Update checking debug.vulkan.layer.* system props

... to scan a fixed range of priorities followed by
consecutive priorities instead of scanning all system
props (property_list()) which causes sepolicy audits
when Vulkan is loaded in a process with a restrictive
sepolicy.

This avoids sepolicy audits in system_server for example
when running on Cuttlefish with SwANGLE (ANGLE GL on top
of SwiftShader Vulkan).

Bug: b/179967574
Test: boot Cuttlefish with SwANGLE and inspect audit logs
Change-Id: I63b3f45113fbdd3ab62c22f062150e25b99d7352

1 files changed, 32 insertions, 22 deletions

diff --git a/vulkan/libvulkan/api.cpp b/vulkan/libvulkan/api.cpp
index 5b9affd03a..9aaac5f1d6 100644
--- a/vulkan/libvulkan/api.cpp
+++ b/vulkan/libvulkan/api.cpp
@@ -33,6 +33,7 @@
 #include <unordered_set>
 #include <utility>
 
+#include <android-base/properties.h>
 #include <android-base/strings.h>
 #include <cutils/properties.h>
 #include <log/log.h>
@@ -134,7 +135,7 @@ class OverrideLayerNames {
         // If no layers specified via Settings, check legacy properties
         if (implicit_layers_.count <= 0) {
             ParseDebugVulkanLayers();
-            property_list(ParseDebugVulkanLayer, this);
+            ParseDebugVulkanLayer();
 
             // sort by priorities
             auto& arr = implicit_layers_;
@@ -181,30 +182,39 @@ class OverrideLayerNames {
             AddImplicitLayer(prio, p, strlen(p));
     }
 
-    static void ParseDebugVulkanLayer(const char* key,
-                                      const char* val,
-                                      void* user_data) {
+    void ParseDebugVulkanLayer() {
+        // Checks for consecutive debug.vulkan.layer.<priority> system
+        // properties after always checking an initial fixed range.
         static const char prefix[] = "debug.vulkan.layer.";
-        const size_t prefix_len = sizeof(prefix) - 1;
-
-        if (strncmp(key, prefix, prefix_len) || val[0] == '\0')
-            return;
-        key += prefix_len;
-
-        // debug.vulkan.layer.<priority>
-        int priority = -1;
-        if (key[0] >= '0' && key[0] <= '9')
-            priority = atoi(key);
+        static constexpr int kFixedRangeBeginInclusive = 0;
+        static constexpr int kFixedRangeEndInclusive = 9;
+
+        bool logged = false;
+
+        int priority = kFixedRangeBeginInclusive;
+        while (true) {
+            const std::string prop_key =
+                std::string(prefix) + std::to_string(priority);
+            const std::string prop_val =
+                android::base::GetProperty(prop_key, "");
+
+            if (!prop_val.empty()) {
+                if (!logged) {
+                    ALOGI(
+                        "Detected Vulkan layers configured with "
+                        "debug.vulkan.layer.<priority>. Checking for "
+                        "debug.vulkan.layer.<priority> in the range [%d, %d] "
+                        "followed by a consecutive scan.",
+                        kFixedRangeBeginInclusive, kFixedRangeEndInclusive);
+                    logged = true;
+                }
+                AddImplicitLayer(priority, prop_val.c_str(), prop_val.length());
+            } else if (priority >= kFixedRangeEndInclusive) {
+                return;
+            }
 
-        if (priority < 0) {
-            ALOGW("Ignored implicit layer %s with invalid priority %s", val,
-                  key);
-            return;
+            ++priority;
         }
-
-        OverrideLayerNames& override_layers =
-            *reinterpret_cast<OverrideLayerNames*>(user_data);
-        override_layers.AddImplicitLayer(priority, val, strlen(val));
     }
 
     void AddImplicitLayer(int priority, const char* name, size_t len) {