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Diffstat (limited to 'tools/include/linux/compiler.h')
-rw-r--r--tools/include/linux/compiler.h32
1 files changed, 24 insertions, 8 deletions
diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 909808386..fa7208a32 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -43,13 +43,29 @@
#include <linux/types.h>
+/*
+ * Following functions are taken from kernel sources and
+ * break aliasing rules in their original form.
+ *
+ * While kernel is compiled with -fno-strict-aliasing,
+ * perf uses -Wstrict-aliasing=3 which makes build fail
+ * under gcc 4.4.
+ *
+ * Using extra __may_alias__ type to allow aliasing
+ * in this case.
+ */
+typedef __u8 __attribute__((__may_alias__)) __u8_alias_t;
+typedef __u16 __attribute__((__may_alias__)) __u16_alias_t;
+typedef __u32 __attribute__((__may_alias__)) __u32_alias_t;
+typedef __u64 __attribute__((__may_alias__)) __u64_alias_t;
+
static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
{
switch (size) {
- case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
- case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
- case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
- case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
+ case 1: *(__u8_alias_t *) res = *(volatile __u8_alias_t *) p; break;
+ case 2: *(__u16_alias_t *) res = *(volatile __u16_alias_t *) p; break;
+ case 4: *(__u32_alias_t *) res = *(volatile __u32_alias_t *) p; break;
+ case 8: *(__u64_alias_t *) res = *(volatile __u64_alias_t *) p; break;
default:
barrier();
__builtin_memcpy((void *)res, (const void *)p, size);
@@ -60,10 +76,10 @@ static __always_inline void __read_once_size(const volatile void *p, void *res,
static __always_inline void __write_once_size(volatile void *p, void *res, int size)
{
switch (size) {
- case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
- case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
- case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
- case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
+ case 1: *(volatile __u8_alias_t *) p = *(__u8_alias_t *) res; break;
+ case 2: *(volatile __u16_alias_t *) p = *(__u16_alias_t *) res; break;
+ case 4: *(volatile __u32_alias_t *) p = *(__u32_alias_t *) res; break;
+ case 8: *(volatile __u64_alias_t *) p = *(__u64_alias_t *) res; break;
default:
barrier();
__builtin_memcpy((void *)p, (const void *)res, size);