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>

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 98b0a2ccc33c6ddfd1c5f5b5617d7e1eefcff08d..052636801b41a67deef5633de2a41853fd7bf825 100644 (file)
--- 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;
 }