[Bug libc/17485] New: [2.20 regression] MIPS: ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section `.dynstr'

[Bug libc/17485] New: [2.20 regression] MIPS: ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section `.dynstr'

[macro@linux-mips.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17485

            Bug ID: 17485
           Summary: [2.20 regression] MIPS: ld: libpthread.so: invalid
                    string offset 2765592330 >= 5154 for section `.dynstr'
           Product: glibc
           Version: 2.20
            Status: NEW
          Severity: critical
          Priority: P1
         Component: libc
          Assignee: macro@linux-mips.org
          Reporter: macro@linux-mips.org
                CC: drepper.fsp at gmail dot com
            Target: mips-linux-gnu

This change:

commit 58eb0862c3471b931bf3412d6d02bac447d5a653
Author: Roland McGrath <roland@hack.frob.com>
Date:   Fri Jun 27 09:58:51 2014 -0700

    MIPS: Consolidate NPTL/non versions of vfork

regressed MIPS builds of librt.so, depending on how the BFD linker
internals work out, which generally depends on multilib options, either
an empty entry is left in the dynamic symbol table or a build failure
is triggered like this:

.../mips-linux-gnu/bin/ld: .../nptl/libpthread.so: invalid string offset
2765592330 >= 5154 for section `.dynstr'
.../nptl/libpthread.so: could not read symbols: File format not recognized
collect2: error: ld returned 1 exit status

This is a bug in GNU LD and also GAS, but I think we have a bug too, in
the MIPS version of pt-vfork.S, that triggers this obscure corner case.

Before the change it assembled to have a symbol table like this:

Symbol table '.symtab' contains 20 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 00000000     0 SECTION LOCAL  DEFAULT    1
     2: 00000000     0 SECTION LOCAL  DEFAULT    3
     3: 00000000     0 SECTION LOCAL  DEFAULT    4
     4: 00000001     0 NOTYPE  LOCAL  DEFAULT  ABS LOCALSZ
     5: 00000018     0 NOTYPE  LOCAL  DEFAULT  ABS FRAMESZ
     6: 00000014     0 NOTYPE  LOCAL  DEFAULT  ABS GPOFF
     7: 00000000     0 SECTION LOCAL  DEFAULT   11
     8: 00000000     0 SECTION LOCAL  DEFAULT   13
     9: 00000000     0 SECTION LOCAL  DEFAULT    9
    10: 00000000     0 SECTION LOCAL  DEFAULT   14
    11: 00000000     0 SECTION LOCAL  DEFAULT   16
    12: 00000000     0 SECTION LOCAL  DEFAULT    5
    13: 00000000     0 SECTION LOCAL  DEFAULT    6
    14: 00000000     0 SECTION LOCAL  DEFAULT    7
    15: 00000000     0 SECTION LOCAL  DEFAULT   18
    16: 00000000   112 FUNC    GLOBAL DEFAULT    1 __vfork
    17: 00000000     0 OBJECT  GLOBAL DEFAULT  UND _gp_disp
    18: 00000000     0 NOTYPE  GLOBAL DEFAULT  UND __syscall_error
    19: 00000000   112 FUNC    WEAK   DEFAULT    1 vfork

With the change in place the symbol table is like this instead:

Symbol table '.symtab' contains 21 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 00000000     0 SECTION LOCAL  DEFAULT    1
     2: 00000000     0 SECTION LOCAL  DEFAULT    3
     3: 00000000     0 SECTION LOCAL  DEFAULT    4
     4: 00000001     0 NOTYPE  LOCAL  DEFAULT  ABS LOCALSZ
     5: 00000018     0 NOTYPE  LOCAL  DEFAULT  ABS FRAMESZ
     6: 00000014     0 NOTYPE  LOCAL  DEFAULT  ABS GPOFF
     7: 00000000     0 SECTION LOCAL  DEFAULT   11
     8: 00000000     0 SECTION LOCAL  DEFAULT   13
     9: 00000000     0 SECTION LOCAL  DEFAULT    9
    10: 00000000     0 SECTION LOCAL  DEFAULT   14
    11: 00000000     0 SECTION LOCAL  DEFAULT   16
    12: 00000000     0 SECTION LOCAL  DEFAULT    5
    13: 00000000     0 SECTION LOCAL  DEFAULT    6
    14: 00000000     0 SECTION LOCAL  DEFAULT    7
    15: 00000000     0 SECTION LOCAL  DEFAULT   18
    16: 00000000   140 FUNC    GLOBAL DEFAULT    1 __vfork
    17: 00000000     0 OBJECT  GLOBAL DEFAULT  UND _gp_disp
    18: 00000000     0 NOTYPE  GLOBAL DEFAULT  UND __syscall_error
    19: 00000000   140 FUNC    WEAK   DEFAULT    1 vfork
    20: 00000000     0 NOTYPE  GLOBAL DEFAULT  UND vfork@GLIBC_2.0

-- notice the undefined versioned entry for `vfork@GLIBC_2.0'.  This is
what confuses LD and also shouldn't have been produced by GAS in the
first place.

