Re: A binary that has PT_LOAD more than 2

[Ryo ONODERA <ryo%tetera.org@localhost>]

Hi,

From: Valery Ushakov <uwe%stderr.spb.ru@localhost>, Date: Tue, 25 Sep 2018 14:51:21 +0300

> On Tue, Sep 25, 2018 at 20:24:24 +0900, Ryo ONODERA wrote:
> 
>> From: Valery Ushakov <uwe%stderr.spb.ru@localhost>, Date: Tue, 25 Sep 2018 13:13:45 +0300
>> 
>> > On Tue, Sep 25, 2018 at 17:57:19 +0900, Ryo ONODERA wrote:
>> > 
>> >> The Go language compiler (pkgsrc/lang/go111) produces
>> >> three PT_LOAD in a ELF executable.
>> >> And I found that LLD linker from LLVM also produces three PT_LOAD.
>> >> 
>> >> Our ldd(8) command cannot accept three PT_LOAD now.
>> >> Can we accept three or more PT_LOAD in our ldd(8)?
>> >> 
>> >> Are there any other issues to be discussed to support three PT_LOAD
>> >> binaries?
>> > 
>> > Define "our"?
>> > 
>> > libexec/ld.elf_so/headers.c:
>> > 
>> >  revision 1.62
>> >  date: 2017-06-23 18:29:21 +0300;  author: joerg;  state: Exp;  lines: +11 -12;  commitid: 9duF2Q9DPoICLvWz;
>> >  branches:  1.62.4;
>> >  Remove old assert that only two segments exist. The rest of the code has
>> >  been changed to cope with more and at least Go actively creates them.
>> >  Adjust the mapping size computation to use the maximum and not depend on
>> >  PT_LOAD segments to be in order.
>> > 
>> > and this is in current and -8.
>> > 
>> > http://gnats.netbsd.org/16983
>> 
>> Thanks for your pointer.
>> I understand that executing executables that have PT_LOAD more than 2
>> is valid for NetBSD 8 and current.
>> It is very good news for me.
>> 
>> However, ldd(8) uses _rtld_map_object() in
>> src/libexec/ld.elf_so/map_object.c file.
>> It has the following condition.
>> 
>>         if (nsegs != 2) {
>>                 _rtld_error("%s: wrong number of segments (%d != 2)", path,
>>                     nsegs);
>>                 goto bad;
>>         }
>> 
>> This part can be removed safely?
> 
> Oh, sorry, I was not paying enough attention.
> 
> This check can't be just removed b/c Elf_Phdr *segs[2]; so I've
> reopened bin/16983.

I understand _rtld_map_object() depends on length of segs[] array is two.
I should read ELF definition again to say more.

Thank you.

> -uwe

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Ryo ONODERA // ryo%tetera.org@localhost
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