CVS commit: src/sys/arch/amd64/amd64

["David Laight" <dsl%netbsd.org@localhost>]

Module Name:    src
Committed By:   dsl
Date:           Tue May 22 21:10:26 UTC 2012

Modified Files:
        src/sys/arch/amd64/amd64: vector.S

Log Message:
If we get a fault setting the user %gs, or on a iret that is returning
to userspace, we must do a 'swapgs' to reload the kernel %gs_base.
Also save the %ds, %es, %fs, %gs selector values in the frame so
they can be restored if we finally return to user (probably after
an application SIGSEGV handler has fixed the error).
Without this any such fault leaves the kernel running with the wrong
%gs offset and it will most likely fault again early in trap().
Repeats until the stack tramples on something important.
iret change works, invalid %gs is a little harder to arrange.


To generate a diff of this commit:
cvs rdiff -u -r1.40 -r1.41 src/sys/arch/amd64/amd64/vector.S

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