Re: [Minios-devel] [UNIKRAFT PATCH 4/8] lib/uklibparam: Add linker script for parameter

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

On 4/11/19 4:17 PM, Florian Schmidt wrote:
> On 3/15/19 6:06 PM, Sharan Santhanam wrote:
> > This patch introduces a linker script to create linker
> > section to place the library arguments meta-data.
> >
> > Signed-off-by: Sharan Santhanam <sharan.santhanam@xxxxxxxxx>
> > ---
> >   Makefile                      |  2 ++
> >   lib/uklibparam/libparam.lds.S | 23 +++++++++++++++++++++++
> >   plat/kvm/Linker.uk            |  2 +-
> >   plat/linuxu/Linker.uk         |  3 ++-
> >   plat/xen/Linker.uk            |  2 +-
> >   support/build/Makefile.rules  | 35 +++++++++++++++++++++++++++++++++++
> >   6 files changed, 64 insertions(+), 3 deletions(-)
> >   create mode 100644 lib/uklibparam/libparam.lds.S
> >
> > diff --git a/Makefile b/Makefile
> > index 8e81c64..e0fc145 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -198,6 +198,8 @@ UK_ALIBS:=
> >   UK_ALIBS-y:=
> >   UK_OLIBS:=
> >   UK_OLIBS-y:=
> > +UK_LDS:=
> > +UK_LDS-y:=
> >   UK_SRCS:=
> >   UK_SRCS-y:=
> >   UK_DEPS:=
> > diff --git a/lib/uklibparam/libparam.lds.S 
> > b/lib/uklibparam/libparam.lds.S
> > new file mode 100644
> > index 0000000..3a9c920
> > --- /dev/null
> > +++ b/lib/uklibparam/libparam.lds.S
> > @@ -0,0 +1,23 @@
> > +#include <uk/config.h>
> > +#include <uk/libparam.h>
> > +
> > +#define create_var(x,y) __STRINGCONCAT(x,y)
> > +#ifdef UK_LIBPARAM_PREFIX
> > +SECTIONS
> > +{
> > +    create_var(UK_LIBPARAM_PREFIX,__param_arg) : {
> > +        _SECTION_START(
> > +                _LIB_PARAM_SECTION_NAME(UK_LIBPARAM_PREFIX,
> > +                            PARAM_SECTION_SUFFIX)
> > +                  ) = .;
> > +
> > +        KEEP (*(create_var(UK_LIBPARAM_PREFIX,PARAM_SECTION_SUFFIX)))
> > +
> > +        _SECTION_STOP(
> > +                _LIB_PARAM_SECTION_NAME(UK_LIBPARAM_PREFIX,
> > +                            PARAM_SECTION_SUFFIX)
> > +                  ) = .;
> > +    }
> > +}
> > +INSERT AFTER .rodata
> > +#endif /* UK_LIBPARAM_PREFIX */
> So, the thing I don't like about this is that it creates a lot of 
> additional sections in the ELF file: one when libparam is activated, and 
> then another 2 for each library that has parameters. My understanding is 
> you don't really care about the section itself, but rather use it to 
> group all your variables together into a contiguous memory space, and to 
> set the START and STOP variables to find it. There should be some way to 
> achieving that without having to carry around those extra section 
> headers, merging those sections into .rodata or another appropriate 
> standard section in the last linking step... I just am not sure yet how.
> I will remove the separate section for the library names.
For the library and parameter metadata section I am not so sure. Maybe 
we could a create a single section separated by start and end variables 
within that section. But I would keep as such for this series and look 
to fix it in the next version.
> > diff --git a/plat/kvm/Linker.uk b/plat/kvm/Linker.uk
> > index f696e25..4b8b167 100644
> > --- a/plat/kvm/Linker.uk
> > +++ b/plat/kvm/Linker.uk
> > @@ -15,7 +15,7 @@ EXTRA_LD_SCRIPT_FLAGS := $(addprefix 
> > -Wl$(comma)-T,$(EXTRA_LD_SCRIPT-y))
> >   $(KVM_IMAGE): $(KVM_ALIBS) $(KVM_ALIBS-y) $(KVM_OLIBS) $(KVM_OLIBS-y) \
> >                 $(UK_ALIBS) $(UK_ALIBS-y) $(UK_OLIBS) $(UK_OLIBS-y) \
> > -              $(KVM_LDSCRIPT)
> > +              $(UK_LDS) $(UK_LDS-y)
> >       $(call build_cmd,LD,,$@.ld.o,\
> >              $(LD) -r $(LIBLDFLAGS) $(LIBLDFLAGS-y) \
> >               $(KVM_LDFLAGS) $(KVM_LDFLAGS-y) \
