PS3 'Other OS' area data.

laichung · Post by **laichung** » Mon Apr 30, 2007 12:12 pm

From the source of kernel , os-area.c, I know that the "OtherOS" will copy into the memory area. So my question is, does anyone try to dump it from ram? Does it encrypted? Does it refer to the otheros.self?

/**
* struct saved_params - Static working copies of data from the 'Other OS' area.
*
* For the convinience of the guest, the HV makes a copy of the 'Other OS' area
* in flash to a high address in the boot memory region and then puts that RAM
* address and the byte count into the repository for retreval by the guest.
* We copy the data we want into a static variable and allow the memory setup
* by the HV to be claimed by the lmb manager.
*/

jimparis · Post by **jimparis** » Mon Apr 30, 2007 3:51 pm

I believe "OtherOS area" just refers to the 4MB block of flash used to store the kernel and boot parameters (compression, boot flag, etc). You can access it directly as a block device. It's typically /dev/sdb if I recall correctly; the find-other-os-flash script in the ps3pf_utils package will locate it.

laichung · Post by **laichung** » Mon Apr 30, 2007 5:13 pm

Oh, yes. After read your post I do some research. That "other os area" should refer to the kboot (which is otheros.bld). Thanks~

jimparis wrote:I believe "OtherOS area" just refers to the 4MB block of flash used to store the kernel and boot parameters (compression, boot flag, etc). You can access it directly as a block device. It's typically /dev/sdb if I recall correctly; the find-other-os-flash script in the ps3pf_utils package will locate it.

urchin · Post by **urchin** » Mon Apr 30, 2007 5:14 pm

Yeah, kboot iterates devices /dev/sd[a-z] looking for the string "cell_ext_os_area" at the start of each. It's /dev/sdb on mine too.

ralferoo · Post by **ralferoo** » Mon Apr 30, 2007 6:36 pm

Also, not all of it is read/write - some is read only, or at least changes aren't persisted directly to flash.

The very start of the area contains various system configuration options - screen mode, OS selection flag, etc and whilst some of this does seem to get stored (e.g. preferred otherOS screen mode) other values such as whether O or X is used for the select button don't survive a reboot, much less affect the Sony OS.

IIRC, the data from sector 4 onwards is the boot zImage (could be kboot, but no real reason) and is persisted to flash. It's also a strange length, not close to a power of 2 (just over 4Mb).