Properly check stack alignment [BZ #27901]

1. Replace

if ((((uintptr_t) &_d) & (__alignof (double) - 1)) != 0)

which may be optimized out by compiler, with

int
__attribute__ ((weak, noclone, noinline))
is_aligned (void *p, int align)
{
  return (((uintptr_t) p) & (align - 1)) != 0;
}

2. Add TEST_STACK_ALIGN_INIT to TEST_STACK_ALIGN.
3. Add a common TEST_STACK_ALIGN_INIT to check 16-byte stack alignment
for both i386 and x86-64.
4. Update powerpc to use TEST_STACK_ALIGN_INIT.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/sysdeps/x86/tst-stack-align.h b/sysdeps/x86/tst-stack-align.h
new file mode 100644
index 0000000000..578d5c4a80
--- /dev/null
+++ b/sysdeps/x86/tst-stack-align.h
@@ -0,0 +1,28 @@
+/* Check stack alignment.  X86 version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+typedef struct { int i[16]; } int_al16 __attribute__((aligned (16)));
+
+#define TEST_STACK_ALIGN_INIT() \
+  ({								\
+    int_al16 _m;						\
+    printf ("int_al16:  %p %zu\n", &_m, __alignof (int_al16));	\
+    is_aligned (&_m, __alignof (int_al16));			\
+   })
+
+#include_next <tst-stack-align.h>