x86-64: Align child stack to 16 bytes

Message ID 20210523172942.3047571-1-hjl.tools@gmail.com
State New
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Series
  • x86-64: Align child stack to 16 bytes
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Commit Message

Wilco Dijkstra via Libc-alpha May 23, 2021, 5:29 p.m.
In the x86-64 clone wrapper, align child stack to 16 bytes per the
x86-64 psABI.
---
 sysdeps/unix/sysv/linux/Makefile             |  2 +-
 sysdeps/unix/sysv/linux/tst-misalign-clone.c | 97 ++++++++++++++++++++
 sysdeps/unix/sysv/linux/x86_64/clone.S       |  3 +
 3 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/unix/sysv/linux/tst-misalign-clone.c

-- 
2.31.1

Comments

Andreas Schwab May 23, 2021, 5:57 p.m. | #1
On Mai 23 2021, H.J. Lu via Libc-alpha wrote:

> +  /* NB: Try to force misaligned child stack.  */

> +  char st[STACK_SIZE + 4] __attribute__ ((aligned (1)));


If you want a misaligned pointer, you need to start with a known
alignment.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Patch

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 9bcd38a732..283b2d0bd8 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -327,5 +327,5 @@  CFLAGS-gai.c += -DNEED_NETLINK
 endif
 
 ifeq ($(subdir),nptl)
-tests += tst-align-clone tst-getpid1
+tests += tst-align-clone tst-misalign-clone tst-getpid1
 endif
diff --git a/sysdeps/unix/sysv/linux/tst-misalign-clone.c b/sysdeps/unix/sysv/linux/tst-misalign-clone.c
new file mode 100644
index 0000000000..3eb91b9b1f
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-misalign-clone.c
@@ -0,0 +1,97 @@ 
+/* 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/>.  */
+
+#include <sched.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <tst-stack-align.h>
+#include <stackinfo.h>
+#include <support/xunistd.h>
+
+static int
+f (void *arg)
+{
+  bool ok = true;
+
+  puts ("in f");
+
+  if (TEST_STACK_ALIGN ())
+    ok = false;
+
+  return ok ? 0 : 1;
+}
+
+static int
+do_test (void)
+{
+  bool ok = true;
+
+  puts ("in main");
+
+  if (TEST_STACK_ALIGN ())
+    ok = false;
+
+#ifdef __ia64__
+# define STACK_SIZE (256 * 1024)
+#else
+# define STACK_SIZE (128 * 1024)
+#endif
+
+  /* NB: Try to force misaligned child stack.  */
+  char st[STACK_SIZE + 4] __attribute__ ((aligned (1)));
+
+#ifdef __ia64__
+  extern int __clone2 (int (*__fn) (void *__arg), void *__child_stack_base,
+		       size_t __child_stack_size, int __flags,
+		       void *__arg, ...);
+  pid_t p = __clone2 (f, st, sizeof (st), 0, 0);
+#else
+# if _STACK_GROWS_DOWN
+  pid_t p = clone (f, st + sizeof (st), 0, 0);
+# elif _STACK_GROWS_UP
+  pid_t p = clone (f, st, 0, 0);
+# else
+#  error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
+# endif
+#endif
+  if (p == -1)
+    {
+      printf("clone failed: %m\n");
+      return 1;
+    }
+
+  int e;
+  xwaitpid (p, &e, __WCLONE);
+  if (!WIFEXITED (e))
+    {
+      if (WIFSIGNALED (e))
+	printf ("died from signal %s\n", strsignal (WTERMSIG (e)));
+      else
+	puts ("did not terminate correctly");
+      return 1;
+    }
+  if (WEXITSTATUS (e) != 0)
+    ok = false;
+
+  return ok ? 0 : 1;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/clone.S b/sysdeps/unix/sysv/linux/x86_64/clone.S
index 31ac12da0c..5f52ce7813 100644
--- a/sysdeps/unix/sysv/linux/x86_64/clone.S
+++ b/sysdeps/unix/sysv/linux/x86_64/clone.S
@@ -57,6 +57,9 @@  ENTRY (__clone)
 	testq	%rsi,%rsi		/* no NULL stack pointers */
 	jz	SYSCALL_ERROR_LABEL
 
+	/* Align stack to 16 bytes per the x86-64 psABI.  */
+	andq	$-16, %rsi
+
 	/* Insert the argument onto the new stack.  */
 	subq	$16,%rsi
 	movq	%rcx,8(%rsi)