Implement static workaround for CVE-2018-3639
For affected CPUs, this approach enables the mitigation during EL3
initialization, following every PE reset. No mechanism is provided to
disable the mitigation at runtime.
This approach permanently mitigates the entire software stack and no
additional mitigation code is required in other software components.
TF-A implements this approach for the following affected CPUs:
* Cortex-A57 and Cortex-A72, by setting bit 55 (Disable load pass store) of
`CPUACTLR_EL1` (`S3_1_C15_C2_0`).
* Cortex-A73, by setting bit 3 of `S3_0_C15_C0_0` (not documented in the
Technical Reference Manual (TRM)).
* Cortex-A75, by setting bit 35 (reserved in TRM) of `CPUACTLR_EL1`
(`S3_0_C15_C1_0`).
Additionally, a new SMC interface is implemented to allow software
executing in lower ELs to discover whether the system is mitigated
against CVE-2018-3639.
Refer to "Firmware interfaces for mitigating cache speculation
vulnerabilities System Software on Arm Systems"[0] for more
information.
[0] https://developer.arm.com/cache-speculation-vulnerability-firmware-specification
Change-Id: I084aa7c3bc7c26bf2df2248301270f77bed22ceb
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
diff --git a/lib/cpus/aarch64/cortex_a75.S b/lib/cpus/aarch64/cortex_a75.S
index f92e4ed..9cc2c01 100644
--- a/lib/cpus/aarch64/cortex_a75.S
+++ b/lib/cpus/aarch64/cortex_a75.S
@@ -18,6 +18,13 @@
1:
#endif
+#if WORKAROUND_CVE_2018_3639
+ mrs x0, CORTEX_A75_CPUACTLR_EL1
+ orr x0, x0, #CORTEX_A75_CPUACTLR_EL1_DISABLE_LOAD_PASS_STORE
+ msr CORTEX_A75_CPUACTLR_EL1, x0
+ isb
+#endif
+
#if ENABLE_AMU
/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
mrs x0, actlr_el3
@@ -57,6 +64,15 @@
ret
endfunc check_errata_cve_2017_5715
+func check_errata_cve_2018_3639
+#if WORKAROUND_CVE_2018_3639
+ mov x0, #ERRATA_APPLIES
+#else
+ mov x0, #ERRATA_MISSING
+#endif
+ ret
+endfunc check_errata_cve_2018_3639
+
/* ---------------------------------------------
* HW will do the cache maintenance while powering down
* ---------------------------------------------
@@ -88,6 +104,7 @@
* checking functions of each errata.
*/
report_errata WORKAROUND_CVE_2017_5715, cortex_a75, cve_2017_5715
+ report_errata WORKAROUND_CVE_2018_3639, cortex_a75, cve_2018_3639
ldp x8, x30, [sp], #16
ret