Fix: x86 and s390 uatomic: __hp() macro warning with gcc 11

The __hp() macro used in the x86 and s390 uatomic code generates the
following warning with gcc-11:

In file included from ../include/urcu/uatomic.h:27,
                 from ../include/urcu/static/wfcqueue.h:35,
                 from ../include/urcu/wfcqueue.h:133,
                 from workqueue.c:39:
workqueue.c: In function ‘workqueue_thread’:
../include/urcu/uatomic/x86.h:155:17: warning: array subscript ‘struct __uatomic_dummy[0]’ is partly outside array bounds of ‘struct cds_wfcq_tail[1]’ [-Warray-bounds]
  155 |                 __asm__ __volatile__(
      |                 ^~~~~~~
workqueue.c:184:38: note: while referencing ‘cbs_tmp_tail’
  184 |                 struct cds_wfcq_tail cbs_tmp_tail;
      |                                      ^~~~~~~~~~~~

The (previously undocumented) reason for this macro is to allow passing the
"void *" parameter as "m" or "+m" operand to the inline assembly. That
motivation was explained in commit 53b8ed6836363 ("s390 uatomic arch fix").

The out of bound access is detected by gcc because struct
__uatomic_dummy's length is quite large: an array of 10 unsigned long,
which is larger than the size pointed to by the void pointer.

So rather than using a fixed-size type, cast to a structure containing
an array of characters of a size matching the @addr input argument.

While we are at it and digging out git archeology, properly document the
__hp() macro for posterity.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I785e30661efe48be1806664a1a14fd3c9fdb0a32

diff --git a/include/urcu/uatomic/s390.h b/include/urcu/uatomic/s390.h
index 62561e000224ccb4c71e244a239eab5ac730f70b..47b97b1da08159e26abc727679f33c9815768461 100644 (file)
--- a/include/urcu/uatomic/s390.h
+++ b/include/urcu/uatomic/s390.h
@@ -61,10 +61,14 @@ extern "C" {
 
 #endif /* !COMPILER_HAVE_SHORT_MEM_OPERAND */
 
-struct __uatomic_dummy {
-       unsigned long v[10];
-};
-#define __hp(x)        ((struct __uatomic_dummy *)(x))
+/*
+ * The __hp() macro casts the void pointer "x" to a pointer to a structure
+ * containing an array of char of the specified size. This allows passing the
+ * @addr arguments of the following inline functions as "m" and "+m" operands
+ * to the assembly.
+ */
+
+#define __hp(size, x)  ((struct { char v[size]; } *)(x))
 
 /* xchg */
 
@@ -79,8 +83,8 @@ unsigned long _uatomic_exchange(volatile void *addr, unsigned long val, int len)
                __asm__ __volatile__(
                        "0:     cs %0,%2," MEMOP_REF(%3) "\n"
                        "       brc 4,0b\n"
-                       : "=&r" (old_val), MEMOP_OUT (__hp(addr))
-                       : "r" (val), MEMOP_IN (__hp(addr))
+                       : "=&r" (old_val), MEMOP_OUT (__hp(len, addr))
+                       : "r" (val), MEMOP_IN (__hp(len, addr))
                        : "memory", "cc");
                return old_val;
        }
@@ -92,8 +96,8 @@ unsigned long _uatomic_exchange(volatile void *addr, unsigned long val, int len)
                __asm__ __volatile__(
                        "0:     csg %0,%2," MEMOP_REF(%3) "\n"
                        "       brc 4,0b\n"
-                       : "=&r" (old_val), MEMOP_OUT (__hp(addr))
-                       : "r" (val), MEMOP_IN (__hp(addr))
+                       : "=&r" (old_val), MEMOP_OUT (__hp(len, addr))
+                       : "r" (val), MEMOP_IN (__hp(len, addr))
                        : "memory", "cc");
                return old_val;
        }
@@ -123,8 +127,8 @@ unsigned long _uatomic_cmpxchg(void *addr, unsigned long old,
 
