tree 2005a7879167f1a0669b8e7124299ec0aab08316
parent 0d087f17f868587ca01259632ba0bd584b66aae4
author Andrew Jeffery <andrew@aj.id.au> 1521770235 +1030
committer Andrew Jeffery <andrew@aj.id.au> 1522828583 +0000

mboxd_windows: Shrink windows accessing the end of flash

The host may request a window over the end of the flash where the window
size combined with the requested offset exceeds the limit of the flash.
This issue was introduced with the virtual PNOR, as copy_flash() now may
return a size less than requested. This leads to offset requests that
are still block aligned, but the windows may no longer be aligned with
respect to the flash size.

This issue triggers the read error reported from the Petitboot
environment in an earlier commit message:

    / # cat /dev/mtd0 > /dev/null
    [  501.061616288,3] MBOX-FLASH: Bad response code from BMC 2
    [  501.150405995,3] MBOX-FLASH: Error waiting for BMC
    cat: read error: Input/output error
    / # echo $?
    1
    / #

With the corresponding mboxd trace on the BMC:

    [ 1519966031.652036815] Received MBOX command: 4
    [ 1519966031.652272613] Host requested flash @ 0x03f1a000
    [ 1519966031.652411603] Tried to open read window past flash limit
    [ 1519966031.652500088] Couldn't create window mapping for offset 0x03f1a000
    [ 1519966031.652607966] Error handling mbox cmd: 4
    [ 1519966031.652661421] Writing MBOX response: 2
    [ 1519966031.652762229] Error handling MBOX event

Instead, shrink the request such that the resulting window exactly maps
the flash limit, and no further.

Change-Id: Id33ae3b14252eb40240ef1925311f22aceb103b4
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>