From 7e36aeaa61b7546b49fba3bb4de3b7f935339893 Mon Sep 17 00:00:00 2001
From: Martin Stjernholm <mast@google.com>
Date: Mon, 11 Nov 2019 15:51:25 +0000
Subject: [PATCH] Retain relevant comments from
 system/core/rootdir/etc/ld.config.txt.

This CL carries over the comments from the old text config that was deleted
in https://r.android.com/1128832.

Test: N/A - comment changes only
Bug: 138920271
Change-Id: I4309599228cace3d19bba7bc992e80fe2eb66c69
---
 contents/configuration/baseconfig.cc      |  6 +++++-
 contents/namespace/art.cc                 |  3 +++
 contents/namespace/conscrypt.cc           |  3 +++
 contents/namespace/media.cc               |  2 ++
 contents/namespace/neuralnetworks.cc      |  3 +++
 contents/namespace/resolv.cc              |  2 ++
 contents/namespace/rs.cc                  |  8 ++++++++
 contents/namespace/runtime.cc             |  6 ++++--
 contents/namespace/sphal.cc               | 16 ++++++++++++++++
 contents/namespace/system.cc              |  3 +++
 contents/namespace/systemdefault.cc       | 17 +++++++++++++++++
 contents/namespace/unrestricteddefault.cc |  3 +++
 contents/namespace/vendordefault.cc       |  6 ++++++
 contents/namespace/vndk.cc                | 14 ++++++++++++++
 contents/namespace/vndkinsystem.cc        | 17 +++++++++++++++++
 contents/section/postinstall.cc           |  9 ++++++++-
 contents/section/unrestricted.cc          |  5 +++++
 contents/section/vendor.cc                |  2 ++
 18 files changed, 121 insertions(+), 4 deletions(-)

diff --git a/contents/configuration/baseconfig.cc b/contents/configuration/baseconfig.cc
index eca4d31..838a40c 100644
--- a/contents/configuration/baseconfig.cc
+++ b/contents/configuration/baseconfig.cc
@@ -22,6 +22,9 @@ using android::linkerconfig::modules::DirToSection;
 using android::linkerconfig::modules::Section;
 
 namespace {
+
+// Don't change the order here. The first pattern that matches with the
+// absolute path of an executable is selected.
 const std::vector<DirToSection> kDirToSection = {
     {"/system/bin/", "system"},
     {"/system/xbin/", "system"},
@@ -51,6 +54,7 @@ const std::vector<DirToSection> kDirToSection = {
     // else. This must be last.
     {"/data", "system"},
 };
+
 }  // namespace
 
 namespace android {
@@ -74,4 +78,4 @@ android::linkerconfig::modules::Configuration CreateBaseConfiguration() {
 }
 }  // namespace contents
 }  // namespace linkerconfig
-}  // namespace android
\ No newline at end of file
+}  // namespace android
diff --git a/contents/namespace/art.cc b/contents/namespace/art.cc
index 559ac0c..c3a0eff 100644
--- a/contents/namespace/art.cc
+++ b/contents/namespace/art.cc
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+// This namespace exposes externally accessible libraries from the ART APEX.
+// Keep in sync with the "art" namespace in art/build/apex/ld.config.txt.
+
 #include "linkerconfig/namespacebuilder.h"
 
 using android::linkerconfig::modules::AsanPath;
diff --git a/contents/namespace/conscrypt.cc b/contents/namespace/conscrypt.cc
index 2bb765d..eb8aa32 100644
--- a/contents/namespace/conscrypt.cc
+++ b/contents/namespace/conscrypt.cc
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+// This namespace is for libraries within the conscrypt APEX.
+// Keep in sync with the "conscrypt" namespace in art/build/apex/ld.config.txt.
+
 #include "linkerconfig/namespacebuilder.h"
 
 #include <string>
diff --git a/contents/namespace/media.cc b/contents/namespace/media.cc
index 0208963..2b41d37 100644
--- a/contents/namespace/media.cc
+++ b/contents/namespace/media.cc
@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+// This namespace is for libraries within the media APEX.
+
 #include "linkerconfig/namespacebuilder.h"
 
 #include <string>
diff --git a/contents/namespace/neuralnetworks.cc b/contents/namespace/neuralnetworks.cc
index 49add82..873f84a 100644
--- a/contents/namespace/neuralnetworks.cc
+++ b/contents/namespace/neuralnetworks.cc
@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
+// This namespace is for libraries within the NNAPI APEX.
+
 #include "linkerconfig/namespacebuilder.h"
 
