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

Michael Tuexen Michael.Tuexen at macmic.franken.de
Tue Oct 30 10:17:44 UTC 2018


> 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:
> 



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