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SubjectRe: PPC KGDB changes and some help?
Tom Rini wrote:
> On Fri, Jan 23, 2004 at 03:38:39PM -0800, George Anzinger wrote:
>
>>Tom Rini wrote:
>>
>>>On Thu, Jan 22, 2004 at 11:05:55AM -0700, Tom Rini wrote:
>>>[snip]
>>>
>>>
>>>>First up:
>>>>We need to call flush_instruction_cache() on a 'c' or 's' command.
>>>>arch/ppc/kernel/ppc-stub.c | 19 ++++++-------------
>>>>1 files changed, 6 insertions(+), 13 deletions(-)
>>>
>>>
>>>On tpo of this patch, there's the following:
>>>Put back some code to figure out what signal we're dealing with.
>>>
>>>arch/ppc/kernel/ppc-stub.c | 63
>>>++++++++++++++++++++++++++++++++++++++++++---
>>>1 files changed, 60 insertions(+), 3 deletions(-)
>>>--- 1.15/arch/ppc/kernel/ppc-stub.c Thu Jan 22 10:53:06 2004
>>>+++ edited/arch/ppc/kernel/ppc-stub.c Fri Jan 23 15:43:10 2004
>>>@@ -3,6 +3,7 @@
>>> *
>>> * PowerPC-specific bits to work with the common KGDB stub.
>>> *
>>>+ * 1998 (c) Michael AK Tesch (tesch@cs.wisc.edu)
>>> * 2003 (c) TimeSys Corporation
>>> * 2004 (c) MontaVista Software, Inc.
>>> * This file is licensed under the terms of the GNU General Public License
>>>@@ -19,13 +20,69 @@
>>>#include <asm/processor.h>
>>>#include <asm/machdep.h>
>>>
>>>+/* Convert the hardware trap type code to a unix signal number. */
>>>+/*
>>>+ * This table contains the mapping between PowerPC hardware trap types,
>>>and
>>>+ * signals, which are primarily what GDB understands.
>>>+ */
>>>+static struct hard_trap_info
>>>+{
>>>+ unsigned int tt; /* Trap type code for powerpc */
>>>+ unsigned char signo; /* Signal that we map this trap into
>>>*/
>>>+} hard_trap_info[] = {
>>>+#if defined(CONFIG_40x)
>>>+ { 0x100, SIGINT }, /* critical input interrupt */
>>>+ { 0x200, SIGSEGV }, /* machine check */
>>>+ { 0x300, SIGSEGV }, /* data storage */
>>>+ { 0x400, SIGBUS }, /* instruction storage */
>>>+ { 0x500, SIGINT }, /* interrupt */
>>>+ { 0x600, SIGBUS }, /* alignment */
>>>+ { 0x700, SIGILL }, /* program */
>>>+ { 0x800, SIGILL }, /* reserved */
>>>+ { 0x900, SIGILL }, /* reserved */
>>>+ { 0xa00, SIGILL }, /* reserved */
>>>+ { 0xb00, SIGILL }, /* reserved */
>>>+ { 0xc00, SIGCHLD }, /* syscall */
>>>+ { 0xd00, SIGILL }, /* reserved */
>>>+ { 0xe00, SIGILL }, /* reserved */
>>>+ { 0xf00, SIGILL }, /* reserved */
>>>+ { 0x2000, SIGTRAP}, /* debug */
>>>+#else
>>>+ { 0x200, SIGSEGV }, /* machine check */
>>>+ { 0x300, SIGSEGV }, /* address error (store) */
>>>+ { 0x400, SIGBUS }, /* instruction bus error */
>>>+ { 0x500, SIGINT }, /* interrupt */
>>>+ { 0x600, SIGBUS }, /* alingment */
>>>+ { 0x700, SIGTRAP }, /* breakpoint trap */
>>>+ { 0x800, SIGFPE }, /* fpu unavail */
>>>+ { 0x900, SIGALRM }, /* decrementer */
>>>+ { 0xa00, SIGILL }, /* reserved */
>>>+ { 0xb00, SIGILL }, /* reserved */
>>>+ { 0xc00, SIGCHLD }, /* syscall */
>>>+ { 0xd00, SIGTRAP }, /* single-step/watch */
>>>+ { 0xe00, SIGFPE }, /* fp assist */
>>>+#endif
>>>+ { 0, 0} /* Must be last */
>>>+};
>>>+
>>>+static int computeSignal(unsigned int tt)
>>>+{
>>>+ struct hard_trap_info *ht;
>>>+
>>>+ for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
>>>+ if (ht->tt == tt)
>>>+ return ht->signo;
>>>+
>>>+ return SIGHUP; /* default for things we don't know about */
>>>+}
>>>+
>>>/*
>>> * Routines
>>> */
>>>static void
>>>kgdb_debugger(struct pt_regs *regs)
>>>{
>>>- (*linux_debug_hook) (0, 0, 0, regs);
>>>+ (*linux_debug_hook) (0, computeSignal(regs->trap), 0, regs);
>>> return;
>>>}
>>>
>>>@@ -52,14 +109,14 @@
>>>int
>>>kgdb_iabr_match(struct pt_regs *regs)
>>>{
>>>- (*linux_debug_hook) (0, 0, 0, regs);
>>>+ (*linux_debug_hook) (0, computeSignal(regs->trap), 0, regs);
>>> return 1;
>>>}
>>>
>>>int
>>>kgdb_dabr_match(struct pt_regs *regs)
>>>{
>>>- (*linux_debug_hook) (0, 0, 0, regs);
>>>+ (*linux_debug_hook) (0, computeSignal(regs->trap), 0, regs);
>>> return 1;
>>>}
>>>
>>>
>>>Now, not being as well versed in all of the debugging infos that can be
>>>passed around, it sounds like this patch could be dropped in the future
>>>for a cleaner method using some of the dwarf2 bits being talked about.
>>>But I don't know, and clarification and pointers (if so) to how to do
>>>this would be appreciated.
>>
>>I am not sure what this buys you. I don't think dwarf2 will help here.
>
>
> OK.
>
>
>>There is a real danger of passing signal info back to gdb as it will want
>>to try to deliver the signal which is a non-compute in most kgdbs in the
>>field. I did put code in the mm-kgdb to do just this, but usually the
>>arrival of such a signal (other than SIGTRAP) is the end of the kernel.
>>All that is left is to read the tea leaves.
>
>
> The gdb I've been testing this with knows better than to try and send a
> singal back, so that's not a worry. The motivation behind doing this
> however is along the lines of "if it ain't broke, don't remove it". The
> original stub was getting all of this information correctly, so why stop
> doing it?
>
OK, but I still don't like losing the return address. Tell me again, why do you
need three different functions all doing the same thing?


--
George Anzinger george@mvista.com
High-res-timers: http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml

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