mips/qemu jails with native-xtools

[Warner Losh]

On Thu, Feb 4, 2016 at 5:26 PM, Ben Morrow <ben at morrow.me.uk> wrote:

> I've finally got a mips/qemu poudriere jail working properly with a
> native toolchain, but it took a bit of fiddling to make it work, so I
> thought I'd report on what I did.
>
> First I tried installing things the way poudriere -x does, with an
> /nxb-bin directory in the jail and redirections in make.conf. That
> doesn't work because /nxb-bin/usr/bin/cc just invokes /usr/libexec/cc1,
> which is still a mips executable.
>
> Then I tried copying the nxb-bin tree directly into the root of the
> jail. This caused a problem immediately: the nxb-bin tree includes the
> static flex libraries (/usr/lib/lib{l,fl,ln}.a) built for amd64.
> Obviously this isn't going to work; it's the cause of the bison build
> failures I found mentioned in the archives.
>
> Having put the proper libraries back, the next problem was that ld was
> failing to find shared libraries that were implicitly linked (DT_NEEDED)
> by other shared libraries. The specific port I was building was
> net/tshark, which links glib, which implicitly pulls in libpcre and
> libiconv. The configure step was failing because ld couldn't find
> libpcre.so.3.
>
> It turns out that ld finds the path to search for DT_NEEDED libraries by
> reading ld-elf.so.hints. That file (in the jail) is BE, because this is
> a mips world with a mips ldconfig, but the ld binary is LE, so it can't
> read the file. With the patch below, it can; since endianness is the
> only difference between architectures, I think it should be safe for
> general use, but I don't really know
>

I'd think it would be better to generate the ld.so in the proper binary
format. How hard is that?

Warner




> Ben
>
> diff --git a/contrib/binutils/ld/emultempl/elf32.em
> b/contrib/binutils/ld/emultempl/elf32.em
> index 4f707ff..5219820 100644
> --- a/contrib/binutils/ld/emultempl/elf32.em
> +++ b/contrib/binutils/ld/emultempl/elf32.em
> @@ -539,6 +539,7 @@ EOF
>  #else
>  #include "elf-hints-local.h"
>  #endif
> +#include <sys/endian.h>
>
>  static bfd_boolean
>  gld${EMULATION_NAME}_check_ld_elf_hints (const struct
> bfd_link_needed_list *l,
> @@ -560,17 +561,28 @@ gld${EMULATION_NAME}_check_ld_elf_hints (const
> struct bfd_link_needed_list *l,
>         {
>           struct elfhints_hdr hdr;
>
> -         if (fread (&hdr, 1, sizeof (hdr), f) == sizeof (hdr)
> -             && hdr.magic == ELFHINTS_MAGIC
> -             && hdr.version == 1)
> -           {
> -             if (fseek (f, hdr.strtab + hdr.dirlist, SEEK_SET) != -1)
> +         if (fread (&hdr, 1, sizeof (hdr), f) == sizeof (hdr))
> +            {
> +              u_int32_t start = 0, len;
> +
> +              if (hdr.magic == ELFHINTS_MAGIC
> +                 && hdr.version == 1)
> +                {
> +                  start = hdr.strtab + hdr.dirlist;
> +                  len = hdr.dirlistlen;
> +                }
> +              if (bswap32(hdr.magic) == ELFHINTS_MAGIC
> +                  && bswap32(hdr.version) == 1)
> +                {
> +                  start = bswap32(hdr.strtab) + bswap32(hdr.dirlist);
> +                  len = bswap32(hdr.dirlistlen);
> +                }
> +              if (start && fseek (f, start, SEEK_SET) != -1)
>                 {
>                   char *b;
>
> -                 b = xmalloc (hdr.dirlistlen + 1);
> -                 if (fread (b, 1, hdr.dirlistlen + 1, f) ==
> -                     hdr.dirlistlen + 1)
> +                 b = xmalloc (len + 1);
> +                 if (fread (b, 1, len + 1, f) == len + 1)
>                     ld_elf_hints = gld${EMULATION_NAME}_add_sysroot (b);
>
>                   free (b);
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