commit b03c5dc36d6d0c0d3bef434936e8b924d253595b
author Tony Reix <tony.reix@bull.net> Wed Oct 11 09:17:24 2017 +0200
committer Ian Lance Taylor <iant@golang.org> Thu Nov 09 21:56:26 2017 +0000
tree d2cfbf15ec145d9a14752bb751869551cac71f1d
parent 7fd845bd9414c348bfa30bd24aa0bb8e4eebf83a

sync/atomic, runtime/internal/atomic: don't assume reads from 0 fail

For a misaligned address force a panic rather than assuming that reading
from the address 0 will cause one.

Change-Id: I25f32be86120d6a4fd33db01f159c5fadac9674e
Reviewed-on: https://go-review.googlesource.com/69850
Reviewed-by: Ian Lance Taylor <iant@golang.org>

libgo/go/runtime/internal/atomic/atomic.c

diff --git a/libgo/go/runtime/internal/atomic/atomic.c b/libgo/go/runtime/internal/atomic/atomic.c
index b584656..24820f2 100644
--- a/libgo/go/runtime/internal/atomic/atomic.c
+++ b/libgo/go/runtime/internal/atomic/atomic.c
@@ -34,7 +34,7 @@
 Load64 (uint64_t *ptr)
 {
   if (((uintptr_t) ptr & 7) != 0)
-    ptr = NULL;
+    panicmem ();
   return __atomic_load_n (ptr, __ATOMIC_ACQUIRE);
 }
 
@@ -66,7 +66,7 @@
 Loadint64 (int64_t *ptr)
 {
   if (((uintptr_t) ptr & 7) != 0)
-    ptr = NULL;
+    panicmem ();
   return __atomic_load_n (ptr, __ATOMIC_ACQUIRE);
 }
 
@@ -88,7 +88,7 @@
 Xadd64 (uint64_t *ptr, int64_t delta)
 {
   if (((uintptr_t) ptr & 7) != 0)
-    ptr = NULL;
+    panicmem ();
   return __atomic_add_fetch (ptr, (uint64_t) delta, __ATOMIC_SEQ_CST);
 }
 
@@ -110,7 +110,7 @@
 Xaddint64 (int64_t *ptr, int64_t delta)
 {
   if (((uintptr_t) ptr & 7) != 0)
-    ptr = NULL;
+    panicmem ();
   return __atomic_add_fetch (ptr, delta, __ATOMIC_SEQ_CST);
 }
 
@@ -132,7 +132,7 @@
 Xchg64 (uint64_t *ptr, uint64_t new)
 {
   if (((uintptr_t) ptr & 7) != 0)
-    ptr = NULL;
+    panicmem ();
   return __atomic_exchange_n (ptr, new, __ATOMIC_SEQ_CST);
 }
 
@@ -184,7 +184,7 @@
 Cas64 (uint64_t *ptr, uint64_t old, uint64_t new)
 {
   if (((uintptr_t) ptr & 7) != 0)
-    ptr = NULL;
+    panicmem ();
   return __atomic_compare_exchange_n (ptr, &old, new, false, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);
 }
 
@@ -226,7 +226,7 @@
 Store64 (uint64_t *ptr, uint64_t val)
 {
   if (((uintptr_t) ptr & 7) != 0)
-    ptr = NULL;
+    panicmem ();
   __atomic_store_n (ptr, val, __ATOMIC_SEQ_CST);
 }
 

libgo/go/runtime/panic.go

diff --git a/libgo/go/runtime/panic.go b/libgo/go/runtime/panic.go
index 2f65603..c39a58d 100644
--- a/libgo/go/runtime/panic.go
+++ b/libgo/go/runtime/panic.go
@@ -22,6 +22,7 @@
 //go:linkname makefuncreturning runtime.makefuncreturning
 //go:linkname gorecover runtime.gorecover
 //go:linkname deferredrecover runtime.deferredrecover
+//go:linkname panicmem runtime.panicmem
 // Temporary for C code to call:
 //go:linkname throw runtime.throw
 

libgo/go/sync/atomic/atomic.c

diff --git a/libgo/go/sync/atomic/atomic.c b/libgo/go/sync/atomic/atomic.c
index 7e04027..32cbf03 100644
--- a/libgo/go/sync/atomic/atomic.c
+++ b/libgo/go/sync/atomic/atomic.c
@@ -26,7 +26,7 @@
 SwapInt64 (int64_t *addr, int64_t new)
 {
   if (((uintptr_t) addr & 7) != 0)
-    addr = NULL;
+    panicmem ();
   return __atomic_exchange_n (addr, new, __ATOMIC_SEQ_CST);
 }
 
@@ -48,7 +48,7 @@
 SwapUint64 (uint64_t *addr, uint64_t new)
 {
   if (((uintptr_t) addr & 7) != 0)
-    addr = NULL;
+    panicmem ();
   return __atomic_exchange_n (addr, new, __ATOMIC_SEQ_CST);
 }
 
@@ -215,7 +215,7 @@
   int64_t v;
 
   if (((uintptr_t) addr & 7) != 0)
-    addr = NULL;
+    panicmem ();
   v = *addr;
   while (! __sync_bool_compare_and_swap (addr, v, v))
     v = *addr;
@@ -247,7 +247,7 @@
   uint64_t v;
 
   if (((uintptr_t) addr & 7) != 0)
-    addr = NULL;
+    panicmem ();
   v = *addr;
   while (! __sync_bool_compare_and_swap (addr, v, v))
     v = *addr;
@@ -308,7 +308,7 @@
   int64_t v;
 
   if (((uintptr_t) addr & 7) != 0)
-    addr = NULL;
+    panicmem ();
   v = *addr;
   while (! __sync_bool_compare_and_swap (addr, v, val))
     v = *addr;
@@ -338,7 +338,7 @@
   uint64_t v;
 
   if (((uintptr_t) addr & 7) != 0)
-    addr = NULL;
+    panicmem ();
   v = *addr;
   while (! __sync_bool_compare_and_swap (addr, v, val))
     v = *addr;

libgo/runtime/runtime.h

diff --git a/libgo/runtime/runtime.h b/libgo/runtime/runtime.h
index dd5a958..39b5ef8 100644
--- a/libgo/runtime/runtime.h
+++ b/libgo/runtime/runtime.h
@@ -211,6 +211,8 @@
 extern	bool	runtime_isstarted;
 extern	bool	runtime_isarchive;
 
+extern	void	panicmem(void) __asm__ (GOSYM_PREFIX "runtime.panicmem");
+
 /*
  * common functions and data
  */