 #include "linkerconfig/environment.h"
diff --git a/contents/namespace/resolv.cc b/contents/namespace/resolv.cc
index 3156fa3..0fae623 100644
--- a/contents/namespace/resolv.cc
+++ b/contents/namespace/resolv.cc
@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+// This namespace is for libraries within the resolv APEX.
+
 #include "linkerconfig/namespacebuilder.h"
 
 #include <string>
diff --git a/contents/namespace/rs.cc b/contents/namespace/rs.cc
index df6e988..c0e3d89 100644
--- a/contents/namespace/rs.cc
+++ b/contents/namespace/rs.cc
@@ -14,6 +14,11 @@
  * limitations under the License.
  */
 
+// This namespace is exclusively for Renderscript internal libraries. This
+// namespace has slightly looser restriction than the vndk namespace because of
+// the genuine characteristics of Renderscript; /data is in the permitted path
+// to load the compiled *.so file and libmediandk.so can be used here.
+
 #include "linkerconfig/namespacebuilder.h"
 
 using android::linkerconfig::modules::AsanPath;
@@ -37,8 +42,11 @@ Namespace BuildRsNamespace([[maybe_unused]] const Context& ctx) {
   ns.AddPermittedPath("/system/vendor/${LIB}", AsanPath::NONE);
   ns.AddPermittedPath("/data", AsanPath::SAME_PATH);
 
+  // Private LLNDK libs (e.g. libft2.so) are exceptionally allowed to this
+  // namespace because RS framework libs are using them.
   ns.GetLink(ctx.GetSystemNamespaceName())
       .AddSharedLib({"@{LLNDK_LIBRARIES}", "@{PRIVATE_LLNDK_LIBRARIES:}"});
+
   ns.GetLink("neuralnetworks").AddSharedLib("libneuralnetworks.so");
 
   return ns;
diff --git a/contents/namespace/runtime.cc b/contents/namespace/runtime.cc
index 564cb17..225f5b1 100644
--- a/contents/namespace/runtime.cc
+++ b/contents/namespace/runtime.cc
@@ -14,6 +14,10 @@
  * limitations under the License.
  */
 
+// Currently, the runtime namespace is only to isolate
+// libc_malloc_hooks/debug.so in the Runtime APEX. libc/l/d are loaded in the
+// default namespace.
+
 #include "linkerconfig/namespacebuilder.h"
 
 using android::linkerconfig::modules::AsanPath;
@@ -24,8 +28,6 @@ namespace linkerconfig {
 namespace contents {
 
 Namespace BuildRuntimeNamespace([[maybe_unused]] const Context& ctx) {
-  // Currently, the runtime namespace is only to isolate
-  // libc_malloc_hooks/debug.so. libc/l/d are loaded in the default namespace.
   Namespace ns("runtime",
                /*is_isolated=*/true,
                /*is_visible=*/true);
diff --git a/contents/namespace/sphal.cc b/contents/namespace/sphal.cc
index 7a605f9..afc2a1d 100644
--- a/contents/namespace/sphal.cc
+++ b/contents/namespace/sphal.cc
@@ -14,6 +14,16 @@
  * limitations under the License.
  */
 
+// SP-HAL(Sameprocess-HAL)s are the only vendor libraries that are allowed to be
+// loaded inside system processes. libEGL_<chipset>.so, libGLESv2_<chipset>.so,
+// android.hardware.graphics.mapper@2.0-impl.so, etc are SP-HALs.
+//
+// This namespace is exclusivly for SP-HALs. When the framework tries to
+// dynamically load SP-HALs, android_dlopen_ext() is used to explicitly specify
+// that they should be searched and loaded from this namespace.
+//
+// Note that there is no link from the default namespace to this namespace.
+
 #include "linkerconfig/namespacebuilder.h"
 
 using android::linkerconfig::modules::AsanPath;
@@ -23,6 +33,8 @@ namespace android {
 namespace linkerconfig {
 namespace contents {
 Namespace BuildSphalNamespace([[maybe_unused]] const Context& ctx) {
+  // Visible to allow use with android_dlopen_ext, and with
+  // android_link_namespaces in libnativeloader.
   Namespace ns("sphal", /*is_isolated=*/true, /*is_visible=*/true);
   ns.AddSearchPath("/odm/${LIB}", AsanPath::WITH_DATA_ASAN);
   ns.AddSearchPath("/vendor/${LIB}", AsanPath::WITH_DATA_ASAN);
@@ -32,6 +44,10 @@ Namespace BuildSphalNamespace([[maybe_unused]] const Context& ctx) {
   ns.AddPermittedPath("/vendor/${LIB}", AsanPath::WITH_DATA_ASAN);
   ns.AddPermittedPath("/system/vendor/${LIB}", AsanPath::NONE);
 
