This is achieved by removing the 'no-map' property from the
'reserved-memory' node when PMP is present, otherwise we keep it as it
offers a small protection if the OS does not map this region at all.
A new callback in platform_override is introduced and allows to fixup the
device-tree. It is used here to override this new default behaviour on
SiFive Fu540 platforms that has an erratum that prevents S-mode software
to access a PMP protected region using 1GB page table mapping.
If PMP is present, telling the OS not to map the reserved regions does not
add much protection since it only avoids access to regions that are already
protected by PMP. But by not allowing the OS to map those regions, it
creates holes in the OS system memory map and prevents the use of
hugepages which would generate, among other benefits, less TLB miss.
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
We add generic FDT based platform support which provides platform
specific functionality based on the FDT passed by previous booting
stage.
By default, the generic FDT platform makes following assumptions:
1. platform FW_TEXT_START is 0x80000000
2. platform features are default
3. platform stack size is default
4. platform has no quirks or work-arounds
The above assumptions (except 1) can be overridden by adding special
platform callbacks which will be called based on the FDT root node
compatible string.
By default, we compile OpenSBI generic platform as follows:
$ make PLATFORM=generic
For a non-standard FW_TEXT_START, we can compile OpenSBI generic
platform as follows:
$ make PLATFORM=generic FW_TEXT_START=<non_standard_text_start>
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
