utrace: Sort syscalls by number of invocations

seccomp and service jailing announce email [1] mentioned that "utrace
tool will sort the syscalls by the number of invocations". The code
did not do that until this commit.

[1] https://lists.openwrt.org/pipermail/openwrt-devel/2015-March/032197.html

Signed-off-by: Michal Sojka <sojkam1@fel.cvut.cz>

diff --git a/trace/trace.c b/trace/trace.c
index 65fe06727e34221f83632edac7714fdac16f088d..35bc548d08ac1f2c4782920135ab0c06157aae4a 100644 (file)
--- a/trace/trace.c
+++ b/trace/trace.c
@@ -77,6 +77,16 @@ static void set_syscall(const char *name, int val)
                }
 }
 
+struct syscall {
+       int syscall;
+       int count;
+};
+
+static int cmp_count(const void *a, const void *b)
+{
+       return ((struct syscall*)b)->count - ((struct syscall*)a)->count;
+}
+
 static void print_syscalls(int policy, const char *json)
 {
        void *c;
@@ -88,19 +98,29 @@ static void print_syscalls(int policy, const char *json)
        set_syscall("exit_group", 1);
        set_syscall("exit", 1);
 
+       struct syscall sorted[ARRAY_SIZE(syscall_names)];
+
+       for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
+               sorted[i].syscall = i;
+               sorted[i].count = syscall_count[i];
+       }
+
+       qsort(sorted, ARRAY_SIZE(syscall_names), sizeof(sorted[0]), cmp_count);
+
        blob_buf_init(&b, 0);
        c = blobmsg_open_array(&b, "whitelist");
 
        for (i = 0; i < ARRAY_SIZE(syscall_names); i++) {
-               if (!syscall_count[i])
-                       continue;
-               if (syscall_names[i]) {
+               int sc = sorted[i].syscall;
+               if (!sorted[i].count)
+                       break;
+               if (syscall_names[sc]) {
                        if (debug)
                                printf("syscall %d (%s) was called %d times\n",
-                                       i, syscall_names[i], syscall_count[i]);
-                       blobmsg_add_string(&b, NULL, syscall_names[i]);
+                                       sc, syscall_names[sc], sorted[i].count);
+                       blobmsg_add_string(&b, NULL, syscall_names[sc]);
                } else {
-                       ERROR("no name found for syscall(%d)\n", i);
+                       ERROR("no name found for syscall(%d)\n", sc);
                }
        }
        blobmsg_close_array(&b, c);