git;a=commit;h=870b84dd8714d dfccc9288025331423efa6d76b7 The patch was then applied to the firmware branch too. The patch solves an issue introduced by a prior commit "isolinux: Update LBA in getlinsec loop". Since the original problematic commit was also originally applied to the 4.xx branch http://git.zytor.com/?p=syslinux/syslinux.git;a=commit;h=cb015497a4e43 3ba81a47b28790b325807185617 and being 4.xx still more stable / predictable and more feature-complete than 6.xx for BIOS systems, I'd like to kindly request for the patch to be applied to the 4.xx branch too. TIA, Ady.
Geert Stappers
2013-Dec-12 05:55 UTC
[syslinux] [syslinux:master] isolinux: Clear upper half of EDX before using
Commit-ID: 88d17d136c21b8afb7d27e091cbb1f757ded80df
Gitweb:
http://www.syslinux.org/commit/88d17d136c21b8afb7d27e091cbb1f757ded80df
Author: H. Peter Anvin <hpa at zytor.com>
AuthorDate: Tue, 26 Nov 2013 09:58:17 -0800
Committer: H. Peter Anvin <hpa at zytor.com>
CommitDate: Wed, 11 Dec 2013 18:04:04 -0800
isolinux: Clear upper half of EDX before using
In checkin:
cb015497a4e4 isolinux: Update LBA in getlinsec loop
... we use EDX as a sector count, but the sector count is actually in
DX, and the upper half of EDX is uninitialized. If the BIOS enters
with a nonzero value in the upper half of EDX, this breaks horribly.
At least one set of BIOSes has been identified where if the LBA > 64K
then the upper half of EDX will be nonzero.
Reported-by: Carl Duff <cdrw2400 at gmail.com>
Reported-by: Philip M?ller <philm at manjaro.org>
Tested-by: Gerardo Exequiel Pozzi <vmlinuz386 at yahoo.com.ar>
Signed-off-by: H. Peter Anvin <hpa at zytor.com>
---
core/isolinux.asm | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/core/isolinux.asm b/core/isolinux.asm
index db6d2d4..dd0fa89 100644
--- a/core/isolinux.asm
+++ b/core/isolinux.asm
@@ -430,7 +430,7 @@ MaxLMA equ 384*1024 ; Reasonable limit (384K)
call getlinsec
pop eax
pop cx
- mov dx,cx
+ movzx edx,cx
pop bp
pop bx
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Groeten
Geert Stappers
--
Leven en laten leven