Status: New
Owner: ----
New issue 2597 by [email protected]: v8 doesn't detect ARM CPU features
properly in Android sandboxed services.
http://code.google.com/p/v8/issues/detail?id=2597
On ARM, the code in src/platform-linux.cc tries to parse /proc/cpuinfo
directly to detect which features the target device's CPU supports.
Unfortunately, when this code runs inside a Chromium renderer process, it
won't be able to open /proc/cpuinfo at all, and thus will fail to detect
any useful CPU feature, including VFP and NEON.
The reason for this is that renderer processes are run inside Android
services that have the "android:isolatedProcess" attribute [1], which adds
extra sandboxing to the process (e.g. it is unable to access the
filesystem, including /proc).
It is possible to solve this specific problem by using the
NDK's "cpufeatures" helper library, because Chrome ensures that the right
features mask is passed (from the browser process) to each renderer process
when it starts.
This bug is to track the issue. I plan to provide a fix that would amount
to the following:
1/ Add a conditional macro test corresponding to the Chromium on Android
compilation case (e.g. CHROMIUM_ON_ANDROID)
2/ Add the following to the source file:
#ifdef CHROMIUM_ON_ANDROID
#include <cpu-features.h>
#endif
...
bool OS::ArmCpuHasFeature(CpuFeature feature) {
const struct {
CPUFeature feature;
uint64_t mask;
} features[] = {
{ VFP2, ANDROID_CPU_ARM_FEATURE_VFPv2 },
{ VFP3, ANDROID_CPU_ARM_FEATURE_VFPv3 },
{ ARMv7, ANDROID_CPU_ARM_FEATURE_ARMv7 },
{ SUDIV, ANDROID_CPU_ARM_FEATURE_IDIV_ARM |
ANDROID_CPU_ARM_FEATURE_IDIV_THUMB },
{ VFP32DREGS, ANDROID_CPU_ARM_FEATURE_VFP_D32 },
};
uint64_t cpu_features = android_getCpuFeatures();
for (size_t i = 0;
i < sizeof(features)/sizeof(features[0]);
++i) {
if (features[i].feature == feature)
return (cpu_features & features[i].mask) != 0;
}
return false;
}
Note that cpu-features doesn't return the implementer name for now. I'll
add this to the library first, so OS::GetCpuImplementer() can be
implemented properly as well.
A similar issue exists for MIPS. cpu-features doesn't report the "FPU"
feature yet, I'll add this too.
[1] See
http://developer.android.com/guide/topics/manifest/service-element.html
--
You received this message because this project is configured to send all
issue notifications to this address.
You may adjust your notification preferences at:
https://code.google.com/hosting/settings
--
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
---
You received this message because you are subscribed to the Google Groups "v8-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.
