diff mbox series

[v2,2/2] kbuild: handle excessively long argument lists

Message ID 1610660990-18812-1-git-send-email-jjohnson@codeaurora.org (mailing list archive)
State New
Headers show
Series None | expand

Commit Message

Jeff Johnson Jan. 14, 2021, 9:49 p.m. UTC
From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>

Modules with a large number of compilation units may be
exceeding AR and LD command argument list. Handle this gracefully by
writing the long argument list in a file. The command line options
read from file are inserted in place of the original @file option.

The usage is well documented at
https://www.gnu.org/software/make/manual/html_node/File-Function.html

Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
---

Changes in v2:
  - Remove spurious endif
  
scripts/Makefile.build | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Nick Desaulniers Jan. 15, 2021, 1 a.m. UTC | #1
On Thu, Jan 14, 2021 at 1:50 PM Jeff Johnson <jjohnson@codeaurora.org> wrote:
>
> From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>
> Modules with a large number of compilation units may be
> exceeding AR and LD command argument list. Handle this gracefully by
> writing the long argument list in a file. The command line options
> read from file are inserted in place of the original @file option.
>
> The usage is well documented at
> https://www.gnu.org/software/make/manual/html_node/File-Function.html
>
> Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
> Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
> ---
>
> Changes in v2:
>   - Remove spurious endif
>
> scripts/Makefile.build | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 252b7d2..787dca2 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -425,7 +425,10 @@ $(obj)/lib.a: $(lib-y) FORCE
>  # module is turned into a multi object module, $^ will contain header file
>  # dependencies recorded in the .*.cmd file.
>  quiet_cmd_link_multi-m = LD [M]  $@
> -      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
> +      cmd_link_multi-m =                                       \
> +       $(file >$@.in,$(filter %.o,$^))                         \
> +       $(LD) $(ld_flags) -r -o $@ @$@.in;                      \
> +       rm -f $@.in

The GNU Make docs linked above use an `@` before the invocation of
`rm`. I don't know what that's about, but that or even this patch
doesn't affect my ability to build negatively. LGTM

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

>
>  $(multi-used-m): FORCE
>         $(call if_changed,link_multi-m)
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
Masahiro Yamada Jan. 15, 2021, 1:12 a.m. UTC | #2
On Fri, Jan 15, 2021 at 6:50 AM Jeff Johnson <jjohnson@codeaurora.org> wrote:
>
> From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>
> Modules with a large number of compilation units may be
> exceeding AR and LD command argument list. Handle this gracefully by
> writing the long argument list in a file. The command line options
> read from file are inserted in place of the original @file option.
>
> The usage is well documented at
> https://www.gnu.org/software/make/manual/html_node/File-Function.html
>
> Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
> Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
> ---




First, is this a real problem?
If so, which module is exceeding the command line limit?


$(file ) is only supported by GNU Make 4.0 or later.

The current minimum version is GNU Make 3.81.

If we need this feature,
Documentation/process/changes.rst must be updated.




But, more importantly, none of your patches
works correctly.



Since $(file ...) is evaluated into an empty string,
your patches would break the Kbuild ability
that detects the command changes.




Steps to reproduce the problem
------------------------------



[1] add a module foo that consists of
    three objects foo1.o, foo2.o, foo3.o

For example, like follows:


obj-m += foo.o
foo-objs := foo1.o foo2.o foo3.o



[2] Run 'make modules'

You will get the module foo.



[3] Drop foo3.o from the module members

Change Makefile as follows:

obj-m += foo.o
foo-objs := foo1.o foo2.o



[4] Re-run 'make modules'





The current build system cleverly
notices the Makefile change, and
correctly rebuilds the foo module.

With your patch set applied,
the build system would not rebuild
the module.







