[RFC PATCH v1 3/6] tee: optee: teach the memory type check about RISC-V page attributes

[marouene . boubakri]

From: Marouene Boubakri <marouene.boubakri@xxxxxxxxxxx>

optee_check_mem_type() only lets normal cacheable memory be registered
with secure world since OP-TEE maps registered pages as such and must
not observe mismatched memory attributes.

On RISC-V the memory type of a mapping is encoded in the Svpbmt bits of
the PTE (or their T-Head equivalent selected at runtime by the
_PAGE_MTMASK alternative): normal cacheable memory (PMA) has them
cleared, pgprot_writecombine() and pgprot_noncached() set them. Without
Svpbmt the memory type is defined by the PMAs alone, _PAGE_MTMASK is
empty and every mapping passes the check, as there is nothing else to
inspect.

Signed-off-by: Marouene Boubakri <marouene.boubakri@xxxxxxxxxxx>
---
 drivers/tee/optee/call.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
index e046aff61..c29bff224 100644
--- a/drivers/tee/optee/call.c
+++ b/drivers/tee/optee/call.c
@@ -604,6 +604,14 @@ static bool is_normal_memory(pgprot_t p)
 #elif defined(CONFIG_ARM64)
 	return ((pgprot_val(p) & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL)) ||
 	       ((pgprot_val(p) & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED));
+#elif defined(CONFIG_RISCV)
+	/*
+	 * Svpbmt, or the T-Head equivalent, encodes non-cacheable and I/O
+	 * memory in the memory type bits of the PTE, normal cacheable memory
+	 * (PMA) has them cleared. Without Svpbmt the memory type only comes
+	 * from the PMAs, the mask is empty and all mappings pass the check.
+	 */
+	return !(pgprot_val(p) & _PAGE_MTMASK);
 #else
 #error "Unsupported architecture"
 #endif
-- 
2.43.0