[PATCH 6/7] kbuild: make source and include paths absolute

[PATCH 6/7] kbuild: make source and include paths absolute

[Peter Oberparleiter]

From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>

Change all source and include paths to absolute form when
CONFIG_GCOV_PROFILE is enabled.

Example:

  gcc -Idir1 -c a.c -o a.o

will become

  gcc -I/path/to/dir1 -c /path/to/a.c -o a.o

Required by the gcov profiling infrastructure: when compiling with
option -fprofile-arcs, gcc stores file names inside object files.
Relative paths prevent the gcov tool from finding corresponding source
files.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
---
 scripts/Kbuild.include |    7 +++++++
 scripts/Makefile.build |    3 ++-
 scripts/Makefile.lib   |    8 +++++++-
 3 files changed, 16 insertions(+), 2 deletions(-)

Index: linux-2.6.26-rc3/scripts/Makefile.lib
===================================================================
--- linux-2.6.26-rc3.orig/scripts/Makefile.lib
+++ linux-2.6.26-rc3/scripts/Makefile.lib
@@ -126,10 +126,16 @@ __a_flags	=                          $(c
 __cpp_flags     =                          $(call flags,_cpp_flags)
 endif
 
-c_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(KBUILD_CPPFLAGS) \
+___c_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(KBUILD_CPPFLAGS) \
 		 $(__c_flags) $(modkern_cflags) \
 		 -D"KBUILD_STR(s)=\#s" $(basename_flags) $(modname_flags)
 
+ifeq ($(CONFIG_GCOV_PROFILE),)
+c_flags = $(___c_flags)
+else
+c_flags = $(call flags_addpath,___c_flags,$(objtree))
+endif
+
 a_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(KBUILD_CPPFLAGS) \
 		 $(__a_flags) $(modkern_aflags)
 
Index: linux-2.6.26-rc3/scripts/Makefile.build
===================================================================
--- linux-2.6.26-rc3.orig/scripts/Makefile.build
+++ linux-2.6.26-rc3/scripts/Makefile.build
@@ -165,7 +165,8 @@ $(obj)/%.symtypes : $(src)/%.c FORCE
 # (See cmd_cc_o_c + relevant part of rule_cc_o_c)
 
 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
-cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
+cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ \
+		$(if $(CONFIG_GCOV_PROFILE),$(call addpath,$<,$(objtree)),$<)
 
 ifdef CONFIG_MODVERSIONS
 # When module versioning is enabled the following steps are executed
Index: linux-2.6.26-rc3/scripts/Kbuild.include
===================================================================
--- linux-2.6.26-rc3.orig/scripts/Kbuild.include
+++ linux-2.6.26-rc3/scripts/Kbuild.include
@@ -149,6 +149,13 @@ addtree = $(if $(filter-out -I/%,$(1)),$
 # Find all -I options and call addtree
 flags = $(foreach o,$($(1)),$(if $(filter -I%,$(o)),$(call addtree,$(o)),$(o)))
 
+# Prefix $(1) with $(2)/ if $(1) does not start with /
+addpath = $(if $(filter-out /%,$(1)),$(2)/$(1),$(1))
+
+# Find all -I options and call addpath
+flags_addpath = $(foreach o,$($(1)),\
+		$(if $(filter -I%,$(o)),-I$(call addpath,$(o:-I%=%),$(2)),$(o)))
+
 # echo command.
 # Short version is used, if $(quiet) equals `quiet_', otherwise full one.
 echo-cmd = $(if $($(quiet)cmd_$(1)),\

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Jan Blunck]

On Mon, 19 May 2008 10:44:56 +0200, Peter Oberparleiter wrote:

> From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
> 
> Change all source and include paths to absolute form when
> CONFIG_GCOV_PROFILE is enabled.
> 
> Example:
> 
>   gcc -Idir1 -c a.c -o a.o
> 
> will become
> 
>   gcc -I/path/to/dir1 -c /path/to/a.c -o a.o
> 
> Required by the gcov profiling infrastructure: when compiling with
> option -fprofile-arcs, gcc stores file names inside object files.
> Relative paths prevent the gcov tool from finding corresponding source
> files.

