From 81afa4f3002dd317ab20959fa430318c4cf35b82 Mon Sep 17 00:00:00 2001
From: Michael Marineau <michael.marineau@coreos.com>
Date: Fri, 16 Aug 2013 15:09:26 -0400
Subject: [PATCH] fix(boot): Enable serial console when booting via syslinux.

Useful for qemu -nographic or any any other situation where serial is
easier to get at than VGA. It may be possible that in some setups ttyS0
isn't appropriate but we can figure out a way to customize kernel
options if/when that ever comes up.
---
 build_library/create_legacy_bootloader_templates.sh | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/build_library/create_legacy_bootloader_templates.sh b/build_library/create_legacy_bootloader_templates.sh
index 7f90302565..2dcc8c0770 100755
--- a/build_library/create_legacy_bootloader_templates.sh
+++ b/build_library/create_legacy_bootloader_templates.sh
@@ -97,7 +97,12 @@ EOF
   SYSLINUX_DIR="${FLAGS_to}/syslinux"
   sudo mkdir -p "${SYSLINUX_DIR}"
 
+  # Add ttyS0 as a secondary console, useful for qemu -nographic
+  # This leaves /dev/console mapped to tty0 (vga) which is reasonable default.
+  syslinux_args="console=ttyS0,115200n8 ${common_args}"
+
   cat <<EOF | sudo dd of="${SYSLINUX_DIR}/syslinux.cfg" 2>/dev/null
+SERIAL 0 115200
 PROMPT 0
 TIMEOUT 0
 DEFAULT boot_kernel
@@ -119,14 +124,14 @@ EOF
 label boot_kernel
   menu label boot_kernel
   kernel vmlinuz-boot_kernel
-  append ${common_args} root=gptprio:
+  append ${syslinux_args} root=gptprio:
 EOF
   info "Emitted ${SYSLINUX_DIR}/boot_kernel.cfg"
   cat <<EOF | sudo dd of="${SYSLINUX_DIR}/root.A.cfg" 2>/dev/null
 label coreos.A
   menu label coreos.A
   kernel vmlinuz.A
-  append ${common_args} root=${ROOTA}
+  append ${syslinux_args} root=${ROOTA}
 EOF
   info "Emitted ${SYSLINUX_DIR}/root.A.cfg"
 
@@ -134,7 +139,7 @@ EOF
 label coreos.B
   menu label coreos.B
   kernel vmlinuz.B
-  append ${common_args} root=${ROOTB}
+  append ${syslinux_args} root=${ROOTB}
 EOF
   info "Emitted ${SYSLINUX_DIR}/root.B.cfg"