public inbox for linuxppc-dev@ozlabs.org 
 help / color / mirror / Atom feed

From: "Mark A. Greer" <mgreer@mvista•com>
To: linuxppc-dev <linuxppc-dev@lists•linuxppc.org>
Subject: patch for _2_4_devel KGDB in arch/ppc/kernel/ppc-stub.c
Date: Tue, 11 Mar 2003 17:11:47 -0700	[thread overview]
Message-ID: <3E6E7B43.2050501@mvista.com> (raw)


The following patch fixes 2 problems with KGDB:

a) On line 617, '&regs' should be 'regs' in the call to mem2hex().  The
resulting improper response packet confuses the GDB client resulting in
step/next and stepi/nexti GDB commands to "lose their grip" and allow
execution to continue unchecked.

b) When executing an 's' command, we don't want to start single stepping
until we *return* from the current exception that we're handling.
Therefore, the MSR_SE bit should not be set in the MSR until the rfi
from this exception is executed (i.e., only need to set that bit in
'regs->msr' and not do an actual 'mtmsr()' at this point).  If the
'mtmsr(msr | MSR_SE);' line is executed at this point, a single-step
exeption will occur inside the exception handler itself which causes
another exception and the 'printk(KERN_ERR "interrupt while in kgdb,
returning\n");' line at the beginning of handle_exception() to be
executed.  Not fatal but somewhat disturbing to see.

Mark
--


===== arch/ppc/kernel/ppc-stub.c 1.22 vs edited =====
--- 1.22/arch/ppc/kernel/ppc-stub.c     Fri Feb 28 10:26:48 2003
+++ edited/arch/ppc/kernel/ppc-stub.c   Tue Mar 11 16:55:19 2003
@@ -614,7 +614,7 @@
        *ptr++ = hexchars[SP_REGNUM >> 4];
        *ptr++ = hexchars[SP_REGNUM & 0xf];
        *ptr++ = ':';
-       ptr = mem2hex(((char *)&regs) + SP_REGNUM*4, ptr, 4);
+       ptr = mem2hex(((char *)regs) + SP_REGNUM*4, ptr, 4);
        *ptr++ = ';';
 #endif

@@ -795,7 +795,11 @@
                        mtmsr(msr);
 #else
                        regs->msr |= MSR_SE;
+                       /* Don't write MSR now, wait for exception return.
+                        * Otherwise, we'll start single stepping
immediately.
+                        * --MAG
                        mtmsr(msr | MSR_SE);
+                        */
 #endif
                        unlock_kernel();
                        kgdb_active = 0;


** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

                 reply	other threads:[~2003-03-12  0:11 UTC|newest]

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=3E6E7B43.2050501@mvista.com \
    --to=mgreer@mvista$(echo .)com \
    --cc=linuxppc-dev@lists$(echo .)linuxppc.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox