The backtrace reads:
| (gdb) bt
| #0 0x0000fc2961bca308 in ?? ()
| #1 0x0000fc2961b9ec10 in __deregister_frame_info_bases ()
| from /usr/lib/libgcc_s.so.1
| #2 0x0000fffff88425b4 in _rtld_call_function_void (obj=0xfc2962917400,
| addr=277254663434168) at /usr/src/libexec/ld.elf_so/rtld.h:514
| ...
The fault address is anon memory w/o exec permission when su exits:
| # pmap -p xxx
| ...
| 0000FC2961BB1000 4K read/write /altroot/lib/libgcc_s.so.1.0
| 0000FC2961BB6000 40K read/write [ anon ]
| 0000FC2961BE6000 40K read/write [ anon ]
| ...