feat: add SYS_GETCAPS syscall to retrieve process capabilities

programs/include/montauk/capabilities.h

@@ -15,7 +15,6 @@ namespace caps {
 
     inline constexpr const char* GRANT_CONFIG = "capabilities";
     inline constexpr const char* GRANT_PREFIX = "grant.";
-    inline constexpr int MAX_SCAN_PROCS = 256;
 
     struct CapName {
         const char* name;
@@ -134,26 +133,7 @@ namespace caps {
     // The calling process's own capability masks.
     inline bool self(montauk::abi::SpawnCapabilities& out) {
         out = {0, 0, 0};
-
-        auto* table = (montauk::abi::ProcInfo*)montauk::malloc(
-            sizeof(montauk::abi::ProcInfo) * MAX_SCAN_PROCS);
-        if (table == nullptr) return false;
-
-        int count = montauk::proclist(table, MAX_SCAN_PROCS);
-        int self_pid = montauk::getpid();
-
-        bool found = false;
-        for (int i = 0; i < count; i++) {
-            if (table[i].pid != self_pid) continue;
-            out.permitted = table[i].permittedCaps;
-            out.effective = table[i].effectiveCaps;
-            out.delegable = table[i].delegableCaps;
-            found = true;
-            break;
-        }
-
-        montauk::mfree(table);
-        return found;
+        return montauk::getcaps(&out) == 0;
     }
 
     inline uint64_t self_delegable() {

programs/include/montauk/syscall.h

@@ -127,6 +127,10 @@ namespace montauk {
                              (uint64_t)args, (uint64_t)user,
                              (uint64_t)&capabilities);
     }
+    // The calling process's own capability masks. Returns 0 on success.
+    inline int getcaps(montauk::abi::SpawnCapabilities* out) {
+        return (int)syscall1(montauk::abi::SYS_GETCAPS, (uint64_t)out);
+    }
     inline int chdir(const char* path) {
         return (int)syscall1(montauk::abi::SYS_CHDIR, (uint64_t)path);
     }