MFC r293613:

Implement vsyscall hack. Prior to 2.13 glibc uses vsyscall
instead of vdso. An upcoming linux_base-c6 needs it.

MFC r283382:

In preparation for switching linuxulator to the use the native 1:1
threads add a hook for cleaning thread resources before the thread die.

MFC r288000:
Add support for weak symbols to the kernel linkers.

MFC 264990, 264994, 265020, 265025:

Call cpu_icache_sync_range() rather than sync_all since we know the range
and flushing the entire icache is needlessly expensive.

Provide a proper armv7 implementation of icache_sync_all rather than
using armv7_idcache_wbinv_all, because wbinv_all doesn't broadcast the
operation to other cores. In elf_cpu_load_file() use icache_sync_all()
and explain why it's needed (and why other sync operations aren't).

Remove cpu_idcache_wbinv_all() from kdb_cpu_trap(), it's no longer needed.

Explain why wbinv_all is SMP-safe when dumping, and add a missing l2 cache
flush. (Either it was missing here, or it isn't needed in the minidump
case. Adding it here seems like the safer path to consistancy.)

MFC r288000:
Add support for weak symbols to the kernel linkers.

MFC 264990, 264994, 265020, 265025:

Call cpu_icache_sync_range() rather than sync_all since we know the range
and flushing the entire icache is needlessly expensive.

Provide a proper armv7 implementation of icache_sync_all rather than
using armv7_idcache_wbinv_all, because wbinv_all doesn't broadcast the
operation to other cores. In elf_cpu_load_file() use icache_sync_all()
and explain why it's needed (and why other sync operations aren't).

Remove cpu_idcache_wbinv_all() from kdb_cpu_trap(), it's no longer needed.

Explain why wbinv_all is SMP-safe when dumping, and add a missing l2 cache
flush. (Either it was missing here, or it isn't needed in the minidump
case. Adding it here seems like the safer path to consistancy.)