| Message ID | 20210115114544.1830068-3-qperret@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | fdt: A couple of no-map fixes | expand |
On Sat, Jan 16, 2021 at 1:30 AM Rob Herring <robh@kernel.org> wrote: > > On Fri, 15 Jan 2021 11:45:44 +0000, Quentin Perret wrote: > > From: Nicolas Boichat <drinkcat@chromium.org> > > > > If the device tree is incorrectly configured, and attempts to > > define a "no-map" reserved memory that overlaps with the kernel > > data/code, the kernel would crash quickly after boot, with no > > obvious clue about the nature of the issue. > > > > For example, this would happen if we have the kernel mapped at > > these addresses (from /proc/iomem): > > 40000000-41ffffff : System RAM > > 40080000-40dfffff : Kernel code > > 40e00000-411fffff : reserved > > 41200000-413e0fff : Kernel data > > > > And we declare a no-map shared-dma-pool region at a fixed address > > within that range: > > mem_reserved: mem_region { > > compatible = "shared-dma-pool"; > > reg = <0 0x40000000 0 0x01A00000>; > > no-map; > > }; > > > > To fix this, when removing memory regions at early boot (which is > > what "no-map" regions do), we need to make sure that the memory > > is not already reserved. If we do, __reserved_mem_reserve_reg > > will throw an error: > > [ 0.000000] OF: fdt: Reserved memory: failed to reserve memory > > for node 'mem_region': base 0x0000000040000000, size 26 MiB > > and the code that will try to use the region should also fail, > > later on. > > > > We do not do anything for non-"no-map" regions, as memblock > > explicitly allows reserved regions to overlap, and the commit > > that this fixes removed the check for that precise reason. > > > > [ qperret: fixed conflicts caused by the usage of memblock_mark_nomap ] > > > > Fixes: 094cb98179f19b7 ("of/fdt: memblock_reserve /memreserve/ regions in the case of partial overlap") > > Signed-off-by: Nicolas Boichat <drinkcat@chromium.org> > > Reviewed-by: Stephen Boyd <swboyd@chromium.org> > > Signed-off-by: Quentin Perret <qperret@google.com> > > --- > > drivers/of/fdt.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > Thanks for picking up this old patch Quentin ,-) > Applied, thanks!
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index 427b534d60d2..dcc1dd96911a 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -1146,8 +1146,16 @@ int __init __weak early_init_dt_mark_hotplug_memory_arch(u64 base, u64 size) int __init __weak early_init_dt_reserve_memory_arch(phys_addr_t base, phys_addr_t size, bool nomap) { - if (nomap) + if (nomap) { + /* + * If the memory is already reserved (by another region), we + * should not allow it to be marked nomap. + */ + if (memblock_is_region_reserved(base, size)) + return -EBUSY; + return memblock_mark_nomap(base, size); + } return memblock_reserve(base, size); }