Re: [Minios-devel] [UNIKRAFT PATCH] build: add functionality to alternate linker script

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

Hello Yuri,

Please find a minor comments inline.

I think the rest of it fine.


Thanks & Regards
Sharan

On 1/28/19 11:02 AM, Yuri Volchkov wrote:
> With this patch libraries can amend the master linker script by
> registering the extra script in EXTRA_LD_SCRIPT-y variable.
>
> See doc/guides/developers-app.rst for details.
>
> Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
> ---
>   doc/guides/developers-app.rst | 26 ++++++++++++++++++++++++++
>   plat/kvm/Linker.uk            |  5 ++++-
>   plat/linuxu/Linker.uk         |  2 ++
>   plat/xen/Linker.uk            |  8 ++++++--
>   4 files changed, 38 insertions(+), 3 deletions(-)
>
> diff --git a/doc/guides/developers-app.rst b/doc/guides/developers-app.rst
> index 97ed2451..5919ab73 100644
> --- a/doc/guides/developers-app.rst
> +++ b/doc/guides/developers-app.rst
> @@ -31,6 +31,9 @@ you need to provide at least the following four files:
>      usually contains only `main` for an application that is developed/ported
>      as a single library to Unikraft.
>   
> + * **extra.ld**: Optional. Contains an amendment to the main linker
> +   script
> +
>   The Makefile is generally short and simple and might remind you to
>   Linux kernel modules that are built off-tree. For most applications
>   the Makefile should contain no more than the following: ::
> @@ -293,6 +296,29 @@ is part of a remotely fetched archive). You can override 
> it by defining the
>   with ``$(APPNAME_BASE)`` to the base directory of your application sources) or
>   relative to the Unikraft sources directory.
>   
> +============================
> +extra.ld
> +============================
> +If your library/application needs a section in the final elf, edit
> +your Makefile.uk to add ::
> +
> +    EXTRA_LD_SCRIPT-$(CONFIG_LIBYOURAPPNAME) += $(LIBYOURAPPNAME_BASE)/extra.ld
> +
> +
> +An example context of extra.ld: ::
> +
> +    SECTIONS
> +    {
> +        .uk_fs_list : {
> +             PROVIDE(uk_fslist_start = .);
> +             KEEP (*(.uk_fs_list))
> +             PROVIDE(uk_fslist_end = .);
> +        }
> +    }
> +    INSERT AFTER .text;
> +
> +This will add section .uk_fs_list after the .text
I think this should be "add the section".

> +
>   
>   ============================
>   Make Targets
> diff --git a/plat/kvm/Linker.uk b/plat/kvm/Linker.uk
> index e0a56774..4587daf7 100644
> --- a/plat/kvm/Linker.uk
> +++ b/plat/kvm/Linker.uk
> @@ -13,6 +13,8 @@ endif
>   ##
>   KVM_IMAGE := $(BUILD_DIR)/$(CONFIG_UK_NAME)_kvm-$(CONFIG_UK_ARCH)
>   
> +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) \
>                 $(KVM_LDSCRIPT)
> @@ -32,7 +34,8 @@ ifneq ($(filter x86_64 arm64,$(CONFIG_UK_ARCH)),)
>         $(call build_cmd,LD,,$@,\
>                $(LD) $(LDFLAGS) $(LDFLAGS-y) \
>                      $(KVM_LDFLAGS) $(KVM_LDFLAGS-y) \
> -                    -Wl$(comma)-T$(comma)$(call strip,$(KVM_LDSCRIPT)) \
> +                    -Wl$(comma)-dT$(comma)$(call strip,$(KVM_LDSCRIPT)) \
> +                    $(EXTRA_LD_SCRIPT_FLAGS) \
>                      $@.o -o $@)
>   ifeq ($(CONFIG_OPTIMIZE_DBGFILE),y)
>         $(call build_cmd,OBJCOPY,,$@.dbg,\
> diff --git a/plat/linuxu/Linker.uk b/plat/linuxu/Linker.uk
> index 9e4b2a9d..dbdf9d96 100644
> --- a/plat/linuxu/Linker.uk
> +++ b/plat/linuxu/Linker.uk
> @@ -4,6 +4,7 @@ LINUXU_LDFLAGS-y += -Wl,-e,_liblinuxuplat_start
>   ## Link image
>   ##
>   LINUXU_IMAGE := $(BUILD_DIR)/$(CONFIG_UK_NAME)_linuxu-$(CONFIG_UK_ARCH)
> +EXTRA_LD_SCRIPT_FLAGS := $(addprefix -Wl$(comma)-T,$(EXTRA_LD_SCRIPT-y))
>   
>   $(LINUXU_IMAGE): $(LINUXU_ALIBS) $(LINUXU_ALIBS-y) \
>                  $(LINUXU_OLIBS) $(LINUXU_OLIBS-y) \
> @@ -17,6 +18,7 @@ $(LINUXU_IMAGE): $(LINUXU_ALIBS) $(LINUXU_ALIBS-y) \
>                      $(LINUXU_ALIBS) $(LINUXU_ALIBS-y) \
>                      $(UK_ALIBS) $(UK_ALIBS-y) \
>                      -Wl$(comma)--end-group \
> +                    $(EXTRA_LD_SCRIPT_FLAGS) \
>                      -o $@)
>   ifeq ($(CONFIG_OPTIMIZE_DBGFILE),y)
>         $(call build_cmd,OBJCOPY,,$@.dbg,\
> diff --git a/plat/xen/Linker.uk b/plat/xen/Linker.uk
> index df84c20f..801f5e2e 100644
> --- a/plat/xen/Linker.uk
> +++ b/plat/xen/Linker.uk
> @@ -18,6 +18,8 @@ endif
>   ##
>   XEN_IMAGE := $(BUILD_DIR)/$(CONFIG_UK_NAME)_xen-$(CONFIG_UK_ARCH)
>   
> +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)
> @@ -36,7 +38,8 @@ $(XEN_IMAGE): $(XEN_ALIBS) $(XEN_ALIBS-y) $(XEN_OLIBS) 
> $(XEN_OLIBS-y) \
>   ifeq (arm,$(CONFIG_UK_ARCH))
>         $(call build_cmd,LD,,$@.elf,\
>                $(LD) $(LDFLAGS) $(LDFLAGS-y) $(XEN_LDFLAGS) $(XEN_LDFLAGS-y) \
> -                    -Wl$(comma)-T$(comma)$(call strip,$(XEN_LDSCRIPT)) \
> +                    -Wl$(comma)-dT$(comma)$(call strip,$(XEN_LDSCRIPT)) \
> +                    $(EXTRA_LD_SCRIPT_FLAGS) \
>                      $@.o -o $@.elf)
>   ifeq ($(CONFIG_OPTIMIZE_DBGFILE),y)
>         $(call build_cmd,OBJCOPY,,$@.dbg,\
> @@ -57,7 +60,8 @@ endif
>   else
>         $(call build_cmd,LD,,$@,\
>                $(LD) $(LDFLAGS) $(LDFLAGS-y) $(XEN_LDFLAGS) $(XEN_LDFLAGS-y) \
> -                    -Wl$(comma)-T$(comma)$(call strip,$(XEN_LDSCRIPT)) \
> +                    -Wl$(comma)-dT$(comma)$(call strip,$(XEN_LDSCRIPT)) \
> +                    $(EXTRA_LD_SCRIPT_FLAGS) \
>                      $@.o -o $@)
>   ifeq ($(CONFIG_OPTIMIZE_DBGFILE),y)
>         $(call build_cmd,OBJCOPY,,$@.dbg,\
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