From: Ivo Raisr <ivosh@ivosh.net>
Date: Sun, 26 Feb 2017 21:37:04 +0000 (+0000)
Subject: Introduce macro ASSUME_ALIGNED and use it in vki-linux.h.
X-Git-Tag: svn/VALGRIND_3_13_0~165
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f1a6076bcfb9605198bd2bb3789008979f76d9e5;p=thirdparty%2Fvalgrind.git

Introduce macro ASSUME_ALIGNED and use it in vki-linux.h.
Reduces the number of compiler warnings on MIPS platforms.
Partial fix for BZ#370028.
Patch by: Aleksandar Rikalo <aleksandar.rikalo@imgtec.com>


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@16256
---

diff --git a/NEWS b/NEWS
index a156093136..f34dc8f50b 100644
--- a/NEWS
+++ b/NEWS
@@ -108,6 +108,7 @@ where XXXXXX is the bug number as listed below.
 368924  WARNING: unhandled arm64-linux syscall: 84 (sync_file_range)
 368925  WARNING: unhandled arm64-linux syscall: 130 (tkill)
 368926  WARNING: unhandled arm64-linux syscall: 97 (unshare)
+370028  Reduce the number of compiler warnings on MIPS platforms (partial fix)
 370635  arm64 missing syscall getcpu
 371225  Fix order of timer_{gettime,getoverrun,settime} syscalls on arm64
 371412  Rename wrap_sys_shmat to sys_shmat like other wrappers
diff --git a/include/pub_tool_basics.h b/include/pub_tool_basics.h
index 6ef37c7bf5..4712c117cf 100644
--- a/include/pub_tool_basics.h
+++ b/include/pub_tool_basics.h
@@ -468,6 +468,17 @@ static inline Bool sr_EQ ( UInt sysno, SysRes sr1, SysRes sr2 ) {
       } var = { .in = x }; var.out;  \
    })
 
+/* Some architectures (eg. mips, arm) do not support unaligned memory access
+   by hardware, so GCC warns about suspicious situations. This macro could
+   be used to avoid these warnings but only after careful examination. */
+#define ASSUME_ALIGNED(D, x)                 \
+   ({                                        \
+      union {                                \
+         void *in;                           \
+         D out;                              \
+      } var = {.in = (void *) (x)}; var.out; \
+   })
+
 // Poor man's static assert
 #define STATIC_ASSERT(x)  extern int VG_(VG_(VG_(unused)))[(x) ? 1 : -1] \
                                      __attribute__((unused))
diff --git a/include/vki/vki-linux.h b/include/vki/vki-linux.h
index b64b52108a..f70be844bf 100644
--- a/include/vki/vki-linux.h
+++ b/include/vki/vki-linux.h
@@ -674,7 +674,8 @@ __KINLINE struct vki_cmsghdr * __vki_cmsg_nxthdr(void *__ctl, __vki_kernel_size_
 {
 	struct vki_cmsghdr * __ptr;
 
-	__ptr = (struct vki_cmsghdr*)(((unsigned char *) __cmsg) +  VKI_CMSG_ALIGN(__cmsg->cmsg_len));
+	__ptr = ASSUME_ALIGNED(struct vki_cmsghdr *,
+        	((unsigned char *) __cmsg) +  VKI_CMSG_ALIGN(__cmsg->cmsg_len));
 	if ((unsigned long)((char*)(__ptr+1) - (char *) __ctl) > __size)
 		return (struct vki_cmsghdr *)0;