[Qemu-devel] [PATCH RFC 1/4] log: Clean up misuse of Range for -dfilter

[Markus Armbruster <armbru@redhat.com>]

Range encodes an integer interval [a,b] as { begin = a, end = b + 1 },
where a \in [0,2^64-1] and b \in [1,2^64].  Thus, zero end is to be
interpreted as 2^64.

The implementation of -dfilter (commit 3514552) uses Range
differently: it encodes [a,b] as { begin = a, end = b }.  The code
works, but it contradicts the specification of Range in range.h.

Switch to the specified representation.  Since it can't represent
[0,UINT64_MAX], we have to reject that now.  Add a test for it.

While we're rejecting anyway: observe that we reject -dfilter LOB..UPB
where LOB > UPB when UPB is zero, but happily create an empty Range
when it isn't.  Reject it then, too, and add a test for it.

While there, add a positive test for the problematic upper bound
UINT64_MAX.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 tests/test-logging.c | 10 ++++++++++
 util/log.c           | 28 +++++++++++++++-------------
 2 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/tests/test-logging.c b/tests/test-logging.c
index 440e75f..b6fa94e 100644
--- a/tests/test-logging.c
+++ b/tests/test-logging.c
@@ -68,6 +68,16 @@ static void test_parse_range(void)
     g_assert(qemu_log_in_addr_range(0x2050));
     g_assert(qemu_log_in_addr_range(0x3050));
 
+    qemu_set_dfilter_ranges("0xffffffffffffffff-1", &error_abort);
+    g_assert(qemu_log_in_addr_range(UINT64_MAX));
+    g_assert_false(qemu_log_in_addr_range(UINT64_MAX - 1));
+
+    qemu_set_dfilter_ranges("0..0xffffffffffffffff", &err);
+    error_free_or_abort(&err);
+
+    qemu_set_dfilter_ranges("2..1", &err);
+    error_free_or_abort(&err);
+
     qemu_set_dfilter_ranges("0x1000+onehundred", &err);
     error_free_or_abort(&err);
 
diff --git a/util/log.c b/util/log.c
index 32e4160..f811d61 100644
--- a/util/log.c
+++ b/util/log.c
@@ -131,8 +131,8 @@ bool qemu_log_in_addr_range(uint64_t addr)
     if (debug_regions) {
         int i = 0;
         for (i = 0; i < debug_regions->len; i++) {
-            struct Range *range = &g_array_index(debug_regions, Range, i);
-            if (addr >= range->begin && addr <= range->end) {
+            Range *range = &g_array_index(debug_regions, Range, i);
+            if (addr >= range->begin && addr <= range->end - 1) {
                 return true;
             }
         }
@@ -158,7 +158,7 @@ void qemu_set_dfilter_ranges(const char *filter_spec, Error **errp)
     for (i = 0; ranges[i]; i++) {
         const char *r = ranges[i];
         const char *range_op, *r2, *e;
-        uint64_t r1val, r2val;
+        uint64_t r1val, r2val, lob, upb;
         struct Range range;
 
         range_op = strstr(r, "-");
@@ -187,27 +187,29 @@ void qemu_set_dfilter_ranges(const char *filter_spec, Error **errp)
                        (int)(r2 - range_op), range_op);
             goto out;
         }
-        if (r2val == 0) {
-            error_setg(errp, "Invalid range");
-            goto out;
-        }
 
         switch (*range_op) {
         case '+':
-            range.begin = r1val;
-            range.end = r1val + (r2val - 1);
+            lob = r1val;
+            upb = r1val + r2val - 1;
             break;
         case '-':
-            range.end = r1val;
-            range.begin = r1val - (r2val - 1);
+            upb = r1val;
+            lob = r1val - (r2val - 1);
             break;
         case '.':
-            range.begin = r1val;
-            range.end = r2val;
+            lob = r1val;
+            upb = r2val;
             break;
         default:
             g_assert_not_reached();
         }
+        if (lob > upb || (lob == 0 && upb == UINT64_MAX)) {
+            error_setg(errp, "Invalid range");
+            goto out;
+        }
+        range.begin = lob;
+        range.end = upb + 1;
         g_array_append_val(debug_regions, range);
     }
 out:
-- 
2.5.5