[PATCH v6 3/4] compiler.h: Allow arch-specific overrides

[Paul Burton <paul.burton@mips.com>]

Include an arch-specific asm/compiler.h and allow for it to define a
custom version of barrier_before_unreachable(), which is needed to
workaround several issues on the MIPS architecture.

This patch includes an effectively empty asm-generic implementation of
asm/compiler.h for all architectures except alpha, arm, arm64, and mips
(which already have an asm/compiler.h) and leaves the architecture
specifics to a further patch.

Signed-off-by: Paul Burton <paul.burton@mips.com>
[jhogan@kernel.org: Forward port and use asm/compiler.h instead of
 asm/compiler-gcc.h]
Signed-off-by: James Hogan <jhogan@kernel.org>
Reviewed-by: Paul Burton <paul.burton@mips.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-arch@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-um@lists.infradead.org

---

Changes in v6: None
Changes in v5:
- Rebase atop v4.18-rc8.
- Add SPDX-License-Identifier to asm-generic/compiler.h.

Changes in v4:
- 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).

Changes in v3:
- Rebase after 4.17 arch removal.
- Use asm/compiler.h instead of compiler-gcc.h (Arnd).
- Drop stable tag for now.

Changes in v2:
- Add generic-y entries to arch Kbuild files. Oops!

 arch/arc/include/asm/Kbuild        |  1 +
 arch/c6x/include/asm/Kbuild        |  1 +
 arch/h8300/include/asm/Kbuild      |  1 +
 arch/hexagon/include/asm/Kbuild    |  1 +
 arch/ia64/include/asm/Kbuild       |  1 +
 arch/m68k/include/asm/Kbuild       |  1 +
 arch/microblaze/include/asm/Kbuild |  1 +
 arch/nds32/include/asm/Kbuild      |  1 +
 arch/nios2/include/asm/Kbuild      |  1 +
 arch/openrisc/include/asm/Kbuild   |  1 +
 arch/parisc/include/asm/Kbuild     |  1 +
 arch/powerpc/include/asm/Kbuild    |  1 +
 arch/riscv/include/asm/Kbuild      |  1 +
 arch/s390/include/asm/Kbuild       |  1 +
 arch/sh/include/asm/Kbuild         |  1 +
 arch/sparc/include/asm/Kbuild      |  1 +
 arch/um/include/asm/Kbuild         |  1 +
 arch/unicore32/include/asm/Kbuild  |  1 +
 arch/x86/include/asm/Kbuild        |  1 +
 arch/xtensa/include/asm/Kbuild     |  1 +
 include/asm-generic/compiler.h     | 10 ++++++++++
 include/linux/compiler-gcc.h       |  2 ++
 include/linux/compiler_types.h     |  3 +++
 23 files changed, 35 insertions(+)
 create mode 100644 include/asm-generic/compiler.h

