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From: "hjl.tools at gmail dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug libc/28531] [x86] Cancelable syscall stubs fail to preserve
 16-byte stack alignment
Date: Wed, 03 Nov 2021 13:16:13 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28531

--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> ---
Do you have a testcase? I tried

diff --git a/nptl/cancellation.c b/nptl/cancellation.c
index 2bd31686fd..ca0b14abc3 100644
--- a/nptl/cancellation.c
+++ b/nptl/cancellation.c
@@ -22,6 +22,14 @@
 #include <futex-internal.h>


+static void
+check (void)
+{
+  char *sp =3D CURRENT_STACK_FRAME;
+  if ((((uintptr_t) sp) + sizeof (char *)) & (sizeof (char *) - 1))
+    asm ("hlt");
+}
+
 /* The next two functions are similar to pthread_setcanceltype() but
    more specialized for the use in the cancelable functions like write().
    They do not need to check parameters etc.  */
@@ -29,6 +37,7 @@ int
 attribute_hidden
 __pthread_enable_asynccancel (void)
 {
+  check ();
   struct pthread *self =3D THREAD_SELF;
   int oldval =3D THREAD_GETMEM (self, cancelhandling);

on release/2.22/master branch.  "hlt" was never triggered.

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