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[ikiwiki.git] / docs / developer / alexh_todo / index.mdwn
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b475db1d 1## Note: this is my personal todo and ideas list (alexh@)
53af51d2 2
fcd780c0 3* add a non-persistent unionfs VFS
4 - while this does not fully replace unionfs, it would deal with a few of the situations where unionfs is useful
5 - additionally the complexity is much lower, since everything can be kept in memory
6
7* bring the samba3 hammer shadow copy foo to maturity
8
d2e33566 9* add a communication channel mechanism to dm
10 - essentially a way to send messages and receive responses to dm target instances
11
38202188 12* cryptdisks
13 - Improve to support external scripts/programs providing passphrases
14
e4eadd94 15* dm_target_crypt
5d279a75 16 - Look at plain64 iv support, what it implies vs plain.
e4eadd94 17 - Think about benbi iv support
e4eadd94 18
6e280d9e 19* Add TrueCrypt support
20 - Simply add a userland tool that sets dm_target_crypt up with the right parameters, extracted from the TrueCrypt header
5d279a75 21 - https://github.com/bwalex/tc-play <- done!
22 - needs OpenSSL with XTS support; probably next major release
6e280d9e 23
e09e6796 24* Update cryptsetup
25
744c3358 26* Update opencrypto
27 - http://www.openbsd.org/cgi-bin/cvsweb/src/sys/crypto/
5d279a75 28 - think about support for other ciphers, such as Serpent and Twofish
744c3358 29
e09e6796 30* Port hwpmc & dig into (boot-up) performance
31
1bf667d1 32* linuxulator
6c260381 33 - port to x86_64
34 - separate out common arch parts (linprocfs, for example)
53af51d2 35
e09e6796 36* Fix the crash analysis script (or rather the programs it calls [some segfault])
0d62372b 37
f3169700 38* Take a look at updating lvm/dm/libdevicemapper
53af51d2 39
f3169700 40* Take a look at importing libdm from NetBSD
41 - would allow tc-play and similarly newly developed foo to avoid GPL license issues
1bf667d1 42
1bf667d1 43* sync up vr
44 o Added VT6105M specific register definitions. VT6105M has the
45 following hardware capabilities.
46 - Tx/Rx IP/TCP/UDP checksum offload.
47 - VLAN hardware tag insertion/extraction. Due to lack of information
48 for getting extracted VLAN tag in Rx path, VLAN hardware support
49 was not implemented yet.
50 - CAM(Content Addressable Memory) based 32 entry perfect multicast/
51 VLAN filtering.
52 - 8 priority queues.
53 o Implemented CAM based 32 entry perfect multicast filtering for
54 VT6105M. If number of multicast entry is greater than 32, vr(4)
55 uses traditional hash based filtering.
56
6c260381 57* rip out the disk partitioning from the disk subsystem and implement it in a more general fashion
58 - crazy idea: as dm targets with an auto-configuration option!
59
6c260381 60* sync some more opencrypto from OpenBSD
1bf667d1 61
62* ATA (automatic) spindown (see FreeBSD current)
0d62372b 63
64* Update callout
65 http://svn.freebsd.org/viewvc/base?view=revision&revision=127969
66
67* inv ctxsw rusage
68 - see irc logs
69 - some incorrect accounting going on, don't remember details :)
70
71* unionfs update
72 - make it work without whiteout
73
74
75
b475db1d 76###Boring:
1bf667d1 77
1bf667d1 78
79* RedZone, a buffer corruption protection for the kernel malloc(9) facility has been implemented.
80 - This detects both buffer underflows and overflows at runtime on free(9) and realloc(9),
81 and prints backtraces from where memory was allocated and from where it was freed.
82 - see irc log below.
83
84* port uart driver (?)
85
0d62372b 86* port wscons (?) or update syscons
87 - probably way too much effort (wscons)
88
89
90* port usb4bsd
91 - wrapper is included for userland; should be easy to port
92 - http://svn.freebsd.org/viewvc/base?view=revision&revision=184610
93 - http://turbocat.net/~hselasky/usb4bsd/
94 - http://gitweb.dragonflybsd.org/~polachok/dragonfly.git/shortlog/refs/heads/usb2
95
1bf667d1 96* suspend/resume for SMP x86
97 - http://lists.freebsd.org/pipermail/freebsd-acpi/2008-May/004879.html
98
1bf667d1 99* AMD64 suspend/resume
100 - http://svn.freebsd.org/viewvc/base?view=revision&revision=189903
6c260381 101
102
6c260381 103* text dumps
104
1bf667d1 105
1bf667d1 106
107[alexh@leaf:~/home] $ roundup-server -p 8080 bt=bugtracker
108
53af51d2 109<pre>
1bf667d1 110-05:48- : dillon@: no, double frees to the object cache are nasty. It can't detect them. the object
111 winds up in the magazine array twice
112-05:48- : dillon@: (and possibly different magazines, too)
113-05:49- : alexh@: can't I just write some magic to a free object on the first objcache_put and check
114 if it's there on objcache_put?
