acrn-kernel/init
Linus Torvalds 3af7236d6d update workarounds for gcc "asm goto" issue
commit 68fb3ca0e408e00db1c3f8fccdfa19e274c033be upstream.

In commit 4356e9f841f7 ("work around gcc bugs with 'asm goto' with
outputs") I did the gcc workaround unconditionally, because the cause of
the bad code generation wasn't entirely clear.

In the meantime, Jakub Jelinek debugged the issue, and has come up with
a fix in gcc [2], which also got backported to the still maintained
branches of gcc-11, gcc-12 and gcc-13.

Note that while the fix technically wasn't in the original gcc-14
branch, Jakub says:

 "while it is true that no GCC 14 snapshots until today (or whenever the
  fix will be committed) have the fix, for GCC trunk it is up to the
  distros to use the latest snapshot if they use it at all and would
  allow better testing of the kernel code without the workaround, so
  that if there are other issues they won't be discovered years later.
  Most userland code doesn't actually use asm goto with outputs..."

so we will consider gcc-14 to be fixed - if somebody is using gcc
snapshots of the gcc-14 before the fix, they should upgrade.

Note that while the bug goes back to gcc-11, in practice other gcc
changes seem to have effectively hidden it since gcc-12.1 as per a
bisect by Jakub.  So even a gcc-14 snapshot without the fix likely
doesn't show actual problems.

Also, make the default 'asm_goto_output()' macro mark the asm as
volatile by hand, because of an unrelated gcc issue [1] where it doesn't
match the documented behavior ("asm goto is always volatile").

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103979 [1]
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113921 [2]
Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/
Requested-by: Jakub Jelinek <jakub@redhat.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Andrew Pinski <quic_apinski@quicinc.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-02-23 09:12:28 +01:00
..
.gitignore kbuild: build init/built-in.a just once 2022-09-29 04:40:15 +09:00
Kconfig update workarounds for gcc "asm goto" issue 2024-02-23 09:12:28 +01:00
Makefile kbuild: generate include/generated/compile.h in top Makefile 2022-09-29 04:40:15 +09:00
build-version kbuild: build init/built-in.a just once 2022-09-29 04:40:15 +09:00
calibrate.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
do_mounts.c rootfs: Fix support for rootfstype= when root= is given 2024-01-25 15:27:43 -08:00
do_mounts.h init: add an init_mknod helper 2020-07-31 08:17:54 +02:00
do_mounts_initrd.c freezer,umh: Clean up freezer/initrd interaction 2022-09-07 21:53:48 +02:00
do_mounts_rd.c init: add an init_unlink helper 2020-07-31 08:17:52 +02:00
init_task.c rcu-tasks: Add data structures for lightweight grace periods 2022-06-20 09:22:28 -07:00
initramfs.c initramfs: mark my_inptr as __initdata 2022-09-11 21:55:11 -07:00
main.c proc: sysctl: prevent aliased sysctls from getting passed to init 2023-11-28 17:07:08 +00:00
noinitramfs.c init: move usermodehelper_enable() to populate_rootfs() 2021-09-08 11:50:27 -07:00
version-timestamp.c kbuild: build init/built-in.a just once 2022-09-29 04:40:15 +09:00
version.c kbuild: build init/built-in.a just once 2022-09-29 04:40:15 +09:00