I think it would be good to fix this in the gcov tool. When I think
of distribution kernels the source usually ends up in a different
place in the packages than the kernel was originally compiled. So
it would be good to extend gcov here or let it search in well known
locations first (/usr/src/linux, /usr/src/debug/...).

Cheers,
Jan

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Andrew Morton]

On Mon, 19 May 2008 10:44:56 +0200 Peter Oberparleiter <peter.oberparleiter@de.ibm.com> wrote:

> From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
> 
> Change all source and include paths to absolute form when
> CONFIG_GCOV_PROFILE is enabled.
> 
> Example:
> 
>   gcc -Idir1 -c a.c -o a.o
> 
> will become
> 
>   gcc -I/path/to/dir1 -c /path/to/a.c -o a.o
> 
> Required by the gcov profiling infrastructure: when compiling with
> option -fprofile-arcs, gcc stores file names inside object files.
> Relative paths prevent the gcov tool from finding corresponding source
> files.

I don't like this.  It converts the compiler error messages from
relative paths to absolute paths which is rather obnoxious when
all kernel developent is (or should be) base-directory-agnostic.

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Adrian Bunk]

On Thu, May 22, 2008 at 08:17:24PM -0700, Andrew Morton wrote:
> On Mon, 19 May 2008 10:44:56 +0200 Peter Oberparleiter <peter.oberparleiter@de.ibm.com> wrote:
> 
> > From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
> > 
> > Change all source and include paths to absolute form when
> > CONFIG_GCOV_PROFILE is enabled.
> > 
> > Example:
> > 
> >   gcc -Idir1 -c a.c -o a.o
> > 
> > will become
> > 
> >   gcc -I/path/to/dir1 -c /path/to/a.c -o a.o
> > 
> > Required by the gcov profiling infrastructure: when compiling with
> > option -fprofile-arcs, gcc stores file names inside object files.
> > Relative paths prevent the gcov tool from finding corresponding source
> > files.
> 
> I don't like this.  It converts the compiler error messages from
> relative paths to absolute paths which is rather obnoxious when
> all kernel developent is (or should be) base-directory-agnostic.

The compiler error messages are already absolute paths when using O=
(see e.g. all error messages sent by me in recent years).

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Andrew Morton]

On Fri, 23 May 2008 20:18:40 +0300
Adrian Bunk <bunk@kernel.org> wrote:

> On Thu, May 22, 2008 at 08:17:24PM -0700, Andrew Morton wrote:
> > On Mon, 19 May 2008 10:44:56 +0200 Peter Oberparleiter <peter.oberparleiter@de.ibm.com> wrote:
> > 
> > > From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
> > > 
> > > Change all source and include paths to absolute form when
> > > CONFIG_GCOV_PROFILE is enabled.
> > > 
> > > Example:
> > > 
> > >   gcc -Idir1 -c a.c -o a.o
> > > 
> > > will become
> > > 
> > >   gcc -I/path/to/dir1 -c /path/to/a.c -o a.o
> > > 
> > > Required by the gcov profiling infrastructure: when compiling with
> > > option -fprofile-arcs, gcc stores file names inside object files.
> > > Relative paths prevent the gcov tool from finding corresponding source
> > > files.
> > 
> > I don't like this.  It converts the compiler error messages from
> > relative paths to absolute paths which is rather obnoxious when
> > all kernel developent is (or should be) base-directory-agnostic.
> 
> The compiler error messages are already absolute paths when using O=
> (see e.g. all error messages sent by me in recent years).
> 

Well I guess that's understandable with O=.

But I find it rather nasty.  (I guess it'd be less nasty if I were to
get off my butt and work out how to teach rxvt that "/" is a word
separator).

What do others think?

