Re: ARM is channeling the IBM 360

Liste des GroupesRevenir à c arch 
Sujet : Re: ARM is channeling the IBM 360
De : cr88192 (at) *nospam* gmail.com (BGB)
Groupes : comp.arch
Date : 22. Jun 2024, 21:37:49
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <v57cn0$3u221$1@dont-email.me>
References : 1 2
User-Agent : Mozilla Thunderbird
On 6/22/2024 5:58 AM, John Dallman wrote:
In article <bebb9f88a6677b4894478a3dabc8b2c9@www.novabbs.org>,
mitchalsup@aol.com (MitchAlsup1) wrote:
 
The 4 seconds part leads me to believe the attackers are using brute
force, since in 4 seconds one can try something like 2^28 patterns.
 Makes sense: there's probably a hash of the block address involved in
generating those 4-bit tags, and they're brute-forcing the salt.
 Memory Tagging Extension doesn't seem to have been heavily used as yet,
which may be why ARM aren't very worried about it.
 
To me, it sounds like they are using something annoying and expensive (memory tagging) in a way that is also not particularly effective (can be brute forced).
Granted, using memory tagging to validate pointers does arguably have less impact on code generation than, say, hardware bounds checking (by encoding bounds-check metadata inside the pointers / capabilities).
But, does add its own problems:
Say, to swap out memory pages, one also needs to keep track of and save/restore the tag bits associated with each memory page.
So, say, if you had 16K pages, one might need an additional 512 bytes or so for the tag bits (assuming 4 bits per 16 bytes or similar).
Would still be 512B with 4K pages, assuming one pads to a multiple of 512B.
So, say (going into OS design thinking here), do we have a separate pagefile, separate region in the pagefile, or do we make pagefile pages non power of 2, etc...
Though, non-power-of-2 pages seems extra bad for something like an SDcard or SSD as one may potentially end up effectively doubling the number of block updates per page-write operation. But, OTOH, if one tries to consolidate the tags into separately managed memory pages from the main memory, this would makes the pagefile management significantly more complex.
Though, admittedly, I had previously considered the possibility of a 2-level scheme where page updates would LZ compress pages, which would be packed into blocks and written out in a similar way to a log file system. While this could be less abusive towards an SDcard, it would have been complicated enough that I didn't want to mess with it (instead, the LZ compression being used merely to reduce the number of sectors read/written, but not necessarily to consolidate writes to the pagefile).
Granted, a linear log isn't too complicated initially, but gets much more complicated when one needs to wrap around back to the start of the log (and then needs to start consolidating any still-live data from these prior blocks into the new blocks being written; or across multiple blocks if consolidating would not free up enough space to add the new data; worst case potentially "pretty bad").
Though, worst case could be reduced if the block-packing code tries to avoid packing blocks to more than around 70% capacity or so.
...

Pointer Authentication Code in ARMv8.3 is usable within functions, but
has problems, in that compilers can't readily tell if stored pointers
have PAC signatures.
 Branch Target Indicators in ARMv8.5 work quite well, but need linker and
loader support.
 PAC and BTI use instructions that are no-ops in earlier versions of ARM64,
but you really ought to test that they work before releasing binaries
that include them. I've done that on Android, where I had the combination
of hardware, OS and compiler to do it.
 Once I can get an ARM Linux server with the hardware support, Linux
kernel 5.0 onwards and modern GCC will let me do it there. Windows and
macOS on ARM both lack some pieces, and iOS requires you to change ABIs
and drop support for older 64-bit devices.
 
Hmm.

