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Quentin Perret 92f76ef499 FROMLIST: kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS
CONFIG_TRIM_UNUSED_KSYMS currently removes all unused exported symbols
from ksymtab. This works really well when using in-tree drivers, but
cannot be used in its current form if some of them are out-of-tree.

Indeed, even if the list of symbols required by out-of-tree drivers is
known at compile time, the only solution today to guarantee these don't
get trimmed is to set CONFIG_TRIM_UNUSED_KSYMS=n. This not only wastes
space, but also makes it difficult to control the ABI usable by vendor
modules in distribution kernels such as Android. Being able to control
the kernel ABI surface is particularly useful to ship a unique Generic
Kernel Image (GKI) for all vendors, which is a first step in the
direction of getting all vendors to contribute their code upstream.

As such, attempt to improve the situation by enabling users to specify a
symbol 'whitelist' at compile time. Any symbol specified in this
whitelist will be kept exported when CONFIG_TRIM_UNUSED_KSYMS is set,
even if it has no in-tree user. The whitelist is defined as a simple
text file, listing symbols, one per line.

Bug: 148277666
Acked-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Tested-by: Matthias Maennich <maennich@google.com>
Reviewed-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/lkml/20200218094139.78835-2-qperret@google.com
Change-Id: Ie9a4bbb8eebb20202623f084859fb89e55a32698
2020-02-27 09:59:18 +00:00
arch ANDROID: gki_defconfig: Disable CONFIG_RT_GROUP_SCHED 2020-02-27 00:17:35 +00:00
block ANDROID: ufs, block: fix crypto power management and move into block layer 2020-02-20 21:21:58 +00:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity 2020-02-20 15:15:16 -08:00
Documentation Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
drivers FROMGIT: of: property: Add device link support for power-domains and hwlocks 2020-02-26 22:59:58 +00:00
fs Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
include Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
init FROMLIST: kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS 2020-02-27 09:59:18 +00:00
ipc Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
kernel ANDROID: Disable wq fp check in CFI builds 2020-02-27 00:07:36 +00:00
lib Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
net Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
samples Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
scripts FROMLIST: kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS 2020-02-27 09:59:18 +00:00
security Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
sound Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
tools Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
usr Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
virt KVM: Disable preemption in kvm_get_running_vcpu() 2020-02-12 12:19:35 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Revert "ANDROID: Revert "Merge tag 'modules-for-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux"" 2019-11-13 10:14:45 +00:00
.mailmap A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
build.config.aarch64 ANDROID: support GKI image that contains an uncompressed Kernel Image. 2020-02-06 11:09:08 +00:00
build.config.allmodconfig ANDROID: Don't base allmodconfig on gki_defconfig 2019-12-05 12:39:45 +00:00
build.config.allmodconfig.aarch64 ANDROID: create build.configs for allmodconfig 2019-09-04 15:49:40 +00:00
build.config.allmodconfig.x86_64 ANDROID: create build.configs for allmodconfig 2019-09-04 15:49:40 +00:00
build.config.common ANDROID: clang: update to 10.0.4 2020-02-19 18:09:28 +00:00
build.config.cuttlefish.aarch64 ANDROID: cf build: Use merge_configs 2020-02-18 21:12:56 +00:00
build.config.cuttlefish.x86_64 ANDROID: cf build: Use merge_configs 2020-02-18 21:12:56 +00:00
build.config.db845c ANDROID: db845c: Add build config 2020-01-15 00:48:32 +00:00
build.config.gki ANDROID: gki: Removed cf modules from gki_defconfig 2020-02-01 00:27:50 +00:00
build.config.gki.aarch64 ANDROID: Remove ABI Monitoring on android-mainline 2020-01-27 13:53:52 +00:00
build.config.gki.x86_64 ANDROID: refactor build.config files to remove duplication 2019-08-30 14:55:29 +01:00
build.config.x86_64 ANDROID: refactor build.config files to remove duplication 2019-08-30 14:55:29 +01:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS open: introduce openat2(2) syscall 2020-01-18 09:19:18 -05:00
cuttlefish.fragment ANDROID: gki_defconfig: Disable SDCARD_FS 2020-02-14 13:35:25 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS csky updates for 5.6-rc3 2020-02-23 09:37:41 -08:00
Makefile Linux 5.6-rc3 2020-02-24 09:22:04 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00
README.md ANDROID: README: Add add user reference to backporting comment 2020-01-08 15:15:09 +00:00

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

    • Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux, additions of EXPORT_SYMBOL_GPL() require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export.
    • When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.
  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass script/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry picked from commit ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry picked from commit ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [joe: Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)