Tweak the GPU process sandbox to allow accelerated video decode.

content/common/sandbox_init_linux.cc

Index: content/common/sandbox_init_linux.cc
diff --git a/content/common/sandbox_init_linux.cc b/content/common/sandbox_init_linux.cc
index a67a784232aa70bcd6c856baf2546384bbab83da..beb45574c7de9c3e1a49088d77a21dc33bf67c5e 100644
--- a/content/common/sandbox_init_linux.cc
+++ b/content/common/sandbox_init_linux.cc
@@ -12,6 +12,7 @@
 #endif
 
 #include <asm/unistd.h>
+#include <dlfcn.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/audit.h>
@@ -146,6 +147,21 @@ bool IsFileSystemSyscall(int sysno) {
   }
 }
 
+bool IsAcceleratedVideoDecodeEnabled() {

[jln (very slow on Chromium), 2012/07/26 17:53:54]

Any chance that gpu/ could export a function like this instead? It looks like
dangerous code duplication, doesn't it?

[Jorge Lucangeli Obes, 2012/07/26 18:33:36]

The code does not live in gpu/, it lives in
content/renderer/render_view_impl.cc. So I don't think so.

It is duplicated, but the only thing that can change is Linux being enabled, and
we should be informed of that in the linked bug.

[jln (very slow on Chromium), 2012/07/26 19:06:39]

Ok, we don't want to start refactoring code just for this, but could you at
least add a comment in renderer_view_impl.cc around use_accelerated_video_decode
and link to the bug?

+  // Accelerated video decode is currently enabled on Chrome OS,
+  // but not on Linux: crbug.com/137247.
+  bool is_enabled = false;
+#if defined(OS_CHROMEOS)

[jln (very slow on Chromium), 2012/07/26 17:53:54]

Please use IsChromeOS().

[Jorge Lucangeli Obes, 2012/07/26 18:33:36]

Done.

[piman, 2012/07/26 20:33:52]

FYI, IsChromeOS is different from #ifdef OS_CHROMEOS.

IsChromeOS is a run-time "detection" of whether you're running on a chrome OS
device - in practice, if $USER==chronos
OS_CHROMEOS is a compile-time define that's set if chromeos=1 is set in
GYP_DEFINES.
We can, and regularly do (including on bots) run a chromeos=1 build on linux,
where OS_CHROMEOS is defined but IsChromeOS is false. Be sure to take that into
account here.

+  is_enabled = true;
+#endif
+
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  is_enabled &= !command_line.HasSwitch(

[jln (very slow on Chromium), 2012/07/26 17:53:54]

please, use && here so that we benefit from lazy evaluation.

[Jorge Lucangeli Obes, 2012/07/26 18:33:36]

Done.

+      switches::kDisableAcceleratedVideoDecode);
+
+  return is_enabled;
+}
+
 static const char kDriRcPath[] = "/etc/drirc";
 
 // TODO(jorgelo): limited to /etc/drirc for now, extend this to cover
@@ -270,10 +286,20 @@ playground2::Sandbox::ErrorCode GpuProcessPolicy_x86_64(int sysno) {
     case __NR_fchmod:
       return EPERM;  // ATI binary driver.
     case __NR_open:
-      // Hook open() in the GPU process to allow opening /etc/drirc,
-      // needed by Mesa.
-      // The hook needs dup(), lseek(), and close() to be allowed.
-      return playground2::Sandbox::ErrorCode(GpuOpenSIGSYS_Handler, NULL);
+      // Accelerated video decode is enabled by default only on Chrome OS.
+      if (IsAcceleratedVideoDecodeEnabled()) {
+        // Accelerated video decode needs to open /dev/dri/card0, and
+        // dup()'ing an already open file descriptor does not work.
+        // Allow open() even though it severely weakens the sandbox,
+        // to test the sandboxing mechanism in general.
+        // TODO(jorgelo): remove this once we solve the libva issue.
+        return playground2::Sandbox::SB_ALLOWED;
+      } else {
+        // Hook open() in the GPU process to allow opening /etc/drirc,
+        // needed by Mesa.
+        // The hook needs dup(), lseek(), and close() to be allowed.
+        return playground2::Sandbox::ErrorCode(GpuOpenSIGSYS_Handler, NULL);
+      }
     default:
       if (IsGettimeSyscall(sysno) ||
           IsKillSyscall(sysno)) { // GPU watchdog.
@@ -390,8 +416,17 @@ playground2::Sandbox::ErrorCode AllowAllPolicy(int sysno) {
 // Warms up/preloads resources needed by the policies.
 void WarmupPolicy(playground2::Sandbox::EvaluateSyscall policy) {
 #if defined(__x86_64__)
-  if (policy == GpuProcessPolicy_x86_64)
+  if (policy == GpuProcessPolicy_x86_64) {
     OpenWithCache(kDriRcPath, O_RDONLY);
+    // Accelerated video decode dlopen()'s this shared object
+    // inside the sandbox, so preload it now.
+    // TODO(jorgelo): generalize this to other platforms.
+    if (IsAcceleratedVideoDecodeEnabled()) {
+      const char kI965DrvVideoPath_64[] =
+          "/usr/lib64/va/drivers/i965_drv_video.so";
+      dlopen(kI965DrvVideoPath_64, RTLD_NOW|RTLD_GLOBAL|RTLD_NODELETE);
+    }
+  }
 #endif
 }