There's no further reference to that symbol, i.e. no relocation
anywhere across this object file, which is why LD removes it from
libpthread.so's dynsym table, however it doesn't realise early enough
it shouldn't be propagating the reference to the dynsym table in the
first place and as a result it leaves an uninitialised slot that may or
may not be empty.

The ultimate reason for this symbol's creation is a:

    .symver    __libc_vfork, vfork@GLIBC_2.0

directive however without any `__libc_vfork' definition or reference.
This is what the GAS manual has to say about this case:

"  For ELF targets, the `.symver' directive can be used like this:
     .symver NAME, NAME2@NODENAME

"  If the symbol NAME is not defined within the file being assembled,
all references to NAME will be changed to NAME2@NODENAME.  If no
reference to NAME is made, NAME2@NODENAME will be removed from the
symbol table."

so the symbol is supposed not to be emitted.  It appears though that
this bug has been present in GNU binutils since forever and our other
targets define `__libc_vfork', possibly just as an alias to `__vfork',
so I think we should simply do the same for MIPS.  The symbol does not
make it to the dynsym table so such a change will not affect our ABI.

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[Bug libc/17485] [2.20 regression] MIPS: ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section `.dynstr'

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17485

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".

The branch, master has been updated
       via  b5af9297d51a43f96c5be1bafab032184690dd6f (commit)
      from  a13d0d745ca3ea5e80506db7de0498d74d44a5b7 (commit)

Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.

- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b5af9297d51a43f96c5be1bafab032184690dd6f

commit b5af9297d51a43f96c5be1bafab032184690dd6f
Author: Maciej W. Rozycki <macro@codesourcery.com>
Date:   Wed Oct 22 15:20:37 2014 +0100

    MIPS: Avoid a dangling `vfork@GLIBC_2.0' reference

    This satisfies a symbol reference created with:

        .symver    __libc_vfork, vfork@GLIBC_2.0

    where `__libc_vfork' has not been defined or referenced.  In this case
    the `vfork@GLIBC_2.0' reference is supposed to be discarded, however a
    bug present in GAS since forever causes an undefined symbol table entry
    to be created.  This in turn triggers a problem in the linker that can
    manifest itself by link errors such as:

    ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section
`.dynstr'

    The GAS and linker bugs need to be resolved, but we can avoid them too
    by providing a `__libc_vfork' definition just like our other platforms.

        [BZ #17485]
        * sysdeps/unix/sysv/linux/mips/vfork.S (__libc_vfork): Define.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                            |    5 +++++
 NEWS                                 |    3 ++-
 sysdeps/unix/sysv/linux/mips/vfork.S |    1 +
 3 files changed, 8 insertions(+), 1 deletions(-)

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[Bug libc/17485] [2.20 regression] MIPS: ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section `.dynstr'

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17485

--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".

The branch, release/2.20/master has been updated
       via  c14e752fc73d34c75d4f84f37fea8e0b1734cf98 (commit)
      from  1b198b7fc764c013d41d1bd7b83fed0ad3dee038 (commit)

Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.

- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c14e752fc73d34c75d4f84f37fea8e0b1734cf98

commit c14e752fc73d34c75d4f84f37fea8e0b1734cf98
Author: Maciej W. Rozycki <macro@codesourcery.com>
Date:   Wed Oct 22 15:20:37 2014 +0100

    MIPS: Avoid a dangling `vfork@GLIBC_2.0' reference

    This satisfies a symbol reference created with:

        .symver    __libc_vfork, vfork@GLIBC_2.0

    where `__libc_vfork' has not been defined or referenced.  In this case
    the `vfork@GLIBC_2.0' reference is supposed to be discarded, however a
    bug present in GAS since forever causes an undefined symbol table entry
    to be created.  This in turn triggers a problem in the linker that can
    manifest itself by link errors such as:

    ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section
`.dynstr'

    The GAS and linker bugs need to be resolved, but we can avoid them too
    by providing a `__libc_vfork' definition just like our other platforms.

        [BZ #17485]
        * sysdeps/unix/sysv/linux/mips/vfork.S (__libc_vfork): Define.

    (cherry picked from commit b5af9297d51a43f96c5be1bafab032184690dd6f)

    Conflicts:
        NEWS

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                            |    5 +++++
 NEWS                                 |    2 +-
 sysdeps/unix/sysv/linux/mips/vfork.S |    1 +
 3 files changed, 7 insertions(+), 1 deletions(-)

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[Bug libc/17485] [2.20 regression] MIPS: ld: libpthread.so: invalid string offset 2765592330 >= 5154 for section `.dynstr'

[macro@linux-mips.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17485

Maciej W. Rozycki <macro@linux-mips.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Maciej W. Rozycki <macro@linux-mips.org> ---
Fixed on trunk and the 2.20 release branch as per the commit messages.

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