> Changes in v2:
>   - Remove spurious endif
>
> scripts/Makefile.build | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 252b7d2..787dca2 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -425,7 +425,10 @@ $(obj)/lib.a: $(lib-y) FORCE
>  # module is turned into a multi object module, $^ will contain header file
>  # dependencies recorded in the .*.cmd file.
>  quiet_cmd_link_multi-m = LD [M]  $@
> -      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
> +      cmd_link_multi-m =                                       \
> +       $(file >$@.in,$(filter %.o,$^))                         \
> +       $(LD) $(ld_flags) -r -o $@ @$@.in;                      \
> +       rm -f $@.in
>
>  $(multi-used-m): FORCE
>         $(call if_changed,link_multi-m)
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
Masahiro Yamada Jan. 15, 2021, 1:25 a.m. UTC | #3
On Fri, Jan 15, 2021 at 10:01 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Thu, Jan 14, 2021 at 1:50 PM Jeff Johnson <jjohnson@codeaurora.org> wrote:
> >
> > From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
> >
> > Modules with a large number of compilation units may be
> > exceeding AR and LD command argument list. Handle this gracefully by
> > writing the long argument list in a file. The command line options
> > read from file are inserted in place of the original @file option.
> >
> > The usage is well documented at
> > https://www.gnu.org/software/make/manual/html_node/File-Function.html
> >
> > Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
> > Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
> > ---
> >
> > Changes in v2:
> >   - Remove spurious endif
> >
> > scripts/Makefile.build | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index 252b7d2..787dca2 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -425,7 +425,10 @@ $(obj)/lib.a: $(lib-y) FORCE
> >  # module is turned into a multi object module, $^ will contain header file
> >  # dependencies recorded in the .*.cmd file.
> >  quiet_cmd_link_multi-m = LD [M]  $@
> > -      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
> > +      cmd_link_multi-m =                                       \
> > +       $(file >$@.in,$(filter %.o,$^))                         \
> > +       $(LD) $(ld_flags) -r -o $@ @$@.in;                      \
> > +       rm -f $@.in
>
> The GNU Make docs linked above use an `@` before the invocation of
> `rm`. I don't know what that's about, but that or even this patch
> doesn't affect my ability to build negatively. LGTM


See this:

https://www.gnu.org/software/make/manual/html_node/Echoing.html#Echoing




> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Tested-by: Nick Desaulniers <ndesaulniers@google.com>
>
> >
> >  $(multi-used-m): FORCE
> >         $(call if_changed,link_multi-m)
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > a Linux Foundation Collaborative Project
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
Jeff Johnson Jan. 15, 2021, 8:15 p.m. UTC | #4
On 2021-01-14 17:12, Masahiro Yamada wrote:
> On Fri, Jan 15, 2021 at 6:50 AM Jeff Johnson <jjohnson@codeaurora.org> 
> wrote:
>> 
>> From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>> 
>> Modules with a large number of compilation units may be
>> exceeding AR and LD command argument list. Handle this gracefully by
>> writing the long argument list in a file. The command line options
>> read from file are inserted in place of the original @file option.
>> 
>> The usage is well documented at
>> https://www.gnu.org/software/make/manual/html_node/File-Function.html
>> 
>> Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>> Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
>> ---
> 
> 
> 
> 
> First, is this a real problem?
> If so, which module is exceeding the command line limit?

On 2021-01-14 17:12, Masahiro Yamada wrote:
> First, is this a real problem?
> If so, which module is exceeding the command line limit?

Mahesh & I appreciate all of the feedback.

The issue is seen in an Android environment with an out-of-tree
driver. The combination of long path names and a large number
of source files is leading to the issue.

Since Mahesh & I are not Kbuild gurus, is there an alternative
solution to this issue?

Jeff

--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
Forum,
a Linux Foundation Collaborative Project
Masahiro Yamada Jan. 15, 2021, 9:53 p.m. UTC | #5
On Sat, Jan 16, 2021 at 5:15 AM <jjohnson@codeaurora.org> wrote:
>
> On 2021-01-14 17:12, Masahiro Yamada wrote:
> > On Fri, Jan 15, 2021 at 6:50 AM Jeff Johnson <jjohnson@codeaurora.org>
> > wrote:
> >>
> >> From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
> >>
> >> Modules with a large number of compilation units may be
> >> exceeding AR and LD command argument list. Handle this gracefully by
> >> writing the long argument list in a file. The command line options
> >> read from file are inserted in place of the original @file option.
> >>
> >> The usage is well documented at
> >> https://www.gnu.org/software/make/manual/html_node/File-Function.html
> >>
> >> Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
> >> Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
> >> ---
> >
> >
> >
> >
> > First, is this a real problem?
> > If so, which module is exceeding the command line limit?
>
> On 2021-01-14 17:12, Masahiro Yamada wrote:
> > First, is this a real problem?
> > If so, which module is exceeding the command line limit?
>
> Mahesh & I appreciate all of the feedback.
>
> The issue is seen in an Android environment with an out-of-tree
> driver. The combination of long path names and a large number
> of source files is leading to the issue.
>
> Since Mahesh & I are not Kbuild gurus, is there an alternative
> solution to this issue?
>
> Jeff


I see.

The support for out-of-tree modules
is not nice in this regard, but fixing it
would need many changes.


The long-term solution might be to upstream your driver,
but it might not be possible.






One cheesy workaround might be to point the module path
via a symbolic link.


Let's say your module is located in a very deep
directory,
/home/foo/long/long/.../path/to/your/module


 make M=/home/foo/long/long/.../path/to/your/module modules

would fail due to the too long command line.




