[PATCH 18/25] powerpc,kgdb: Introduce low level trap catching
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From: Jason Wessel on 18 May 2010 21:50 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(a)kernel.crashing.org: move debugger_bpt instead of #ifdef] CC: Paul Mackerras <paulus(a)samba.org> Signed-off-by: Jason Wessel <jason.wessel(a)windriver.com> Acked-by: Benjamin Herrenschmidt <benh(a)kernel.crashing.org> --- arch/powerpc/kernel/kgdb.c | 6 ++++-- arch/powerpc/kernel/traps.c | 7 +++++-- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c index c81e3de..82a7b22 100644 --- a/arch/powerpc/kernel/kgdb.c +++ b/arch/powerpc/kernel/kgdb.c @@ -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)) diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 29d128e..b6859aa 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -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) { -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |