[patch] /* */ for target_thread_architecture [Re: [patch] Fix i386 memory-by-register access on amd64]

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Tue, 07 Jul 2009 18:24:06 +0200, Ulrich Weigand wrote:
> Jan Kratochvil wrote:
> > @@ -452,8 +452,20 @@ inf_ptrace_xfer_partial (struct target_ops *ops, enum target_object object,
> >  			 const gdb_byte *writebuf,
> >  			 ULONGEST offset, LONGEST len)
> >  {
> > +  struct gdbarch *gdbarch = target_thread_architecture (inferior_ptid);
> > +  int addr_bit = gdbarch_addr_bit (gdbarch);
> 
> target_thread_architecture is wrong for this purpose; it is the user-visible
> architecture to be used for this thread.  The architecture to be used for
> target (e.g. ptrace) operations is target_gdbarch.
> 
> For example, on an SPU thread on the Cell/B.E. target_thread_architecture might 
> be SPU, while target_gdbarch is PPC32 or PPC64.  ptrace operations need to operate
> according to the latter.

While thanks for the explanation I believe it should be in the sources.  It is
mostly your text from:
	http://sourceware.org/ml/gdb-patches/2008-09/msg00133.html

OK to check-in?


Thanks,
Jan


2009-07-08  Ulrich Weigand  <uweigand@de.ibm.com>
	    Jan Kratochvil  <jan.kratochvil@redhat.com>

	* target.h (struct target_ops <to_thread_architecture>): Describe it.
	(target_thread_architecture): Refer to to_thread_architecture.

--- a/gdb/target.h
+++ b/gdb/target.h
@@ -543,7 +543,16 @@ struct target_ops
        simultaneously?  */
     int (*to_supports_multi_process) (void);
 
-    /* Determine current architecture of thread PTID.  */
+    /* Determine current architecture of thread PTID.
+
+       The target is supposed to determine the architecture of the code where
+       the target is currently stopped at (on Cell, if a target is in spu_run,
+       to_thread_architecture would return SPU, otherwise PPC32 or PPC64).
+       This is architecture used to perform decr_pc_after_break adjustment,
+       and also determines the frame architecture of the innermost frame.
+       ptrace operations need to operate according to target_gdbarch.
+
+       The default implementation always returns target_gdbarch.  */
     struct gdbarch *(*to_thread_architecture) (struct target_ops *, ptid_t);
 
     int to_magic;
@@ -1043,7 +1052,7 @@ extern char *normal_pid_to_str (ptid_t ptid);
 #define target_pid_to_exec_file(pid) \
      (current_target.to_pid_to_exec_file) (pid)
 
-/* Determine current architecture of thread PTID.  */
+/* See the to_thread_architecture description in struct target_ops.  */
 
 #define target_thread_architecture(ptid) \
      (current_target.to_thread_architecture (&current_target, ptid))