Next over function with Secure PLT

[Michael Eager <eager at eagerm dot com>]

Hi --

When using PowerPC Secure PLT, trying to "next" over a
library function in a shared library does not work correctly.
Instead of skipping over the function, gdb steps through
the PLT entry which shows up as code in
call___do_global_ctors_aux.

This doesn't happen when "nexting" over a library function
in the executable.  Next works the same as with a local function.

When reading the executable, ppc_elf_get_synthetic_symtab()
calls is_nonpic_glink_stub() to recognizes the PLT stub and
then generates internal symbols for each PLT stub like foo@plt.
It also creates an entry for __glink and __glink_PLTresolve.

If I modify is_nonpic_glink_stub() to recognize the shared
library PLT stub format, similar internal symbols are created
and gdb seems to work correctly.

There's a comment before the call:
 /* If the stubs are those for -shared/-pie then we might have
     multiple stubs for each plt entry.  If that is the case then
     there is no way to associate stubs with their plt entries short
     of figuring out the GOT pointer value used in the stub.  */
  if (!is_nonpic_glink_stub (abfd, glink,
			     glink_vma - GLINK_ENTRY_SIZE - glink->vma))

What is this trying to tell me?  What are the circumstances where
there would be multiple stubs for each PLT entry?  If there are
multiple stubs, then this might create multiple foo@plt symbols
with different values.  Would this cause any problems?


--
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077