+  // Once in this namespace, access to libraries in /system/lib is restricted.
+  // Only libs listed here can be used. Order is important here as the
+  // namespaces are tried in this order. rs should be before vndk because both
+  // are capable of loading libRS_internal.so
   ns.GetLink("rs").AddSharedLib("libRS_internal.so");
   ns.GetLink(ctx.GetSystemNamespaceName()).AddSharedLib("@{LLNDK_LIBRARIES:}");
   ns.GetLink("vndk").AddSharedLib("@{VNDK_SAMEPROCESS_LIBRARIES:}");
diff --git a/contents/namespace/system.cc b/contents/namespace/system.cc
index 841abbb..262a162 100644
--- a/contents/namespace/system.cc
+++ b/contents/namespace/system.cc
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+// This namespace is where system libs (VNDK and LLNDK libs) are loaded for a
+// vendor process.
+
 #include "linkerconfig/namespacebuilder.h"
 
 using android::linkerconfig::modules::AsanPath;
diff --git a/contents/namespace/systemdefault.cc b/contents/namespace/systemdefault.cc
index 03bee7c..1d7563b 100644
--- a/contents/namespace/systemdefault.cc
+++ b/contents/namespace/systemdefault.cc
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+// Framework-side code runs in this namespace. Libs from /vendor partition can't
+// be loaded in this namespace.
+
 #include "linkerconfig/environment.h"
 #include "linkerconfig/namespace.h"
 #include "linkerconfig/namespacebuilder.h"
@@ -22,6 +25,8 @@ using android::linkerconfig::modules::AsanPath;
 using android::linkerconfig::modules::Namespace;
 
 namespace {
+
+// Keep in sync with the "platform" namespace in art/build/apex/ld.config.txt.
 const std::vector<std::string> kLibsFromArt = {
     "libdexfile_external.so",
     "libdexfiled_external.so",
@@ -29,6 +34,7 @@ const std::vector<std::string> kLibsFromArt = {
     "libnativehelper.so",
     "libnativeloader.so",
     "libandroidicu.so",
+    // TODO(b/122876336): Remove libpac.so once it's migrated to Webview
     "libpac.so",
     // TODO(b/120786417 or b/134659294): libicuuc.so
     // and libicui18n.so are kept for app compat.
@@ -36,15 +42,24 @@ const std::vector<std::string> kLibsFromArt = {
     "libicuuc.so",
 };
 
+// We can't have entire /system/${LIB} as permitted paths because doing so makes
+// it possible to load libs in /system/${LIB}/vndk* directories by their
+// absolute paths, e.g. dlopen("/system/lib/vndk/libbase.so"). VNDK libs are
+// built with previous versions of Android and thus must not be loaded into this
+// namespace where libs built with the current version of Android are loaded.
+// Mixing the two types of libs in the same namespace can cause unexpected
+// problems.
 const std::vector<std::string> kPermittedPaths = {
     "/system/${LIB}/drm",
     "/system/${LIB}/extractors",
     "/system/${LIB}/hw",
     "/@{SYSTEM_EXT:system_ext}/${LIB}",
     "/@{PRODUCT:product}/${LIB}",
+
     // These are where odex files are located. libart has to be able to
     // dlopen the files
     "/system/framework",
+
     "/system/app",
     "/system/priv-app",
     "/@{SYSTEM_EXT:system_ext}/framework",
@@ -80,6 +95,8 @@ namespace linkerconfig {
 namespace contents {
 Namespace BuildSystemDefaultNamespace([[maybe_unused]] const Context& ctx) {
   bool is_fully_treblelized = ctx.IsDefaultConfig();
+  // Visible to allow links to be created at runtime, e.g. through
+  // android_link_namespaces in libnativeloader.
   Namespace ns("default",
                /*is_isolated=*/is_fully_treblelized,
                /*is_visible=*/true);
diff --git a/contents/namespace/unrestricteddefault.cc b/contents/namespace/unrestricteddefault.cc
index 11408a4..24c1474 100644
--- a/contents/namespace/unrestricteddefault.cc
+++ b/contents/namespace/unrestricteddefault.cc
@@ -23,6 +23,8 @@ using android::linkerconfig::modules::AsanPath;
 using android::linkerconfig::modules::Namespace;
 
