Fix QEMU build on OpenBSD on x86 archs

This resolves the build issue with building the ROMs on OpenBSD on x86 archs.
As of OpenBSD 5.3 the compiler builds PIE binaries by default and thus the
whole OS/packages and so forth. The ROMs need to have PIE disabled. This
is my initial attempt at trying to get somehting upstream so that QEMU
both builds out of the box and to resolve the build issue with the
buildbots that has been around for awhile. We have a patch in our ports
tree but it is just the flags hardcoded into the Makefile which obviously
is not appropriate for upstream.

From the OpenBSD buildbots..
  Building optionrom/multiboot.img
ld: multiboot.o: relocation R_X86_64_16 can not be used when making a shared object; recompile with -fPIC

Signed-off by: Brad Smith <brad@comstyle.com>
Reviewed-by: Stefan Hajoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Brad Smith <brad@comstyle.com>
configure: Disable libtool if -fPIE does not work with it (bug #1257099)

Adjust TMPO and added TMPB, TMPL, and TMPA.  libtool needs the names
to be fixed (TMPB).

Add new functions do_libtool and libtool_prog.

Add check for broken gcc and libtool.

Signed-off-by: Don Slutz <dslutz@verizon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
rules.mak: fix $(obj) to a real relative path

Makefile.target includes rule.mak and unnested common-obj-y, then prefix
them with '../', this will ignore object specific QEMU_CFLAGS in subdir
Makefile.objs:

    $(obj)/curl.o: QEMU_CFLAGS += $(CURL_CFLAGS)

Because $(obj) here is './block', instead of '../block'. This doesn't
hurt compiling because we basically build all .o from top Makefile,
before entering Makefile.target, but it will affact arriving per-object
libs support.

The starting point of $(obj) is passed in as argument of unnest-vars, as
well as nested variables, so that different Makefiles can pass in a
right value.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
rules.mak: allow per object cflags and libs

Adds extract-libs in LINK to expand any "per object libs", the syntax to define
such a libs options is like:

        foo.o-libs := $(CURL_LIBS)

in block/Makefile.objs.

Similarly,

        foo.o-cflags := $(FOO_CFLAGS)

is also supported.

"foo.o" must be listed in a nested var (e.g. common-obj-y) to make the
option variables effective.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
block: use per-object cflags and libs

No longer adds flags and libs for them to global variables, instead
create config-host.mak variables like FOO_CFLAGS and FOO_LIBS, which is
used as per object cflags and libs.

This removes unwanted dependencies from libcacard.

Signed-off-by: Fam Zheng <famz@redhat.com>
[Split from Fam's patch to enable modules. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
darwin: do not use -mdynamic-no-pic

While -mdynamic-no-pic can speed up the code somewhat, it is only used
on the legacy PowerPC Mac OS X, and I am not sure if anyone is still
testing that.  Disabling PIC can cause problems when enabling modules,
so do not do that.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
build-sys: introduce common-obj-m and block-obj-m for DSO

Add necessary rules and flags for shared object generation.
$(common-obj-m) will include $(block-obj-m), like $(common-obj-y) does
for $(block-obj-y). The new rules introduced here are:

0) For all %.so compiling:

    QEMU_CFLAGS += -fPIC

1) %.o in $(common-obj-m) is compiled to %.o, then linked to %.so.

2) %.mo in $(common-obj-m) is the placeholder for %.so for pattern
matching in Makefile. It's linked to "-shared" with all its dependencies
(multiple *.o) as input. Which means the list of depended objects must
be specified in each sub-Makefile.objs:

    foo.mo-objs := bar.o baz.o qux.o

in the same style with foo.o-cflags and foo.o-libs. The objects here
will be prefixed with "$(obj)/" if it's a subdirectory Makefile.objs.

Also introduce --enable-modules in configure, the option will enable
support of shared object build. Otherwise objects are static linked to
executables.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
module: implement module loading

This patch adds loading, stamp checking and initialization of modules.

The init function of dynamic module is no longer directly called as
__attribute__((constructor)) in static linked version, it is called
only after passed the checking of presense of stamp symbol:

    qemu_stamp_$RELEASEHASH

where $RELEASEHASH is generated by hashing version strings and content
of configure script.

With this, modules built from a different tree/version/configure will
not be loaded.

The module loading code requires gmodule-2.0.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Makefile: install modules with "make install"

Install all the modules to ${MODDIR}.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
.gitignore: ignore module related files (dll, so, mo)

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
block: convert block drivers linked with libs to modules

The converted block drivers are:

    curl
    iscsi
    rbd
    ssh
    glusterfs

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
build: softmmu targets do not have a "main.o" file

Thus this rule is useless.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>