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Linux: Do not align the stack for __clone3

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All internal callers of __clone3 should provide an already aligned
stack.  Removing the stack alignment in __clone3 is a net gain: it
simplifies the internal function contract (mask/unmask signals) along
with the arch-specific code.

Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Adhemerval Zanella Netto 2023-01-12 10:58:50 -03:00 • committed by Adhemerval Zanella
parent 2fe58919a0
commit 2290cf73cc
3 changed files with 3 additions and 77 deletions
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3
include/clone_internal.h
View file

@ -11,6 +11,9 @@
Different than kernel, the implementation also returns EINVAL for an Different than kernel, the implementation also returns EINVAL for an
invalid NULL __CL_ARGS or __FUNC (similar to __clone). invalid NULL __CL_ARGS or __FUNC (similar to __clone).
All callers are responsible for correctly aligning the stack. The stack is
not aligned prior to the syscall (this differs from the exported __clone).
This function is only implemented if the ABI defines HAVE_CLONE3_WRAPPER. This function is only implemented if the ABI defines HAVE_CLONE3_WRAPPER.
*/ */
extern int __clone3 (struct clone_args *__cl_args, size_t __size, extern int __clone3 (struct clone_args *__cl_args, size_t __size,

74
sysdeps/unix/sysv/linux/tst-misalign-clone-internal.c
View file

@ -1,74 +0,0 @@
/* Verify that __clone_internal properly aligns the child stack.
Copyright (C) 2021-2023 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 <libc-pointer-arith.h>
#include <tst-stack-align.h>
#include <clone_internal.h>
#include <support/xunistd.h>
#include <support/check.h>
static int
check_stack_alignment (void *arg)
{
puts ("in f");
return TEST_STACK_ALIGN () ? 1 : 0;
}
static int
do_test (void)
{
puts ("in do_test");
if (TEST_STACK_ALIGN ())
FAIL_EXIT1 ("stack isn't aligned\n");
#ifdef __ia64__
# define STACK_SIZE (256 * 1024)
#else
# define STACK_SIZE (128 * 1024)
#endif
char st[STACK_SIZE + 1];
/* NB: Align child stack to 1 byte. */
char *stack = PTR_ALIGN_UP (&st[0], 2) + 1;
struct clone_args clone_args =
{
.stack = (uintptr_t) stack,
.stack_size = STACK_SIZE,
};
pid_t p = __clone_internal (&clone_args, check_stack_alignment, 0);
/* Clone must not fail. */
TEST_VERIFY_EXIT (p != -1);
int e;
xwaitpid (p, &e, __WCLONE);
TEST_VERIFY (WIFEXITED (e));
TEST_COMPARE (WEXITSTATUS (e), 0);
return 0;
}
#include <support/test-driver.c>

3
sysdeps/unix/sysv/linux/x86_64/clone3.S
View file

@ -73,9 +73,6 @@ L(thread_start):
the outermost frame obviously. */ the outermost frame obviously. */
xorl %ebp, %ebp xorl %ebp, %ebp
/* Align stack to 16 bytes per the x86-64 psABI. */
and $-16, %RSP_LP
/* Set up arguments for the function call. */ /* Set up arguments for the function call. */
mov %R8_LP, %RDI_LP /* Argument. */ mov %R8_LP, %RDI_LP /* Argument. */
call *%rdx /* Call function. */ call *%rdx /* Call function. */