diff --git a/arch/arc/include/asm/Kbuild b/arch/arc/include/asm/Kbuild
index feed50ce89fa..55c955621deb 100644
--- a/arch/arc/include/asm/Kbuild
+++ b/arch/arc/include/asm/Kbuild
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 generic-y += bugs.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += device.h
 generic-y += div64.h
 generic-y += dma-mapping.h
diff --git a/arch/c6x/include/asm/Kbuild b/arch/c6x/include/asm/Kbuild
index 33a2c94fed0d..0bbdfe6481fd 100644
--- a/arch/c6x/include/asm/Kbuild
+++ b/arch/c6x/include/asm/Kbuild
@@ -2,6 +2,7 @@ generic-y += atomic.h
 generic-y += barrier.h
 generic-y += bugs.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/h8300/include/asm/Kbuild b/arch/h8300/include/asm/Kbuild
index a5d0b2991f47..09c6d8cac8be 100644
--- a/arch/h8300/include/asm/Kbuild
+++ b/arch/h8300/include/asm/Kbuild
@@ -4,6 +4,7 @@ generic-y += bugs.h
 generic-y += cacheflush.h
 generic-y += checksum.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += delay.h
 generic-y += device.h
diff --git a/arch/hexagon/include/asm/Kbuild b/arch/hexagon/include/asm/Kbuild
index dd2fd9c0d292..ef5f1ca92d64 100644
--- a/arch/hexagon/include/asm/Kbuild
+++ b/arch/hexagon/include/asm/Kbuild
@@ -3,6 +3,7 @@ generic-y += barrier.h
 generic-y += bug.h
 generic-y += bugs.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/ia64/include/asm/Kbuild b/arch/ia64/include/asm/Kbuild
index 557bbc8ba9f5..5c5a5721fe89 100644
--- a/arch/ia64/include/asm/Kbuild
+++ b/arch/ia64/include/asm/Kbuild
@@ -1,4 +1,5 @@
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += exec.h
 generic-y += irq_work.h
 generic-y += mcs_spinlock.h
diff --git a/arch/m68k/include/asm/Kbuild b/arch/m68k/include/asm/Kbuild
index 4d8d68c4e3dd..e920ada07719 100644
--- a/arch/m68k/include/asm/Kbuild
+++ b/arch/m68k/include/asm/Kbuild
@@ -1,5 +1,6 @@
 generic-y += barrier.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += device.h
 generic-y += emergency-restart.h
 generic-y += exec.h
diff --git a/arch/microblaze/include/asm/Kbuild b/arch/microblaze/include/asm/Kbuild
index fe6a6c6e5003..01317fc236e3 100644
--- a/arch/microblaze/include/asm/Kbuild
+++ b/arch/microblaze/include/asm/Kbuild
@@ -3,6 +3,7 @@ generic-y += bitops.h
 generic-y += bug.h
 generic-y += bugs.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += device.h
 generic-y += div64.h
 generic-y += emergency-restart.h
diff --git a/arch/nds32/include/asm/Kbuild b/arch/nds32/include/asm/Kbuild
index dbc4e5422550..a5f2b9058b4c 100644
--- a/arch/nds32/include/asm/Kbuild
+++ b/arch/nds32/include/asm/Kbuild
@@ -10,6 +10,7 @@ generic-y += clkdev.h
 generic-y += cmpxchg.h
 generic-y += cmpxchg-local.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += cputime.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/nios2/include/asm/Kbuild b/arch/nios2/include/asm/Kbuild
index 64ed3d656956..a157f2049d74 100644
--- a/arch/nios2/include/asm/Kbuild
+++ b/arch/nios2/include/asm/Kbuild
@@ -5,6 +5,7 @@ generic-y += bug.h
 generic-y += bugs.h
 generic-y += cmpxchg.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/openrisc/include/asm/Kbuild b/arch/openrisc/include/asm/Kbuild
index 65964d390b10..54849e38da6f 100644
--- a/arch/openrisc/include/asm/Kbuild
+++ b/arch/openrisc/include/asm/Kbuild
@@ -3,6 +3,7 @@ generic-y += bug.h
 generic-y += bugs.h
 generic-y += checksum.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/parisc/include/asm/Kbuild b/arch/parisc/include/asm/Kbuild
index 2013d639e735..e458cba4f5ae 100644
--- a/arch/parisc/include/asm/Kbuild
+++ b/arch/parisc/include/asm/Kbuild
@@ -1,4 +1,5 @@
 generic-y += barrier.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
index 3196d227e351..636a1dae6adc 100644
--- a/arch/powerpc/include/asm/Kbuild
+++ b/arch/powerpc/include/asm/Kbuild
@@ -1,3 +1,4 @@
+generic-y += compiler.h
 generic-y += div64.h
 generic-y += export.h
 generic-y += irq_regs.h
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index 576ffdca06ba..f6a7fcd72d37 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -1,6 +1,7 @@
 generic-y += bugs.h
 generic-y += cacheflush.h
 generic-y += checksum.h
+generic-y += compiler.h
 generic-y += cputime.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/s390/include/asm/Kbuild b/arch/s390/include/asm/Kbuild
index e3239772887a..689993a319d6 100644
--- a/arch/s390/include/asm/Kbuild
+++ b/arch/s390/include/asm/Kbuild
@@ -6,6 +6,7 @@ generated-y += unistd_nr.h
 