                __asm__ __volatile__(
                        "       cs %0,%2," MEMOP_REF(%3) "\n"
-                       : "+r" (old_val), MEMOP_OUT (__hp(addr))
-                       : "r" (_new), MEMOP_IN (__hp(addr))
+                       : "+r" (old_val), MEMOP_OUT (__hp(len, addr))
+                       : "r" (_new), MEMOP_IN (__hp(len, addr))
                        : "memory", "cc");
                return old_val;
        }
@@ -133,8 +137,8 @@ unsigned long _uatomic_cmpxchg(void *addr, unsigned long old,
        {
                __asm__ __volatile__(
                        "       csg %0,%2," MEMOP_REF(%3) "\n"
-                       : "+r" (old), MEMOP_OUT (__hp(addr))
-                       : "r" (_new), MEMOP_IN (__hp(addr))
+                       : "+r" (old), MEMOP_OUT (__hp(len, addr))
+                       : "r" (_new), MEMOP_IN (__hp(len, addr))
                        : "memory", "cc");
                return old;
        }

diff --git a/include/urcu/uatomic/x86.h b/include/urcu/uatomic/x86.h
index ec71e5151fa07b4115f5d4b62fce6d7a3e4c30cd..e9f2f78275f472618d2ad302205eda8bb37629c8 100644 (file)
--- a/include/urcu/uatomic/x86.h
+++ b/include/urcu/uatomic/x86.h
@@ -36,10 +36,14 @@ extern "C" {
  * Derived from AO_compare_and_swap() and AO_test_and_set_full().
  */
 
-struct __uatomic_dummy {
-       unsigned long v[10];
-};
-#define __hp(x)        ((struct __uatomic_dummy *)(x))
+/*
+ * The __hp() macro casts the void pointer "x" to a pointer to a structure
+ * containing an array of char of the specified size. This allows passing the
+ * @addr arguments of the following inline functions as "m" and "+m" operands
+ * to the assembly.
+ */
+
+#define __hp(size, x)  ((struct { char v[size]; } *)(x))
 
 #define _uatomic_set(addr, v)  ((void) CMM_STORE_SHARED(*(addr), (v)))
 
@@ -56,7 +60,7 @@ unsigned long __uatomic_cmpxchg(void *addr, unsigned long old,
 
                __asm__ __volatile__(
                "lock; cmpxchgb %2, %1"
-                       : "+a"(result), "+m"(*__hp(addr))
+                       : "+a"(result), "+m"(*__hp(len, addr))
                        : "q"((unsigned char)_new)
                        : "memory");
                return result;
@@ -67,7 +71,7 @@ unsigned long __uatomic_cmpxchg(void *addr, unsigned long old,
 
                __asm__ __volatile__(
                "lock; cmpxchgw %2, %1"
-                       : "+a"(result), "+m"(*__hp(addr))
+                       : "+a"(result), "+m"(*__hp(len, addr))
                        : "r"((unsigned short)_new)
                        : "memory");
                return result;
@@ -78,7 +82,7 @@ unsigned long __uatomic_cmpxchg(void *addr, unsigned long old,
 
                __asm__ __volatile__(
                "lock; cmpxchgl %2, %1"
-                       : "+a"(result), "+m"(*__hp(addr))
+                       : "+a"(result), "+m"(*__hp(len, addr))
                        : "r"((unsigned int)_new)
                        : "memory");
                return result;
@@ -90,7 +94,7 @@ unsigned long __uatomic_cmpxchg(void *addr, unsigned long old,
 
                __asm__ __volatile__(
                "lock; cmpxchgq %2, %1"
-                       : "+a"(result), "+m"(*__hp(addr))
+                       : "+a"(result), "+m"(*__hp(len, addr))
                        : "r"((unsigned long)_new)
                        : "memory");
                return result;
@@ -123,7 +127,7 @@ unsigned long __uatomic_exchange(void *addr, unsigned long val, int len)
                unsigned char result;
                __asm__ __volatile__(
                "xchgb %0, %1"
-                       : "=q"(result), "+m"(*__hp(addr))
+                       : "=q"(result), "+m"(*__hp(len, addr))
                        : "0" ((unsigned char)val)
                        : "memory");
                return result;
@@ -133,7 +137,7 @@ unsigned long __uatomic_exchange(void *addr, unsigned long val, int len)
                unsigned short result;
                __asm__ __volatile__(
                "xchgw %0, %1"
-                       : "=r"(result), "+m"(*__hp(addr))
+                       : "=r"(result), "+m"(*__hp(len, addr))
                        : "0" ((unsigned short)val)
                        : "memory");
                return result;
@@ -143,7 +147,7 @@ unsigned long __uatomic_exchange(void *addr, unsigned long val, int len)
                unsigned int result;
                __asm__ __volatile__(
                "xchgl %0, %1"
-                       : "=r"(result), "+m"(*__hp(addr))
+                       : "=r"(result), "+m"(*__hp(len, addr))
                        : "0" ((unsigned int)val)
                        : "memory");
                return result;
@@ -154,7 +158,7 @@ unsigned long __uatomic_exchange(void *addr, unsigned long val, int len)
                unsigned long result;
                __asm__ __volatile__(
                "xchgq %0, %1"
-                       : "=r"(result), "+m"(*__hp(addr))
+                       : "=r"(result), "+m"(*__hp(len, addr))
                        : "0" ((unsigned long)val)
                        : "memory");
                return result;
@@ -187,7 +191,7 @@ unsigned long __uatomic_add_return(void *addr, unsigned long val,
 
