ptrace interface is quite limited.

only for ia32 (not 64 or sparc)
 0  child must call ptrace(0) (PTRACEME)
 1  read a word from addr .text
 2  read a word from addr .data
 3  read a word from user area (sys/user.h fmi)
 4  write word .text
 5  write word .data
 6  set registers and status reg
 7  resume execution
 8  kill child
 9  set trace bit for stepping

man 4 proc for proc debugging:

 - pcred   - change credentials
 - pldd    - list linked libs
 - psig    - show signal handlers
 - pstack  - show stack trace
 - pfiles  - show opened files
 - pstop   - stop process and lwps
 
Cores

 - coreadm - change core options
 - gcore -F (Force - grab process control)