115-05:49- : alexh@: and clear it on objcache_get, anyways
116-05:50- : dillon@: no, because the object is still may have live-initialized fields
117-05:50- : dillon@: because it hasn't been dtor'ed yet (one of the features of the objcache, to avoid
118 having to reinitialize objects every time)
119-05:50- : dillon@: the mbuf code uses that feature I think, probably other bits too
120-05:51- : dillon@: theoretically we could allocate slightly larger objects and store a magic number at
121 offset [-1] or something like that, but it gets a little iffy doing that
122-05:52- : dillon@: the objcache with the objcache malloc default could probably do something like that
123 I guess.
124-05:52- : dillon@: I don't consider memory tracking to be a huge issue w/ dragonfly, though I like the
125 idea of being able to do it. It is a much bigger problem in FreeBSD due to the
126 large number of committers
127
128
129-05:55- : dillon@: For the slab allocator you may be able to do something using the Zone header.
130-05:55- : dillon@: the slab allocator in fact I think already has optional code to allocate a tracking
131 bitmap to detect double-frees
132-05:56- : dillon@: sorry, I just remembered the bit about the power-of-2 allocations
133-05:56- : dillon@: for example, power-of-2-sized allocations are guaranteed not only to be aligned on
134 that particular size boundary, but also to not cross a PAGE_BOUNDARY (unless the
135 size is > PAGE_SIZE)
136-05:57- : dillon@: various subsystems such as AHCI depend on that behavior to allocate system
137 structures for which the chipsets only allow one DMA descriptor.
138-05:59- : alexh@: http://svn.freebsd.org/viewvc/base/head/sys/vm/redzone.c?view=markup&pathrev=155086
139 < this is redzone. it basically calls redzone_addr_ntor() to increase the size in
140 malloc(), and then redzone_setup() just before returning the chunk
141-06:02- : dillon@: jeeze. that looks horrible.
142-06:03- : alexh@: I don't quite get that nsize + redzone_roundup(nsize)
143-06:03- : dillon@: I don't get it either. It would completely break power-of-2-sized alignments in the
144 original request
145-06:04- : dillon@: hmmm. well, no it won't break them, but the results are oging to be weird
146-06:04- : dillon@: ick.
147
148-06:15- : dillon@: if the original request is a power of 2 the redzone adjusted request must be a power
149 of 2
150-06:15- : dillon@: basically
151-06:16- : dillon@: so original request 64, redzone request must be 128, 256, 512, 1024, etc.
152-06:16- : alexh@: yah, k
153-06:16- : dillon@: original request 32, current redzone code would be 32+128 which is WRONG.
154-06:16- : alexh@: how big is PAGE_SIZE ?
155-06:16- : dillon@: 4096 on i386 and amd64
156-06:17- : alexh@: and one single malloc can't be bigger than that?
157-06:17- : dillon@: I'm fairly sure our kmalloc does not guarantee alignment past PAGE_SIZE (that is,
158 the alignment will be only PAGE_SIZE eve if you allocate PAGE_SIZE*2)
159-06:17- : dillon@: a single kmalloc can be larger then PAGE_SIZe
160-06:18- : dillon@: it will use the zone up to around 1/2 the zone size (~64KB I think), after which it
161 allocates pages directly with the kernel kvm allocator
162-06:18- : dillon@: if you look at the kmalloc code you will see the check for oversized allocations
163-06:18- : alexh@: yah, saw that
164-06:18- : alexh@: "handle large allocations directly"
165-06:19- : alexh@: not sure how to do this, really, as the size is obviously also changed in
166 kmem_slab_alloc
167-06:20- : alexh@: but kmem_slab_alloc isn't called always, is it?
168-06:20- : alexh@: only if the req doesn't fit into an existant zone
169-06:20- : dillon@: right
170-06:20- : dillon@: you don't want to redzone the zone allocation itself
53af51d2 171
172</pre>