On Fri, Oct 19, 2018 at 03:04:22PM +0900, Masahiro Yamada wrote: > Hi Josh, > > > On Wed, Oct 17, 2018 at 1:16 AM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > > > > On Wed, Oct 17, 2018 at 12:51:40AM +0900, Masahiro Yamada wrote: > > > > ifdef CONFIG_UNWINDER_ORC > > > > > > > > chk_unwinder_orc = echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf - > > > > msg_unwinder_orc = "Cannot build objtool to generate ORC metadata for CONFIG_UNWINDER_ORC=y. " \ > > > > "Please install libelf-dev, libelf-devel or elfutils-libelf-devel." > > > > toolcheck-$(CONFIG_UNWINDER_ORC) += unwinder_orc > > > > > > > > else > > > > > > > > chk_stack_validation = echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf - > > > > msg_stack_validation = "Cannot build objtool for CONFIG_STACK_VALIDATION=y. " \ > > > > "Please install libelf-dev, libelf-devel or elfutils-libelf-devel." > > > > toolcheck-$(CONFIG_STACK_VALIDATION) += stack_validation > > > > > > > > endif > > > > > > > > > > > > What do you think? > > > > > > > > > It is ugly. > > > > > > Do you need such detailed information like ORC metadata stuff here? > > > > > > This Makefile aims to error out, showing why the build failed. > > > That's it. > > > > Yeah, it is kind of ugly. But the "showing why the build failed" part > > is important. I was trying to give the user a clear error message, > > similar to what we have today. > > > > Without context, the user won't know what objtool is, or why it needs to > > be built. > > > > If we have just a single error message for all cases, it should at least > > mention the config option. Like > > > > "Cannot build objtool for CONFIG_STACK_VALIDATION." > > > > But then, most users will only have that enabled because of ORC. So an > > ORC-specific message would be more appropriate in most cases. > > > > So maybe it can just be something more vague: > > > > msg_stack_validation = "Cannot build objtool for CONFIG_UNWINDER_ORC and/or CONFIG_STACK_VALIDATION. " \ > > "Please install libelf-dev, libelf-devel or elfutils-libelf-devel." > > > > That would probably be good enough. Then we could drop the ugly ifdef. > > > Fair point, but I am confused by the current > STACK_VALIDATION / UNWINDER_ORC logic. > > In my understanding, objtool is > an all-in-one object check/manipulation tool. > > STACK_VALIDATION and UNWINDER_ORC > is a selection of a sub-command, 'check' or 'orc generate'. > > (Correct me if am wrong.) > > > However, STACK_VALIDATION is still used to > decide whether or not to compile the objtool. > > > Adding a new symbol OBJTOOL would clarify the logic. > > > > config OBJTOOL > bool > > config STACK_VALIDATION > bool "Compile-time stack metadata validation" > depends on HAVE_STACK_VALIDATION > select OBJTOOL > ... > > > config UNWINDER_ORC > bool "ORC unwinder" > depends on X86_64 > select OBJTOOL > ... While 'orc generate' and 'check' are indeed separate subcommands of objtool, the functionality of 'orc generate' is actually a superset of the functionality of 'check'. In other words, ORC generation relies on the stack validation feature, which is consistent with the current config logic. -- Josh