Minimum build config for boot messages
Hello, what is the minimum config to build a linux kernel that just prints boot messages/errors? I was going through my old experiments/notes and found that we used to get kernel boot message with vanilla allnoconfig. make ARCH=x86_64 allnoconfig make all qemu-system-x86_64 -kernel arch/x86/boot/bzImage Those commands above used to be enough, but now the produced kernel doesn't print any messages on the qemu screen. With some trial-and-error i was able to track down this commit https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/... and if i add CONFIG_EMBEDDED=n to my KCONFIG_ALLCONFIG file, i can see kernel errors again. I didn't investigate further cause i don't really know what i'm doing, but do wonder: Can you reproduce this? Is this (now) expected behavior? (and it was luck before, to get kernel messages with vanilla allnoconfig) Do we (now) need some specific option to enable kernel messages with allnoconfig? (CONFIG_EMBEDDED=n sounds pretty generic and doesn't feel right) Am i doing it all wrong? :D Curiously, Andre Schmidt ps. i'm aware of defconfig, but i would like to experiment/learn from bottom-up, rather than top-down.
On Fri, Aug 19, 2016 at 04:17:22PM +0200, Andre Schmidt wrote:
make ARCH=x86_64 allnoconfig make all qemu-system-x86_64 -kernel arch/x86/boot/bzImage
Those commands above used to be enough, but now the produced kernel doesn't print any messages on the qemu screen.
With some trial-and-error i was able to track down this commit https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/... and if i add CONFIG_EMBEDDED=n to my KCONFIG_ALLCONFIG file, i can see kernel errors again. (CONFIG_EMBEDDED=n sounds pretty generic and doesn't feel right)
Can you reproduce this?
yes
ps. i'm aware of defconfig, but i would like to experiment/learn from bottom-up, rather than top-down.
I've done the same and would have expected the the previous behavior, too.
Hi, Am 19.08.16 um 16:17 schrieb Andre Schmidt:
Hello,
what is the minimum config to build a linux kernel that just prints boot messages/errors?
I was going through my old experiments/notes and found that we used to get kernel boot message with vanilla allnoconfig.
make ARCH=x86_64 allnoconfig make all qemu-system-x86_64 -kernel arch/x86/boot/bzImage
Those commands above used to be enough, but now the produced kernel doesn't print any messages on the qemu screen.
Did you also disable CONFIG_PRINTK ? Without that kernel will not print anything, as far as I know. HTH, Best, - Johannes
On Mon, 22 Aug 2016 20:50:49 +0200 Johannes Thoma <johannes@johannesthoma.com> wrote:
Did you also disable CONFIG_PRINTK ? Without that kernel will not print anything, as far as I know.
hmm, i tried with following: CONFIG_PRINTK=y CONFIG_EARLY_PRINTK=y both adding through KCONFIG_ALLCONFIG and `make menuconfig`. still no kernel messages :/ FWIW, heres the `diffconfig` of adding above with `make menuconfig` over allnoconfig: EARLY_PRINTK n -> y PRINTK n -> y +BOOT_PRINTK_DELAY n +LOG_BUF_SHIFT 17 +NMI_LOG_BUF_SHIFT 13 +PRINTK_NMI y +PRINTK_TIME n i assume something is still missing (from the 289 changes that CONFIG_EMBEDDED=n does over allnoconfig). Cheers Andre Schmidt
participants (3)
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Andre Schmidt -
Johannes Thoma -
John de la Garza