refactor(cpufeat): convert FEAT_PAuth setup to C
An oversimplified view of FEAT_PAuth is that it's a symmetric encryption
of the LR. PAC instructions execute as NOPs until explicitly turned on.
So in a function that turns PAuth on, the signing would have executed as
a NOP and the authentication will encrypt the address, leading to a
failure. That's why enablement is in assembly - we have full control of
when pointer authentications happen.
However, assembly is hard to read, is opaque to the compiler for
optimisations, and we need to call into C anyway for the platform hook
to get the key. So convert it to C. We can instruct the compiler to not
generate branch protection for the enable function only and as long as
the caller doesn't do branch protection (and all callers are entrypoints
written in assembly) everything will work.
Change-Id: I8917a26e1293033c910e3058664e3ca9207359b7
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
diff --git a/lib/el3_runtime/aarch64/context_mgmt.c b/lib/el3_runtime/aarch64/context_mgmt.c
index c155329..0cfabb3 100644
--- a/lib/el3_runtime/aarch64/context_mgmt.c
+++ b/lib/el3_runtime/aarch64/context_mgmt.c
@@ -30,6 +30,7 @@
#include <lib/extensions/fgt2.h>
#include <lib/extensions/fpmr.h>
#include <lib/extensions/mpam.h>
+#include <lib/extensions/pauth.h>
#include <lib/extensions/pmuv3.h>
#include <lib/extensions/sme.h>
#include <lib/extensions/spe.h>
@@ -844,20 +845,6 @@
#endif /* IMAGE_BL31 */
}
-/* TODO: move to lib/extensions/pauth when it has been ported to FEAT_STATE */
-static __unused void enable_pauth_el2(void)
-{
- u_register_t hcr_el2 = read_hcr_el2();
- /*
- * For Armv8.3 pointer authentication feature, disable traps to EL2 when
- * accessing key registers or using pointer authentication instructions
- * from lower ELs.
- */
- hcr_el2 |= (HCR_API_BIT | HCR_APK_BIT);
-
- write_hcr_el2(hcr_el2);
-}
-
#if INIT_UNUSED_NS_EL2
/*******************************************************************************
* Enable architecture extensions in-place at EL2 on first entry to Non-secure
@@ -904,9 +891,9 @@
write_hcrx_el2(read_hcrx_el2() | HCRX_EL2_MSCEn_BIT);
}
-#if ENABLE_PAUTH
- enable_pauth_el2();
-#endif /* ENABLE_PAUTH */
+ if (is_feat_pauth_supported()) {
+ pauth_enable_el2();
+ }
#endif /* IMAGE_BL31 */
}
#endif /* INIT_UNUSED_NS_EL2 */