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

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

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
+
 
 ============================
 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,\
-- 
2.19.2


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