Enable SCR_EL3.SIF bit
This patch enables the SCR_EL3.SIF (Secure Instruction Fetch) bit in BL1 and
BL31 common architectural setup code. When in secure state, this disables
instruction fetches from Non-secure memory.
NOTE: THIS COULD BREAK PLATFORMS THAT HAVE SECURE WORLD CODE EXECUTING FROM
NON-SECURE MEMORY, BUT THIS IS CONSIDERED UNLIKELY AND IS A SERIOUS SECURITY
RISK.
Fixes ARM-Software/tf-issues#372
Change-Id: I684e84b8d523c3b246e9a5fabfa085b6405df319
diff --git a/docs/firmware-design.md b/docs/firmware-design.md
index fe3c3f0..87bdb88 100644
--- a/docs/firmware-design.md
+++ b/docs/firmware-design.md
@@ -176,7 +176,9 @@
- `SCR_EL3`. The register width of the next lower exception level is set
to AArch64 by setting the `SCR.RW` bit. The `SCR.EA` bit is set to trap
- both External Aborts and SError Interrupts in EL3.
+ both External Aborts and SError Interrupts in EL3. The `SCR.SIF` bit is
+ also set to disable instruction fetches from Non-secure memory when in
+ secure state.
- `CPTR_EL3`. Accesses to the `CPACR_EL1` register from EL1 or EL2, or the
`CPTR_EL2` register from EL2 are configured to not trap to EL3 by
diff --git a/include/common/el3_common_macros.S b/include/common/el3_common_macros.S
index ba80d95..9b22a73 100644
--- a/include/common/el3_common_macros.S
+++ b/include/common/el3_common_macros.S
@@ -70,11 +70,12 @@
isb
/* ---------------------------------------------------------------------
- * Early set RES1 bits in SCR_EL3. Set EA bit as well to catch both
- * External Aborts and SError Interrupts in EL3.
+ * Early set RES1 bits in SCR_EL3. Set EA bit to catch both
+ * External Aborts and SError Interrupts in EL3 and also the SIF bit
+ * to disable instruction fetches from Non-secure memory.
* ---------------------------------------------------------------------
*/
- mov x0, #(SCR_RES1_BITS | SCR_EA_BIT)
+ mov x0, #(SCR_RES1_BITS | SCR_EA_BIT | SCR_SIF_BIT)
msr scr_el3, x0
/* ---------------------------------------------------------------------
* Enable External Aborts and SError Interrupts now that the exception
