libgo: ensure memmove, memset 8 byte atomicity on ppc64x
Go requires that pointer moves are done 8 bytes at a time,
but gccgo uses libc's memmove and memset which does not require
that, and there are some cases where an 8 byte move might be
done as 4+4.
To enforce 8 byte moves for memmove and memset, this adds a
C implementation in libgo/runtime for memmove and memset to be
used on ppc64le and ppc64. Asm implementations were considered
but discarded to avoid different implementations for different
target ISAs.
Fixes golang/go#41428
Change-Id: I4f3a0969a501054efdcbca8b771a07c006cad9b0
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/294931
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>
diff --git a/libgo/Makefile.am b/libgo/Makefile.am
index eea7ff1..dec9875 100644
--- a/libgo/Makefile.am
+++ b/libgo/Makefile.am
@@ -454,6 +454,7 @@
runtime/go-fieldtrack.c \
runtime/go-matherr.c \
runtime/go-memclr.c \
+ runtime/go-memmove.c \
runtime/go-memequal.c \
runtime/go-nanotime.c \
runtime/go-now.c \
diff --git a/libgo/Makefile.in b/libgo/Makefile.in
index 8938eba..da72149 100644
--- a/libgo/Makefile.in
+++ b/libgo/Makefile.in
@@ -244,8 +244,9 @@
runtime/go-caller.lo runtime/go-callers.lo runtime/go-cgo.lo \
runtime/go-construct-map.lo runtime/go-ffi.lo \
runtime/go-fieldtrack.lo runtime/go-matherr.lo \
- runtime/go-memclr.lo runtime/go-memequal.lo \
- runtime/go-nanotime.lo runtime/go-now.lo runtime/go-nosys.lo \
+ runtime/go-memclr.lo runtime/go-memmove.lo \
+ runtime/go-memequal.lo runtime/go-nanotime.lo \
+ runtime/go-now.lo runtime/go-nosys.lo \
runtime/go-reflect-call.lo runtime/go-setenv.lo \
runtime/go-signal.lo runtime/go-unsafe-pointer.lo \
runtime/go-unsetenv.lo runtime/go-unwind.lo \
@@ -906,6 +907,7 @@
runtime/go-fieldtrack.c \
runtime/go-matherr.c \
runtime/go-memclr.c \
+ runtime/go-memmove.c \
runtime/go-memequal.c \
runtime/go-nanotime.c \
runtime/go-now.c \
@@ -1367,6 +1369,8 @@
runtime/$(DEPDIR)/$(am__dirstamp)
runtime/go-memclr.lo: runtime/$(am__dirstamp) \
runtime/$(DEPDIR)/$(am__dirstamp)
+runtime/go-memmove.lo: runtime/$(am__dirstamp) \
+ runtime/$(DEPDIR)/$(am__dirstamp)
runtime/go-memequal.lo: runtime/$(am__dirstamp) \
runtime/$(DEPDIR)/$(am__dirstamp)
runtime/go-nanotime.lo: runtime/$(am__dirstamp) \
@@ -1435,6 +1439,7 @@
@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-matherr.Plo@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-memclr.Plo@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-memequal.Plo@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-memmove.Plo@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-nanotime.Plo@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-nosys.Plo@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-now.Plo@am__quote@
diff --git a/libgo/go/runtime/stubs.go b/libgo/go/runtime/stubs.go
index 6d20c38..dea7234 100644
--- a/libgo/go/runtime/stubs.go
+++ b/libgo/go/runtime/stubs.go
@@ -106,9 +106,7 @@
memclrNoHeapPointers(ptr, n)
}
-// memmove copies n bytes from "from" to "to".
//go:noescape
-//extern __builtin_memmove
func memmove(to, from unsafe.Pointer, n uintptr)
//go:linkname reflect_memmove reflect.memmove
diff --git a/libgo/runtime/go-memclr.c b/libgo/runtime/go-memclr.c
index b5d4975..53b8117 100644
--- a/libgo/runtime/go-memclr.c
+++ b/libgo/runtime/go-memclr.c
@@ -13,5 +13,48 @@
void
memclrNoHeapPointers (void *p1, uintptr len)
{
- __builtin_memset (p1, 0, len);
+
+#if !defined(__PPC64__)
+ __builtin_memset(p1, 0, len);
+#else
+ int64 rem,drem,i;
+ uint64 offset;
+ volatile uint64 *vp;
+
+ if (len == 0) {
+ return;
+ }
+ rem = len;
+
+ offset = (uint64)p1 % 8;
+ // This memset is OK since it can't contain
+ // an 8 byte aligned pointer.