First, create a symbolic link as follows:

 ln -s /home/foo/long/long/.../path/to/your/module mod_dir


Then, pass the symbolic link to M= option.

 make M=mod_dir modules
mkalikot@codeaurora.org Jan. 19, 2021, 8:02 p.m. UTC | #6
On 2021-01-15 13:53, Masahiro Yamada wrote:
> On Sat, Jan 16, 2021 at 5:15 AM <jjohnson@codeaurora.org> wrote:
>> 
>> On 2021-01-14 17:12, Masahiro Yamada wrote:
>> > On Fri, Jan 15, 2021 at 6:50 AM Jeff Johnson <jjohnson@codeaurora.org>
>> > wrote:
>> >>
>> >> From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>> >>
>> >> Modules with a large number of compilation units may be
>> >> exceeding AR and LD command argument list. Handle this gracefully by
>> >> writing the long argument list in a file. The command line options
>> >> read from file are inserted in place of the original @file option.
>> >>
>> >> The usage is well documented at
>> >> https://www.gnu.org/software/make/manual/html_node/File-Function.html
>> >>
>> >> Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>> >> Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
>> >> ---
>> >
>> >
>> >
>> >
>> > First, is this a real problem?
>> > If so, which module is exceeding the command line limit?
>> 
>> On 2021-01-14 17:12, Masahiro Yamada wrote:
>> > First, is this a real problem?
>> > If so, which module is exceeding the command line limit?
>> 
>> Mahesh & I appreciate all of the feedback.
>> 
>> The issue is seen in an Android environment with an out-of-tree
>> driver. The combination of long path names and a large number
>> of source files is leading to the issue.
>> 
>> Since Mahesh & I are not Kbuild gurus, is there an alternative
>> solution to this issue?
>> 
>> Jeff
> 
> 
> I see.
> 
> The support for out-of-tree modules
> is not nice in this regard, but fixing it
> would need many changes.
> 

Agree with that. I checked the same after your first comment on this 
thread.
It needs changes in multiple layers of makefiles.

> 
> The long-term solution might be to upstream your driver,
> but it might not be possible.
> 
> 
> 
> 
> 
> 
> One cheesy workaround might be to point the module path
> via a symbolic link.
> 
> 
> Let's say your module is located in a very deep
> directory,
> /home/foo/long/long/.../path/to/your/module
> 
> 
>  make M=/home/foo/long/long/.../path/to/your/module modules
> 
> would fail due to the too long command line.
> 
> 
> 
> 
> First, create a symbolic link as follows:
> 
>  ln -s /home/foo/long/long/.../path/to/your/module mod_dir
> 
> 
> Then, pass the symbolic link to M= option.
> 
>  make M=mod_dir modules

Thanks for the suggestion. Earlier, we have used a similar workaround
of using relative path instead of absolute to reduce the command line
length.


What's your input on the following approach where we link object
files in different stages to reduce the command line length.


./Makefile

  # foo.c is combined and final module.

  obj-m = fooa.o foob.o fooc.o

  # link already combined object files
  fooc-y := fooa.o foob.o

  # combine into different groups
  fooa-y := foo1.o foo2.o
  foob-y := foo3.o foo4.o

  ....


Note: We need to add MODULE_LICENSE in every group.


make -C ../linux-kbuild M=/local/mnt2/workspace/dev/foo modules

   CC [M]  /local/mnt2/workspace/dev/foo/foo1.o
   CC [M]  /local/mnt2/workspace/dev/foo/foo2.o
   LD [M]  /local/mnt2/workspace/dev/foo/fooa.o
   CC [M]  /local/mnt2/workspace/dev/foo/foo3.o
   CC [M]  /local/mnt2/workspace/dev/foo/foo4.o
   LD [M]  /local/mnt2/workspace/dev/foo/foob.o
   LD [M]  /local/mnt2/workspace/dev/foo/fooc.o
   MODPOST /local/mnt2/workspace/dev/foo/Module.symvers
   CC [M]  /local/mnt2/workspace/dev/foo/fooa.mod.o
   LD [M]  /local/mnt2/workspace/dev/foo/fooa.ko
   CC [M]  /local/mnt2/workspace/dev/foo/foob.mod.o
   LD [M]  /local/mnt2/workspace/dev/foo/foob.ko
   CC [M]  /local/mnt2/workspace/dev/foo/fooc.mod.o
   LD [M]  /local/mnt2/workspace/dev/foo/fooc.ko
diff mbox series

Patch

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 252b7d2..787dca2 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -425,7 +425,10 @@  $(obj)/lib.a: $(lib-y) FORCE
 # module is turned into a multi object module, $^ will contain header file
 # dependencies recorded in the .*.cmd file.
 quiet_cmd_link_multi-m = LD [M]  $@
-      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
+      cmd_link_multi-m =					\
+	$(file >$@.in,$(filter %.o,$^))				\
+	$(LD) $(ld_flags) -r -o $@ @$@.in;			\
+	rm -f $@.in
 
 $(multi-used-m): FORCE
 	$(call if_changed,link_multi-m)