From mboxrd@z Thu Jan  1 00:00:00 1970
From: Colin Ian King <colin.king-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
Subject: aarch64 clone() man page omission
Date: Mon, 25 Apr 2016 20:42:18 +0100
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Hi there,

currently, the aarch64 clone() system call requires the stack to be
aligned at a 16 byte boundary, see arch/arm64/kernel/process.c,
copy_thread():

                if (stack_start) {
                        if (is_compat_thread(task_thread_info(p)))
                                childregs->compat_sp = stack_start;
                        /* 16-byte aligned stack mandatory on AArch64 */
                        else if (stack_start & 15)
                                return -EINVAL;
                        else
                                childregs->sp = stack_start;
                }


..and returns -EINVAL if not aligned correctly.  This should be added to
the manual page clone(2) as it took me a while to figure out why clone()
was failing with -EINVAL for aarch64 but not on x86.

Colin
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