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SubjectRe: [PATCH 4/5 v2] x86 boot: show pfn addresses in hex not decimal in some kernel info printks

* Sam Ravnborg <sam@ravnborg.org> wrote:

> Hi Ingo
>
> > Sparse is a cool tool that extends upon C types (and more), but it's
> > been made too hard to use widely:
> >
> > - right now it's opt-in with no ability for testers to use it
> > transparently while also building the kernel. Forcing a second
> > kernel build just for 'debugging' reduces the userbase.
>
> This is waht make C=1 is for. If this is broken then we should
> fix it.
> Just trying it out:
> $ make C=1 kernel/sched.o
> CHECK kernel/sched.c
> kernel/sched_fair.c:37:14: warning: symbol 'sysctl_sched_latency' was not declar ed. Should it be static?
> kernel/sched_fair.c:43:14: warning: symbol 'sysctl_sched_min_granularity' was no t declared. Should it be static?
> kernel/sched_fair.c:72:14: warning: symbol 'sysctl_sched_wakeup_granularity' was not declared. Should it be static?
> ...
> CC kernel/sched.o
>
>
> So make C=1 works as intended and let you run sparse on the files that
> are built - and only those.

ah, ok - i was confused about that.

> > Fortunately these problems are all solvable gradually:
> >
> > - a kbuild mechanism to get _parallel_ Sparse checks. I.e. both the
> > real .o gets produced but also the "make C=1" output is produced.
> > Testers would be enabled to do Sparse checks "alongside" of a normal
> > kernel build. (Sparse is plenty fast for this to be practical)
> Already present.
>
> >
> > - kbuild mechanism with which subsystem maintainers could mark specific
> > files (or all of their subdirectories) of their subsystem as to be
> > Sparse-checked by default. [if a .config debug option is enabled]
> > For example we'd mark all of arch/x86/*.o and kernel/sched*.o in such
> > a way for example.
> That would then be on a directory basis.
> You can do:
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 1c9938a..1ba00aa 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -2,6 +2,7 @@
> # Makefile for the linux kernel.
> #
>
> +KBUILD_CHECKSRC=1
> obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
> exit.o itimer.o time.o softirq.o resource.o \
> sysctl.o capability.o ptrace.o timer.o user.o \
>
> already today.
> It applies recursively so we will then run sparse on kernel/time/*.o too.
>
> There is no easy way to cover all of arch/x86/*.o as the files are distributed
> in several Makefiles and there is no common one.
>
> >
> > - a second layer would be very useful as well: failures would turn into
> > build failures if a debug .config switch is enabled.
> This could be a simple:
> ifdef CONFIG_CHECK_IS_ERROR
> CHECKFLAGS += -Werror
> endif
>
> And teach sparse about -Werror
>
> > On a similar note, it would be nice if subsystem maintainers had a
> > kbuild mechanism to have the fails they maintain to be built via -Werr
> > (if an opt-in .config option is enabled).
>
> For each Makefile (does not apply recursively):
> ccflags-$(CONFIG_PROMOTE_WARNINGS_TO_ERROR) += -Werror
>
> When I get around to it:
> ccflags-sched.o-$(CONFIG_PROMOTE_WARNINGS_TO_ERROR) += -Werror

if there's a generic kbuild facility for it i'd love to try something
like that out, on files that i maintain. There should perhaps be a
shortcut for it? Something like:

ccflags-sched.o += -Werror

and kbuild would decide whether CONFIG_PROMOTE_WARNINGS_TO_ERROR is set
and whether to filter out -Werror or not?

Ingo


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