                __asm__ __volatile__(
                "lock; xaddb %1, %0"
-                       : "+m"(*__hp(addr)), "+q" (result)
+                       : "+m"(*__hp(len, addr)), "+q" (result)
                        :
                        : "memory");
                return result + (unsigned char)val;
@@ -198,7 +202,7 @@ unsigned long __uatomic_add_return(void *addr, unsigned long val,
 
                __asm__ __volatile__(
                "lock; xaddw %1, %0"
-                       : "+m"(*__hp(addr)), "+r" (result)
+                       : "+m"(*__hp(len, addr)), "+r" (result)
                        :
                        : "memory");
                return result + (unsigned short)val;
@@ -209,7 +213,7 @@ unsigned long __uatomic_add_return(void *addr, unsigned long val,
 
                __asm__ __volatile__(
                "lock; xaddl %1, %0"
-                       : "+m"(*__hp(addr)), "+r" (result)
+                       : "+m"(*__hp(len, addr)), "+r" (result)
                        :
                        : "memory");
                return result + (unsigned int)val;
@@ -221,7 +225,7 @@ unsigned long __uatomic_add_return(void *addr, unsigned long val,
 
                __asm__ __volatile__(
                "lock; xaddq %1, %0"
-                       : "+m"(*__hp(addr)), "+r" (result)
+                       : "+m"(*__hp(len, addr)), "+r" (result)
                        :
                        : "memory");
                return result + (unsigned long)val;
@@ -251,7 +255,7 @@ void __uatomic_and(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; andb %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "iq" ((unsigned char)val)
                        : "memory");
                return;
@@ -260,7 +264,7 @@ void __uatomic_and(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; andw %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "ir" ((unsigned short)val)
                        : "memory");
                return;
@@ -269,7 +273,7 @@ void __uatomic_and(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; andl %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "ir" ((unsigned int)val)
                        : "memory");
                return;
@@ -279,7 +283,7 @@ void __uatomic_and(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; andq %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "er" ((unsigned long)val)
                        : "memory");
                return;
@@ -307,7 +311,7 @@ void __uatomic_or(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; orb %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "iq" ((unsigned char)val)
                        : "memory");
                return;
@@ -316,7 +320,7 @@ void __uatomic_or(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; orw %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "ir" ((unsigned short)val)
                        : "memory");
                return;
@@ -325,7 +329,7 @@ void __uatomic_or(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; orl %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "ir" ((unsigned int)val)
                        : "memory");
                return;
@@ -335,7 +339,7 @@ void __uatomic_or(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; orq %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "er" ((unsigned long)val)
                        : "memory");
                return;
@@ -363,7 +367,7 @@ void __uatomic_add(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; addb %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "iq" ((unsigned char)val)
                        : "memory");
                return;
@@ -372,7 +376,7 @@ void __uatomic_add(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; addw %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "ir" ((unsigned short)val)
                        : "memory");
                return;
@@ -381,7 +385,7 @@ void __uatomic_add(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; addl %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "ir" ((unsigned int)val)
                        : "memory");
                return;
@@ -391,7 +395,7 @@ void __uatomic_add(void *addr, unsigned long val, int len)
        {
                __asm__ __volatile__(
                "lock; addq %1, %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        : "er" ((unsigned long)val)
                        : "memory");
                return;
@@ -420,7 +424,7 @@ void __uatomic_inc(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; incb %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;
@@ -429,7 +433,7 @@ void __uatomic_inc(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; incw %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;
@@ -438,7 +442,7 @@ void __uatomic_inc(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; incl %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;
@@ -448,7 +452,7 @@ void __uatomic_inc(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; incq %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;
@@ -473,7 +477,7 @@ void __uatomic_dec(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; decb %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;
@@ -482,7 +486,7 @@ void __uatomic_dec(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; decw %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;
@@ -491,7 +495,7 @@ void __uatomic_dec(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; decl %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;
@@ -501,7 +505,7 @@ void __uatomic_dec(void *addr, int len)
        {
                __asm__ __volatile__(
                "lock; decq %0"
-                       : "=m"(*__hp(addr))
+                       : "=m"(*__hp(len, addr))
                        :
                        : "memory");
                return;