John

Date Sujet#  Auteur
20 Jun 24 * ARM is channeling the IBM 360102John Savard
20 Jun 24 +* Re: ARM is sort of channeling the IBM 36095John Levine
21 Jun 24 i`* Re: ARM is sort of channeling the IBM 36094Lynn Wheeler
24 Jun 24 i `* Re: ARM is sort of channeling the IBM 36093Lawrence D'Oliveiro
24 Jun 24 i  +* Re: ancient OS history, ARM is sort of channeling the IBM 36090John Levine
24 Jun 24 i  i+* Re: ancient OS history, ARM is sort of channeling the IBM 36087Lynn Wheeler
24 Jun 24 i  ii+* Re: ancient OS history, ARM is sort of channeling the IBM 36082Lawrence D'Oliveiro
25 Jun 24 i  iii`* Re: ancient OS history, ARM is sort of channeling the IBM 36081John Levine
25 Jun 24 i  iii +* Re: ancient OS history, ARM is sort of channeling the IBM 36073Lawrence D'Oliveiro
25 Jun 24 i  iii i`* Re: ancient OS history, ARM is sort of channeling the IBM 36072Stephen Fuld
25 Jun 24 i  iii i +* Re: ancient OS history, ARM is sort of channeling the IBM 36064Stephen Fuld
26 Jun 24 i  iii i i`* Re: ancient OS history, ARM is sort of channeling the IBM 36063Stephen Fuld
26 Jun 24 i  iii i i `* Re: ancient OS history, ARM is sort of channeling the IBM 36062Lawrence D'Oliveiro
26 Jun 24 i  iii i i  +* Re: ancient OS history, ARM is sort of channeling the IBM 36057John Levine
26 Jun 24 i  iii i i  i`* Re: ancient OS history, ARM is sort of channeling the IBM 36056Lawrence D'Oliveiro
27 Jun 24 i  iii i i  i `* Re: ancient OS history, ARM is sort of channeling the IBM 36055John Levine
27 Jun 24 i  iii i i  i  `* Re: ancient OS history, ARM is sort of channeling the IBM 36054MitchAlsup1
28 Jun 24 i  iii i i  i   `* Re: ancient OS history, ARM is sort of channeling the IBM 36053Lawrence D'Oliveiro
28 Jun 24 i  iii i i  i    +- Re: TSS I/O, ancient OS history1John Levine
28 Jun 24 i  iii i i  i    `* Re: ancient OS history, ARM is sort of channeling the IBM 36051MitchAlsup1
28 Jun 24 i  iii i i  i     `* Re: ancient OS history, ARM is sort of channeling the IBM 36050Lawrence D'Oliveiro
29 Jun 24 i  iii i i  i      `* Re: ancient OS history, ARM is sort of channeling the IBM 36049Stephen Fuld
29 Jun 24 i  iii i i  i       `* Re: ancient OS history, ARM is sort of channeling the IBM 36048John Levine
30 Jun 24 i  iii i i  i        +* Re: ancient OS history, ARM is sort of channeling the IBM 36032Lawrence D'Oliveiro
30 Jun 24 i  iii i i  i        i+- Re: ancient OS history, ARM is sort of channeling the IBM 3601MitchAlsup1
30 Jun 24 i  iii i i  i        i`* Re: ancient OS history, ARM is sort of channeling the IBM 36030Stephen Fuld
30 Jun 24 i  iii i i  i        i +* Re: ancient OS history, ARM is sort of channeling the IBM 36024Lawrence D'Oliveiro
30 Jun 24 i  iii i i  i        i i+* Re: ancient OS history, ARM is sort of channeling the IBM 36022Lynn Wheeler
30 Jun 24 i  iii i i  i        i ii`* Re: ancient OS history, ARM is sort of channeling the IBM 36021John Dallman
30 Jun 24 i  iii i i  i        i ii +* Re: ancient OS history, ARM is sort of channeling the IBM 36019Thomas Koenig
30 Jun 24 i  iii i i  i        i ii i+* Re: ancient OS history, ARM is sort of channeling the IBM 3608Michael S
30 Jun 24 i  iii i i  i        i ii ii+* Re: ancient OS history, ARM is sort of channeling the IBM 3606Thomas Koenig
30 Jun 24 i  iii i i  i        i ii iii+* Re: ancient OS history, ARM is sort of channeling the IBM 3604Stephen Fuld
30 Jun 24 i  iii i i  i        i ii iiii`* Re: base registers, ancient OS history, ARM is sort of channeling the IBM 3603John Levine
1 Jul 24 i  iii i i  i        i ii iiii `* Re: base registers, ancient OS history, ARM is sort of channeling the IBM 3602Lawrence D'Oliveiro
