[PATCH] Properly compute offsets of note descriptor and next note [BZ #22370]

[H.J. Lu]

On Fri, Nov 24, 2017 at 6:45 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Nov 20, 2017 at 5:04 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Thu, Nov 16, 2017 at 5:24 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Wed, Nov 15, 2017 at 3:03 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> On Sun, Nov 12, 2017 at 8:03 AM, Andreas Schwab <schwab@linux-m68k.org> wrote:
>>>>> On Nov 12 2017, "H.J. Lu" <hjl.tools@gmail.com> wrote:
>>>>>
>>>>>> Data after Elf64_Nhdr is the "name" field which is a 4-byte string, "GNU".
>>>>>> There is no misalignment.
>>>>>
>>>>> That's not what your patch does.  You are aligning both the name length
>>>>> and the data length to a 8 byte boundary, making the note size
>>>>> unaligned.
>>>>>
>>>>
>>>> You are right.  Both glibc and binutils get this wrong.  I opened a
>>>> binutils bug:
>>>>
>>>> https://sourceware.org/bugzilla/show_bug.cgi?id=22444
>>>>
>>>> I will fix it first and take care of glibc next.
>>>>
>>>
>>> Here is the glibc path.
>>>
>>> Any comments?
>>>
>>
>> Any comments or objections?
>>
>
> I updated Linux Extensions to gABI to clarify alignments of NOTE section
> and segments:
>
> https://sourceware.org/ml/gnu-gabi/2017-q4/msg00003.html
>
> I will check it in next week.
>

Here is the updated patch I will check in next week.  It added:

+     /* NB: Some PT_NOTE segment may have alignment value of 0
+        or 1.  gABI specifies that PT_NOTE segments should be
+        aligned to 4 bytes in 32-bit objects and to 8 bytes in
+        64-bit objects.  As a Linux extension, we also support
+        4 byte alignment in 64-bit objects.  If p_align is less
+        than 4, we treate alignment as 4 bytes.   */
+     ElfW(Addr) align = phdr[i].p_align;
+     if (align < 4)
+       align = 4;

to prevent infinite loop with incorrect segment alignment.


-- 
H.J.
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