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powerpc,kgdb: Introduce low level trap catching 

The only way the debugger can handle a trap in inside rcu_lock,
notify_die, or atomic_notifier_call_chain without a recursive fault is
to allow the kernel debugger to handle the exception first in
program_check_exception().

The other change here is to make sure that kgdb_handle_exception() is
called with correct parameters when catching an oops, because kdb
needs to know if the entry was an oops, single step, or breakpoint
exception.

[benh@kernel.crashing.org: move debugger_bpt instead of #ifdef]

CC: Paul Mackerras <paulus@samba.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Jason Wessel 2010-05-20 21:04:25 -05:00
parent f503b5ae53
commit ba797b2813
2 changed files with 9 additions and 4 deletions
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6
arch/powerpc/kernel/kgdb.c
View File

@ -20,6 +20,7 @@
#include <linux/smp.h>
#include <linux/signal.h>
#include <linux/ptrace.h>
#include <linux/kdebug.h>
#include <asm/current.h>
#include <asm/processor.h>
#include <asm/machdep.h>
@ -115,7 +116,8 @@ void kgdb_roundup_cpus(unsigned long flags)
/* KGDB functions to use existing PowerPC64 hooks. */
static int kgdb_debugger(struct pt_regs *regs)
{
return kgdb_handle_exception(0, computeSignal(TRAP(regs)), 0, regs);
return !kgdb_handle_exception(1, computeSignal(TRAP(regs)),
DIE_OOPS, regs);
}
static int kgdb_handle_breakpoint(struct pt_regs *regs)
@ -123,7 +125,7 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
if (user_mode(regs))
return 0;
if (kgdb_handle_exception(0, SIGTRAP, 0, regs) != 0)
if (kgdb_handle_exception(1, SIGTRAP, 0, regs) != 0)
return 0;
if (*(u32 *) (regs->nip) == *(u32 *) (&arch_kgdb_ops.gdb_bpt_instr))

7
arch/powerpc/kernel/traps.c
View File

@ -815,12 +815,15 @@ void __kprobes program_check_exception(struct pt_regs *regs)
return;
}
if (reason & REASON_TRAP) {
/* Debugger is first in line to stop recursive faults in
* rcu_lock, notify_die, or atomic_notifier_call_chain */
if (debugger_bpt(regs))
return;
/* trap exception */
if (notify_die(DIE_BPT, "breakpoint", regs, 5, 5, SIGTRAP)
== NOTIFY_STOP)
return;
if (debugger_bpt(regs))
return;
if (!(regs->msr & MSR_PR) && /* not user-mode */
report_bug(regs->nip, regs) == BUG_TRAP_TYPE_WARN) {