 namespace {
+
+// Keep in sync with the "platform" namespace in art/build/apex/ld.config.txt.
 const std::vector<std::string> kLibsFromArt = {
     "libdexfile_external.so",
     "libdexfiled_external.so",
@@ -35,6 +37,7 @@ const std::vector<std::string> kLibsFromArt = {
     // for app compat.
     "libicui18n.so",
     "libicuuc.so"};
+
 }  // namespace
 
 namespace android {
diff --git a/contents/namespace/vendordefault.cc b/contents/namespace/vendordefault.cc
index efbfc03..3361a15 100644
--- a/contents/namespace/vendordefault.cc
+++ b/contents/namespace/vendordefault.cc
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+// This is the default linker namespace for a vendor process (a process started
+// from /vendor/bin/*).
+
 #include "linkerconfig/environment.h"
 #include "linkerconfig/namespacebuilder.h"
 
@@ -22,6 +25,8 @@ using android::linkerconfig::modules::GetVendorVndkVersion;
 using android::linkerconfig::modules::Namespace;
 
 namespace {
+
+// Keep in sync with the "platform" namespace in art/build/apex/ld.config.txt.
 const std::vector<std::string> kVndkLiteArtLibs = {
     "libdexfile_external.so",
     "libdexfiled_external.so",
@@ -33,6 +38,7 @@ const std::vector<std::string> kVndkLiteArtLibs = {
     "libicui18n.so",
     "libicuuc.so",
 };
+
 }  // namespace
 
 namespace android {
diff --git a/contents/namespace/vndk.cc b/contents/namespace/vndk.cc
index 2ffeef7..8b24c28 100644
--- a/contents/namespace/vndk.cc
+++ b/contents/namespace/vndk.cc
@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+// This namespace is exclusively for vndk-sp libs.
+
 #include "linkerconfig/namespacebuilder.h"
 
 #include "linkerconfig/environment.h"
@@ -27,6 +29,9 @@ namespace contents {
 Namespace BuildVndkNamespace([[maybe_unused]] const Context& ctx) {
   bool is_system_section = ctx.IsSystemSection();
   bool is_vndklite = ctx.IsVndkliteConfig();
+  // Isolated but visible when used in the [system] section to allow links to be
+  // created at runtime, e.g. through android_link_namespaces in
+  // libnativeloader. Otherwise it isn't isolated, so visibility doesn't matter.
   Namespace ns("vndk",
                /*is_isolated=*/is_system_section,
                /*is_visible=*/is_system_section);
@@ -52,16 +57,25 @@ Namespace BuildVndkNamespace([[maybe_unused]] const Context& ctx) {
       ns.AddPermittedPath("/system/vendor/${LIB}/hw", AsanPath::NONE);
     }
     ns.AddPermittedPath("/system/vendor/${LIB}/egl", AsanPath::NONE);
+
+    // This is exceptionally required since android.hidl.memory@1.0-impl.so is here
     ns.AddPermittedPath("/apex/com.android.vndk.v@{VNDK_VER}/${LIB}/hw",
                         AsanPath::SAME_PATH);
   }
 
+  // For the [vendor] section, the links should be identical to that of the
+  // 'vndk_in_system' namespace, except the links to 'default' and 'vndk_in_system'.
+
   ns.GetLink(ctx.GetSystemNamespaceName()).AddSharedLib({"@{LLNDK_LIBRARIES}"});
 
   if (!is_vndklite) {
     if (is_system_section) {
+      // The "vndk" namespace links to the system namespace for LLNDK libs above
+      // and links to "sphal" namespace for vendor libs. The ordering matters;
+      // the system namespace has higher priority than the "sphal" namespace.
       ns.GetLink("sphal").AllowAllSharedLibs();
     } else {
+      // [vendor] section
       ns.GetLink("default").AllowAllSharedLibs();
 
       if (android::linkerconfig::modules::IsVndkInSystemNamespace()) {
diff --git a/contents/namespace/vndkinsystem.cc b/contents/namespace/vndkinsystem.cc
index 87beb8b..0bee29b 100644
--- a/contents/namespace/vndkinsystem.cc
+++ b/contents/namespace/vndkinsystem.cc
@@ -14,6 +14,17 @@
  * limitations under the License.
  */
 
