feat(fvp): emulate trapped RNDR
When a platform decides to use FEAT_RNG_TRAP, every RNDR or RNDRSS read
will trap into EL3. The platform can then emulate those instructions, by
either executing the real CPU instructions, potentially conditioning the
results, or use rate-limiting or filtering to protect the hardware
entropy pool. Another possiblitiy would be to use some platform specific
TRNG device to get entropy and returning this.
To demonstrate platform specific usage, add a demo implementation for the
FVP: It will execute the actual CPU instruction and just return the
result. This should serve as reference code to implement platform specific
policies.
We change the definition of read_rndr() and read_rndrrs() to use the
alternative sysreg encoding, so that all assemblers can handle that.
Add documentation about the new platform specific RNG handler function.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Change-Id: Ibce817b3b06ad20129d15531b81402e3cc3e9a9e
diff --git a/include/arch/aarch64/arch.h b/include/arch/aarch64/arch.h
index f63e923..9e13c3d 100644
--- a/include/arch/aarch64/arch.h
+++ b/include/arch/aarch64/arch.h
@@ -1282,6 +1282,12 @@
#define GCR_EL1 S3_0_C1_C0_6
/*******************************************************************************
+ * Armv8.5 - Random Number Generator Registers
+ ******************************************************************************/
+#define RNDR S3_3_C2_C4_0
+#define RNDRRS S3_3_C2_C4_1
+
+/*******************************************************************************
* FEAT_HCX - Extended Hypervisor Configuration Register
******************************************************************************/
#define HCRX_EL2 S3_4_C1_C2_2
diff --git a/include/arch/aarch64/arch_helpers.h b/include/arch/aarch64/arch_helpers.h
index 50a5ad4..fe9b5a5 100644
--- a/include/arch/aarch64/arch_helpers.h
+++ b/include/arch/aarch64/arch_helpers.h
@@ -546,8 +546,8 @@
DEFINE_RENAME_SYSREG_RW_FUNCS(gcr_el1, GCR_EL1)
/* Armv8.5 FEAT_RNG Registers */
-DEFINE_SYSREG_READ_FUNC(rndr)
-DEFINE_SYSREG_READ_FUNC(rndrrs)
+DEFINE_RENAME_SYSREG_READ_FUNC(rndr, RNDR)
+DEFINE_RENAME_SYSREG_READ_FUNC(rndrrs, RNDRRS)
/* FEAT_HCX Register */
DEFINE_RENAME_SYSREG_RW_FUNCS(hcrx_el2, HCRX_EL2)