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configs/qemu{x86, x86_64}: add a serial console

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The current Buildroot defconfigs for qemu_x86 and qemu_x86_64
instantiate a console on tty1, which appears on QEMU's
graphical window. Add a console on the serial port (ttyS0) to
be used later for gitlab testing.

This change is need since the script used for gitlab testing
needs to use a serial output with pexpect.

This change is similar to the one made for raspberrypi [1] to
handle HDMI and serial console:

This requires three changes:
 1. have two 'console=' entries in the kernel command line: tty1,
    then ttyS0;
 2. change BR2_TARGET_GENERIC_GETTY_PORT to "console", so it starts
    a getty on the last console= passed to the kernel, ttyS0;
 3. add a new getty on tty1 to the generated inittab.

Step 2 is actually obtained by removing BR2_TARGET_GENERIC_GETTY_PORT
entirely from the defconfigs, since "console" is the default value.

Step 3 requires a post-build script since the Buildroot makefiles can
configure only one console.

Note: instead of simply adding a new getty on ttyS0 (which would
work) this patch actually changes BR2_TARGET_GENERIC_GETTY_PORT to
instantiate a console on UART, then adds back tty1 via
post-build.sh. This is done only to avoid the "GENERIC_SERIAL" comment
where we instantiate a console on QEMU graphical window, then
instantiate a really-serial console on another line.

The result is these two inittab lines:

  console::respawn:/sbin/getty -L  console 0 vt100 # GENERIC_SERIAL
  tty1::respawn:/sbin/getty -L  tty1 0 vt100 # QEMU graphical window

[1] 20878a1017

Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
This commit is contained in:
Romain Naour 2020-02-09 19:03:22 +01:00 committed by Peter Korsgaard
parent 722f8effec
commit 278f908d55
6 changed files with 30 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
board/qemu/x86/post-build.sh Executable file
View File

@ -0,0 +1,11 @@
#!/bin/sh
set -u
set -e
# Add a console on tty1
if [ -e ${TARGET_DIR}/etc/inittab ]; then
grep -qE '^tty1::' ${TARGET_DIR}/etc/inittab || \
sed -i '/GENERIC_SERIAL/a\
tty1::respawn:/sbin/getty -L tty1 0 vt100 # QEMU graphical window' ${TARGET_DIR}/etc/inittab
fi

2
board/qemu/x86/readme.txt
View File

@ -1,6 +1,6 @@
Run the emulation with:
qemu-system-i386 -M pc -kernel output/images/bzImage -drive file=output/images/rootfs.ext2,if=virtio,format=raw -append "rootwait root=/dev/vda" -net nic,model=virtio -net user
qemu-system-i386 -M pc -kernel output/images/bzImage -drive file=output/images/rootfs.ext2,if=virtio,format=raw -append "rootwait root=/dev/vda console=tty1 console=ttyS0" -serial stdio -net nic,model=virtio -net user
Optionally add -smp N to emulate a SMP system with N CPUs.

11
board/qemu/x86_64/post-build.sh Executable file
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@ -0,0 +1,11 @@
#!/bin/sh
set -u
set -e
# Add a console on tty1
if [ -e ${TARGET_DIR}/etc/inittab ]; then
grep -qE '^tty1::' ${TARGET_DIR}/etc/inittab || \
sed -i '/GENERIC_SERIAL/a\
tty1::respawn:/sbin/getty -L tty1 0 vt100 # QEMU graphical window' ${TARGET_DIR}/etc/inittab
fi

2
board/qemu/x86_64/readme.txt
View File

@ -1,6 +1,6 @@
Run the emulation with:
qemu-system-x86_64 -M pc -kernel output/images/bzImage -drive file=output/images/rootfs.ext2,if=virtio,format=raw -append "rootwait root=/dev/vda" -net nic,model=virtio -net user
qemu-system-x86_64 -M pc -kernel output/images/bzImage -drive file=output/images/rootfs.ext2,if=virtio,format=raw -append "rootwait root=/dev/vda console=tty1 console=ttyS0" -serial stdio -net nic,model=virtio -net user
Optionally add -smp N to emulate a SMP system with N CPUs.

4
configs/qemu_x86_64_defconfig
View File

@ -3,12 +3,14 @@ BR2_x86_64=y
# System
BR2_SYSTEM_DHCP="eth0"
BR2_TARGET_GENERIC_GETTY_PORT="tty1"
# Filesystem
BR2_TARGET_ROOTFS_EXT2=y
# BR2_TARGET_ROOTFS_TAR is not set
# Image
BR2_ROOTFS_POST_BUILD_SCRIPT="board/qemu/x86_64/post-build.sh"
# Linux headers same as kernel, a 4.19 series
BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_19=y

4
configs/qemu_x86_defconfig
View File

@ -4,12 +4,14 @@ BR2_x86_pentiumpro=y
# System
BR2_SYSTEM_DHCP="eth0"
BR2_TARGET_GENERIC_GETTY_PORT="tty1"
# Filesystem
BR2_TARGET_ROOTFS_EXT2=y
# BR2_TARGET_ROOTFS_TAR is not set
# Image
BR2_ROOTFS_POST_BUILD_SCRIPT="board/qemu/x86/post-build.sh"
# Linux headers same as kernel, a 4.19 series
BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_19=y