perf/hw_breakpoint: Clean up and consolidate modify_user_hw_breakpoint_check()

Remove the dance around old and new attributes. Just don't modify the
previous breakpoint at all until we have verified everything.

Original-patch-by: Andy Lutomirski <luto@kernel.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-13-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 71387703b5f16e388a3496a7d7b8ffdef06f3548..b3814fce5ecb6bf7729ea858ec17ddb9018105f1 100644 (file)
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -461,37 +461,43 @@ register_user_hw_breakpoint(struct perf_event_attr *attr,
 }
 EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
 
+static void hw_breakpoint_copy_attr(struct perf_event_attr *to,
+                                   struct perf_event_attr *from)
+{
+       to->bp_addr = from->bp_addr;
+       to->bp_type = from->bp_type;
+       to->bp_len  = from->bp_len;
+       to->disabled = from->disabled;
+}
+
 int
 modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *attr,
                                bool check)
 {
-       u64 old_addr = bp->attr.bp_addr;
-       u64 old_len  = bp->attr.bp_len;
-       int old_type = bp->attr.bp_type;
-       bool modify  = attr->bp_type != old_type;
        struct arch_hw_breakpoint hw;
-       int err = 0;
+       int err;
 
-       bp->attr.bp_addr = attr->bp_addr;
-       bp->attr.bp_type = attr->bp_type;
-       bp->attr.bp_len  = attr->bp_len;
+       err = hw_breakpoint_parse(bp, attr, &hw);
+       if (err)
+               return err;
 
-       if (check && memcmp(&bp->attr, attr, sizeof(*attr)))
-               return -EINVAL;
+       if (check) {
+               struct perf_event_attr old_attr;
 
-       err = hw_breakpoint_parse(bp, attr, &hw);
-       if (!err && modify)
-               err = modify_bp_slot(bp, old_type, bp->attr.bp_type);
+               old_attr = bp->attr;
+               hw_breakpoint_copy_attr(&old_attr, attr);
+               if (memcmp(&old_attr, attr, sizeof(*attr)))
+                       return -EINVAL;
+       }
 
-       if (err) {
-               bp->attr.bp_addr = old_addr;
-               bp->attr.bp_type = old_type;
-               bp->attr.bp_len  = old_len;
-               return err;
+       if (bp->attr.bp_type != attr->bp_type) {
+               err = modify_bp_slot(bp, bp->attr.bp_type, attr->bp_type);
+               if (err)
+                       return err;
        }
 
+       hw_breakpoint_copy_attr(&bp->attr, attr);
        bp->hw.info = hw;
-       bp->attr.disabled = attr->disabled;
 
        return 0;
 }