syslinux: fix booting memtest86+ using pxelinux regression

After syslinux was updated from 4.07 to 6.01, booting memtest86+ using
pxelinux would fail:
PXELINUX 6.01 2013-07-04 Copyright (C) 1994-2013 H. Peter Anvin et al
Loading memtest86... ok
Booting kernel failed: invalid argument

This backports the necessary upstream patches to allow memtest86+ to
boot using pxelinux again.

[YOCTO #5501]

(From OE-Core rev: ed9ccb8622b347173602be8b2126324d4fdf54d8)

Signed-off-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 87 insertions, 0 deletions

diff --git a/meta/recipes-devtools/syslinux/files/0003-PXELINUX-Add-bios-memscan-function.patch b/meta/recipes-devtools/syslinux/files/0003-PXELINUX-Add-bios-memscan-function.patch
new file mode 100644
index 0000000000..70d65fd71d
--- /dev/null
+++ b/meta/recipes-devtools/syslinux/files/0003-PXELINUX-Add-bios-memscan-function.patch
@@ -0,0 +1,87 @@
+Upstream-Status: Backport [d2f94e74fbd60bf491753895d2474105efb3dedf]
+Signed-off-by: Jonathan Liu <net147@gmail.com>
+
+From 5d57e8eb46f209481069d70eaa778481f6fa3edb Mon Sep 17 00:00:00 2001
+From: Matt Fleming <matt.fleming@intel.com>
+Date: Wed, 17 Jul 2013 13:04:30 +0100
+Subject: [PATCH 3/4] PXELINUX: Add bios memscan function
+
+We can mark the memory region occupied by the PXE stack as SMT_TERMINAL
+provided that KeepPXE isn't set. Historically some very old
+non-relocatable kernel images (memtest86+) have a load address that
+falls within the PXE stack region, so we need to attempt to load into
+that region if at all possible.
+
+Signed-off-by: Matt Fleming <matt.fleming@intel.com>
+---
+ core/fs/pxe/bios.c | 35 +++++++++++++++++++++++++++++++++++
+ 1 file changed, 35 insertions(+)
+
+diff --git a/core/fs/pxe/bios.c b/core/fs/pxe/bios.c
+index 81aa715..5f61824 100644
+--- a/core/fs/pxe/bios.c
++++ b/core/fs/pxe/bios.c
+@@ -1,4 +1,5 @@
+ #include <syslinux/firmware.h>
++#include <syslinux/memscan.h>
+ #include <core.h>
+ #include "pxe.h"
+ #include <net.h>
+@@ -10,6 +11,9 @@ static uint16_t real_base_mem;           /* Amount of DOS memory after freeing */
+ static bool has_gpxe;
+ static uint32_t gpxe_funcs;
+ 
++static addr_t pxe_code_start, pxe_code_size;
++static addr_t pxe_data_start, pxe_data_size;
++
+ /*
+  * Validity check on possible !PXE structure in buf
+  * return 1 for success, 0 for failure.
+@@ -88,6 +92,29 @@ static const struct pxenv_t *memory_scan_for_pxenv_struct(void)
+     return memory_scan(0x10000, is_pxenv);
+ }
+ 
++static int pxelinux_scan_memory(scan_memory_callback_t callback, void *data)
++{
++    int rv = 0;
++
++    /*
++     * If we are planning on calling unload_pxe() and unmapping the PXE
++     * region before we transfer control away from PXELINUX we can mark
++     * that region as SMT_TERMINAL to indicate that the region will
++     * become free at some point in the future.
++     */
++    if (!KeepPXE) {
++       dprintf("Marking PXE code region 0x%x - 0x%x as SMT_TERMINAL\n",
++               pxe_code_start, pxe_code_start + pxe_code_size);
++       rv = callback(data, pxe_code_start, pxe_code_size, SMT_TERMINAL);
++
++       dprintf("Marking PXE data region 0x%x - 0x%x as SMT_TERMINAL\n",
++               pxe_data_start, pxe_data_start + pxe_data_size);
++       rv = callback(data, pxe_data_start, pxe_data_size, SMT_TERMINAL);
++    }
++
++    return rv;
++}
++
+ /*
+  * Find the !PXE structure; we search for the following, in order:
+  *
+@@ -204,6 +231,14 @@ int pxe_init(bool quiet)
+        printf("UNDI data segment at %04X len %04X\n", data_seg, data_len);
+     }
+ 
++    pxe_code_start = code_seg << 4;
++    pxe_code_size = code_len;
++
++    pxe_data_start = data_seg << 4;
++    pxe_data_size = data_len;
++
++    syslinux_memscan_new(pxelinux_scan_memory);
++
+     code_seg = code_seg + ((code_len + 15) >> 4);
+     data_seg = data_seg + ((data_len + 15) >> 4);
+ 
+-- 
+1.8.5.3
+