linux-kernel - [PATCH] optee: extend normal memory check to also write-through

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Message-Id: <20201202071057.4877-1-andrey.zhizhikin@leica-geosystems.com>
Date:   Wed,  2 Dec 2020 07:10:57 +0000
From:   Andrey Zhizhikin <andrey.zhizhikin@...ca-geosystems.com>
To:     jens.wiklander@...aro.org, op-tee@...ts.trustedfirmware.org,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org
Subject: [PATCH] optee: extend normal memory check to also write-through

ARMv7 Architecture Reference Manual [1] section A3.5.5 details Normal
memory type, together with cacheability attributes that could be applied
to memory regions defined as "Normal memory".

Section B2.1.2 of the Architecture Reference Manual [1] also provides
details regarding the Memory attributes that could be assigned to
particular memory regions, which includes the descrption of cacheability
attributes and cache allocation hints.

Memory type and cacheability attributes forms 2 separate definitions,
where cacheability attributes defines a mechanism of coherency control
rather than the type of memory itself.

In other words: Normal memory type can be configured with several
combination of cacheability attributes, namely:
- Write-Through (WT)
- Write-Back (WB) followed by cache allocation hint:
  - Write-Allocate
  - No Write-Allocate (also known as Read-Allocate)

Those types are mapped in the kernel to corresponding macros:
- Write-Through: L_PTE_MT_WRITETHROUGH
- Write-Back Write-Allocate: L_PTE_MT_WRITEALLOC
- Write-Back Read-Allocate: L_PTE_MT_WRITEBACK

Current implementation of the op-tee driver takes in account only 2 last
memory region types, while performing a check if the memory block is
allocated as "Normal memory", leaving Write-Through allocations to be
not considered.

Extend verification mechanism to include also Normal memory regios,
which are designated with Write-Through cacheability attributes.

Link: [1]: https://developer.arm.com/documentation/ddi0406/cd
Fixes: 853735e40424 ("optee: add writeback to valid memory type")
Cc: stable@...r.kernel.org
Signed-off-by: Andrey Zhizhikin <andrey.zhizhikin@...ca-geosystems.com>
---
 drivers/tee/optee/call.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
index c981757ba0d4..8da27d02a2d6 100644
--- a/drivers/tee/optee/call.c
+++ b/drivers/tee/optee/call.c
@@ -535,7 +535,8 @@ static bool is_normal_memory(pgprot_t p)
 {
 #if defined(CONFIG_ARM)
 	return (((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITEALLOC) ||
-		((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITEBACK));
+		((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITEBACK) ||
+		((pgprot_val(p) & L_PTE_MT_MASK) == L_PTE_MT_WRITETHROUGH));
 #elif defined(CONFIG_ARM64)
 	return (pgprot_val(p) & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL);
 #else
-- 
2.17.1