On Mon, Feb 20, 2012 at 06:37:09PM +0000, Will Deacon wrote:

quoted

Commit 68b7f715 ("nommu: ptrace support") added definitions for
PT_TEXT_ADDR and friends, as well as adding ptrace support for reading
from these magic offsets.

Unfortunately, this has probably never worked, since ptrace_read_user
predicates reading on off < sizeof(struct user), returning -EOI
otherwise.

This patch moves the offset size check until after we have tried to
match it against either a magic value or an offset into pt_regs.

Does this actually get used?  The fact that it's been broken from day one
and no one's raised the issue in 2.5 years suggests that it's dead code.

I suspect I submitted the original patch.  I don't remember the details, but 
it definitely worked at the time.   IIRC some other targets (m68k?) used an 
even less palatable hack.

This (or equivalent) is necessary to do any debugging on an mmu-less (i.e. 
uclinux) system.

Paul