Re: lug-bg: cpuinfo

[sheib@email.domain.hidden (sheib)]

hi,

<em class="quotelev1">> Az imam edin drug vypros malko v strani: Kak se detect-va (ili se znae
<em class="quotelev1">> predvaritelno za vseki cpu type) kolko rings na privileges za code execution
<em class="quotelev1">> ima cpu-to i kak Linux kernel-a upravlqva cpu-to da execute-va (izteglq ot
<em class="quotelev1">> pametta i execute-va s opredelqni privileges) code na edin ili drug ring.
<em class="quotelev1">> (kyde se gleda tova v source-a na kernel-a, qvno ste e nqkyde iz asm's ama
<em class="quotelev1">> vinagi kogato sym se opitval da go razbera maj go podminavam ;-). 4uval sym
<em class="quotelev1">> 4e za x86 cpu's obiknoveno za 4 rings ot kojto kernel-a polzva 2 , e.g. 0 -
<em class="quotelev1">> kernel code i 3 - user code ? Solaris i OS/2 maj polzvat i 4-te ring-a na
<em class="quotelev1">> code execution privileges na x86 ili ne vinagi e taka ?

dokolkoto znam tezi rings se narichat 'privilege/protection levels' i
pri x86 alike cpu-ta sa naistina 4. spored definiciite na intel, level
0 se polzva ot kernela na os-a, 1 i 2 sa za device drivers/modules,
a 3 - userland apps. drugo - ne vsichki os-i gi polzvat - naprimer win 9x
i dos se vodiat za real mode os i gi usevat samo chastichno, dokato
unix/linux si rabotiat po design v protected mode. pri solaris x86
se polzvat priv.rings otnovo; za sparc/usparc ne sym mnogo naiasno, no e
mnogo veroiatno da se polzva similar tech. pri linux, userland apps
ne mogat direktno da accessvat memory prez cpu-to, a poluchavat/ne
poluchavat priviliges by kernel capabilities.

tova e utterly polezen faq ;)

http://www.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.4/capfaq-0.2.txt

+arch/i386/kernel/setup.c
+arch/i386/kernel/ioport.c

/s

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