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From: Florian Weimer <fweimer@redhat.com>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>
Subject: Re: [PATCH v7 1/8] arm: Add the clone3 wrapper
References: <20230803163558.991832-1-adhemerval.zanella@linaro.org>
	<20230803163558.991832-2-adhemerval.zanella@linaro.org>
	<878rahx4r5.fsf@oldenburg.str.redhat.com>
	<d85afd0c-3150-0504-48ef-3e84f96b8879@linaro.org>
Date: Fri, 11 Aug 2023 16:21:01 +0200
In-Reply-To: <d85afd0c-3150-0504-48ef-3e84f96b8879@linaro.org> (Adhemerval
	Zanella Netto's message of "Fri, 11 Aug 2023 11:12:33 -0300")
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* Adhemerval Zanella Netto:

> On 11/08/23 07:17, Florian Weimer wrote:
>> * Adhemerval Zanella via Libc-alpha:
>> 
>>> +	/* Do the syscall, the kernel expects:
>>> +	   r7: system call number:
>>> +	   r0: cl_args
>>> +	   r1: size  */
>>> +	push    { r7 }
>>> +	cfi_adjust_cfa_offset (4)
>>> +	cfi_rel_offset (r7, 0)
>>> +	ldr     r7, =SYS_ify(clone3)
>>> +	swi	0x0
>>> +	cfi_endproc
>>> +
>>> +	cmp	r0, #0
>>> +	beq	1f
>>> +	pop     {r7}
>> 
>>> +1:
>>> +	.fnstart
>>> +	.cantunwind
>>> +	mov	r0, r3
>>> +	mov	ip, r2
>>> +	BLX (ip)
>> 
>> I think the stack is misaligned at the BNLX call because only one 4-byte
>> register is pushed.
>
> It should not matter because the stack is defined by the cl_args::stack
> argument.  We might add a alignment check on clone-internal.c, but I
> think since it uses solely on internal usage, it should be required.

You are right, my mistake.

Thanks,
Florian