 generic-y += asm-offsets.h
 generic-y += cacheflush.h
+generic-y += compiler.h
 generic-y += device.h
 generic-y += dma-contiguous.h
 generic-y += dma-mapping.h
diff --git a/arch/sh/include/asm/Kbuild b/arch/sh/include/asm/Kbuild
index 46dd82ab2c29..dd49f6b7f036 100644
--- a/arch/sh/include/asm/Kbuild
+++ b/arch/sh/include/asm/Kbuild
@@ -1,4 +1,5 @@
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += delay.h
 generic-y += div64.h
diff --git a/arch/sparc/include/asm/Kbuild b/arch/sparc/include/asm/Kbuild
index 410b263ef5c8..e944aac9b198 100644
--- a/arch/sparc/include/asm/Kbuild
+++ b/arch/sparc/include/asm/Kbuild
@@ -1,6 +1,7 @@
 # User exported sparc header files
 
 
+generic-y += compiler.h
 generic-y += div64.h
 generic-y += emergency-restart.h
 generic-y += exec.h
diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index b10dde6cb793..14b4f6f09816 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -2,6 +2,7 @@ generic-y += barrier.h
 generic-y += bpf_perf_event.h
 generic-y += bug.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += delay.h
 generic-y += device.h
diff --git a/arch/unicore32/include/asm/Kbuild b/arch/unicore32/include/asm/Kbuild
index bfc7abe77905..614a0d99e02e 100644
--- a/arch/unicore32/include/asm/Kbuild
+++ b/arch/unicore32/include/asm/Kbuild
@@ -1,6 +1,7 @@
 generic-y += atomic.h
 generic-y += bugs.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += current.h
 generic-y += device.h
 generic-y += div64.h
diff --git a/arch/x86/include/asm/Kbuild b/arch/x86/include/asm/Kbuild
index de690c2d2e33..de4246599536 100644
--- a/arch/x86/include/asm/Kbuild
+++ b/arch/x86/include/asm/Kbuild
@@ -6,6 +6,7 @@ generated-y += unistd_32_ia32.h
 generated-y += unistd_64_x32.h
 generated-y += xen-hypercalls.h
 
+generic-y += compiler.h
 generic-y += dma-contiguous.h
 generic-y += early_ioremap.h
 generic-y += mcs_spinlock.h
diff --git a/arch/xtensa/include/asm/Kbuild b/arch/xtensa/include/asm/Kbuild
index e5e1e61c538c..bf08e8a4fb57 100644
--- a/arch/xtensa/include/asm/Kbuild
+++ b/arch/xtensa/include/asm/Kbuild
@@ -1,5 +1,6 @@
 generic-y += bug.h
 generic-y += compat.h
+generic-y += compiler.h
 generic-y += device.h
 generic-y += div64.h
 generic-y += dma-contiguous.h
diff --git a/include/asm-generic/compiler.h b/include/asm-generic/compiler.h
new file mode 100644
index 000000000000..0653ff193b40
--- /dev/null
+++ b/include/asm-generic/compiler.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __LINUX_COMPILER_TYPES_H
+#error "Please don't include <asm/compiler.h> directly, include <linux/compiler.h> instead."
+#endif
+
+/*
+ * We have nothing architecture-specific to do here, simply leave everything to
+ * the generic linux/compiler.h.
+ */
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 573f5a7d42d4..5caf71f15c71 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -233,7 +233,9 @@
  *
  * Adding an empty inline assembly before it works around the problem
  */
+#ifndef barrier_before_unreachable
 #define barrier_before_unreachable() asm volatile("")
+#endif
 
 /*
  * Mark a position in code as unreachable.  This can be used to
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index a8ba6b04152c..c66b9222fcf0 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -54,6 +54,9 @@ extern void __chk_io_ptr(const volatile void __iomem *);
 
 #ifdef __KERNEL__
 
+/* Allow architectures to override some definitions where necessary */
+#include <asm/compiler.h>
+
 #ifdef __GNUC__
 #include <linux/compiler-gcc.h>
 #endif
-- 
2.18.0