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Extending the use of RO and NX

Extending the use of RO and NX

Posted Jan 13, 2011 17:47 UTC (Thu) by nevets (subscriber, #11875)
In reply to: Extending the use of RO and NX by kronos
Parent article: Extending the use of RO and NX

The SMP alternatives are performed during boot up before setting of RO takes effect. As for tracing, there are two ways:

1) (slower) method is to allocate a new page table entry that points to the same page but with write permission and make the modification via this new page table entrty.

2) (ftrace function tracer use) just before calling stop machine, all pages are converted back to RW, then stop machine is called and all changes are made, when stop machine finishes, the pages are put back to RO.


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Extending the use of RO and NX

Posted Jan 13, 2011 22:46 UTC (Thu) by PaXTeam (guest, #24616) [Link]

> The SMP alternatives are performed during boot up before setting of RO takes effect.

they're also performed whenever all but one CPUs are offlined (SMP->UP) or when the second CPU comes online later (UP->SMP). this can be achieved by explicit action for a CPU (via /sys/devices/system/cpu/cpu*/online) or when suspend/reboot/halt occurs.


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