[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, 2 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 0e2b16241dfa..d5e3e6007447 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -180,9 +180,9 @@ STACK_SIZE  = 1 << STACK_SHIFT
         s       %r15,BASED(.Lc_spsize)  # make room for registers & psw
         mvc     SP_PSW(8,%r15),0(%r12)  # move user PSW to stack
         st      %r2,SP_ORIG_R2(%r15)    # store original content of gpr 2
-        icm     %r12,3,__LC_SVC_ILC
+        icm     %r12,12,__LC_SVC_ILC
         stm     %r0,%r11,SP_R0(%r15)    # store gprs %r0-%r11 to kernel stack
-        st      %r12,SP_SVCNR(%r15)
+        st      %r12,SP_ILC(%r15)
         mvc     SP_R12(16,%r15),\savearea # move %r12-%r15 to stack
         la      %r12,0
         st      %r12,__SF_BACKCHAIN(%r15)       # clear back chain