+// This namespace is where no-vendor-variant VNDK libraries are loaded for a
+// vendor process.  Note that we do not simply export these libraries from the
+// "system" namespace, because in some cases both the core variant and the
+// vendor variant of a VNDK library may be loaded.  In such cases, we do not
+// want to eliminate double-loading because doing so means the global states
+// of the library would be shared.
+//
+// Only the no-vendor-variant VNDK libraries are whitelisted in this namespace.
+// This is to ensure that we do not load libraries needed by no-vendor-variant
+// VNDK libraries into vndk_in_system namespace.
+
 #include "linkerconfig/namespacebuilder.h"
 
 #include "linkerconfig/environment.h"
@@ -28,6 +39,7 @@ Namespace BuildVndkInSystemNamespace([[maybe_unused]] const Context& ctx) {
   Namespace ns("vndk_in_system", /*is_isolated=*/true,
                /*is_visible=*/true);
 
+  // The search paths here should be kept the same as that of the 'system' namespace.
   ns.AddSearchPath("/system/${LIB}", AsanPath::WITH_DATA_ASAN);
   ns.AddSearchPath("/@{SYSTEM_EXT:system_ext}/${LIB}", AsanPath::WITH_DATA_ASAN);
   ns.AddSearchPath("/@{PRODUCT:product}/${LIB}", AsanPath::WITH_DATA_ASAN);
@@ -36,6 +48,11 @@ Namespace BuildVndkInSystemNamespace([[maybe_unused]] const Context& ctx) {
     ns.AddWhitelisted("@{VNDK_USING_CORE_VARIANT_LIBRARIES}");
   }
 
+  // The links here should be identical to that of the 'vndk' namespace for the
+  // [vendor] section, with the following exceptions:
+  //   1. 'vndk_in_system' needs to be freely linked back to 'vndk'.
+  //   2. 'vndk_in_system' does not need to link to 'default', as any library that
+  //      requires anything vendor would not be a vndk_in_system library.
   ns.GetLink(ctx.GetSystemNamespaceName()).AddSharedLib("@{LLNDK_LIBRARIES}");
   ns.GetLink("vndk").AllowAllSharedLibs();
   ns.GetLink("neuralnetworks").AddSharedLib("libneuralnetworks.so");
diff --git a/contents/section/postinstall.cc b/contents/section/postinstall.cc
index 0f54c45..4091e4f 100644
--- a/contents/section/postinstall.cc
+++ b/contents/section/postinstall.cc
@@ -14,6 +14,13 @@
  * limitations under the License.
  */
 
+// Namespace config for binaries under /postinstall.
+// Only default namespace is defined and default has no directories
+// other than /system/lib in the search paths. This is because linker calls
+// realpath on the search paths and this causes selinux denial if the paths
+// (/vendor, /odm) are not allowed to the postinstall binaries. There is no
+// reason to allow the binaries to access the paths.
+
 #include "linkerconfig/sectionbuilder.h"
 
 #include "linkerconfig/namespacebuilder.h"
@@ -35,4 +42,4 @@ Section BuildPostInstallSection(Context& ctx) {
 }
 }  // namespace contents
 }  // namespace linkerconfig
-}  // namespace android
\ No newline at end of file
+}  // namespace android
diff --git a/contents/section/unrestricted.cc b/contents/section/unrestricted.cc
index ae57426..de94b55 100644
--- a/contents/section/unrestricted.cc
+++ b/contents/section/unrestricted.cc
@@ -14,6 +14,11 @@
  * limitations under the License.
  */
 
+// Linker config for native tests that need access to both system and vendor
+// libraries. This replicates the default linker config (done by
+// init_default_namespace_no_config in bionic/linker/linker.cpp), except that it
+// includes the requisite namespace setup for APEXes.
+
 #include "linkerconfig/sectionbuilder.h"
 
 #include "linkerconfig/common.h"
diff --git a/contents/section/vendor.cc b/contents/section/vendor.cc
index f872be3..9aab0db 100644
--- a/contents/section/vendor.cc
+++ b/contents/section/vendor.cc
@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+// Namespace config for vendor processes.
+
 #include "linkerconfig/sectionbuilder.h"
 
 #include "linkerconfig/common.h"
-- 
2.11.0