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Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archi
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols |
Date: |
Mon, 01 Sep 2014 12:37:35 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 |
Il 01/09/2014 12:35, Fam Zheng ha scritto:
> This fixes an issue with module build system. block/iscsi.so is
> currently broken:
>
> $ ~/build/last/qemu-img
> Failed to open module: /home/fam/build/master/block-iscsi.so:
> undefined symbol: qmp_query_uuid
> qemu-img: Not enough arguments
> Try 'qemu-img --help' for more information
>
> To fix this, we should (at least) let qemu-img link qmp_query_uuid from
> libqemustub.a. (There are a few other symbols missing, as well.)
>
> This patch changes the linking rules to:
>
> 1) Build ".mo" with "ld -r -o $@ $^" for each ".so", and later build .so
> with it.
>
> 2) Always build all the .mo before linking the executables. This is
> achieved by adding those .mo files to the executables' "-y"
> variables.
>
> 3) When linking an executable, those .mo files in its "-y" variables are
> filtered out, and replaced by one or more -Wl,-u,$symbol flags. This
> is done in the added macro "process-archive-undefs".
>
> These "-Wl,-u,$symbol" flags will force ld to pull in the function
> definition from the archives when linking.
>
> Note that the .mo objects, that are actually meant to be linked in
> the executables, are already expanded in unnest-vars, before the
> linking command. So we are safe to simply filter out .mo for the
> purpose of pulling undefined symbols.
>
> process-archive-undefs works as this: For each ".mo", find all the
> undefined symbols in it, filter ones that are defined in the
> archives. For each of these symbols, generate a "-Wl,-u,$symbol" in
> the link command, and put them before archive names in the command
> line.
>
> Suggested-by: H.J. Lu <address@hidden>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
> rules.mak | 43 ++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 40 insertions(+), 3 deletions(-)
>
> diff --git a/rules.mak b/rules.mak
> index ba2f4c1..1d73293 100644
> --- a/rules.mak
> +++ b/rules.mak
> @@ -22,6 +22,32 @@ QEMU_DGFLAGS += -MMD -MP -MT $@ -MF $(*D)/$(*F).d
> # Same as -I$(SRC_PATH) -I., but for the nested source/object directories
> QEMU_INCLUDES += -I$(<D) -I$(@D)
>
> +WL_U := -Wl,-u,
> +find-symbols = $(if $1, $(sort $(shell nm -P -g $1 | $2)))
> +defined-symbols = $(call find-symbols,$1,awk '$$2!="U"{print $$1}')
> +undefined-symbols = $(call find-symbols,$1,awk '$$2=="U"{print $$1}')
> +
> +# All the .mo objects in -m variables are also added into corresponding -y
> +# variable in unnest-vars, but filtered out here, when LINK is called.
> +#
> +# The .mo objects are supposed to be linked as a DSO, for module build. So
> here
> +# they are only used as a placeholders to generate those "archive undefined"
> +# symbol options (-Wl,-u,$symbol_name), which are the archive functions
> +# referenced by the code in the DSO.
> +#
> +# Also the presence in -y variables will also guarantee they are built before
> +# linking executables that will load them. So we can look up symbol reference
> +# in LINK.
> +#
> +# This is necessary because the exectuable itself may not use the function,
> in
> +# which case the function would not be linked in. Then the DSO loading will
> +# fail because of the missing symbol.
> +process-archive-undefs = $(filter-out %.a %.mo,$1) \
> + $(addprefix $(WL_U), \
> + $(filter $(call defined-symbols,$(filter %.a, $1)), \
> + $(call undefined-symbols,$(filter %.mo,$1)))) \
> + $(filter %.a,$1)
> +
> extract-libs = $(strip $(foreach o,$1,$($o-libs)))
> expand-objs = $(strip $(sort $(filter %.o,$1)) \
> $(foreach o,$(filter %.mo,$1),$($o-objs)) \
> @@ -38,7 +64,8 @@ LINKPROG = $(or $(CXX),$(CC))
>
> ifeq ($(LIBTOOL),)
> LINK = $(call quiet-command, $(LINKPROG) $(QEMU_CFLAGS) $(CFLAGS) $(LDFLAGS)
> -o $@ \
> - $1 $(version-obj-y) $(call extract-libs,$1) $(LIBS)," LINK
> $(TARGET_DIR)$@")
> + $(call process-archive-undefs, $1) \
> + $(version-obj-y) $(call extract-libs,$1) $(LIBS)," LINK
> $(TARGET_DIR)$@")
> else
> LIBTOOL += $(if $(V),,--quiet)
> %.lo: %.c
> @@ -50,7 +77,8 @@ LIBTOOL += $(if $(V),,--quiet)
>
> LINK = $(call quiet-command,\
> $(if $(filter %.lo %.la,$1),$(LIBTOOL) --mode=link --tag=CC \
> - )$(LINKPROG) $(QEMU_CFLAGS) $(CFLAGS) $(LDFLAGS) -o $@ $1 \
> + )$(LINKPROG) $(QEMU_CFLAGS) $(CFLAGS) $(LDFLAGS) -o $@ \
> + $(call process-archive-undefs, $1)\
> $(if $(filter %.lo %.la,$1),$(version-lobj-y),$(version-obj-y)) \
> $(if $(filter %.lo %.la,$1),$(LIBTOOLFLAGS)) \
> $(call extract-libs,$(1:.lo=.o)) $(LIBS),$(if $(filter %.lo
> %.la,$1),"lt LINK ", " LINK ")"$(TARGET_DIR)$@")
> @@ -76,11 +104,17 @@ endif
>
> %$(DSOSUF): CFLAGS += -fPIC -DBUILD_DSO
> %$(DSOSUF): LDFLAGS += $(LDFLAGS_SHARED)
> -%$(DSOSUF):
> +%$(DSOSUF): %.mo
> $(call LINK,$^)
> @# Copy to build root so modules can be loaded when program started
> without install
> $(if $(findstring /,$@),$(call quiet-command,cp $@ $(subst /,-,$@), "
> CP $(subst /,-,$@)"))
>
> +
> +LD_REL := $(CC) -nostdlib -Wl,-r
> +
> +%.mo:
> + $(call quiet-command,$(LD_REL) -o $@ $^," LD -r $(TARGET_DIR)$@")
> +
> .PHONY: modules
> modules:
>
> @@ -306,6 +340,9 @@ define unnest-vars
> # For module build, build shared libraries during "make modules"
> # For non-module build, add -m to -y
> $(if $(CONFIG_MODULES),
> + $(foreach o,$($v),
> + $(eval $o: $($o-objs)))
> + $(eval $(patsubst %-m,%-y,$v) += $($v))
> $(eval modules: $($v:%.mo=%$(DSOSUF))),
> $(eval $(patsubst %-m,%-y,$v) += $(call expand-objs, $($v)))))
>
>
Thanks,
Reviewed-by: Paolo Bonzini <address@hidden>
- [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Fam Zheng, 2014/09/01
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Peter Maydell, 2014/09/01
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Paolo Bonzini, 2014/09/01
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Peter Maydell, 2014/09/01
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Paolo Bonzini, 2014/09/01
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Peter Maydell, 2014/09/01
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Fam Zheng, 2014/09/01
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Paolo Bonzini, 2014/09/02
- Re: [Qemu-devel] [PATCH v2] rules.mak: Fix DSO build by pulling in archive symbols, Fam Zheng, 2014/09/02