[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, 68 insertions, 0 deletions

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 9f654da4cecc..83339d33c4b1 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -57,6 +57,7 @@
 enum s390_regset {
         REGSET_GENERAL,
         REGSET_FP,
+        REGSET_LAST_BREAK,
         REGSET_GENERAL_EXTENDED,
 };
 
@@ -381,6 +382,10 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                         copied += sizeof(unsigned long);
                 }
                 return 0;
+        case PTRACE_GET_LAST_BREAK:
+                put_user(task_thread_info(child)->last_break,
+                         (unsigned long __user *) data);
+                return 0;
         default:
                 /* Removing high order bit from addr (only for 31 bit). */
                 addr &= PSW_ADDR_INSN;
@@ -633,6 +638,10 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
                         copied += sizeof(unsigned int);
                 }
                 return 0;
+        case PTRACE_GET_LAST_BREAK:
+                put_user(task_thread_info(child)->last_break,
+                         (unsigned int __user *) data);
+                return 0;
         }
         return compat_ptrace_request(child, request, addr, data);
 }
@@ -797,6 +806,28 @@ static int s390_fpregs_set(struct task_struct *target,
         return rc;
 }
 
+#ifdef CONFIG_64BIT
+
+static int s390_last_break_get(struct task_struct *target,
+                               const struct user_regset *regset,
+                               unsigned int pos, unsigned int count,
+                               void *kbuf, void __user *ubuf)
+{
+        if (count > 0) {
+                if (kbuf) {
+                        unsigned long *k = kbuf;
+                        *k = task_thread_info(target)->last_break;
+                } else {
+                        unsigned long  __user *u = ubuf;
+                        if (__put_user(task_thread_info(target)->last_break, u))
+                                return -EFAULT;
+                }
+        }
+        return 0;
+}
+
+#endif
+
 static const struct user_regset s390_regsets[] = {
         [REGSET_GENERAL] = {
                 .core_note_type = NT_PRSTATUS,
@@ -814,6 +845,15 @@ static const struct user_regset s390_regsets[] = {
                 .get = s390_fpregs_get,
                 .set = s390_fpregs_set,
         },
+#ifdef CONFIG_64BIT
+        [REGSET_LAST_BREAK] = {
+                .core_note_type = NT_S390_LAST_BREAK,
+                .n = 1,
+                .size = sizeof(long),
+                .align = sizeof(long),
+                .get = s390_last_break_get,
+        },
+#endif
 };
 
 static const struct user_regset_view user_s390_view = {
@@ -948,6 +988,27 @@ static int s390_compat_regs_high_set(struct task_struct *target,
         return rc;
 }
 
+static int s390_compat_last_break_get(struct task_struct *target,
+                                      const struct user_regset *regset,
+                                      unsigned int pos, unsigned int count,
+                                      void *kbuf, void __user *ubuf)
+{
+        compat_ulong_t last_break;
+
+        if (count > 0) {
+                last_break = task_thread_info(target)->last_break;
+                if (kbuf) {
+                        unsigned long *k = kbuf;
+                        *k = last_break;
+                } else {
+                        unsigned long  __user *u = ubuf;
+                        if (__put_user(last_break, u))
+                                return -EFAULT;
+                }
+        }
+        return 0;
+}
+
 static const struct user_regset s390_compat_regsets[] = {
         [REGSET_GENERAL] = {
                 .core_note_type = NT_PRSTATUS,
@@ -965,6 +1026,13 @@ static const struct user_regset s390_compat_regsets[] = {
                 .get = s390_fpregs_get,
                 .set = s390_fpregs_set,
         },
+        [REGSET_LAST_BREAK] = {
+                .core_note_type = NT_S390_LAST_BREAK,
+                .n = 1,
+                .size = sizeof(long),
+                .align = sizeof(long),
+                .get = s390_compat_last_break_get,
+        },
         [REGSET_GENERAL_EXTENDED] = {
                 .core_note_type = NT_S390_HIGH_GPRS,
                 .n = sizeof(s390_compat_regs_high) / sizeof(compat_long_t),