tree b7aefd286560ae943421006456ad2ed7951aff98
parent bb04803b8daf08e186b327d18e14c78378f44e37
author Alistair Delva <adelva@google.com> 1612905054 -0800
committer swiftshader-scoped@luci-project-accounts.iam.gserviceaccount.com <swiftshader-scoped@luci-project-accounts.iam.gserviceaccount.com> 1613585442 +0000

Fix support for named mmap usage on Android

Using a memfd name to annotate swiftshader_jit allocations is quite
clever, but it doesn't work on Android because memfds can be shared
and so writing to mappings of them promotes CoW/shared, which is
classified by selinux as 'execmod' permission. Android prohibits
'execmod' permission for new app processes, because this is usually a
sign the app relies on shared text relocations, which are insecure. In
this case, that isn't actually happening, but we are subject to the
same blanket ban :)

Fortunately, Android has a longtime non-upstreamed prctl() to allow
private mappings to be named as well, PR_SET_VMA_ANON_NAME. As this
isn't generally available for Linux, wrap it in checks for __ANDROID__.

This enables the naming without tripping the 'execmod' permission check.

Bug: b/171498948
Bug: b/174801963
Change-Id: Ic4375bc4407e21ecdafb42a7cec651dc3b2ad13e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/52669
Reviewed-by: Jason Macnak <natsu@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Presubmit-Ready: Jason Macnak <natsu@google.com>
Tested-by: Jason Macnak <natsu@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Commit-Queue: Jason Macnak <natsu@google.com>