[PATCH 01/18] tools headers barrier: Fix arm64 tools build failure wrt smp_load_{acquire,release}

Arnaldo Carvalho de Melo
2018-11-06T12:06:34Z

From: Will Deacon <will.deacon@arm.com>

Cheers for reporting this. I managed to reproduce the build failure with
gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1).

The code in question is the arm64 versions of smp_load_acquire() and
smp_store_release(). Unlike other architectures, these are not built
around READ_ONCE() and WRITE_ONCE() since we have instructions we can
use instead of fences. Bringing our macros up-to-date with those (i.e.
tweaking the union initialisation and using the special "uXX_alias_t"
types) appears to fix the issue for me.

Committer notes:

Testing it in the systems previously failing:

# time dm android-ndk:r12b-arm \
android-ndk:r15c-arm \
debian:experimental-x-arm64 \
ubuntu:14.04.4-x-linaro-arm64 \
ubuntu:16.04-x-arm \
ubuntu:16.04-x-arm64 \
ubuntu:18.04-x-arm \
ubuntu:18.04-x-arm64
1 android-ndk:r12b-arm : Ok arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
2 android-ndk:r15c-arm : Ok arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
3 debian:experimental-x-arm64 : Ok aarch64-linux-gnu-gcc (Debian 8.2.0-7) 8.2.0
4 ubuntu:14.04.4-x-linaro-arm64 : Ok aarch64-linux-gnu-gcc (Linaro GCC 5.5-2017.10) 5.5.0
5 ubuntu:16.04-x-arm : Ok arm-linux-gnueabihf-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
6 ubuntu:16.04-x-arm64 : Ok aarch64-linux-gnu-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
7 ubuntu:18.04-x-arm : Ok arm-linux-gnueabihf-gcc (Ubuntu/Linaro 7.3.0-27ubuntu1~18.04) 7.3.0
8 ubuntu:18.04-x-arm64 : Ok aarch64-linux-gnu-gcc (Ubuntu/Linaro 7.3.0-27ubuntu1~18.04) 7.3.0

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20181031174408.GA27871@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/arch/arm64/include/asm/barrier.h | 133 +++++++++++++++++----------------
1 file changed, 67 insertions(+), 66 deletions(-)

diff --git a/tools/arch/arm64/include/asm/barrier.h b/tools/arch/arm64/include/asm/barrier.h
index 12835ea0e417..378c051fa177 100644
--- a/tools/arch/arm64/include/asm/barrier.h
+++ b/tools/arch/arm64/include/asm/barrier.h
@@ -14,74 +14,75 @@
#define wmb() asm volatile("dmb ishst" ::: "memory")
#define rmb() asm volatile("dmb ishld" ::: "memory")

-#define smp_store_release(p, v) \
-do { \
- union { typeof(*p) __val; char __c[1]; } __u = \
- { .__val = (__force typeof(*p)) (v) }; \
- \
- switch (sizeof(*p)) { \
- case 1: \
- asm volatile ("stlrb %w1, %0" \
- : "=Q" (*p) \
- : "r" (*(__u8 *)__u.__c) \
- : "memory"); \
- break; \
- case 2: \
- asm volatile ("stlrh %w1, %0" \
- : "=Q" (*p) \
- : "r" (*(__u16 *)__u.__c) \
- : "memory"); \
- break; \
- case 4: \
- asm volatile ("stlr %w1, %0" \
- : "=Q" (*p) \
- : "r" (*(__u32 *)__u.__c) \
- : "memory"); \
- break; \
- case 8: \
- asm volatile ("stlr %1, %0" \
- : "=Q" (*p) \
- : "r" (*(__u64 *)__u.__c) \
- : "memory"); \
- break; \
- default: \
- /* Only to shut up gcc ... */ \
- mb(); \
- break; \
- } \
+#define smp_store_release(p, v) \
+do { \
+ union { typeof(*p) __val; char __c[1]; } __u = \
+ { .__val = (v) }; \
+ \
+ switch (sizeof(*p)) { \
+ case 1: \
+ asm volatile ("stlrb %w1, %0" \
+ : "=Q" (*p) \
+ : "r" (*(__u8_alias_t *)__u.__c) \
+ : "memory"); \
+ break; \
+ case 2: \
+ asm volatile ("stlrh %w1, %0" \
+ : "=Q" (*p) \
+ : "r" (*(__u16_alias_t *)__u.__c) \
+ : "memory"); \
+ break; \
+ case 4: \
+ asm volatile ("stlr %w1, %0" \
+ : "=Q" (*p) \
+ : "r" (*(__u32_alias_t *)__u.__c) \
+ : "memory"); \
+ break; \
+ case 8: \
+ asm volatile ("stlr %1, %0" \
+ : "=Q" (*p) \
+ : "r" (*(__u64_alias_t *)__u.__c) \
+ : "memory"); \
+ break; \
+ default: \
+ /* Only to shut up gcc ... */ \
+ mb(); \
+ break; \
+ } \
} while (0)

-#define smp_load_acquire(p) \
-({ \
- union { typeof(*p) __val; char __c[1]; } __u; \
- \
- switch (sizeof(*p)) { \
- case 1: \
- asm volatile ("ldarb %w0, %1" \
- : "=r" (*(__u8 *)__u.__c) \
- : "Q" (*p) : "memory"); \
- break; \
- case 2: \
- asm volatile ("ldarh %w0, %1" \
- : "=r" (*(__u16 *)__u.__c) \
- : "Q" (*p) : "memory"); \
- break; \
- case 4: \
- asm volatile ("ldar %w0, %1" \
- : "=r" (*(__u32 *)__u.__c) \
- : "Q" (*p) : "memory"); \
- break; \
- case 8: \
- asm volatile ("ldar %0, %1" \
- : "=r" (*(__u64 *)__u.__c) \
- : "Q" (*p) : "memory"); \
- break; \
- default: \
- /* Only to shut up gcc ... */ \
- mb(); \
- break; \
- } \
- __u.__val; \
+#define smp_load_acquire(p) \
+({ \
+ union { typeof(*p) __val; char __c[1]; } __u = \
+ { .__c = { 0 } }; \
+ \
+ switch (sizeof(*p)) { \
+ case 1: \
+ asm volatile ("ldarb %w0, %1" \
+ : "=r" (*(__u8_alias_t *)__u.__c) \
+ : "Q" (*p) : "memory"); \
+ break; \
+ case 2: \
+ asm volatile ("ldarh %w0, %1" \
+ : "=r" (*(__u16_alias_t *)__u.__c) \
+ : "Q" (*p) : "memory"); \
+ break; \
+ case 4: \
+ asm volatile ("ldar %w0, %1" \
+ : "=r" (*(__u32_alias_t *)__u.__c) \
+ : "Q" (*p) : "memory"); \
+ break; \
+ case 8: \
+ asm volatile ("ldar %0, %1" \
+ : "=r" (*(__u64_alias_t *)__u.__c) \
+ : "Q" (*p) : "memory"); \
+ break; \
+ default: \
+ /* Only to shut up gcc ... */ \
+ mb(); \
+ break; \
+ } \
+ __u.__val; \
})

#endif /* _TOOLS_LINUX_ASM_AARCH64_BARRIER_H */
--
2.14.4