+ if ((rem < 8) || (offset > 0 && offset+rem <= 16)) {
+ __builtin_memset(p1, 0, rem);
+ return;
+ }
+ // Move initial bytes to get to 8 byte boundary
+ if (offset > 0) {
+ __builtin_memset(p1, 0, 8-offset);
+ p1 = (void*)((char*)p1+8-offset);
+ rem -= 8-offset;
+ }
+
+ // If at least 8 bytes left, clear
+ drem = rem>>3;
+
+ vp = (volatile uint64*)(p1);
+ // Without the use of volatile here, the compiler
+ // might convert the loop into a memset.
+ for (i=0; i<drem; i++) {
+ *vp = 0;
+ vp++;
+ rem -= 8;
+ }
+ p1 = (void*)((char*)p1 + 8*drem);
+ // Clear any remaining
+ if (rem > 0) {
+ __builtin_memset (p1, 0, rem);
+ }
+#endif
}
diff --git a/libgo/runtime/go-memmove.c b/libgo/runtime/go-memmove.c
new file mode 100644
index 0000000..1ca3f48
--- /dev/null
+++ b/libgo/runtime/go-memmove.c
@@ -0,0 +1,89 @@
+/* go-memmove.c -- memmove
+
+ Copyright 2021 The Go Authors. All rights reserved.
+ Use of this source code is governed by a BSD-style
+ license that can be found in the LICENSE file. */
+
+#include "runtime.h"
+
+void gomemmove(void *, void *, uintptr)
+ __asm__ (GOSYM_PREFIX "runtime.memmove")
+ __attribute__ ((no_split_stack));
+
+// This implementation is necessary since
+// the __builtin_memmove might use __libc_memmove
+// which doesn't require atomicity of 8 byte
+// moves.
+
+void
+gomemmove (void *dst, void *src, uintptr len)
+{
+#if !defined(__PPC64__)
+ __builtin_memmove(dst, src, len);
+#else
+ uint64 offset, tail;
+ int64 rem;
+ uint64 dwords;
+ uint64 i;
+ char *bdst,*bsrc;
+
+ rem = len;
+
+ if (len == 0) {
+ return;
+ }
+
+ // If src and dst don't have the same 8 byte alignment then
+ // there is no issue with copying pointer atomicity. Use the
+ // builtin.
+ if (((uint64)dst % 8) != ((uint64)src % 8) || len < 8) {
+ __builtin_memmove(dst, src, len);
+ return;
+ }
+
+ // Length >= 8 && same ptr alignment
+ offset = (uint64)dst % 8;
+
+ // If not 8 byte alignment, move the intial bytes.
+ if (offset > 0) {
+ __builtin_memmove(dst, src, 8-offset);
+ dst += (8-offset);
+ src += (8-offset);
+ rem -= (8-offset);
+ }
+
+ // Move the tail bytes to make the backward move
+ // easier.
+ tail = rem % 8;
+ if (tail > 0) {
+ __builtin_memmove(dst+rem-tail, src+rem-tail, tail);
+ rem -= tail;
+ }
+
+ if (rem == 0) {
+ return;
+ }
+
+ // Must now be 8 byte alignment and rem is multiple of 8.
+ dwords = len>>3;
+
+ // Determine if a backwards move is needed
+ // Forward or backward, move all doublewords
+
+ if ((uint64)(dst - src) < (uint64)rem) {
+ bdst = dst+rem-8;
+ bsrc = src+rem-8;
+ for (i = 0; i<dwords; i++) {
+ *(uint64*)bdst = *(uint64*)bsrc;
+ bdst -= 8;
+ bsrc -= 8;
+ }
+ } else {
+ for (i = 0; i<dwords; i++) {
+ *(uint64*)dst = *(uint64*)src;
+ dst += 8;
+ src += 8;
+ }
+ }
+#endif
+}
diff --git a/libgo/runtime/runtime.h b/libgo/runtime/runtime.h
index 3a65d44..b3dc4fd 100644
--- a/libgo/runtime/runtime.h
+++ b/libgo/runtime/runtime.h
@@ -221,7 +221,8 @@
void runtime_printf(const char*, ...);
int32 runtime_snprintf(byte*, int32, const char*, ...);
#define runtime_mcmp(a, b, s) __builtin_memcmp((a), (b), (s))
-#define runtime_memmove(a, b, s) __builtin_memmove((a), (b), (s))
+void runtime_memmove(void*, void*, uint64)
+ __asm__ (GOSYM_PREFIX "runtime.memmove");
String runtime_gostringnocopy(const byte*)
__asm__ (GOSYM_PREFIX "runtime.gostringnocopy");
void runtime_ginit(void)
