mips gdb not loading shared lib info automatically - gdb

Question

I have seen gdb reading and loading symbols automatically. (like the below code reading from ld-linux-x86-64.so.2)
----------
gdb 86exec 86core
...
Reading symbols from 86exec...done.
Illegal process-id: 86core.
[New Thread 14983]
[New Thread 14978]
[New Thread 14980]
[New Thread 14981]
[New Thread 14982]
Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Core was generated by `./86exec'.
Program terminated with signal 11, Segmentation fault.
----------
But in my mips platform I am not getting that automatic reading done.
---------
Reading symbols from /mipsexec...done.
[New LWP 1333]
[New LWP 1328]
[New LWP 1330]
[New LWP 1331]
[New LWP 1332]
Core was generated by `./mipsexec'.
Program terminated with signal 11, Segmentation fault.
----------
I wanted to know, from where does this information come.
If it is from core file, how can I analyze whether my mipscore is having the specific info.

Answer 1

I doubt that mips gdb doesn't support PIE well. As I know, in PIC, mips use rld_map but not DE_DEBUG for dynamic information but in PIE mode, mips likes other architectures, using DT_DEBUG.
In dynamic linker, there are statements like this:
#if !defined __mips__
/* we disable for mips because normally this page is readonly
* and modifying the value here needlessly dirties a page.
* see this post for more info:
* http://uclibc.org/lists/uclibc/2006-April/015224.html */
if (dpnt->d_tag == DT_DEBUG)
dpnt->d_un.d_val = (unsigned long)debug_addr;
#endif
this statement in PIC is ok, but not work in PIE. If you remove this #ifdef, you will get a segment fault because .dynamic section in mips is readonly. .dynamic section in arm and x86 etc is writeable.
if you change .dynamic section of mips to writeable, and open DT_DEBUG handling in dynamic linker, it works, but still has some problems. For example, the readonly VMA is writeable, and need more page copy when fork a subprocess.
I suffered the problem weeks ago and I don't know whether mips gdb works well in Android 4.2 or not. In Android 4.2, all c/c++ files are built with PIE.