* Don't skip the TLS initialization (Fixes#9083)
* Add a test case where a PIE program is built and run
* Refactor the common initialization code in the Linux startup
sequence.
There are some small problems here and there, mostly due to the pointers
having the lsb set and disrupting the fn alignment tests and the
`@FrameSize` implementation.
Everybody gets what they want!
* AT_RANDOM is completely ignored.
* On Linux, MADV_WIPEONFORK is used to provide fork safety.
* On pthread systems, `pthread_atfork` is used to provide fork safety.
* For systems that do not have the capability to provide fork safety,
the implementation falls back to calling getrandom() every time.
* If madvise is unavailable or returns an error, or pthread_atfork
fails for whatever reason, it falls back to calling getrandom() every
time.
* Applications may choose to opt-out of fork safety.
* Applications may choose to opt-in to unconditionally calling
getrandom() for every call to std.crypto.random.fillFn.
* Added `std.meta.globalOption`.
* Added `std.os.madvise` and related bits.
* Bumped up the size of the main thread TLS buffer. See the comment
there for justification.
* Simpler hot path in TLS initialization.
ad05509 introduced a fix for the wrong problem, the logic to align the
start of main_thread_tls_buffer was already there but was flawed.
Fix it for good and avoid wasting too many bytes for alignment purposes.
Calling @panic made the executable ~30x times bigger, use a simple
`abort()` and let the user figure out what went wrong.
Supporting ARMv6 (and earlier?) platforms is not a priority.
Closes#6676
* Always allocate an info block per-thread so that libc can store
important stuff there.
* Respect ABI-mandated alignment in more places.
* Nicer code, use slices/pointers instead of raw addresses whenever
possible.
This reverts commit ee6fda2297bf75432b8d7115ec4c60c213535bbe, reversing
changes made to f313ab18aecea1ade0b6a90d671352a641ad351a.
This caused a test failure:
```
behavior.misc.test "behavior-arm-linux-none-Debug-bare-multi thread local variable"...test failure
/home/vsts/work/1/s/lib/std/testing.zig:191:14: 0x4608f in std.testing.expect (test)
if (!ok) @panic("test failure");
^
/home/vsts/work/1/s/test/stage1/behavior/misc.zig:616:11: 0x53e93 in behavior.misc.test "behavior-arm-linux-none-Debug-bare-multi thread local variable" (test)
expect(S.t == 1235);
^
```
* Always allocate an info block per-thread so that libc can store
important stuff there.
* Respect ABI-mandated alignment in more places.
* Nicer code, use slices/pointers instead of raw addresses whenever
possible.
