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
..
boot	LoongArch: dts: DeviceTree for Loongson-2K2000	2024-01-17 12:43:08 +08:00
configs	LoongArch changes for v6.8	2024-01-19 13:30:49 -08:00
crypto	crypto: loongarch/crc32 - remove redundant setting of alignmask to 0	2023-10-27 18:04:24 +08:00
include	work around gcc bugs with 'asm goto' with outputs	2024-02-09 15:57:48 -08:00
kernel	LoongArch: Change acpi_core_pic[NR_CPUS] to acpi_core_pic[MAX_CORE_PIC]	2024-02-06 12:32:05 +08:00
kvm	LoongArch: KVM: Fix build due to API changes	2024-01-26 16:22:07 +08:00
lib	LoongArch: Add KASAN (Kernel Address Sanitizer) support	2023-09-06 22:54:16 +08:00
mm	LoongArch: Fix earlycon parameter if KASAN enabled	2024-02-06 12:32:05 +08:00
net	LoongArch: BPF: Prevent out-of-bounds memory access	2024-01-17 12:43:13 +08:00
pci	LoongArch: Add FDT booting support from efi system table	2022-12-14 08:41:53 +08:00
power	LoongArch: Export some arch-specific pm interfaces	2023-06-29 20:58:44 +08:00
vdso	LoongArch: vDSO: Disable UBSAN instrumentation	2024-02-06 12:32:05 +08:00
Kbuild	LoongArch: Allow device trees be built into the kernel	2024-01-17 12:43:00 +08:00
Kconfig	LoongArch: Select HAVE_ARCH_SECCOMP to use the common SECCOMP menu	2024-02-06 12:32:05 +08:00
Kconfig.debug	LoongArch: Add prologue unwinder support	2022-08-12 13:10:11 +08:00
Makefile	LoongArch: Allow device trees be built into the kernel	2024-01-17 12:43:00 +08:00