ptrace/x86: introduce ptrace_register_breakpoint()

No functional changes, preparation.

Extract the "register breakpoint" code from ptrace_get_debugreg() into
the new/generic helper, ptrace_register_breakpoint().  It will have more
users.

The patch also adds another simple helper, ptrace_fill_bp_fields(), to
factor out the arch_bp_generic_fields() logic in register/modify.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 50 insertions, 36 deletions

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 98b0a2ccc33c..052636801b41 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -601,22 +601,48 @@ static unsigned long ptrace_get_dr7(struct perf_event *bp[])
         return dr7;
 }
 
-static int
-ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
-                         struct task_struct *tsk, int disabled)
+static int ptrace_fill_bp_fields(struct perf_event_attr *attr,
+                                        int len, int type, bool disabled)
+{
+        int err, bp_len, bp_type;
+
+        err = arch_bp_generic_fields(len, type, &bp_len, &bp_type);
+        if (!err) {
+                attr->bp_len = bp_len;
+                attr->bp_type = bp_type;
+                attr->disabled = disabled;
+        }
+
+        return err;
+}
+
+static struct perf_event *
+ptrace_register_breakpoint(struct task_struct *tsk, int len, int type,
+                                unsigned long addr, bool disabled)
 {
-        int err;
-        int gen_len, gen_type;
         struct perf_event_attr attr;
+        int err;
+
+        ptrace_breakpoint_init(&attr);
+        attr.bp_addr = addr;
 
-        err = arch_bp_generic_fields(len, type, &gen_len, &gen_type);
+        err = ptrace_fill_bp_fields(&attr, len, type, disabled);
         if (err)
-                return err;
+                return ERR_PTR(err);
+
+        return register_user_hw_breakpoint(&attr, ptrace_triggered,
+                                                 NULL, tsk);
+}
 
-        attr = bp->attr;
-        attr.bp_len = gen_len;
-        attr.bp_type = gen_type;
-        attr.disabled = disabled;
+static int ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
+                                        int disabled)
+{
+        struct perf_event_attr attr = bp->attr;
+        int err;
+
+        err = ptrace_fill_bp_fields(&attr, len, type, disabled);
+        if (err)
+                return err;
 
         return modify_user_hw_breakpoint(bp, &attr);
 }
@@ -653,7 +679,7 @@ restore:
                         break;
                 }
 
-                rc = ptrace_modify_breakpoint(bp, len, type, tsk, disabled);
+                rc = ptrace_modify_breakpoint(bp, len, type, disabled);
                 if (rc)
                         break;
         }
@@ -693,26 +719,14 @@ static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n)
 static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
                                       unsigned long addr)
 {
-        struct perf_event *bp;
         struct thread_struct *t = &tsk->thread;
-        struct perf_event_attr attr;
+        struct perf_event *bp = t->ptrace_bps[nr];
         int err = 0;
 
-        if (!t->ptrace_bps[nr]) {
-                ptrace_breakpoint_init(&attr);
-                /*
-                 * Put stub len and type to register (reserve) an inactive but
-                 * correct bp
-                 */
-                attr.bp_addr = addr;
-                attr.bp_len = HW_BREAKPOINT_LEN_1;
-                attr.bp_type = HW_BREAKPOINT_W;
-                attr.disabled = 1;
-
-                bp = register_user_hw_breakpoint(&attr, ptrace_triggered,
-                                                 NULL, tsk);
-
+        if (!bp) {
                 /*
+                 * Put stub len and type to create an inactive but correct bp.
+                 *
                  * CHECKME: the previous code returned -EIO if the addr wasn't
                  * a valid task virtual addr. The new one will return -EINVAL in
                  *  this case.
@@ -721,20 +735,20 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
                  * writing for the user. And anyway this is the previous
                  * behaviour.
                  */
-                if (IS_ERR(bp)) {
+                bp = ptrace_register_breakpoint(tsk,
+                                X86_BREAKPOINT_LEN_1, X86_BREAKPOINT_WRITE,
+                                addr, true);
+                if (IS_ERR(bp))
                         err = PTR_ERR(bp);
-                        goto out;
-                }
-
-                t->ptrace_bps[nr] = bp;
+                else
+                        t->ptrace_bps[nr] = bp;
         } else {
-                bp = t->ptrace_bps[nr];
+                struct perf_event_attr attr = bp->attr;
 
-                attr = bp->attr;
                 attr.bp_addr = addr;
                 err = modify_user_hw_breakpoint(bp, &attr);
         }
-out:
+
         return err;
 }