[BUG] It seems that all official kernels are built with option SMALL_FLASH

For Developers
1

I wanted to make my OpenWrt firmware (ipq806x) compatible with the official one. And it fails to do so. It's all because in my .config file there is an option CONFIG_KERNEL_KALLSYMS=y, and in the official kernel there is no this option.

Probably guilty of this:

config KERNEL_KALLSYMS
  bool "Compile the kernel with symbol table information"
  default y if !SMALL_FLASH
  help
    This will give you more information in stack traces from kernel oopses.

That is, it can be seen that there is a difference when build one target and build all targets at a time.

Recently there was a similar problem with the build system:

PS. It's too bad that the all official firmwares does not contain a kernel config! This really needs to be fixed!

2

No, it is explicitly disabled for official release builds:

config_seed = CONFIG_BUILDBOT=y
    CONFIG_DEVEL=y
    CONFIG_IMAGEOPT=y
    CONFIG_VERSIONOPT=y
    CONFIG_CCACHE=n
    CONFIG_KERNEL_KALLSYMS=n
    CONFIG_AUTOREMOVE=y
    CONFIG_PACKAGE_luci=y
    CONFIG_PACKAGE_luci-ssl=y
    CONFIG_IB=y
    CONFIG_SDK=y

You can also find the build configuration in each target specific firmware download folder:
https://downloads.openwrt.org/releases/21.02.1/targets/ipq806x/generic/config.buildinfo

You can install kmod-ikconfig to get /proc/config.gz which contains the config the kernel was built with.

2 Likes
3

XZ-packed kernel dimensions (ipq806x):

  1. CONFIG_KERNEL_KALLSYMS=y : 2928495 bytes
  2. CONFIG_KERNEL_KALLSYMS=n : 2749079 bytes

Reducing the size by 175 KiB is very very useful?

4

That is more than the entire available overlay space on certain devices. OpenWrt caters to the lowest common denominator, not to the most capable device.

1 Like
5

I understand it. It's just strange that this parameter is used for all platforms (boards).
I have never seen a QCOM IPQxxxx device with flash drive less than 64MB.

6

There are surprisingly more then you think with 32MB NOR-s and IPQ40xx

7

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