1 Jul 24 i  iii i i  i        i ii iiii  `- Re: base registers, ancient OS history, ARM is sort of channeling the IBM 3601John Levine
30 Jun 24 i  iii i i  i        i ii iii`- Re: ancient OS history, ARM is sort of channeling the IBM 3601MitchAlsup1
30 Jun 24 i  iii i i  i        i ii ii`- Re: ancient OS history, ARM is sort of channeling the IBM 3601MitchAlsup1
30 Jun 24 i  iii i i  i        i ii i`* Re: ancient OS history, ARM is sort of channeling the IBM 36010John Dallman
30 Jun 24 i  iii i i  i        i ii i +- Re: ancient OS history, ARM is sort of channeling the IBM 3601MitchAlsup1
30 Jun 24 i  iii i i  i        i ii i `* Re: ancient OS history, ARM is sort of channeling the IBM 3608Stephen Fuld
30 Jun 24 i  iii i i  i        i ii i  +- Re: small old machines, ancient OS history, ARM is sort of channeling the IBM 3601John Levine
30 Jun 24 i  iii i i  i        i ii i  +* Re: ancient OS history, ARM is sort of channeling the IBM 3604John Dallman
30 Jun 24 i  iii i i  i        i ii i  i+* Re: ancient OS history, ARM is sort of channeling the IBM 3602Stephen Fuld
30 Jun 24 i  iii i i  i        i ii i  ii`- Re: ancient OS history, ARM is sort of channeling the IBM 3601John Dallman
30 Jun 24 i  iii i i  i        i ii i  i`- Re: ancient OS history, ARM is sort of channeling the IBM 3601Lynn Wheeler
30 Jun 24 i  iii i i  i        i ii i  `* Re: ancient OS history, ARM is sort of channeling the IBM 3602MitchAlsup1
1 Jul 24 i  iii i i  i        i ii i   `- Re: ancient OS history, ARM is sort of channeling the IBM 3601moi
30 Jun 24 i  iii i i  i        i ii `- Re: ancient OS history, ARM is sort of channeling the IBM 3601Lynn Wheeler
30 Jun 24 i  iii i i  i        i i`- Re: ancient OS history, ARM is sort of channeling the IBM 3601Stephen Fuld
1 Jul 24 i  iii i i  i        i `* Re: ancient OS history, ARM is sort of channeling the IBM 3605Lawrence D'Oliveiro
2 Jul 24 i  iii i i  i        i  `* Re: ancient OS history, ARM is sort of channeling the IBM 3604John Levine
2 Jul 24 i  iii i i  i        i   `* Re: ancient OS history, ARM is sort of channeling the IBM 3603Lawrence D'Oliveiro
2 Jul 24 i  iii i i  i        i    `* Re: ancient OS history, ARM is sort of channeling the IBM 3602John Levine
2 Jul 24 i  iii i i  i        i     `- Re: ancient OS history, ARM is sort of channeling the IBM 3601Dan Cross
30 Jun 24 i  iii i i  i        `* Re: ancient OS history, ARM is sort of channeling the IBM 36015Anton Ertl
30 Jun 24 i  iii i i  i         `* Re: ancient OS history, ARM is sort of channeling the IBM 36014Anton Ertl
30 Jun 24 i  iii i i  i          `* Re: streams and file locks, ancient OS history, ARM is sort of channeling the IBM 36013John Levine
1 Jul 24 i  iii i i  i           +* Re: streams and file locks, ancient OS history, ARM is sort of channeling the IBM 36010MitchAlsup1
1 Jul 24 i  iii i i  i           i`* Re: streams and file locks, ancient OS history, ARM is sort of channeling9John Levine
1 Jul 24 i  iii i i  i           i `* Re: streams and file locks, ancient OS history, ARM is sort of channeling8MitchAlsup1
1 Jul 24 i  iii i i  i           i  `* Re: streams and file locks, ancient OS history, ARM is sort of channeling7John Levine
1 Jul 24 i  iii i i  i           i   +* Re: streams and file locks, ancient OS history, ARM is sort of channeling2Lawrence D'Oliveiro
1 Jul 24 i  iii i i  i           i   i`- Re: streams and file locks, ancient OS history, ARM is sort of channeling1John Levine
1 Jul 24 i  iii i i  i           i   `* Re: streams and file locks, ancient OS history, ARM is sort of channeling4Michael S
