sstate_readonly: only allowed sstate-cache objects to be built (read-only sstate-cache)

Changed in V4:
- Enable read-only sstate-cache by inheriting the bbclass rather than by the SSTATECACHE_WHITELIST value is not null. There will be cases where customers don't want to build -anything- from source. In V3, So they would need to enter a dummy value to get that behavior, and that would not be intuitive.

Changed in V3:
- remove bitbake patch, which was sent to bitbake-devel
- rebase 'bbclass/sstate' patch, which was conflicted with 'sstate: Add extra intercept functions' patch in master-next

Changed in V2:

- add hook SSTATE_CHECK_FUNCTIONS for sstate checking, and add a new bbclass/sstate_readonly, rather than directly modify bbclass/sstate

- terminate build safely while RunQueueExecuteScenequeue init failed, the previous bb.msg.fatal is too hack.

Test Steps:

1) Prepare an existed sstate_cache with cache directory "Sstate_Cache_Dir" It contained db-native sstate_cache.

2) Enable read-only sstate-cache by inheriting, and assign SSTATE_DIR with Sstate_Cache_Dir, vim local.conf
...
INHERIT += 'sstate_readonly'
SSTATE_DIR = "Sstate_Cache_Dir"
...

3) bitbake db-native

4) tweak db's do_configure task by adding comments

@@ -82,6 +82,7 @@ do_configure() {
        gnu-configize --force ${S}
        export STRIP="true"
        oe_runconf
+       echo "hello"
 }
 
 

5) build db-native and there is a build failure

$ bitbake db-native
...
ERROR: Read-only sstate-cache is enabled, the build of 
"db-native"
did not come from sstate-cache. Only the recipe listed in
SSTATECACHE_WHITELIST is allowed to build from source
ERROR: Hash validation failed in RunQueueExecuteScenequeue Function failed: sstate_readonly_check
...

6) clean db-native failed

$ bitbake db-native -ccleansstate
...
ERROR: Read-only sstate-cache is enabled, the clean of 
db-native is not allowed. Only the recipe listed in
SSTATECACHE_WHITELIST is allowed to clean sstate-cache
...

$ bitbake db-native -ccleanall
...
ERROR: Read-only sstate-cache is enabled, the clean of 
db-native is not allowed. Only the recipe listed in
SSTATECACHE_WHITELIST is allowed to clean sstate-cache
...

7) Add db-native to SSTATECACHE_WHITELIST
vim local.conf
...
SSTATECACHE_WHITELIST = 'db-native'
...

8) build/clean db-native succee

$ bitbake db-native
$ bitbake db-native -ccleansstate
$ bitbake db-native -ccleanall

//Hongxu

The following changes since commit 669c07d6022174d01fe5a95b7b0faa9ef86da1e2:

bitbake: build/data: Write out more complete python run files (2014-08-28 15:12:45 +0100)

are available in the git repository at:

git://git.pokylinux.org/poky-contrib hongxu/readonly-sstatecache
http://git.pokylinux.org/cgit.cgi/poky-contrib/log/?h=hongxu/readonly-sstatecache

Hongxu Jia (2):
bbclass/sstate: add hook SSTATE_CHECK_FUNCTIONS for sstate checking bbclass/sstate_readonly: only allowed sstate-cache objects to be built
(read-only sstate-cache)

 meta/classes/sstate.bbclass          | 26 ++++++++++++++++++
 meta/classes/sstate_readonly.bbclass | 53 ++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)
 create mode 100644 meta/classes/sstate_readonly.bbclass

1.9.1