How specify optimization level of compilation for kernel module

Asked Aug 08 '19 at 08:27

Active Aug 08 '19 at 08:30

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I am writing a simple makefile for loadable kernel module, in below you can see makefile content:

obj-m += ali.o
all:
   make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
   make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

this make file work, but i do't know how specify optimization level of compilation in this makefile.

can anyone help to set the optimization level of compilation??

edited Aug 08 '19 at 08:30

asked Aug 08 '19 at 08:27

alireza sadeghpour

Optimization level of what? a gcc compilation? – Reda Drissi Aug 08 '19 at 08:29
yes, optimization of compilation. – alireza sadeghpour Aug 08 '19 at 08:30
That question is for the free-bsd kernel – Bryan Aug 08 '19 at 08:34
are you using Kbuild? – Reda Drissi Aug 08 '19 at 08:42
@RedaDrissi no, that is my makefile and i just use make command to build the module. – alireza sadeghpour Aug 08 '19 at 08:58
you should be able to set some variables, but I don't know exactly which, try `EXTRA_CFLAGS := -O2` or `ccflags-y := -O2` or `CFLAGS_ali.o := -O2`. Also add `V=1` to your make commands to activate verbose mode and see whether the flags were included while ali.c was compiled. – Reda Drissi Aug 08 '19 at 09:04
Optimization level for specific modules or the whole compilation? – kurtfu Aug 08 '19 at 09:10
The kernel Makefiles will already apply the `-O2` or `-Os` option. If you add competing `-O` options in the module's Makefile, I'm not sure which one will take precedence. – Ian Abbott Aug 08 '19 at 09:23
This, I think: https://stackoverflow.com/questions/18478859/is-it-possible-to-set-cflags-to-a-linux-kernel-module-makefile – Victor Sergienko Aug 09 '19 at 21:47

How specify optimization level of compilation for kernel module

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