Historically, Android defaulted to EXPLICIT but with a special case
because SCHED_NORMAL/priority 0 was awkward. Because the code couldn't
actually tell whether SCHED_NORMAL/priority 0 was a genuine attempt to
explicitly set those attributes (because the parent thread is SCHED_FIFO,
say) or just because the pthread_attr_t was left at its defaults.
Now we support INHERIT, we could call sched_getscheduler to see whether
we actually need to call sched_setscheduler, but since the major cost
is the fixed syscall overhead, we may as well just conservatively
call sched_setscheduler and let the kernel decide whether it's a
no-op. (Especially because we'd then have to add both sched_getscheduler
and sched_setscheduler to any seccomp filter.)
Platform code (or app code that only needs to support >= P) can actually
add a call to pthread_attr_setinheritsched to say that they just want
to inherit (if they know that none of their threads actually mess with
scheduler attributes at all), which will save them a sched_setscheduler
call except in the doubly-special case of SCHED_RESET_ON_FORK (which we
do handle).
An alternative would be "make pthread_attr_setschedparams and
pthread_attr_setschedprio set EXPLICIT and change the platform default
to INHERIT", but even though I can only think of weird pathological
examples where anyone would notice that change, that behavior -- of
pthread_attr_setschedparams/pthread_attr_setschedprio overriding an
earlier call to pthread_attr_setinheritsched -- isn't allowed by POSIX
(whereas defaulting to EXPLICIT is).
If we have a lot of trouble with this change in the app compatibility
testing phase, though, we'll want to reconsider this decision!
-*-
This change also removes a comment about setting the scheduler attributes
in main_thread because we'd have to actually keep them up to date,
and it's not clear that doing so would be worth the trouble.
Also make async_safe_format_log preserve errno so we don't have to be
so careful around it.
Bug: http://b/67471710
Test: ran tests
Change-Id: Idd026c4ce78a536656adcb57aa2e7b2c616eeddf
Return EAGAIN rather than aborting if we fail to set up the TLS for a new
thread.
Add a test that uses all the VMAs so we can properly test these edge cases.
Add an explicit test for pthread_attr_setdetachstate, which we use in the
previous test, but other than that has no tests.
Remove support for ro.logd.timestamp/persist.logd.timestamp, which doesn't
seem to be used, and which prevents us from logging failures in cases where
mmap fails (because we need to mmap in the system property implementation).
Bug: http://b/65608572
Test: ran tests
Change-Id: I9009f06546e1c2cc55eff996d08b55eff3482343
The GCE breakage caused by 78a52f19bb was
due to TLS_SLOT_SELF being uninitialized before the use of errno by
syscall. Separate stack guard initialization from TLS initialization so
that stack guard initialization can make syscalls.
Bug: http://b/29622562
Bug: http://b/31251721
Change-Id: Id0e4379e0efb7194a2df7bd16211ff11c6598033
When arc4random can get entropy (which is true for basically everyone
but init on kernels that don't support getrandom), use it instead of
AT_RANDOM.
Bug: http://b/29622562
Change-Id: I6932803af2c477e65562ff531bd959f199fad1df
Before, dynamic executables would initialize the global stack protector
twice, once for the linker, and once for the executable. This worked
because the result was the same for both initializations, because it
used getauxval(AT_RANDOM), which won't be the case once arc4random gets
used for it.
Bug: http://b/29622562
Change-Id: I7718b1ba8ee8fac7127ab2360cb1088e510fef5c
Test: ran the stack protector tests on angler (32/64bit, static/dynamic)
This patch uses __kernel_vsyscall instead of "int 0x80"
as the syscall entry point. AT_SYSINFO points to
an adapter to mask the arch specific difference and gives a
performance boost on i386 architecture.
Change-ID: Ib340c604d02c6c25714a95793737e3cfdc3fc5d7
Signed-off-by: Mingwei Shi <mingwei.shi@intel.com>
Exactly which functions get a stack protector is up to the compiler, so
let's separate the code that sets up the environment stack protection
requires and explicitly build it with -fno-stack-protector.
Bug: http://b/26276517
Change-Id: I8719e23ead1f1e81715c32c1335da868f68369b5
