linux.git/Documentation/kbuild, branch v2.6.18

[PATCH] vDSO hash-style fix

2006-07-31T20:28:43+00:00

The latest toolchains can produce a new ELF section in DSOs and
dynamically-linked executables.  The new section ".gnu.hash" replaces
".hash", and allows for more efficient runtime symbol lookups by the
dynamic linker.  The new ld option --hash-style={sysv|gnu|both} controls
whether to produce the old ".hash", the new ".gnu.hash", or both.  In some
new systems such as Fedora Core 6, gcc by default passes --hash-style=gnu
to the linker, so that a standard invocation of "gcc -shared" results in
producing a DSO with only ".gnu.hash".  The new ".gnu.hash" sections need
to be dealt with the same way as ".hash" sections in all respects; only the
dynamic linker cares about their contents.  To work with older dynamic
linkers (i.e.  preexisting releases of glibc), a binary must have the old
".hash" section.  The --hash-style=both option produces binaries that a new
dynamic linker can use more efficiently, but an old dynamic linker can
still handle.

The new section runs afoul of the custom linker scripts used to build vDSO
images for the kernel.  On ia64, the failure mode for this is a boot-time
panic because the vDSO's PT_IA_64_UNWIND segment winds up ill-formed.

This patch addresses the problem in two ways.

First, it mentions ".gnu.hash" in all the linker scripts alongside ".hash".
 This produces correct vDSO images with --hash-style=sysv (or old tools),
with --hash-style=gnu, or with --hash-style=both.

Second, it passes the --hash-style=sysv option when building the vDSO
images, so that ".gnu.hash" is not actually produced.  This is the most
conservative choice for compatibility with any old userland.  There is some
concern that some ancient glibc builds (though not any known old production
system) might choke on --hash-style=both binaries.  The optimizations
provided by the new style of hash section do not really matter for a DSO
with a tiny number of symbols, as the vDSO has.  If someone wants to use
=gnu or =both for their vDSO builds and worry less about that
compatibility, just change the option and the linker script changes will
make any choice work fine.

Signed-off-by: Roland McGrath 
Cc: "Luck, Tony" 
Cc: Kyle McMartin 
Cc: Paul Mackerras 
Cc: Benjamin Herrenschmidt 
Cc: Jeff Dike 
Cc: Andi Kleen 
Cc: Sam Ravnborg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kbuild: add option for stripping modules while installing them

2006-06-24T21:16:45+00:00

Add option for stripping modules while installing them.

This function adds support for stripping modules while they are being
installed.  CONFIG_DEBUG_KERNEL (which will probably become more
popular as developers use kdump) causes the size of the installed
modules to grow by a factor of 9 or so.

Some kernel package systems solve this problem by stripping the debug
information from /lib/modules after running "make modules_install",
but that may not work for people who are installing directly into
/lib/modules --- root partitions that were sized to handle 16 megs
worth of modules may not be quite so happy with 145 megs of modules,
so the "make modules_install" never succeeds.

This patch allows such users to request modules_install to strip the
modules as they are installed.

Signed-off-by: "Theodore Ts'o" 
Signed-off-by: Sam Ravnborg

kbuild: fix garbled text in modules.txt

2006-04-04T13:28:21+00:00

Signed-off-by: Brian Gerst 
Signed-off-by: Sam Ravnborg

kbuild: in makefile.txt note that Makefile is preferred name for kbuild files

2006-03-09T23:23:32+00:00

As noted by Roland Dreier  makefiles.txt told
one to use the name 'Kbuild' as preferred name for kbuild files.
This is not yet true so let makefiles.txt reflect reality.

Signed-off-by: Sam Ravnborg

kbuild: make cc-version available in kbuild files

2006-02-19T08:51:20+00:00

Move $(CC) support functions to Kbuild.include so they are available
in the kbuild files.
In addition the following was done:
	o as-option documented in Documentation/kbuild/makefiles.txt
	o Moved documentation to new section to match
	  new scope of functions
	o added cc-ifversion used to conditionally select a text string
	  dependent on actual $(CC) version
	o documented cc-ifversion
	o change so Kbuild.include is read before the kbuild file

Signed-off-by: Sam Ravnborg

kbuild: improved modversioning support for external modules

2006-02-19T08:51:18+00:00

With following patch a second option is enabled to obtain
symbol information from a second external module when a
external module is build.
The recommended approach is to use a common kbuild file but
that may be impractical in certain cases.
With this patch one can copy over a Module.symvers from one
external module to make symbols (and symbol versions) available
for another external module.

Updated documentation in Documentation/kbuild/modules.txt

Signed-off-by: Sam Ravnborg

kbuild: support building individual files for external modules

2006-02-19T08:51:17+00:00

Support building individual files when dealing with separate modules.
So say you have a module named "foo" which consist of two .o files bar.o
and fun.o.

You can then do:
make -C $KERNELSRC M=`pwd` bar.o
make -C $KERNELSRC M=`pwd` bar.lst
make -C $KERNELSRC M=`pwd` bar.i
make -C $KERNELSRC M=`pwd` /            <= will build all .o files
                                           and link foo.o
make -C $KERNELSRC M=`pwd` foo.ko       <= will build the module
                                           and do the modpost step
					   to create foo.ko

The above will also work if the external module is placed in a
subdirectory using a hirachy of kbuild files.
Thanks to Andreas Gruenbacher  for initial feature
request / bug report.

Signed-off-by: Sam Ravnborg

kbuild: remove GCC_VERSION

2006-01-08T18:58:51+00:00

This was causing some ordering problems.  Remove the up-front evaluation
and just revaluate the compiler version each time we need it.

(The up-front evaluation was problematic because some architectures modify
the value of $(CC)).

Signed-off-by: Andrew Morton 
Signed-off-by: Sam Ravnborg

kbuild: document howto build external modules using several directories

2006-01-06T19:33:41+00:00

Update modules.txt with info how to build external modules
with files in several directories.
The question popped up on lkml often enough to warrant this,
let's see if people read this stuff - or google hits it.

Signed-off-by: Sam Ravnborg

kbuild: patch to Documentation/kbuild/modules.txt

2005-12-16T22:15:41+00:00

First off, thanks for the kbuild docs, they are very useful!  Second,
I've attached a patch to modules.txt (from 2.6.14.2) with a "compile"
fix to a Makefile example, and some trivial spelling/grammar nits.
Please let me know if you want the patch in some other format (eg not
MIME), or if I should go bother someone else about it.

Signed-off-by: Sam Ravnborg