This series overrides barrier_before_unreachable() for MIPS to add a .insn assembler directive. Due to the subsequent __builtin_unreachable(), the assembler can't tell that a label on the empty inline asm is code rather than data, so any microMIPS branches targeting it (which sadly can't be removed) raise errors due to the mismatching ISA mode, Adding the .insn in patch 2 tells the assembler that it should be treated as code. Applies cleanly atop v4.18. Changes in v9 (Paul): - Use a simple #include conditional upon a Kconfig symbol, as suggested by Masahiro. - Move back to asm/compiler.h instead of asm/compiler_types.h. Changes in v8 (Paul): - Try something different... including a header that might be an asm-generic wrapper in linux/compiler_types.h creates build ordering problems for any C file which can be built before the asm-generic target. Patch 1 changes tact to avoid asm-generic & the ordering problem. - Commit message improvements in patch 2. Changes in v7 (Paul): - Elaborate on affected GCC versions in patch 4. Changes in v6 (Paul): - Fix patch 2 to find the generated headers in $(objtree). - Remove CC's for defunct MIPS email addresses (Matthew & Robert). - CC linux-um@xxxxxxxxxxxxxxxxxxx. Changes in v5 (Paul): - Rebase atop v4.18-rc8. - Comment & commit message tweaks. - Add SPDX-License-Identifier to asm-generic/compiler.h. Changes in v4 (James): - Fix asm-generic/compiler.h include from check, compiler_types.h is included on the command line so linux/compiler.h may not be included (kbuild test robot). - New patch 2 to fix um (kbuild test robot). Changes in v3 (James): - New patch 1. - Rebase after 4.17 arch removal and update commit messages. - Use asm/compiler.h instead of compiler-gcc.h (Arnd). - Drop stable tag for now. Changes in v2 (Paul): - Add generic-y entries to arch Kbuild files. Oops! Previous versions: v1: https://www.linux-mips.org/archives/linux-mips/2016-05/msg00399.html v2: https://www.linux-mips.org/archives/linux-mips/2016-05/msg00401.html v3: https://lkml.org/lkml/2018/4/17/228 v4: https://www.linux-mips.org/archives/linux-mips/2018-05/msg00069.html v5: https://www.spinics.net/lists/mips/msg74408.html v6: https://www.spinics.net/lists/mips/msg74425.html v7: https://www.spinics.net/lists/linux-arch/msg47934.html v8: https://www.spinics.net/lists/mips/msg74562.html Older #ifdef-based attempt: https://marc.info/?l=linux-mips&m=145555921408274&w=2 Paul Burton (2): kbuild: Allow arch-specific asm/compiler.h MIPS: Workaround GCC __builtin_unreachable reordering bug arch/Kconfig | 8 ++++++++ arch/mips/Kconfig | 1 + arch/mips/include/asm/compiler.h | 35 ++++++++++++++++++++++++++++++++ include/linux/compiler_types.h | 12 +++++++++++ 4 files changed, 56 insertions(+) -- 2.18.0
