On 17 September 2014 12:48, Marcus Shawcroft <marcus.shawcr...@gmail.com> wrote:
> On 9 September 2014 13:08, Christophe Lyon <christophe.l...@linaro.org> wrote:
>> On 9 September 2014 12:03, <pins...@gmail.com> wrote:
>>>
>>>
>>>> On Sep 9, 2014, at 2:50 AM, Marcus Shawcroft <marcus.shawcr...@gmail.com>
>>>> wrote:
>>>>
>>>> +static unsigned HOST_WIDE_INT
>>>> +aarch64_asan_shadow_offset (void)
>>>> +{
>>>> + return (HOST_WIDE_INT_1 << 36);
>>>> +}
>>>> +
>>>>
>>>> Looking around various other ports I see magic numbers including 29,
>>>> 41, 44.... Help me understand why 36 is the right choice for aarch64?
>>>
>>> Also why 36? What is the min virtual address space aarch64 Linux kernel
>>> supports with 4k pages and 3 level page table? Also does this need to
>>> conditionalized on lp64? Since I am about to post glibc patches turning on
>>> address sanitizer breaks that.
>>>
>>
>> The address space is 2^39 according to /proc/self/maps:
>> [...]
>>
>> The shadow offset is obtained by dividing this value by 8 -> 2^36.
>>
>> Note that this value has to match kAArch64_ShadowOffset64 as defined
>> in libsanitizer/asan/asan_mapping.h.
>>
>> I do expect a followup patch to support ilp32, but I wouldn't post a
>> patch which I haven't tested.
>
> Presumably for ILP32 the shadow offset should be 1<<29 and we will
> need to make both asan_mapping.h and aarch64_asan_shadow_offset
> conditional.
>
Indeed. We'll do that once Andrew has committed all his IPL32 patches (glibc).
> This patch for LP64 is OK.
I will commit it once the libsanitizer runtime has been updated to at
least r209641 otherwise GCC will fail to build for AArch64.
> Thanks
> /Marcus