1 Jul 24 i  iii i i  i           i    `* Re: streams and file locks, ancient OS history, ARM is sort of channeling3MitchAlsup1
2 Jul 24 i  iii i i  i           i     +- Re: streams and file locks, ancient OS history, ARM is sort of channeling1Michael S
2 Jul 24 i  iii i i  i           i     `- Re: streams and file locks, ancient OS history, ARM is sort of channeling1Michael S
1 Jul 24 i  iii i i  i           `* Re: streams and file locks, ancient OS history, ARM is sort of channeling the IBM 3602Lawrence D'Oliveiro
1 Jul 24 i  iii i i  i            `- Re: streams and file locks, ancient OS history1John Levine
26 Jun 24 i  iii i i  `* Re: ancient OS history, ARM is sort of channeling the IBM 3604Stephen Fuld
26 Jun 24 i  iii i i   +* Re: ancient OS history, ARM is sort of channeling the IBM 3602John Levine
26 Jun 24 i  iii i i   i`- Re: ancient OS history, ARM is sort of channeling the IBM 3601Stephen Fuld
27 Jun 24 i  iii i i   `- Re: ancient OS history, ARM is sort of channeling the IBM 3601MitchAlsup1
26 Jun 24 i  iii i `* Re: ancient OS history, ARM is sort of channeling the IBM 3607John Levine
26 Jun 24 i  iii i  `* Re: ancient OS history, ARM is sort of channeling the IBM 3606John Levine
27 Jun 24 i  iii i   `* Re: ancient OS history, ARM is sort of channeling the IBM 3605Thomas Koenig
27 Jun 24 i  iii i    `* Re: ancient OS history, ARM is sort of channeling the IBM 3604John Levine
27 Jun 24 i  iii i     +- Re: ancient OS history, ARM is sort of channeling the IBM 3601Thomas Koenig
28 Jun 24 i  iii i     +- Re: ancient OS history, ARM is sort of channeling the IBM 3601Lawrence D'Oliveiro
28 Jun 24 i  iii i     `- Re: ancient OS history, ARM is sort of channeling the IBM 3601Lawrence D'Oliveiro
25 Jun 24 i  iii +* Re: ancient OS history, ARM is sort of channeling the IBM 3606Terje Mathisen
25 Jun 24 i  iii i+* Re: ancient OS history, ARM is sort of channeling the IBM 3602Lawrence D'Oliveiro
25 Jun 24 i  iii ii`- Re: ancient OS history, ARM is sort of channeling the IBM 3601Terje Mathisen
25 Jun 24 i  iii i`* Re: ancient OS history, ARM is sort of channeling the IBM 3603Michael S
26 Jun 24 i  iii i `* Re: ancient OS history, ARM is sort of channeling the IBM 3602Michael S
26 Jun 24 i  iii i  `- Re: ancient OS history, ARM is sort of channeling the IBM 3601Terje Mathisen
25 Jun 24 i  iii `- Re: ancient OS history, ARM is sort of channeling the IBM 3601Lynn Wheeler
24 Jun 24 i  ii`* Re: ancient OS history, ARM is sort of channeling the IBM 3604Terje Mathisen
24 Jun 24 i  ii +* Re: ancient OS history, ARM is sort of channeling the IBM 3602Lawrence D'Oliveiro
24 Jun 24 i  ii i`- Re: ancient OS history, ARM is sort of channeling the IBM 3601Stephen Fuld
24 Jun 24 i  ii `- Re: ancient OS history, ARM is sort of channeling the IBM 3601Thomas Koenig
24 Jun 24 i  i`* Re: ancient OS history, ARM is sort of channeling the IBM 3602Thomas Koenig
24 Jun 24 i  i `- Re: ancient OS history, ARM is sort of channeling the IBM 3601Lawrence D'Oliveiro
24 Jun 24 i  `* Re: ARM is sort of channeling the IBM 3602Stephen Fuld
24 Jun 24 i   `- Re: ARM is sort of channeling the IBM 3601Stephen Fuld
20 Jun 24 +* Re: ARM is channeling the IBM 3602moi
24 Jun 24 i`- Re: ARM is channeling the IBM 3601Lawrence D'Oliveiro
21 Jun 24 `* Re: ARM is channeling the IBM 3604MitchAlsup1
22 Jun 24  `* Re: ARM is channeling the IBM 3603John Dallman
22 Jun 24   +- Re: ARM is channeling the IBM 3601MitchAlsup1
22 Jun 24   `- Re: ARM is channeling the IBM 3601BGB

Haut de la page

Les messages affichés proviennent d'usenet.

NewsPortal