CVS commit: [netbsd-9] src/sys/kern

["Martin Husemann" <martin%netbsd.org@localhost>]

Module Name:    src
Committed By:   martin
Date:           Mon Jun 21 16:14:14 UTC 2021

Modified Files:
        src/sys/kern [netbsd-9]: kern_ksyms.c

Log Message:
Pull up following revision(s) (requested by riastradh in ticket #1299):

        sys/kern/kern_ksyms.c: revision 1.90
        sys/kern/kern_ksyms.c: revision 1.91
        sys/kern/kern_ksyms.c: revision 1.92
        sys/kern/kern_ksyms.c: revision 1.93
        sys/kern/kern_ksyms.c: revision 1.94
        sys/kern/kern_ksyms.c: revision 1.95
        sys/kern/kern_ksyms.c: revision 1.96
        sys/kern/kern_ksyms.c: revision 1.97

ksyms(4): Fix ksymsread synchronization.

Fixes crash on concurrent update and read of /dev/ksyms.
XXX Unclear why we have to skip sd_gone entries here -- it seems like
they should be preserved until ksymsclose.
ksyms(4): Modify ksyms_symtabs only at IPL_HIGH.

This limits the opportunities for ddb to witness an inconsistent
state of the symbol table list.
ksyms(4): Don't skip symbol tables that are soon to be freed.

They will not actually be freed until /dev/ksyms is closed, so
continued access to them remains kosher.
Revert "ksyms(4): Don't skip symbol tables that are soon to be freed."

Apparently the equality kassert this restored doesn't work; to be
analyzed.

Fix regression introduced in rev 1.90
in which the last element of ksyms_symtabs is skipped by mistake.

ksyms(4): Fix race in ksymsread iteration.
TAILQ_NEXT(ksyms_last_snapshot) might change while we are iterating,
but ksyms_last_snapshot itself cannot, so invert the loop structure.

Discussed with rin@.

ksyms(4): Don't skip symbol tables that are soon to be freed, take 2.

They will not actually be freed until /dev/ksyms is closed, so
continued access to them remains kosher.
The previous change was busted because of an off-by-one error in a
previous previous change's iteration over the symtabs; that error has
since been corrected.

ksyms(4): Allow multiple concurrent opens of /dev/ksyms.

First one takes a snapshot; others all agree with the snapshot.
Previously this code path was just broken (could fail horribly if
modules were unloaded after one of the opens is closed), so I just
blocked it off in an earlier commit, but that broke crash(8).  So
let's continue allowing multiple opens seeing the same snapshot, but
without the horrible bugs.


To generate a diff of this commit:
cvs rdiff -u -r1.87.8.1 -r1.87.8.2 src/sys/kern/kern_ksyms.c

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