[PATCH] Use PT_IO ptrace request if available

Mark Kettenis
2002-11-08T23:58:06Z

The attached patch makes use of the PT_IO ptrace request that's
available in *BSD for data transfers to/from the inferior. It's a
couple of weeks ago now that my patch that fixes the FreeBSD
5.0-CURRENT kernel went in, and I hope that OpenBSD and NetBSD don't
have any problems. We'll probably find out soon :-). Note that if
you run FreeBSD 5.0-CURRENT from before October 16 and after March 16,
your machine will probably lock up when using GDB. However, since
-CURRENT is a development version, I think it's acceptable to ask
people to upgrade.

It would be great if we could get Linux to support the same interface.

Committed.

Mark

Index: ChangeLog
from Mark Kettenis <kettenis@gnu.org>

* infptrace.c (child_xfer_memory): Make use of the new PT_IO
request that's available in *BSD.

Index: infptrace.c
===================================================================
RCS file: /cvs/src/src/gdb/infptrace.c,v
retrieving revision 1.21
diff -u -p -r1.21 infptrace.c
--- infptrace.c 19 Jan 2002 03:32:36 -0000 1.21
+++ infptrace.c 8 Nov 2002 23:45:18 -0000
@@ -514,6 +514,37 @@ child_xfer_memory (CORE_ADDR memaddr, ch
PTRACE_XFER_TYPE *buffer;
struct cleanup *old_chain = NULL;

+#ifdef PT_IO
+ /* OpenBSD 3.1, NetBSD 1.6 and FreeBSD 5.0 have a new PT_IO request
+ that promises to be much more efficient in reading and writing
+ data in the traced process's address space. */
+
+ {
+ struct ptrace_io_desc piod;
+
+ /* NOTE: We assume that there are no distinct address spaces for
+ instruction and data. */
+ piod.piod_op = write ? PIOD_WRITE_D : PIOD_READ_D;
+ piod.piod_offs = (void *) memaddr;
+ piod.piod_addr = myaddr;
+ piod.piod_len = len;
+
+ if (ptrace (PT_IO, PIDGET (inferior_ptid), (caddr_t) &piod, 0) == -1)
+ {
+ /* If the PT_IO request is somehow not supported, fallback on
+ using PT_WRITE_D/PT_READ_D. Otherwise we will return zero
+ to indicate failure. */
+ if (errno != EINVAL)
+ return 0;
+ }
+ else
+ {
+ /* Return the actual number of bytes read or written. */
+ return piod.piod_len;
+ }
+ }
+#endif
+
/* Allocate buffer of that many longwords. */
if (len < GDB_MAX_ALLOCA)
{