Re: [PATCH 1/4] arm64: compat: Alloc separate pages for vectors and sigpage

[Vincenzo Frascino <vincenzo.frascino@arm.com>]

On 02/04/2019 11:06, Catalin Marinas wrote:
> On Tue, Apr 02, 2019 at 11:01:04AM +0100, Vincenzo Frascino wrote:
>> On 01/04/2019 15:27, Catalin Marinas wrote:
>>> On Mon, Apr 01, 2019 at 12:20:22PM +0100, Vincenzo Frascino wrote:
>>>> +static int aarch32_sigreturn_setup(struct mm_struct *mm)
>>>> +{
>>>> +	unsigned long addr;
>>>>  	void *ret;
>>>>  
>>>> -	if (down_write_killable(&mm->mmap_sem))
>>>> -		return -EINTR;
>>>> -	current->mm->context.vdso = (void *)addr;
>>>> +	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
>>>> +	if (IS_ERR_VALUE(addr)) {
>>>> +		ret = ERR_PTR(addr);
>>>> +		goto out;
>>>> +	}
>>>>  
>>>> -	/* Map vectors page at the high address. */
>>>>  	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
>>>> -				       VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC,
>>>> -				       &spec);
>>>> +				       VM_READ | VM_EXEC | VM_MAYREAD |
>>>> +				       VM_MAYWRITE | VM_MAYEXEC,
>>>> +				       &aarch32_vdso_spec[1]);
>>>
>>> Any reason for setting VM_MAYWRITE here?
>>
>> VM_MAYWRITE is required to allow gdb to Copy-on-Write and set breakpoints.
> 
> Thanks. Please add a comment to the code so I don't ask again ;).
> 

No problem, my bad for not adding it in the first place ;).

-- 
Regards,
Vincenzo