[Qemu-devel] [PATCH] monitor: HMP: fix consecutive integer expression parsing

[Alon Levy <alevy@redhat.com>]

Currently a command that takes two consecutive integer operations, like
client_migrate_info, will be incorrectly parsed by the human monitor if
the second expression begins with a minus ('-') or plus ('+') sign:

client_migrate_info <protocol> <hostname> <port> <tls-port>
client_migrate_info spice localhost 5900 -1
=> port = 5899 = 5900 - 1
   tls-port = -1
But expected by the user to be:
   port = 5900
   tls-port = -1

The fix is that for any required integer (ilM) expression followed by another
integer expression (ilM) the first expression will be parsed by expr_unary
instead of expr_sum. So you can still use arithmetic, but you have to enclose
it in parenthesis:

Command line | Old parsed result | With patch result
(1+1) 2      | 2, 2              | 2, 2
1 -1         | 0, -1             | 1, -1
The rest are bizarre but not any worse then before
1+2+3        | 6, 5              | 1, 5
(1+2)+3      | 3, 3              | 3, 3

Signed-off-by: Alon Levy <alevy@redhat.com>
---
 monitor.c |   27 ++++++++++++++++++++++++---
 1 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/monitor.c b/monitor.c
index 1b8ba2c..45e2d6c 100644
--- a/monitor.c
+++ b/monitor.c
@@ -3889,7 +3889,7 @@ static int64_t expr_sum(Monitor *mon)
     return val;
 }
 
-static int get_expr(Monitor *mon, int64_t *pval, const char **pp)
+static int get_expr(Monitor *mon, int64_t *pval, const char **pp, int unary)
 {
     pch = *pp;
     if (setjmp(expr_env)) {
@@ -3898,7 +3898,11 @@ static int get_expr(Monitor *mon, int64_t *pval, const char **pp)
     }
     while (qemu_isspace(*pch))
         pch++;
-    *pval = expr_sum(mon);
+    if (unary) {
+        *pval = expr_unary(mon);
+    } else {
+        *pval = expr_sum(mon);
+    }
     *pp = pch;
     return 0;
 }
@@ -4267,6 +4271,9 @@ static const mon_cmd_t *monitor_parse_command(Monitor *mon,
         case 'M':
             {
                 int64_t val;
+                int unary = 0;
+                char *next_key;
+                char *next;
 
                 while (qemu_isspace(*p))
                     p++;
@@ -4288,7 +4295,21 @@ static const mon_cmd_t *monitor_parse_command(Monitor *mon,
                     }
                     typestr++;
                 }
-                if (get_expr(mon, &val, &p))
+                next = key_get_info(typestr, &next_key);
+                qemu_free(next_key);
+                if (*next == 'i' || *next == 'l' || *next == 'M') {
+                    /* If a command has two consecutive ii parameters the first
+                     * get_expr will also parse the second parameter if it
+                     * starts with a - or +. To avoid this only parse unary in
+                     * this case, i.e.:
+                     * client_migrate_info spice localhost 1 -1
+                     *  => 1, -1
+                     * client_migrate_info spice localhost (1+3) -1
+                     *  => 4, -1
+                     */
+                    unary = 1;
+                }
+                if (get_expr(mon, &val, &p, unary))
                     goto fail;
                 /* Check if 'i' is greater than 32-bit */
                 if ((c == 'i') && ((val >> 32) & 0xffffffff)) {
-- 
1.7.6