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Sam Ravnborg]

On Fri, May 23, 2008 at 11:17:07AM -0700, Andrew Morton wrote:
> On Fri, 23 May 2008 20:18:40 +0300
> Adrian Bunk <bunk@kernel.org> wrote:
> 
> > On Thu, May 22, 2008 at 08:17:24PM -0700, Andrew Morton wrote:
> > > On Mon, 19 May 2008 10:44:56 +0200 Peter Oberparleiter <peter.oberparleiter@de.ibm.com> wrote:
> > > 
> > > > From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
> > > > 
> > > > Change all source and include paths to absolute form when
> > > > CONFIG_GCOV_PROFILE is enabled.
> > > > 
> > > > Example:
> > > > 
> > > >   gcc -Idir1 -c a.c -o a.o
> > > > 
> > > > will become
> > > > 
> > > >   gcc -I/path/to/dir1 -c /path/to/a.c -o a.o
> > > > 
> > > > Required by the gcov profiling infrastructure: when compiling with
> > > > option -fprofile-arcs, gcc stores file names inside object files.
> > > > Relative paths prevent the gcov tool from finding corresponding source
> > > > files.
> > > 
> > > I don't like this.  It converts the compiler error messages from
> > > relative paths to absolute paths which is rather obnoxious when
> > > all kernel developent is (or should be) base-directory-agnostic.
> > 
> > The compiler error messages are already absolute paths when using O=
> > (see e.g. all error messages sent by me in recent years).
> > 
> 
> Well I guess that's understandable with O=.
> 
> But I find it rather nasty.  (I guess it'd be less nasty if I were to
> get off my butt and work out how to teach rxvt that "/" is a word
> separator).
> 
> What do others think?

That the gcov tool has a bug if it insist on using absolute paths.
And thus we should fix gcov and not workaround it in the kernel.

	Sam

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Vegard Nossum]

On Fri, May 23, 2008 at 9:09 PM, Sam Ravnborg <sam@ravnborg.org> wrote:
> On Fri, May 23, 2008 at 11:17:07AM -0700, Andrew Morton wrote:
>> On Fri, 23 May 2008 20:18:40 +0300
>> Adrian Bunk <bunk@kernel.org> wrote:
>>
>> > On Thu, May 22, 2008 at 08:17:24PM -0700, Andrew Morton wrote:
>> > > On Mon, 19 May 2008 10:44:56 +0200 Peter Oberparleiter <peter.oberparleiter@de.ibm.com> wrote:
>> > >
>> > > > From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
>> > > >
>> > > > Change all source and include paths to absolute form when
>> > > > CONFIG_GCOV_PROFILE is enabled.
>> > > >
>> > > > Example:
>> > > >
>> > > >   gcc -Idir1 -c a.c -o a.o
>> > > >
>> > > > will become
>> > > >
>> > > >   gcc -I/path/to/dir1 -c /path/to/a.c -o a.o
>> > > >
>> > > > Required by the gcov profiling infrastructure: when compiling with
>> > > > option -fprofile-arcs, gcc stores file names inside object files.
>> > > > Relative paths prevent the gcov tool from finding corresponding source
>> > > > files.
>> > >
>> > > I don't like this.  It converts the compiler error messages from
>> > > relative paths to absolute paths which is rather obnoxious when
>> > > all kernel developent is (or should be) base-directory-agnostic.
>> >
>> > The compiler error messages are already absolute paths when using O=
>> > (see e.g. all error messages sent by me in recent years).
>> >
>>
>> Well I guess that's understandable with O=.
>>
>> But I find it rather nasty.  (I guess it'd be less nasty if I were to
>> get off my butt and work out how to teach rxvt that "/" is a word
>> separator).
>>
>> What do others think?
>
> That the gcov tool has a bug if it insist on using absolute paths.
> And thus we should fix gcov and not workaround it in the kernel.

IIRC, there was also the slight problem that all uses of __FILE__
(there are quite a few in the kernel) will also now be absolute and
increase the size of the vmlinux image by quite a bit.

Yeah... http://lkml.org/lkml/2006/4/25/40


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Sam Ravnborg]

> >>
> >> Well I guess that's understandable with O=.
> >>
> >> But I find it rather nasty.  (I guess it'd be less nasty if I were to
> >> get off my butt and work out how to teach rxvt that "/" is a word
> >> separator).
> >>
> >> What do others think?
> >
> > That the gcov tool has a bug if it insist on using absolute paths.
> > And thus we should fix gcov and not workaround it in the kernel.
> 
> IIRC, there was also the slight problem that all uses of __FILE__
> (there are quite a few in the kernel) will also now be absolute and
> increase the size of the vmlinux image by quite a bit.
> 
> Yeah... http://lkml.org/lkml/2006/4/25/40
This is specific to O=.. build kernels.
I recall this is not an issue for the gcov patchset (if O=... is not used).
But I have not checked it.

