MFC r324243:

Remove an unneeded and incorrect memset().

On Variant I TLS architectures (aarch64, arm, mips, powerpc, and riscv)
the __libc_allocate_tls function allocates thread local storage memory
with calloc(). It then copies initialization data over the portions with
non-zero initial values. Before this change it would then pointlessly
zero the already zeroed remainder of the storage. Unfortunately the
calculation was wrong and it would zero TLS_TCB_SIZE (2*sizeof(void *))
additional bytes.

In practice, this overflow only matters if the TLS segment is sized such
that calloc() allocates less than TLS_TCB_SIZE extra memory. Even
then, the likely result will be zeroing part of the next bucket. This
coupled with the impact being confined to Tier II platforms means there
will be no security advisory for this issue.

Reviewed by: kib, dfr
Discussed with: security-officer (delphij)
Found by: CHERI
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D12547

MFC r297790:
r297790 (by pfg):

libc: replace 0 with NULL for pointers.

While here also cleanup some surrounding code; particularly
drop some malloc() casts.

Found with devel/coccinelle.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Import jemalloc a8f8d7540d66ddee7337db80c92890916e1063ca (dev branch,
prior to 3.0.0 release). This fixes several bugs related to memory
initialization.

Mangle __jemalloc_a0{malloc,calloc,free}() just like all the other
library-internal symbols in jemalloc, and adjust the tls allocation code
in libc to use the mangled names.

Import jemalloc 9ef7f5dc34ff02f50d401e41c8d9a4a928e7c2aa (dev branch,
prior to 3.0.0 release) as contrib/jemalloc, and integrate it into libc.
The code being imported by this commit diverged from
lib/libc/stdlib/malloc.c in March 2010, which means that a portion of
the jemalloc 1.0.0 ChangeLog entries are relevant, as are the entries
for all subsequent releases.

- Switch ARM and MIPS to TLS Variant I
- Fix TLS allocation for Variant I: both rtld and libc allocators
assume that tls_static_space includes space for TLS structure.
So increment calculated static size by the size of it.

The static TLS size as given by tls_static_space includes TLS_TCB_SIZE
bytes of TCB in variant I.

o Add MIPS to the list of architectures with defined TLS_TCB_ALIGN
o Stick with TLS Variant II for MIPS for the moment.

Approved by: imp

Don't assert() the TLS allocation requested is big enough; just
fix the argument.

In particular, this is a step towards breaking crt1's dependence on stdio.

Fix TLS on sparc64 for statically and dynamically linked binaries
Approved by: rwatson (mentor)
Reviewed by: jmg and marcel

Fix style(9) in code copied from rtld.

Fix the variant I allocation for KSE: Allow a larger TCB and assume
that the documented TCB is at the tail of the extended TCB. In other
words, the base of the TCB has a negative offset from the TLS.

Remove stale comment about arm

Allocate space for thread pointer, this allows thread library to access
its pointer from begin, and simplifies _get_curthread() in libthr.

Use __weak_reference macro to define weak symbols.

Fix incorrect comment.

Mark _rtld_allocate_tls and _rtld_free_tls as weak symbols for Variant I
tls.

Reviewed by: dfr

Arbitraly choose the Variant II for arm.

Make sure we allocate at least enough space for the TCB for variant I TLS.

MFC after: 3 days

Always allocate a TLS area even if its empty - libpthread relies on
having a valid %gs when it initialises.

MFC after: 2 days

Add support for TLS in statically linked programs.

Add stubs for TLS functions. These will be replaced at runtime by the
functional versions in rtld.