[PATCH] compiler.h: Raise minimum version of GCC to 5.1 for arm64

[Will Deacon]

GCC versions >= 4.9 and < 5.1 have been shown to emit memory references
beyond the stack pointer, resulting in memory corruption if an interrupt
is taken after the stack pointer has been adjusted but before the
reference has been executed. This leads to subtle, infrequent data
corruption such as the EXT4 problems reported by Russell King at the
link below.

Life is too short for buggy compilers, so raise the minimum GCC version
required by arm64 to 5.1.

Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Florian Weimer <fweimer@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Reported-by: Russell King <linux@xxxxxxxxxxxxxxx>
Suggested-by: Arnd Bergmann <arnd@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210105154726.GD1551@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
 include/linux/compiler-gcc.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 74c6c0486eed..555ab0fddbef 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -13,6 +13,12 @@
 /* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 */
 #if GCC_VERSION < 40900
 # error Sorry, your version of GCC is too old - please use 4.9 or newer.
+#elif defined(CONFIG_ARM64) && GCC_VERSION < 50100
+/*
+ * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293
+ * https://lore.kernel.org/r/20210107111841.GN1551@xxxxxxxxxxxxxxxxxxxxx
+ */
+# error Sorry, your version of GCC is too old - please use 5.1 or newer.
 #endif
 
 /*
-- 
2.30.0.284.gd98b1dd5eaa7-goog