Re: [PATCH] of: Fix comparison of reserved memory regions

On Wed, Nov 18 2015 at 09:46:38 PM, Michael Ellerman [off-list ref] wrote:

In order to check for overlapping reserved memory regions, we first need
to sort the array of memory regions. This is implemented using sort(),
and a custom comparison function __rmem_cmp().

Unfortunatley __rmem_cmp() doesn't work in all cases. Because the two
base values are phys_addr_t, they may be u64 on some platforms, in which
case subtracting one from the other and then (implicitly) casting to int
does not give us the -ve/0/+ve value we need.

This leads to incorrect reports about overlaps, eg:

  ibm,slw-image@1ffe600000 (0x0000001ffe600000--0x0000001ffe700000) overlaps with
  ibm,firmware-allocs-memory@1000000000 (0x0000001000000000--0x0000001000dc0200)

Fix it by just doing the standard double if and return 0 logic.

Fixes: ae1add247bf8 ("of: Check for overlap in reserved memory regions")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 drivers/of/of_reserved_mem.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Woops, thanks.

Tested-by: Mitchel Humpherys <redacted>

-Mitch

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