efi_loader: Don't limit the StMM buffer size explicitly

Currently we allow and explicitly check a single shared page with
StandAloneMM.  This is dictated by OP-TEE which runs the application.
However there's no way for us dynamically discover the number of pages we
are allowed to use.  Since writing big EFI signature list variable
requires more than a page, OP-TEE has bumped the number of shared pages to
four.

Let's remove our explicit check and allow the request to reach OP-TEE even
if it's bigger than what it supports.  There's no need to sanitize the
number of pages internally.  OP-TEE will fail if we try to write more
than it's allowed. The error will just trigger later on,  during the
StMM access.

While at it add an error message to help users figure out what failed.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Tested-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Signed-off-by: Ilias Apalodimas <apalos@gmail.com>

diff --git a/include/tee.h b/include/tee.h
index 44e9cd4321bcab2a0b7d2385655943c0651b519c..087810bd12e4215b56085be30f5e6d55ef120591 100644 (file)
--- a/include/tee.h
+++ b/include/tee.h
@@ -39,6 +39,7 @@
 #define TEE_SUCCESS                    0x00000000
 #define TEE_ERROR_STORAGE_NOT_AVAILABLE        0xf0100003
 #define TEE_ERROR_GENERIC              0xffff0000
+#define TEE_ERROR_EXCESS_DATA          0xffff0004
 #define TEE_ERROR_BAD_PARAMETERS       0xffff0006
 #define TEE_ERROR_ITEM_NOT_FOUND       0xffff0008
 #define TEE_ERROR_NOT_IMPLEMENTED      0xffff0009

diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c
index 281f886124af5a778c262a9f970d496c6a51de01..a2c65e369478ff33a8c9f11bd149188c681a7473 100644 (file)
--- a/lib/efi_loader/efi_variable_tee.c
+++ b/lib/efi_loader/efi_variable_tee.c
@@ -15,7 +15,6 @@
 #include <malloc.h>
 #include <mm_communication.h>
 
-#define OPTEE_PAGE_SIZE BIT(12)
 extern struct efi_var_file __efi_runtime_data *efi_var_buf;
 static efi_uintn_t max_buffer_size;    /* comm + var + func + data */
 static efi_uintn_t max_payload_size;   /* func + data */
@@ -114,7 +113,11 @@ static efi_status_t optee_mm_communicate(void *comm_buf, ulong dsize)
        rc = tee_invoke_func(conn.tee, &arg, 2, param);
        tee_shm_free(shm);
        tee_close_session(conn.tee, conn.session);
-       if (rc || arg.ret != TEE_SUCCESS)
+       if (rc)
+               return EFI_DEVICE_ERROR;
+       if (arg.ret == TEE_ERROR_EXCESS_DATA)
+               log_err("Variable payload too large\n");
+       if (arg.ret != TEE_SUCCESS)
                return EFI_DEVICE_ERROR;
 
        switch (param[1].u.value.a) {
@@ -255,15 +258,6 @@ efi_status_t EFIAPI get_max_payload(efi_uintn_t *size)
                goto out;
        }
        *size = var_payload->size;
-       /*
-        * Although the max payload is configurable on StMM, we only share a
-        * single page from OP-TEE for the non-secure buffer used to communicate
-        * with StMM. Since OP-TEE will reject to map anything bigger than that,
-        * make sure we are in bounds.
-        */
-       if (*size > OPTEE_PAGE_SIZE)
-               *size = OPTEE_PAGE_SIZE - MM_COMMUNICATE_HEADER_SIZE  -
-                       MM_VARIABLE_COMMUNICATE_SIZE;
        /*
         * There seems to be a bug in EDK2 miscalculating the boundaries and
         * size checks, so deduct 2 more bytes to fulfill this requirement. Fix