path: root/bl31
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authorHarry Liebel <Harry.Liebel@arm.com>2014-01-14 18:11:48 +0000
committerDan Handley <dan.handley@arm.com>2014-01-17 10:27:53 +0000
commit4f6036834fb7f53e3002c37af1c9d0681e8ef675 (patch)
treeaf1bdd052679342b63b7b7a0d44cb51d34dc1e19 /bl31
parente83b0cadc67882c1ba7f430d16dab80c9b3a0228 (diff)
Do not trap access to floating point registers
Traps when accessing architectural features are disabled by clearing bits in CPTR_EL3 during early boot, including accesses to floating point registers. The value of this register was previously undetermined, causing unwanted traps to EL3. Future EL3 code (for example, context save/restore code) may use floating point registers, although they are not used by current code. Also, the '-mgeneral-regs-only' flag is enabled in the GCC settings to prevent generation of code that uses floating point registers. Change-Id: I9a03675f6387bbbee81a6f2c9ccf81150db03747
Diffstat (limited to 'bl31')
2 files changed, 23 insertions, 3 deletions
diff --git a/bl31/aarch64/bl31_arch_setup.c b/bl31/aarch64/bl31_arch_setup.c
index 0079f0f..492c45b 100644
--- a/bl31/aarch64/bl31_arch_setup.c
+++ b/bl31/aarch64/bl31_arch_setup.c
@@ -62,9 +62,6 @@ void bl31_arch_setup(void)
- /* Do not trap coprocessor accesses from lower ELs to EL3 */
- write_cptr_el3(0);
/* Read the frequency from Frequency modes table */
counter_base_frequency = mmio_read_32(SYS_CNTCTL_BASE + CNTFID_OFF);
/* The first entry of the frequency modes table must not be 0 */
diff --git a/bl31/aarch64/bl31_entrypoint.S b/bl31/aarch64/bl31_entrypoint.S
index 62d44e2..cbbae7b 100644
--- a/bl31/aarch64/bl31_entrypoint.S
+++ b/bl31/aarch64/bl31_entrypoint.S
@@ -61,6 +61,29 @@ bl31_entrypoint:; .type bl31_entrypoint, %function
adr x1, runtime_exceptions
msr vbar_el3, x1
+ /* ---------------------------------------------------------------------
+ * The initial state of the Architectural feature trap register
+ * (CPTR_EL3) is unknown and it must be set to a known state. All
+ * feature traps are disabled. Some bits in this register are marked as
+ * Reserved and should not be modified.
+ *
+ * CPTR_EL3.TCPAC: This causes a direct access to the CPACR_EL1 from EL1
+ * or the CPTR_EL2 from EL2 to trap to EL3 unless it is trapped at EL2.
+ * CPTR_EL3.TTA: This causes access to the Trace functionality to trap
+ * to EL3 when executed from EL0, EL1, EL2, or EL3. If system register
+ * access to trace functionality is not supported, this bit is RES0.
+ * CPTR_EL3.TFP: This causes instructions that access the registers
+ * associated with Floating Point and Advanced SIMD execution to trap
+ * to EL3 when executed from any exception level, unless trapped to EL1
+ * or EL2.
+ * ---------------------------------------------------------------------
+ */
+ mrs x1, cptr_el3
+ bic w1, w1, #TCPAC_BIT
+ bic w1, w1, #TTA_BIT
+ bic w1, w1, #TFP_BIT
+ msr cptr_el3, x1
/* ---------------------------------------------
* Enable the instruction cache.
* ---------------------------------------------