> > diff --git a/plat/linuxu/Linker.uk b/plat/linuxu/Linker.uk
> > index dbdf9d9..f4387fa 100644
> > --- a/plat/linuxu/Linker.uk
> > +++ b/plat/linuxu/Linker.uk
> > @@ -8,7 +8,8 @@ EXTRA_LD_SCRIPT_FLAGS := $(addprefix 
> > -Wl$(comma)-T,$(EXTRA_LD_SCRIPT-y))
> >   $(LINUXU_IMAGE): $(LINUXU_ALIBS) $(LINUXU_ALIBS-y) \
> >            $(LINUXU_OLIBS) $(LINUXU_OLIBS-y) \
> > -         $(UK_ALIBS) $(UK_ALIBS-y) $(UK_OLIBS) $(UK_OLIBS-y)
> > +         $(UK_ALIBS) $(UK_ALIBS-y) $(UK_OLIBS) $(UK_OLIBS-y) \
> > +         $(UK_LDS) $(UK_LDS-y)
> >       $(call build_cmd,LD,,$@,\
> >              $(LD) $(LDFLAGS) $(LDFLAGS-y) \
> >                $(LINUXU_LDFLAGS) $(LINUXU_LDFLAGS-y) \
> > diff --git a/plat/xen/Linker.uk b/plat/xen/Linker.uk
> > index 801f5e2..aea1089 100644
> > --- a/plat/xen/Linker.uk
> > +++ b/plat/xen/Linker.uk
> > @@ -22,7 +22,7 @@ EXTRA_LD_SCRIPT_FLAGS := $(addprefix 
> > -Wl$(comma)-T,$(EXTRA_LD_SCRIPT-y))
> >   $(XEN_IMAGE): $(XEN_ALIBS) $(XEN_ALIBS-y) $(XEN_OLIBS) $(XEN_OLIBS-y) \
> >                 $(UK_ALIBS) $(UK_ALIBS-y) $(UK_OLIBS) $(UK_OLIBS-y) \
> > -              $(XEN_LDSCRIPT)
> > +              $(UK_LDS) $(UK_LDS-y)
> >       $(call build_cmd,LD,,$@.ld.o,\
> >              $(LD) -r $(LIBLDFLAGS) $(LIBLDFLAGS-y) \
> >               $(XEN_LDFLAGS) $(XEN_LDFLAGS-y) \
> > diff --git a/support/build/Makefile.rules b/support/build/Makefile.rules
> > index 04f2f0d..631fee3 100644
> > --- a/support/build/Makefile.rules
> > +++ b/support/build/Makefile.rules
> > @@ -157,6 +157,26 @@ $(call addlib,$(1))
> >   endif
> >   endef
> > +# add_paramprefix $name $libname
> > +define add_paramprefix =
> > +$(eval 
> > UK_LIB_PARAM_LDS:=$(CONFIG_UK_BASE)/lib/uklibparam/libparam.lds.S)
> > +$(eval $(call uc,$(2))_CFLAGS += -DUK_LIBPARAM_PREFIX=$(1))
> > +$(eval $(call uc,$(2))_CXXFLAGS += -DUK_LIBPARAM_PREFIX=$(1))
> > +$(eval $(call uc,$(2))_ASFLAGS += -DUK_LIBPARAM_PREFIX=$(1))
> > +$(eval $(call uc,$(2))_LD_SCRIPT := $(call 
> > src2lds,$(2),$(UK_LIB_PARAM_LDS)))
> > +endef
> > +
> > +# addlib_paramprefix $libname,$paramname(optional)
> > +define addlib_paramprefix =
> > +$(if $(2),\
> > +$(eval name := $(2)),\
> > +$(eval name := $(1)))
> > +$(eval $(call add_paramprefix,$(name),$(1),$(call uc,$(1))))
> > +$(eval EXTRA_LD_SCRIPT-$(CONFIG_LIBUKLIBPARAM) += $($(call 
> > uc,$(1))_LD_SCRIPT))
> > +$(eval $(call uc,$(1))_SRCS-$(CONFIG_LIBUKLIBPARAM) += 
> > $(UK_LIB_PARAM_LDS))
> > +$(eval $(call uc,$(1))_CLEAN-$(CONFIG_LIBUKLIBPARAM) += \
> > +                        $($(call uc,$(1))_LD_SCRIPT))
> > +endef
> >   # addplatlib $platname,$libname
> >   define addplatlib =
> > @@ -173,6 +193,20 @@ $(if $(filter y,$(3)),$(call addplatlib,$(1),$(2)),)
> >   endef
> > +# addplatlib_paramprefix,$plat,$libname,$paramname(optional)
> > +define addplatlib_paramprefix =
> > +$(if $(3),\
> > +$(eval name:=$(3)),\
> > +$(eval name:=$(2)))
> > +$(eval $(call add_paramprefix,$(name),$(2)))
> > +$(eval $(call uc,$(1))_LD_SCRIPT-$(CONFIG_LIBUKLIBPARAM) +=\
> > +                        $($(call uc,$(2))_LD_SCRIPT))
> > +$(eval $(call uc,$(2))_SRCS-$(CONFIG_LIBUKLIBPARAM) += \
> > +                        $(UK_LIB_PARAM_LDS))
> > +$(eval $(call uc,$(2))_CLEAN-$(CONFIG_LIBUKLIBPARAM) +=\
> > +                        $($(call uc,$(2))_LD_SCRIPT))
> > +endef
> > +
> >   
> > ################################################################################ 
> >
> >   #
> >   # Command calling
> > @@ -420,6 +454,7 @@ $(3): $(2) | prepare
> >       )
> >   UK_SRCS-y += $(2)
> > +UK_LDS-y += $(3)
> >   UK_DEPS-y += $(call out2dep,$(3))
> >   $(eval $(call vprefix_lib,$(1),CLEAN-y) += $(call build_clean,$(3)) 
> > $(call out2dep,$(3)))
> >   endef
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