A problem when ptrace accessing a bad address

[Chen Qi-A18263]

Hi, guys:

        Here I have encountered a problem when the ptrace function call trying 
to accessing a bad address.
        ( This problem happed in the ColdFire uClinux )

        Description:

        When calling : ptrace(PT_READ_I, PID, Address ... ), and when the 
Address is a an invalid address, the program will crashed on uClinux.
        
        I have compared the same problem in x86 redhat linux8.0, and find that 
when the ptrace trying to read an invalid memory address, it will not crash but 
putting the following error message:
        
---------------------------------------------------------------------------
                ptrace memory read failed: Input/output error
        
---------------------------------------------------------------------------

        But In my uClinux for Coldfire, it just crash without any error message 
( I think that maybe it's cause by the mmu-less feature on Coldfire. )

        To avoid this problem, I have trying the following way, it they seems 
not workable, wish you could give you some suggestions:
        
        1. Normally, when the program attempting to access a bad address, the 
system will raise SIGSEGV or SIGBUS signal, for example:
        I can catch the signal and restore the context by :
        --------------------------------------------------------------------
        #include <setjmp.h>
        #include <signal.h>
        void SIGSEGV_Handler()
        {               
                printf("SIGSEGV111 Id: %d is handled\n",SIGSEGV);
                longjmp( gTrkExceptionJmpBuf, 1 );
        }       
        jmp_buf gTrkExceptionJmpBuf;    
        int main()
        {
                if (setjmp( gTrkExceptionJmpBuf ) == 0)
                {
                        int* pointer = 0xFF000000;
                        int value = *pointer;                   //can catch 
SIGSEGV singal by this memory accessing
                        //ptrace(PT_READ_I, PID, pointer... )   //can't catch 
ANY type singal by this memory accessing.
                }
                else
                {
                        printf("Bad address access\n");
                }
        }
        --------------------------------------------------------------------
        But unfortuattly, when the ptrace accessing the bad address, I can't 
catch ANY type of signal. Could someone tell me why? and how can I catch the 
signal? 

        2. If the we can't catch the ptrace signal ( or it did not raise any 
signal ), I am thinking of add a memory validate function before ptrace call, 
the memory validate function can be implemented by the normal memory access 
with setjmp and longjmp protect. But this way can't be use in my Coldfire board.
        Because in ColdFire board, the address from 0xFFE00000 to 0xFFFFFFFF is 
Flash rom address and we can accessing them, while the ptrace function can't 
access it and it will crash too!

Thanks and Best Regards!
ChenQi(v)