kernel build note

README

# linux kernel "slab virtual" edition
https://github.com/thejh/linux/commit/aa0a1fb37ba0c2180da51254dce2268cb7c34813

# kernel source
https://www.kernel.org/pub/linux/kernel/
https://cdn.kernel.org/pub/linux/kernel/

# builder gcc
https://github.com/a13xp0p0v/kernel-build-containers

# compile
make menuconfig
make -j$(nproc)

# enable debug kconfig
Kernel hacking -> Generic Kernel Debugging Instruments -> KGDB: kernel debugger
Kernel hacking -> Compile-time checks and compiler options -> Compile the kernel with debug info
scripts/config --enable DEBUG_INFO
scripts/config --enable DEBUG_KERNEL
scripts/config --disable CC_OPTIMIZE_FOR_SIZE
scripts/config --enable GDB_SCRIPTS

# we want below file
- vmlinux: uncompressed kernel with full symbols (you want this!)
- arch/x86/boot/bzImage: bootable compressed image (x86_64)
- arch/arm64/boot/Image (aarch64)

Android.txt

# android kernel  
> emulator:
  | specific qemu for running the android vm
  https://github.com/f-droid/android-sdk-transparency-log/blob/master/signed/checksums.json
  - https://dl.google.com/android/repository/emulator-windows_x64-<num>.zip
  - https://dl.google.com/android/repository/emulator-linux_x64-<num>.zip
  - https://mirrors.cloud.tencent.com/AndroidSDK/ (index file listing)
> aosp/sdk
  | image and stuff
  | get info from source.properties, https://dl.google.com/android/repository/sys-img/android/$arch-$api_$revision.zip
  | $arch     = SystemImage.Abi
  | $api      = AndroidVersion.ApiLevel
  | $revision = Pkg.Revision
  | arm64-v8a-25_r01.zip, x86_64-25_r01.zip
> build
  | yay -S jdk8-openjdk python2 ncurses5-compat-libs repo
  

# case study
- emulate Android 7.1.1_r20, Kernel version: Linux 3.10.0
- host linux (arch linux x64)
  | Android emulator version 30.3.5.0
  | Emulator linux_x64-7033400
  | target kernel-ranchu aarch64/arm64
> emulator:
  - https://dl.google.com/android/repository/emulator-linux_x64-7033400.zip
> build kernel-ranchu
cd /opt/
# --- kernel ---
git clone --branch android-goldfish-3.10 https://android.googlesource.com/kernel/goldfish.git android-goldfish-3.10
# --- toolchain ---
git clone --branch android-7.1.1_r20 https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9.git aarch64-gcc-4.9-7.1.1_r20
# --- toolchain setup ---
export CC_PATH=$PWD/aarch64-gcc-4.9-7.1.1_r20/bin
export ARCH=arm64 SUBARCH=arm64 CROSS_COMPILE=$CC_PATH/aarch64-linux-android-
# --- build ---
make ARCH=arm64 ranchu_defconfig 
make -j`nproc`


# case error
================================================
```
emulator: CPU Acceleration: DISABLED
emulator: CPU Acceleration status: KVM requires a CPU that supports vmx or svm
emulator: ERROR: CPU acceleration is not supported on this machine!
emulator: ERROR: Reason: KVM requires a CPU that supports vmx or svm
```
> check for kvm support :
$ egrep --color '(vmx|svm)' /proc/cpuinfo
> fix by run emulator with :
  -accel off
  -qemu -accel tcg
================================================
================================================
```
/usr/bin/ld: scripts/dtc/dtc-parser.tab.o:(.bss+0x50): multiple definition of `yylloc'; scripts/dtc/dtc-lexer.lex.o:(.bss+0x0): first defined here
collect2: error: ld returned 1 exit status
make[2]: *** [scripts/Makefile.host:127: scripts/dtc/dtc] Error 1
make[1]: *** [scripts/Makefile.build:455: scripts/dtc] Error 2
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:518: scripts] Error 2
```
> apply https://github.com/BPI-SINOVOIP/BPI-M4-bsp/issues/4#issuecomment-1140414552
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WORKAROUND

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# compile older kernel in modern kernel #
================================================
arch/x86/entry/thunk_64.o: warning: objtool: missing symbol table
make[2]: *** [scripts/Makefile.build:361: arch/x86/entry/thunk_64.o] Error 1
make[2]: *** Deleting file 'arch/x86/entry/thunk_64.o'
make[1]: *** [scripts/Makefile.build:497: arch/x86/entry] Error 2
make: *** [Makefile:1752: arch/x86] Error 2
user@bcaa1fe2e35a:/src$ exit
================================================
solution: https://www.reddit.com/r/archlinux/comments/pl9pak/compiling_older_versions_of_the_kernel_using/
`Apply this patch to fix builds with binutils 2.36: https://github.com/torvalds/linux/commit/1d489151e9f9d1647110277ff77282fe4d96d09b.patch`
`Or presumably also: https://github.com/torvalds/linux/commit/de979c83574abf6e78f3fa65b716515c91b2613d.patch`
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-
================================================
Can't use 'defined(@array)' (Maybe you should just omit the defined()?) at kernel/timeconst.pl line 373.
/src/kernel/Makefile:133: recipe for target 'kernel/timeconst.h' failed
make[1]: *** [kernel/timeconst.h] Error 255
Makefile:791: recipe for target 'kernel' failed
make: *** [kernel] Error 2
================================================
version: 3.7.1
solution: https://lkml.org/lkml/2012/11/18/159
basically remove all "defined()" inside kernel/timeconst.pl
================================================

================================================
# enable some non-builtin module like userfaultfd #
================================================
In file included from help.c:12:
In function 'xrealloc',
    inlined from 'add_cmdname' at help.c:24:2:
subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
   56 |                 ret = realloc(ptr, size);
      |                       ^~~~~~~~~~~~~~~~~~
subcmd-util.h:52:21: note: call to 'realloc' here
   52 |         void *ret = realloc(ptr, size);
      |                     ^~~~~~~~~~~~~~~~~~
subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
   58 |                         ret = realloc(ptr, 1);
      |                               ^~~~~~~~~~~~~~~
subcmd-util.h:52:21: note: call to 'realloc' here
   52 |         void *ret = realloc(ptr, size);
      |                     ^~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[4]: *** [/src/tools/build/Makefile.build:97: /src/tools/objtool/help.o] Error 1
make[3]: *** [Makefile:59: /src/tools/objtool/libsubcmd-in.o] Error 2
make[2]: *** [Makefile:71: /src/tools/objtool/libsubcmd.a] Error 2
make[1]: *** [Makefile:68: objtool] Error 2
make: *** [Makefile:1854: tools/objtool] Error 2
user@5ec1f7f69896:/src$ exit
================================================
solution: https://unix.stackexchange.com/a/767697
`Add -Wno-use-after-free to the makefile tools/lib/subcmd/Makefile Line 22.`
specifically at CFLAGS like below
`CFLAGS := -ggdb3 -Wall -Wextra -std=gnu99 -fPIC -Wno-use-after-free`
================================================