Linus Torvalds 4356e9f841 work around gcc bugs with 'asm goto' with outputs ... We've had issues with gcc and 'asm goto' before, and we created a 'asm_volatile_goto()' macro for that in the past: see commits 3f0116c323 ("compiler/gcc4: Add quirk for 'asm goto' miscompilation bug") and a9f180345f ("compiler/gcc4: Make quirk for asm_volatile_goto() unconditional"). Then, much later, we ended up removing the workaround in commit 43c249ea0b ("compiler-gcc.h: remove ancient workaround for gcc PR 58670") because we no longer supported building the kernel with the affected gcc versions, but we left the macro uses around. Now, Sean Christopherson reports a new version of a very similar problem, which is fixed by re-applying that ancient workaround. But the problem in question is limited to only the 'asm goto with outputs' cases, so instead of re-introducing the old workaround as-is, let's rename and limit the workaround to just that much less common case. It looks like there are at least two separate issues that all hit in this area: (a) some versions of gcc don't mark the asm goto as 'volatile' when it has outputs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420 which is easy to work around by just adding the 'volatile' by hand. (b) Internal compiler errors: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422 which are worked around by adding the extra empty 'asm' as a barrier, as in the original workaround. but the problem Sean sees may be a third thing since it involves bad code generation (not an ICE) even with the manually added 'volatile'. but the same old workaround works for this case, even if this feels a bit like voodoo programming and may only be hiding the issue. Reported-and-tested-by: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/ Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Uros Bizjak <ubizjak@gmail.com> Cc: Jakub Jelinek <jakub@redhat.com> Cc: Andrew Pinski <quic_apinski@quicinc.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2024-02-09 15:57:48 -08:00
..
abiv1	mm: Introduce flush_cache_vmap_early()	2023-12-14 00:23:17 -08:00
abiv2	mm: Introduce flush_cache_vmap_early()	2023-12-14 00:23:17 -08:00
boot	csky: Remove unused $(dtb-y) from boot/Makefile	2022-05-13 14:45:09 +08:00
configs	netfs, fscache: Combine fscache with netfs	2023-12-24 15:08:46 +00:00
include	work around gcc bugs with 'asm goto' with outputs	2024-02-09 15:57:48 -08:00
kernel	arch: vdso: consolidate gettime prototypes	2023-11-23 11:32:32 +01:00
lib	csky: delay: Add function alignment	2022-12-29 23:47:52 -05:00
mm	csky: fix up lock_mm_and_find_vma() conversion	2023-06-29 23:34:29 -07:00
Kbuild	csky: Move $(core-y) into arch/csky/Kbuild	2022-05-13 15:09:28 +08:00
Kconfig	Merge branch 'expand-stack'	2023-06-28 20:35:21 -07:00
Kconfig.debug	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
Kconfig.platforms	csky/Kconfig: Add Kconfig.platforms to support some drivers	2020-02-21 15:43:24 +08:00
Makefile	kbuild: remove head-y syntax	2022-10-02 18:06:03 +09:00