K 10
svn:author
V 3
sjg
K 8
svn:date
V 27
2020-06-16T17:02:56.232707Z
K 7
svn:log
V 530
Make KENV_MVALLEN tunable

When doing secure boot, loader wants to export loader.ve.hashed
the value of which typically exceeds KENV_MVALLEN.

Replace use of KENV_MVALLEN with tunable kenv_mvallen.

Add getenv_string_buffer() for the case where a stack buffer cannot be
created and use uma_zone_t kenv_zone for suitably sized buffers.

Reviewed by:	stevek, kevans
Obtained from:	Abhishek Kulkarni <abkulkarni@juniper.net>
MFC after:	1 week
Sponsored by:	Juniper Networks
Differential Revision: https://reviews.freebsd.org//D25259

END