linux/init
Linus Torvalds 68fb3ca0e4 update workarounds for gcc "asm goto" issue
In commit 4356e9f841 ("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>
2024-02-15 11:14:33 -08:00
..
.gitignore kbuild: build init/built-in.a just once 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
do_mounts_initrd.c init: pass root_device_name explicitly 2023-06-05 10:55:20 -06:00
do_mounts_rd.c
do_mounts.c rootfs: Fix support for rootfstype= when root= is given 2023-12-07 10:29:21 +09:00
do_mounts.h init: pass root_device_name explicitly 2023-06-05 10:55:20 -06:00
init_task.c header cleanups for 6.8 2024-01-10 16:43:55 -08:00
initramfs.c initramfs: Expose retained initrd as sysfs file 2023-12-15 17:23:00 +01:00
Kconfig update workarounds for gcc "asm goto" issue 2024-02-15 11:14:33 -08:00
main.c proc: sysctl: prevent aliased sysctls from getting passed to init 2023-11-01 12:10:02 -07:00
Makefile x86/retpoline: Make sure there are no unconverted return thunks due to KCSAN 2023-10-20 13:02:23 +02:00
noinitramfs.c
version-timestamp.c init/version-timestamp.c: remove unneeded #include <linux/version.h> 2023-01-09 07:34:38 +09:00
version.c init/version.c: Replace strlcpy with strscpy 2023-09-22 09:50:56 -07:00