From: Michael Brown <mcb30@ipxe.org>
Date: Fri, 12 Feb 2016 13:59:06 +0000 (+0000)
Subject: [prefix] Pad .text16 and .data16 segment sizes at build time
X-Git-Tag: v1.20.1~608
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7ecfe7159f94193a666200a17057d4cd5981b850;p=thirdparty%2Fipxe.git

[prefix] Pad .text16 and .data16 segment sizes at build time

Commit c64747d ("[librm] Speed up real-to-protected mode transition
under KVM") rounded down the .text16 segment address calculated in
alloc_basemem() to a multiple of 64 bytes in order to speed up mode
transitions under KVM.

This creates a potential discrepancy between alloc_basemem() and
free_basemem(), meaning that free_basemem() may free less memory than
was allocated by alloc_basemem().

Fix by padding the calculated sizes of both .text16 and .data16 to a
multiple of 64 bytes at build time.

Debugged-by: Yossef Efraim <yossefe@mellanox.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
---

diff --git a/src/arch/i386/prefix/libprefix.S b/src/arch/i386/prefix/libprefix.S
index 7d5c1ed53..3cdb6ec9a 100644
--- a/src/arch/i386/prefix/libprefix.S
+++ b/src/arch/i386/prefix/libprefix.S
@@ -558,14 +558,11 @@ alloc_basemem:
 	shlw	$6, %ax
 
 	/* Calculate .data16 segment address */
-	subw	$_data16_memsz_pgh, %ax
+	subw	$_data16_memsz_ppgh, %ax
 	pushw	%ax
 
-	/* Calculate .text16 segment address.  Round down to ensure
-	 * low bits are zero, to speed up mode transitions under KVM.
-	 */
-	subw	$_text16_memsz_pgh, %ax
-	andb	$~0x03, %al
+	/* Calculate .text16 segment address */
+	subw	$_text16_memsz_ppgh, %ax
 	pushw	%ax
 
 	/* Update FBMS */
@@ -616,8 +613,8 @@ free_basemem:
 
 	/* OK to free memory */
 	movw	%cs, %ax
-	addw	$_text16_memsz_pgh, %ax
-	addw	$_data16_memsz_pgh, %ax
+	addw	$_text16_memsz_ppgh, %ax
+	addw	$_data16_memsz_ppgh, %ax
 	shrw	$6, %ax
 	movw	%ax, %fs:0x13
 	xorw	%ax, %ax
diff --git a/src/arch/i386/scripts/i386.lds b/src/arch/i386/scripts/i386.lds
index 38c89e14b..865591ae2 100644
--- a/src/arch/i386/scripts/i386.lds
+++ b/src/arch/i386/scripts/i386.lds
@@ -247,8 +247,8 @@ SECTIONS {
      * Values calculated to save code from doing it
      *
      */
-    _text16_memsz_pgh	= ( ( _text16_memsz + 15 ) / 16 );
-    _data16_memsz_pgh	= ( ( _data16_memsz + 15 ) / 16 );
+    _text16_memsz_ppgh	= ( ( ( _text16_memsz + 63 ) / 64 ) * 4 );
+    _data16_memsz_ppgh	= ( ( ( _data16_memsz + 63 ) / 64 ) * 4 );
     _textdata_memsz_pgh	= ( ( _textdata_memsz + 15 ) / 16 );
     _textdata_memsz_kb	= ( ( _textdata_memsz + 1023 ) / 1024 );
 }