[S390] add breaking event address for user space

Copy the last breaking event address from the lowcore to a new
field in the thread_struct on each system entry. Add a new
ptrace request PTRACE_GET_LAST_BREAK and a new utrace regset
REGSET_LAST_BREAK to query the last breaking event.

This is useful for debugging wild branches in user space code.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/s390/kernel/signal.c b/arch/s390/kernel/signal.c
index 6289945562b0..ee7ac8b11782 100644
--- a/arch/s390/kernel/signal.c
+++ b/arch/s390/kernel/signal.c
@@ -313,6 +313,7 @@ static int setup_frame(int sig, struct k_sigaction *ka,
            To avoid breaking binary compatibility, they are passed as args. */
         regs->gprs[4] = current->thread.trap_no;
         regs->gprs[5] = current->thread.prot_addr;
+        regs->gprs[6] = task_thread_info(current)->last_break;
 
         /* Place signal number on stack to allow backtrace from handler.  */
         if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
@@ -376,6 +377,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
         regs->gprs[2] = map_signal(sig);
         regs->gprs[3] = (unsigned long) &frame->info;
         regs->gprs[4] = (unsigned long) &frame->uc;
+        regs->gprs[5] = task_thread_info(current)->last_break;
         return 0;
 
 give_sigsegv: