core/sdk: don't mangle symlinks with '.' or '..' at start

The previous transform of changing any '.' at the start of a line to $(BR2_SDK_PREFIX) mangles any symlinks with a relative path starting with '.' or '..' in the host folder, as --transform operates on the link target as opposed to the link name.

You might end up with something like:
$(BR2_SDK_PREFIX)/bin/aarch64-linux-gnu-ar -> $(BR2_SDK_PREFIX)./opt/ext-toolchain/bin/aarch64-linux-gnu-ar

when it should be:
$(BR2_SDK_PREFIX)/bin/aarch64-linux-gnu-ar ->
../opt/ext-toolchain/bin/aarch64-linux-gnu-ar

Instead, don't change to HOST_DIR when creating the tarball, and pass the path to HOST_DIR. Tar will strip the leading / from member names, so then transform that path (HOST_DIR with leading / removed) to BR2_SDK_PREFIX.

However hardlinks are still linking to HOST_DIR, so do an additional transform of $(HOST_DIR) (keeping the leading slash) to BR2_SDK_PREFIX in order to catch those.

Signed-off-by Joel Carlson <[email protected]>

---
If accepted, this should probably get put on 2018.11.x.

---
 Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Makefile +1 -0

index 37df98520e..668c3e09e0 100644
@@ -591,6 +591,7 @@ prepare-sdk: world
 	echo $(HOST_DIR) > $(HOST_DIR)/share/buildroot/sdk-location
 
 BR2_SDK_PREFIX ?= $(GNU_TARGET_NAME)_sdk-buildroot
+HOST_DIR_NO_LEAD_SLASH=$(shell echo $(HOST_DIR) | tail -c +2)
 .PHONY: sdk
 sdk: prepare-sdk $(BR2_TAR_HOST_DEPENDENCY)
 	@$(call MESSAGE,"Generating SDK tarball")

Makefile +0 -0

 RSYNC_VCS_EXCLUSIONS = \
 	--exclude .svn --exclude .git --exclude .hg --exclude .bzr \

Signature · 1 line

2.17.1

Quoted 17 lines

---
 Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Makefile +1 -0

index 37df98520e..668c3e09e0 100644
@@ -591,6 +591,7 @@ prepare-sdk: world
      echo $(HOST_DIR) > $(HOST_DIR)/share/buildroot/sdk-location
 
 BR2_SDK_PREFIX ?= $(GNU_TARGET_NAME)_sdk-buildroot
+HOST_DIR_NO_LEAD_SLASH=$(shell echo $(HOST_DIR) | tail -c +2)
 .PHONY: sdk
 sdk: prepare-sdk $(BR2_TAR_HOST_DEPENDENCY)
      @$(call MESSAGE,"Generating SDK tarball")

Makefile sdk: prepare-sdk $(BR2_TAR_HOST_DEPENDENCY) · line 603

Quoted 7 lines

Makefile +2 -2

@@ -598,8 +599,8 @@ sdk: prepare-sdk $(BR2_TAR_HOST_DEPENDENCY)
      $(Q)mkdir -p $(BINARIES_DIR)
      $(TAR) czf "$(BINARIES_DIR)/$(BR2_SDK_PREFIX).tar.gz" \
              --owner=0 --group=0 --numeric-owner \
-             --transform='s#^\.#$(BR2_SDK_PREFIX)#' \
-             -C $(HOST_DIR) "."
+             --transform='s#^$(HOST_DIR_NO_LEAD_SLASH)#$(BR2_SDK_PREFIX)#' \
+             --transform='s#^$(HOST_DIR)#$(BR2_SDK_PREFIX)#' $(HOST_DIR)

Well, I am not too fond of this new HOST_DIR_NO_LEAD_SLASH variable, since it is used in a single location. And calling to the shell is not nice either.

What about replaciong that with just:

    $(patsubst /%,%,$(HOST_DIR))

Now, this fixup is not enough, in fact, because thisleaves symlinks to absolute paths borked, e.g.:

    /path/to/host/bin/foo -> /path/to/host/bin/bar

is turned into:

    /path/to/new/host/bin/foo -> sdkprefix/bin/bar

which obviously is incorrect.

So we need more work in this area, and the first thing we should do is to transform absolute symlinks into relative ones, to be done in the prepare-sdk rule, I suppose...

Quoted 1 line

    $(patsubst /%,%,$(HOST_DIR))

I didn't read the documentation on patsubst close enough and didn't realize you could make it replace only the first occurrence. That suggestion works and I'll use it.

Quoted 2 lines

Now, this fixup is not enough, in fact, because thisleaves symlinks to absolute paths borked, e.g.:

Symlinks with an absolute path is not a case I had considered. I will work this further and submit a v2 patch. Thanks!