From: Daniel Jacobowitz <dan@debian.org>
To: linux-kernel@vger.kernel.org
Subject: [PATCH?] Crash in 2.4.17/ptrace
Date: Mon, 28 Jan 2002 15:32:10 -0500 [thread overview]
Message-ID: <20020128153210.A3032@nevyn.them.org> (raw)
I've been debugging frame buffer graphics lately, and encountering a
very annoying problem. If the debugee has /dev/fb/0 mapped, and I try
to print out the contents of a pointer into that buffer, GDB crashes in
kernel/ptrace.c:access_process_vm. The problem seems to be that
get_user_pages returns a NULL page. Something as simple as this
prevents the crash:
--- 2.4.18-pre7/2.4.18-pre7/kernel/ptrace.c Fri Dec 21 12:42:04 2001
+++ 2.4.17/kernel-source-2.4.17/kernel/ptrace.c Mon Jan 28 15:30:39 2002
@@ -160,6 +160,18 @@ int access_process_vm(struct task_struct
flush_cache_page(vma, addr);
+#if 1
+ if (!page)
+ {
+ /* FIXME: Writes? */
+ if (!write) memset (buf, 0, bytes);
+ len -= bytes;
+ buf += bytes;
+ continue;
+ }
+#endif
+
+
maddr = kmap(page);
if (write) {
memcpy(maddr + offset, buf, bytes);
Of course, I would much rather be able to see the contents of the
framebuffer. Any suggestions?
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer
next reply other threads:[~2002-01-28 20:34 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-28 20:32 Daniel Jacobowitz [this message]
2002-01-28 21:03 ` [PATCH?] Crash in 2.4.17/ptrace Andrew Morton
2002-01-28 21:19 ` Daniel Jacobowitz
2002-01-28 21:29 ` Andrew Morton
2002-01-28 21:55 ` Alan Cox
2002-01-28 22:12 ` Andrew Morton
2002-01-29 22:59 ` [Linux-fbdev-devel] " James Simmons
2002-01-29 23:02 ` Andrew Morton
2002-01-30 0:13 ` James Simmons
2002-01-28 22:15 ` Benjamin Herrenschmidt
2002-01-28 23:57 ` Andrea Arcangeli
2002-01-28 23:54 ` Andrea Arcangeli
2002-01-29 5:35 ` Andrew Morton
2002-01-28 23:47 ` Andrea Arcangeli
2002-01-28 21:42 ` Andrew Morton
2002-01-28 21:33 Manfred Spraul
2002-01-28 22:05 ` Alan Cox
2002-01-28 22:07 ` Manfred Spraul
2002-01-28 22:26 ` Daniel Jacobowitz
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