Fix the documentation and DOS port

Update the DOS cross-compile documentation,
and workaround issue with valloc() with the
latest DJGPP.

Change-Id: I909c5635aec5076440d2fde73d943f8ad10b8051
Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Reviewed-on: https://review.coreboot.org/23044
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/README b/README
index 449103d..b5ed946 100644
--- a/README
+++ b/README
@@ -97,27 +97,43 @@
  Get packages of the DJGPP cross compiler and install them:
  djgpp-filesystem djgpp-gcc djgpp-cpp djgpp-runtime djgpp-binutils
  As an alternative, the DJGPP web site offers packages for download as well:
- djcross-binutils-2.19.1-10ap.i386.rpm
- djcross-gcc-4.3.2-8ap.i686.rpm
- djcrx-2.04pre_20090725-13ap.i386.rpm
+ djcross-binutils-2.29.1-1ap.x86_64.rpm
+ djcross-gcc-7.2.0-1ap.x86_64.rpm
+ djcrx-2.05-5.x86_64.rpm
  The cross toolchain packages for your distribution may have slightly different
  names (look for packages named *djgpp*).
 
- You will need the following library source trees containing their compiled
- static libraries either in the parent directory of the flashrom source or
- specify the base folder on compile time with the LIBS_BASE parameter.
- The default as described above is equal to calling
-   'make djgpp-dos LIBS_BASE=..'
+ Alternatively, you could use a script to build it from scratch:
+ https://github.com/andrewwutw/build-djgpp
 
- To get and build said libraries...
- Download pciutils 3.1.5 and apply http://flashrom.org/File:Pciutils.patch.gz
- Compile pciutils, see README.DJGPP for instructions.
- Download and compile http://flashrom.org/File:Libgetopt.tar.gz
+ You will need the libpci and libgetopt library source trees and
+ their compiled static libraries and header files installed in some
+ directory say libpci-libgetopt/, which will be later specified with
+ LIBS_BASE parameter during flashrom compilation. Easiest way to
+ handle it is to put pciutils, libgetopt and flashrom directories
+ in one subdirectory. There will be an extra subdirectory libpci-libgetopt
+ created, which will contain compiled libpci and libgetopt.
+
+ Download pciutils 3.5.6 and apply http://flashrom.org/File:Pciutils-3.5.6.patch.gz
+ Compile pciutils, using following command line:
+
+ make ZLIB=no DNS=no HOST=i386-djgpp-djgpp CROSS_COMPILE=i586-pc-msdosdjgpp- \
+     PREFIX=/ DESTDIR=$PWD/../libpci-libgetopt  \
+     STRIP="--strip-program=i586-pc-msdosdjgpp-strip -s" install install-lib
+
+ Download and compile with 'make' http://flashrom.org/File:Libgetopt.tar.gz
+
+ Copy the libgetopt.a to ../libpci-libgetopt/lib and
+ getopt.h to ../libpci-libgetopt/include
+
  Enter the flashrom directory.
- Run either (change settings where appropriate)
- make CC=i586-pc-msdosdjgpp-gcc STRIP=i586-pc-msdosdjgpp-strip
- or (above settings hardcoded)
- make djgpp-dos
+
+ make CC=i586-pc-msdosdjgpp-gcc STRIP=i586-pc-msdosdjgpp-strip LIBS_BASE=../libpci-libgetopt/ strip
+
+ If you like, you can compress the resulting executable with UPX:
+
+ upx -9 flashrom.exe
+
  To run flashrom.exe, download http://flashrom.org/File:Csdpmi7b.zip and
  unpack CWSDPMI.EXE into the current directory or one in PATH.
 
diff --git a/physmap.c b/physmap.c
index a261ccd..3338b62 100644
--- a/physmap.c
+++ b/physmap.c
@@ -38,29 +38,40 @@
 
 #ifdef __DJGPP__
 #include <dpmi.h>
+#include <malloc.h>
 #include <sys/nearptr.h>
 
+#define ONE_MEGABYTE (1024 * 1024)
 #define MEM_DEV "dpmi"
 
-static void *realmem_map;
+static void *realmem_map_aligned;
 
 static void *map_first_meg(uintptr_t phys_addr, size_t len)
 {
-	if (realmem_map)
-		return realmem_map + phys_addr;
+	void *realmem_map;
+	size_t pagesize;
 
-	realmem_map = valloc(1024 * 1024);
+	if (realmem_map_aligned)
+		return realmem_map_aligned + phys_addr;
+
+	/* valloc() from DJGPP 2.05 does not work properly */
+	pagesize = getpagesize();
+
+	realmem_map = malloc(ONE_MEGABYTE + pagesize);
 
 	if (!realmem_map)
 		return ERROR_PTR;
 
-	if (__djgpp_map_physical_memory(realmem_map, (1024 * 1024), 0)) {
+	realmem_map_aligned = (void *)(((size_t) realmem_map +
+		(pagesize - 1)) & ~(pagesize - 1));
+
+	if (__djgpp_map_physical_memory(realmem_map_aligned, ONE_MEGABYTE, 0)) {
 		free(realmem_map);
-		realmem_map = NULL;
+		realmem_map_aligned = NULL;
 		return ERROR_PTR;
 	}
 
-	return realmem_map + phys_addr;
+	return realmem_map_aligned + phys_addr;
 }
 
 static void *sys_physmap(uintptr_t phys_addr, size_t len)
@@ -72,7 +83,7 @@
 	if (!__djgpp_nearptr_enable())
 		return ERROR_PTR;
 
-	if ((phys_addr + len - 1) < (1024 * 1024)) {
+	if ((phys_addr + len - 1) < ONE_MEGABYTE) {
 		/* We need to use another method to map first 1MB. */
 		return map_first_meg(phys_addr, len);
 	}
@@ -97,8 +108,8 @@
 	/* There is no known way to unmap the first 1 MB. The DPMI server will
 	 * do this for us on exit.
 	 */
-	if ((virt_addr >= realmem_map) &&
-	    ((virt_addr + len) <= (realmem_map + (1024 * 1024)))) {
+	if ((virt_addr >= realmem_map_aligned) &&
+	    ((virt_addr + len) <= (realmem_map_aligned + ONE_MEGABYTE))) {
 		return;
 	}