Fwd: svn commit: r339876 - head/libexec/rtld-elf

[Michael Tuexen]

FYI

> Begin forwarded message:
> 
> From: Michael Tuexen <Michael.Tuexen at macmic.franken.de>
> Subject: Re: svn commit: r339876 - head/libexec/rtld-elf
> Date: 30. October 2018 at 11:17:39 CET
> To: Alex Richardson <arichardson at FreeBSD.org>
> Cc: src-committers <src-committers at freebsd.org>, svn-src-all at freebsd.org, svn-src-head at freebsd.org
> 
>> On 29. Oct 2018, at 22:08, Alex Richardson <arichardson at FreeBSD.org> wrote:
>> 
>> Author: arichardson
>> Date: Mon Oct 29 21:08:02 2018
>> New Revision: 339876
>> URL: https://svnweb.freebsd.org/changeset/base/339876
>> 
>> Log:
>> rtld: set obj->textsize correctly
>> 
>> With lld-generated binaries the first PT_LOAD will usually be a read-only
>> segment unless you pass --no-rosegment. For those binaries the textsize is
>> determined by the next PT_LOAD. To allow both LLD and bfd 2.17 binaries to
>> be parsed correctly use the end of the last PT_LOAD that is marked as
>> executable instead.
>> 
>> I noticed that the value was wrong while adding some debug prints for some rtld
>> changes for CHERI binaries. `obj->textsize` only seems to be used by PPC so the
>> effect is untested. However, the value before was definitely wrong and the new
>> result matches the phdrs.
> I build kernel and world with a revision later than this on a PPC. Buildword
> ends up with a world where almost all binaries are segfaulting.... Especially gdb
> (but svn, ls or so all segfault).
> 
> Best regards
> Michael
>> 
>> Reviewed By:	kib
>> Approved By:	brooks (mentor)
>> Differential Revision: https://reviews.freebsd.org/D17117
>> 
>> Modified:
>> head/libexec/rtld-elf/map_object.c
>> head/libexec/rtld-elf/rtld.c
>> 
>> Modified: head/libexec/rtld-elf/map_object.c
>> ==============================================================================
>> --- head/libexec/rtld-elf/map_object.c	Mon Oct 29 21:03:43 2018	(r339875)
>> +++ head/libexec/rtld-elf/map_object.c	Mon Oct 29 21:08:02 2018	(r339876)
>> @@ -93,6 +93,7 @@ map_object(int fd, const char *path, const struct stat
>>    Elf_Addr note_end;
>>    char *note_map;
>>    size_t note_map_len;
>> +    Elf_Addr text_end;
>> 
>>    hdr = get_elf_header(fd, path, sb);
>>    if (hdr == NULL)
>> @@ -116,6 +117,7 @@ map_object(int fd, const char *path, const struct stat
>>    note_map = NULL;
>>    segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
>>    stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
>> +    text_end = 0;
>>    while (phdr < phlimit) {
>> 	switch (phdr->p_type) {
>> 
>> @@ -130,6 +132,10 @@ map_object(int fd, const char *path, const struct stat
>> 		    path, nsegs);
>> 		goto error;
>> 	    }
>> +	    if ((segs[nsegs]->p_flags & PF_X) == PF_X) {
>> +		text_end = MAX(text_end,
>> +		    round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz));
>> +	    }
>> 	    break;
>> 
>> 	case PT_PHDR:
>> @@ -280,8 +286,7 @@ map_object(int fd, const char *path, const struct stat
>>    }
>>    obj->mapbase = mapbase;
>>    obj->mapsize = mapsize;
>> -    obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
>> -      base_vaddr;
>> +    obj->textsize = text_end - base_vaddr;
>>    obj->vaddrbase = base_vaddr;
>>    obj->relocbase = mapbase - base_vaddr;
>>    obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
>> 
>> Modified: head/libexec/rtld-elf/rtld.c
>> ==============================================================================
>> --- head/libexec/rtld-elf/rtld.c	Mon Oct 29 21:03:43 2018	(r339875)
>> +++ head/libexec/rtld-elf/rtld.c	Mon Oct 29 21:08:02 2018	(r339876)
>> @@ -1390,13 +1390,15 @@ digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t e
>> 	    if (nsegs == 0) {	/* First load segment */
>> 		obj->vaddrbase = trunc_page(ph->p_vaddr);
>> 		obj->mapbase = obj->vaddrbase + obj->relocbase;
>> -		obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
>> -		  obj->vaddrbase;
>> 	    } else {		/* Last load segment */
>> 		obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) -
>> 		  obj->vaddrbase;
>> 	    }
>> 	    nsegs++;
>> +	    if ((ph->p_flags & PF_X) == PF_X) {
>> +		obj->textsize = MAX(obj->textsize,
>> +		    round_page(ph->p_vaddr + ph->p_memsz) - obj->vaddrbase);
>> +	    }
>> 	    break;
>> 
>> 	case PT_DYNAMIC:
>> 
> 
>