[PATCH] download: improve handling of invalid local files

[Eneas U de Queiroz]

4e19cbc5533: [download: handle possibly invalid local tarballs] added a
FORCE rule to downloaded files, so that they will be always checked by
download.pl.

As a side-effect, check-compile will fail, forcing unnecessary package
rebuilds.
The check-compile.txt log shows (for libxml2 for example):
  Considering target file '.../dl/libxml2-2.9.12.tar.gz'.
    ...
    prerequisite 'FORCE' of target '.../dl/libxml2-2.9.12.tar.gz' does
    not exist.
    Must remake target '.../dl/libxml2-2.9.12.tar.gz'.
    ...
   Giving up on target file '...libxml2-2.9.12/.prepared_...'.
   Giving up on target file '...libxml2-2.9.12/.configured_...'.
   Giving up on target file '...libxml2-2.9.12/.built'.
   Giving up on target file '...stamp/.libxml2_installed'.
  Giving up on target file '.compile'.

Then the package is rebuilt even if it is not otherwise needed.

To fix this, instead of always forcing the download target to be remade,
check its hash first: if it matches, then the FORCE is not added.

Signed-off-by: Eneas U de Queiroz <cotequeiroz at gmail.com>
---
 include/download.mk   | 17 +++++++++++++++--
 include/host-build.mk |  2 +-
 include/package.mk    |  2 +-
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/download.mk b/include/download.mk
index 609956b004..76bd374cf7 100644
--- a/include/download.mk
+++ b/include/download.mk
@@ -59,6 +59,21 @@ define dl_tar_pack
 		$$$${TAR_TIMESTAMP:+--mtime="$$$$TAR_TIMESTAMP"} -c $(2) | $(call dl_pack,$(1))
 endef
 
+gen_sha256sum = $(shell $(MKHASH) sha256 $(DL_DIR)/$(1))
+
+# Used in Build/CoreTargets and HostBuild/Core as an integrity check for
+# downloaded files.  It will add a FORCE rule if the sha256 hash does not
+# match, so that the download can be more thoroughly handled by download.pl.
+define check_download_integrity
+  expected_hash:=$(strip $(if $(filter-out x,$(HASH)),$(HASH),$(MIRROR_HASH)))
+  $$(if $$(and $(FILE),$$(wildcard $(DL_DIR)/$(FILE)), \
+	       $$(filter undefined,$$(flavor DownloadChecked/$(FILE)))), \
+    $$(eval DownloadChecked/$(FILE):=1) \
+    $$(if $$(filter-out $$(call gen_sha256sum,$(FILE)),$$(expected_hash)), \
+      $(DL_DIR)/$(FILE): FORCE) \
+  )
+endef
+
 ifdef CHECK
 check_escape=$(subst ','\'',$(1))
 #')
@@ -74,8 +89,6 @@ else
   check_warn = $(if $(filter-out undefined,$(origin F_$(1))),$(filter ,$(shell $(call F_$(1),$(2),$(3),$(4)) >&2)),$(check_warn_nofix))
 endif
 
-gen_sha256sum = $(shell $(MKHASH) sha256 $(DL_DIR)/$(1))
-
 ifdef FIXUP
 F_hash_deprecated = $(SCRIPT_DIR)/fixup-makefile.pl $(CURDIR)/Makefile fix-hash $(3) $(call gen_sha256sum,$(1)) $(2)
 F_hash_mismatch = $(F_hash_deprecated)
diff --git a/include/host-build.mk b/include/host-build.mk
index e4a5c48e72..cfa29419aa 100644
--- a/include/host-build.mk
+++ b/include/host-build.mk
@@ -180,7 +180,7 @@ ifndef DUMP
     clean-build: host-clean-build
   endif
 
-  $(DL_DIR)/$(FILE): FORCE
+  $(call check_download_integrity)
 
   $(_host_target)host-prepare: $(HOST_STAMP_PREPARED)
   $(_host_target)host-configure: $(HOST_STAMP_CONFIGURED)
diff --git a/include/package.mk b/include/package.mk
index db0a869dab..55d9352072 100644
--- a/include/package.mk
+++ b/include/package.mk
@@ -183,7 +183,7 @@ define Build/CoreTargets
   $(call Build/Autoclean)
   $(call DefaultTargets)
 
-  $(DL_DIR)/$(FILE): FORCE
+  $(call check_download_integrity)
 
   download:
 	$(foreach hook,$(Hooks/Download),