CVS commit: src/sys/arch

["Maxime Villard" <maxv%netbsd.org@localhost>]

Module Name:    src
Committed By:   maxv
Date:           Thu Oct 19 19:05:53 UTC 2017

Modified Files:
        src/sys/arch/amd64/amd64: locore.S machdep.c
        src/sys/arch/x86/x86: sys_machdep.c

Log Message:
Improve our segregs model. Pass 2/3.

Treat %fs the same way we treat %ds and %es. For a new 32bit LWP %fs is
set to GUDATA32_SEL, and always updated in INTRFASTEXIT.

This solves an important issue we had until now: we couldn't handle the
faults generated by the "movw $val,%fs" instructions, because they were
deep into the kernel context. Now %fs can fault only in INTRFASTEXIT,
which is safe.

Note that it also fixes a bug I believe affected the kernel: on AMD CPUs,
setting %fs to zero does not flush the internal register state, and
therefore we could leak the %fs base address when context-switching. This
being said, I couldn't trigger the issue on the AMD cpu I have. Whatever,
it's fixed now, since we first set %fs to GUDATA32 - which does flush the
register state.


To generate a diff of this commit:
cvs rdiff -u -r1.134 -r1.135 src/sys/arch/amd64/amd64/locore.S
cvs rdiff -u -r1.270 -r1.271 src/sys/arch/amd64/amd64/machdep.c
cvs rdiff -u -r1.40 -r1.41 src/sys/arch/x86/x86/sys_machdep.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.