[glibc] String: test-memcpy used unaligned types for buffers [BZ 28572]

[glibc] String: test-memcpy used unaligned types for buffers [BZ 28572]

[Noah Goldstein]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=409a73581687914ac0555f6a468469578f97e70f

commit 409a73581687914ac0555f6a468469578f97e70f
Author: John David Anglin <danglin@gcc.gnu.org>
Date:   Tue Dec 7 16:10:20 2021 -0600

    String: test-memcpy used unaligned types for buffers [BZ 28572]
    
    commit d585ba47fcda99fdf228e3e45a01b11a15efbc5a
    Author: Noah Goldstein <goldstein.w.n@gmail.com>
    Date:   Mon Nov 1 00:49:48 2021 -0500
    
        string: Make tests birdirectional test-memcpy.c
    
    Add tests that had src/dst non 4-byte aligned. Since src/dst are
    initialized/compared as uint32_t type which is 4-byte aligned this can
    break on some targets.
    
    Fix the issue by specifying a new non-aligned 4-byte
    `unaligned_uint32_t` for src/dst.
    
    Another alternative is to rely on memcpy/memcmp for
    initializing/testing src/dst. Using memcpy for initializing in memcpy
    tests, however, could lead to future bugs.
    
    Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>

Diff:
---
 string/test-memcpy-support.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/string/test-memcpy-support.h b/string/test-memcpy-support.h
index 419158a420..b6cc434905 100644
--- a/string/test-memcpy-support.h
+++ b/string/test-memcpy-support.h
@@ -51,6 +51,7 @@ builtin_memcpy (char *dst, const char *src, size_t n)
 }
 #endif
 typedef char *(*proto_t) (char *, const char *, size_t);
+typedef uint32_t __attribute__ ((may_alias, aligned (1))) unaligned_uint32_t;
 
 static void
 do_one_test (impl_t *impl, char *dst, const char *src, size_t len)
@@ -134,8 +135,8 @@ do_test1 (size_t align1, size_t align2, size_t size)
     error (EXIT_FAILURE, errno, "mprotect failed");
 
   size_t array_size = size / sizeof (uint32_t);
-  uint32_t *dest = large_buf + align1;
-  uint32_t *src = large_buf + region_size + 2 * page_size + align2;
+  unaligned_uint32_t *dest = large_buf + align1;
+  unaligned_uint32_t *src = large_buf + region_size + 2 * page_size + align2;
   size_t i;
   size_t repeats;
   for (repeats = 0; repeats < 2; repeats++)