[PATCH v4 6/9] target/arm: Implement FEAT_EPAC

[Richard Henderson <richard.henderson@linaro.org>]

From: Aaron Lindsay <aaron@os.amperecomputing.com>

Signed-off-by: Aaron Lindsay <aaron@os.amperecomputing.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230609172324.982888-5-aaron@os.amperecomputing.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 docs/system/arm/emulation.rst |  1 +
 target/arm/tcg/cpu64.c        |  2 +-
 target/arm/tcg/pauth_helper.c | 16 +++++++++++-----
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/docs/system/arm/emulation.rst b/docs/system/arm/emulation.rst
index 06af20d10f..4866a73ca0 100644
--- a/docs/system/arm/emulation.rst
+++ b/docs/system/arm/emulation.rst
@@ -27,6 +27,7 @@ the following architecture extensions:
 - FEAT_DotProd (Advanced SIMD dot product instructions)
 - FEAT_DoubleFault (Double Fault Extension)
 - FEAT_E0PD (Preventing EL0 access to halves of address maps)
+- FEAT_EPAC (Enhanced pointer authentication)
 - FEAT_ETS (Enhanced Translation Synchronization)
 - FEAT_EVT (Enhanced Virtualization Traps)
 - FEAT_FCMA (Floating-point complex number instructions)
diff --git a/target/arm/tcg/cpu64.c b/target/arm/tcg/cpu64.c
index fec6a4875d..85bf94ee40 100644
--- a/target/arm/tcg/cpu64.c
+++ b/target/arm/tcg/cpu64.c
@@ -758,7 +758,7 @@ void aarch64_max_tcg_initfn(Object *obj)
 
     t = cpu->isar.id_aa64isar1;
     t = FIELD_DP64(t, ID_AA64ISAR1, DPB, 2);      /* FEAT_DPB2 */
-    t = FIELD_DP64(t, ID_AA64ISAR1, APA, PauthFeat_1);
+    t = FIELD_DP64(t, ID_AA64ISAR1, APA, PauthFeat_EPAC);
     t = FIELD_DP64(t, ID_AA64ISAR1, API, 1);
     t = FIELD_DP64(t, ID_AA64ISAR1, JSCVT, 1);    /* FEAT_JSCVT */
     t = FIELD_DP64(t, ID_AA64ISAR1, FCMA, 1);     /* FEAT_FCMA */
diff --git a/target/arm/tcg/pauth_helper.c b/target/arm/tcg/pauth_helper.c
index bb03409ee5..63e1009ea7 100644
--- a/target/arm/tcg/pauth_helper.c
+++ b/target/arm/tcg/pauth_helper.c
@@ -326,8 +326,10 @@ static uint64_t pauth_computepac(CPUARMState *env, uint64_t data,
 static uint64_t pauth_addpac(CPUARMState *env, uint64_t ptr, uint64_t modifier,
                              ARMPACKey *key, bool data)
 {
+    ARMCPU *cpu = env_archcpu(env);
     ARMMMUIdx mmu_idx = arm_stage1_mmu_idx(env);
     ARMVAParameters param = aa64_va_parameters(env, ptr, mmu_idx, data, false);
+    ARMPauthFeature pauth_feature = cpu_isar_feature(pauth_feature, cpu);
     uint64_t pac, ext_ptr, ext, test;
     int bot_bit, top_bit;
 
@@ -351,11 +353,15 @@ static uint64_t pauth_addpac(CPUARMState *env, uint64_t ptr, uint64_t modifier,
      */
     test = sextract64(ptr, bot_bit, top_bit - bot_bit);
     if (test != 0 && test != -1) {
-        /*
-         * Note that our top_bit is one greater than the pseudocode's
-         * version, hence "- 2" here.
-         */
-        pac ^= MAKE_64BIT_MASK(top_bit - 2, 1);
+        if (pauth_feature == PauthFeat_EPAC) {
+            pac = 0;
+        } else {
+            /*
+             * Note that our top_bit is one greater than the pseudocode's
+             * version, hence "- 2" here.
+             */
+            pac ^= MAKE_64BIT_MASK(top_bit - 2, 1);
+        }
     }
 
     /*
-- 
2.34.1