This change implements the following property:
Any 2**N aligned memory region on size 2**N contains no more than one DSO.
The value N can be configured, with 16 or 18 looking like a good choice.
Additionally, DSOs are loaded at random page-aligned address inside these large
regions.
This change has dual purpose:
1. Larger values of N allow a lot more compact CFI shadow implementation.
See change I14dfea630de468eb5620e7f55f92b1397ba06217.
For example, CFI shadow for the system_server process has the following size (RSS, KB):
152 for N = 12, 32 for N = 16, 16 for N = 18.
2. Extra randomization is good for security.
This change does not result in extra RAM usage, because everything is still page-aligned.
It does result in a bit more VM fragmentation because of the gaps between shared libraries.
As it turns out, this fragmentation is barely noticeable because the kernel creates new mapping
at the highest possible address, and we do enough small mappings to almost completely fill the
gaps (ex. in the Zygote the gaps are filled with .ttf file mappings and thread stacks).
I've measured VM fragmentation as the sum of all VM gaps (unmapped regions) that are larger
than 1MB according to /proc/$PID/maps. On aosp_angler-userdebug, the numbers are (in GB):
| N = 12 | N = 18
system_server | 521.9 | 521.1
zygote64 | 522.1 | 521.3
zygote32 | 2.55 | 2.55
mediaserver | 4.00 | 4.00
Change-Id: Ia6df840dd409c82837efd1f263be420d9723c84a
We have much better control over visibility now, so we don't need to
pollute the headers with cruft.
Bug: http://b/24767418
Change-Id: I349f4c3bc30102477375ad9f80926e560c7c1d8b
Move all of the uapi kernel headers that are only found in the android
kernel, and are still used by the tree into their own directory.
Delete all of these files that are not used.
Also, delete binder.h from the linux directory since it already exists
in the linux/android directory.
Bug: 30072483
Change-Id: I879f16e366f7670b8be3546b0a9cf9567fce6526
gnustl is using this. It would be easy to change gnustl to *not* use
it for Android, but we've had this in released NDKs for years now so
we probably need this anyway.
Change-Id: I398a550664bf4ccbd9ea54f53c65428293a599a4
The compile-time tests and a few custom libraries for dynamic linker
testing are still compiled in make.
Also converts the make rules to run tests on the host to shell scripts
in tests/run-on-host.sh and benchmarks/run-on-host.sh
Change-Id: I6f174b3a69d58c4ed74d29f4e79332d483681534