	Sam

Re: [PATCH 6/7] kbuild: make source and include paths absolute

[Peter Oberparleiter]

Sam Ravnborg wrote:
> On Fri, May 23, 2008 at 11:17:07AM -0700, Andrew Morton wrote:
>> On Fri, 23 May 2008 20:18:40 +0300
>> Adrian Bunk <bunk@kernel.org> wrote:
>> 
>> > On Thu, May 22, 2008 at 08:17:24PM -0700, Andrew Morton wrote:
>> > > On Mon, 19 May 2008 10:44:56 +0200 Peter Oberparleiter <peter.oberparleiter@de.ibm.com> wrote:
>> > > 
>> > > > From: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
>> > > > 
>> > > > Change all source and include paths to absolute form when
>> > > > CONFIG_GCOV_PROFILE is enabled.
>> > > > 
>> > > > Example:
>> > > > 
>> > > >   gcc -Idir1 -c a.c -o a.o
>> > > > 
>> > > > will become
>> > > > 
>> > > >   gcc -I/path/to/dir1 -c /path/to/a.c -o a.o
>> > > > 
>> > > > Required by the gcov profiling infrastructure: when compiling with
>> > > > option -fprofile-arcs, gcc stores file names inside object files.
>> > > > Relative paths prevent the gcov tool from finding corresponding source
>> > > > files.
>> > > 
>> > > I don't like this.  It converts the compiler error messages from
>> > > relative paths to absolute paths which is rather obnoxious when
>> > > all kernel developent is (or should be) base-directory-agnostic.
>> > 
>> > The compiler error messages are already absolute paths when using O=
>> > (see e.g. all error messages sent by me in recent years).
>> > 
>> 
>> Well I guess that's understandable with O=.
>> 
>> But I find it rather nasty.  (I guess it'd be less nasty if I were to
>> get off my butt and work out how to teach rxvt that "/" is a word
>> separator).
>> 
>> What do others think?
> 
> That the gcov tool has a bug if it insist on using absolute paths.
> And thus we should fix gcov and not workaround it in the kernel.

I've given this some more thought and came up with a possible
alternative solution that doesn't require paths to be absolute:

For a given source file x.c, gcov requires x.c (main source),
x.gcno (static coverage meta data) and x.gcda (dynamically created
coverage data) to work. x.gcno may refer to further source files. To
find these files the corresponding paths need to be either absolute or
gcov must be called from gcc's current working directory during
compilation (which always should be $(objtree)).

Currently these files are placed like this:

  sysfs:
    x.gcda
    x.gcno -> symbolic link to $(objtree)/rel/path/x.gcno
    x.c -> symbolic link to $(srctree)/rel/path/x.c

  objtree:
    x.gcno

  srctree:
    x.c

Instead, kbuild could be modified to create links to x.gcda in
$(objtree) like this:

  sysfs:
    x.gcda
 
  objtree:
    x.gcno
    x.gcda -> symbolic link to /sys/kernel/debug/gcov/rel/path/x.gcda

  srctree:
    x.c

gcov could then be called like this:

  cd $(objtree)
  gcov -o rel/path/ $(srctree)/rel/path/x.c

Would this be an acceptable approach? Also, for automated collection of
coverage data, there must be some algorithm to find the source file for
a given .gcda file. Is the assumption correct that the "rel/path/" part
is the same for $(srctree) and $(objtree), i.e. can the source file
be derived like this?:

    $(objtree)/rel/path/x.o -> $(srctree)/rel/path/x.c

Alternatively, kbuild could also create a link to x.c in $(objtree),
though I'm not sure if that wouldn't have side effects like e.g. naming
conflicts with generated .c files in $(objtree).