A signal delivered between a hw_breakpoint_handler() and the
single_step_dabr_instruction() will not have the breakpoint active during
signal handling (since breakpoint will not be restored through single-stepping
due to absence of MSR_SE bit on the signal frame). Enable breakpoints before
signal delivery.
Restore hw-breakpoints if the user-context is altered in the signal handler.
Signed-off-by: K.Prasad <pra...@linux.vnet.ibm.com>
---
arch/powerpc/include/asm/hw_breakpoint.h | 3 +++
arch/powerpc/kernel/hw_breakpoint.c | 18 ++++++++++++++++++
arch/powerpc/kernel/signal.c | 3 +++
3 files changed, 24 insertions(+)
Index: linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/include/asm/hw_breakpoint.h
+++ linux-2.6.ppc64_test/arch/powerpc/include/asm/hw_breakpoint.h
@@ -65,9 +65,12 @@ static inline void hw_breakpoint_disable
{
set_dabr(0);
}
+extern void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs);
#else /* CONFIG_HAVE_HW_BREAKPOINT */
static inline void hw_breakpoint_disable(void) { }
+static inline void thread_change_pc(struct task_struct *tsk,
+ struct pt_regs *regs) { }
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif /* __KERNEL__ */
#endif /* _PPC_BOOK3S_64_HW_BREAKPOINT_H */
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/hw_breakpoint.c
+++ linux-2.6.ppc64_test/arch/powerpc/kernel/hw_breakpoint.c
@@ -174,6 +174,24 @@ int arch_validate_hwbkpt_settings(struct
}
/*
+ * Restores the breakpoint on the debug registers.
+ * Invoke this function if it is known that the execution context is about to
+ * change to cause loss of MSR_SE settings.
+ */
+void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
+{
+ struct arch_hw_breakpoint *info;
+
+ if (likely(!tsk->thread.last_hit_ubp))
+ return;
+
+ info = counter_arch_bp(tsk->thread.last_hit_ubp);
+ regs->msr &= ~MSR_SE;
+ set_dabr(info->address | info->type | DABR_TRANSLATION);
+ tsk->thread.last_hit_ubp = NULL;
+}
+
+/*
* Handle debug exception notifications.
*/
int __kprobes hw_breakpoint_handler(struct die_args *args)
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/signal.c
===================================================================
--- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/signal.c
+++ linux-2.6.ppc64_test/arch/powerpc/kernel/signal.c
@@ -11,6 +11,7 @@
#include <linux/tracehook.h>
#include <linux/signal.h>
+#include <asm/hw_breakpoint.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -149,6 +150,8 @@ static int do_signal_pending(sigset_t *o
if (current->thread.dabr)
set_dabr(current->thread.dabr);
#endif
+ /* Re-enable the breakpoints for the signal stack */
+ thread_change_pc(current, regs);
if (is32) {
if (ka.sa.sa_flags & SA_SIGINFO)
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
