x86: Check IFUNC definition in unrelocated executable [BZ #20019]

Calling an IFUNC function defined in unrelocated executable also leads to
segfault.  Issue a fatal error message when calling IFUNC function defined
in the unrelocated executable from a shared library.

On x86, ifuncmain6pie failed with:

[hjl@gnu-cfl-2 build-i686-linux]$ ./elf/ifuncmain6pie --direct
./elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in '/export/build/gnu/tools-build/glibc-32bit/build-i686-linux/elf/ifuncmod6.so' is defined in the executable and creates an unsatisfiable circular dependency.
[hjl@gnu-cfl-2 build-i686-linux]$ readelf -rW elf/ifuncmod6.so | grep foo
00003ff4  00000706 R_386_GLOB_DAT         0000400c   foo_ptr
00003ff8  00000406 R_386_GLOB_DAT         00000000   foo
0000400c  00000401 R_386_32               00000000   foo
[hjl@gnu-cfl-2 build-i686-linux]$

Remove non-JUMP_SLOT relocations against foo in ifuncmod6.so, which
trigger the circular IFUNC dependency, and build ifuncmain6pie with
-Wl,-z,lazy.

(cherry picked from commits 6ea5b57afa5cdc9ce367d2b69a2cebfb273e4617
 and 7137d682ebfcb6db5dfc5f39724718699922f06c)

1 files changed, 1 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 6b3c7db..de7afbf 100644
--- a/NEWS
+++ b/NEWS
@@ -25,6 +25,7 @@ The following bugs are resolved with this release:
 
   [16573] malloc: Set and reset all hooks for tracing
   [18035] Fix pldd hang
+  [20019] NULL pointer dereference in libc.so.6 IFUNC due to uninitialized GOT
   [20568] Fix crash in _IO_wfile_sync
   [24155] x32 memcmp can treat positive length as 0 (if sign bit in RDX is set) (CVE-2019-7309)
   [24164] Systemtap probes need to use "nr" constraint on 32-bit Arm