i#7779: Store Aarch64 SVE registers in arrays of dr_simd_t and dr_svp_t. (#7780)

SVE registers (Z0-Z31) and predicate registers (P0-P15) are encapsulated
within arrays of dr_simd_t and dr_sve_t types, respectively.

When the SVE registers are written to the dstack using
insert_save_or_restore_sve_registers(),
create_base_disp_for_save_restore() is used to compute the offset of the
SVE registers, i.e.
```
   case SVE_ZREG_TYPE:
        opsz = opnd_size_from_bytes(proc_get_vector_length_bytes());
        offset = num_saved * proc_get_vector_length_bytes();
        break;
    case SVE_PREG_TYPE:
        opsz = opnd_size_from_bytes(proc_get_vector_length_bytes() / 8);
        offset = num_saved * (proc_get_vector_length_bytes() / 8);
        break;
```
The offset calculation considers the size of the register supported on
the platform based on roc_get_vector_length_bytes(), but not arrays of
dr_simd_t and dr_sve_t. In effect, all the registers are packed together
without considering the size of dr_simd_t and dr_svep_t.

When other functions retrieve the register values based on the arrays,
they get incorrect values (except for z0).

This PR changes the code to use the size of the array element to compute
the offset, so that register values are stored in the corresponding
elements.

Add a test to verify SVE registers are saved and restored properly using
dr_redirect_ececution().

Fixes: #7779

Author: ivankyluk

core/arch/aarchxx/mangle.c

@@ -99,11 +99,17 @@ create_base_disp_for_save_restore(uint base_reg, bool is_single_reg, reg_type_t
         break;
     case SVE_ZREG_TYPE:
         opsz = opnd_size_from_bytes(proc_get_vector_length_bytes());
-        offset = num_saved * proc_get_vector_length_bytes();
+        // SVE registers (Z0-Z31) are mapped to a contiguous array of dr_simd_t.
+        // Each Z-register occupies a distinct element in the array, indexed by its
+        // architectural register number.
+        offset = num_saved * sizeof(dr_simd_t);
         break;
     case SVE_PREG_TYPE:
         opsz = opnd_size_from_bytes(proc_get_vector_length_bytes() / 8);
-        offset = num_saved * (proc_get_vector_length_bytes() / 8);
+        // SVE predicate registers (P0-P15) are mapped to a contiguous array of dr_svep_t.
+        // Each P-register occupies a distinct element in the array, indexed by its
+        // architectural register number.
+        offset = num_saved * sizeof(dr_svep_t);
         break;
     default: ASSERT_NOT_REACHED();
     }

suite/tests/CMakeLists.txt

@@ -525,7 +525,8 @@ set(sve_tests
       client.drbbdup-drwrap-test client.drbbdup-emul-test client.process-id
       client.drreg-test client.low_on_memory client.tls client.drwrap-test
       client.drwrap-drreg-test drstatecmp-fuzz-app client.drutil-test client.stolen-reg
-      client.ldstex client.drsyms-test client.drwrap-test-detach api.dis-a64
+      client.ldstex client.drsyms-test client.drwrap-test-detach
+      client.save-restore-sve-registers api.dis-a64
       api.reenc-a64 api.opnd api.detach api.detach_state api.detach_signal
       api.detach_spawn api.detach_spawn_stress_FLAKY api.detach_spawn_quick_exit
       api.ibl-stress api.ibl-stress-aarch64-far-link_LONG api.static_startstop
@@ -6111,6 +6112,17 @@ if (UNIX)
     torunonly(linux.steal-switch linux.thread linux/thread.c
       "-enable_reset -reset_at_fragment_count 100 -steal_reg_at_reset ${new_reg}" "")
   endif ()
+  if (AARCH64 AND LINUX)
+    if (proc_supports_sve OR proc_supports_sve2)
+      set(client.save-restore-sve-registers_client_source
+        "client-interface/redirect_execution.dll.c")
+      tobuild_ci(client.save-restore-sve-registers common/aarch64_sve.asm "" "" "")
+      set_target_properties(
+        client.save-restore-sve-registers PROPERTIES LINKER_LANGUAGE C)
+      append_link_flags(client.save-restore-sve-registers
+        "-nostartfiles -nodefaultlibs -static")
+    endif()
+  endif()
   tobuild(pthreads.pthreads pthreads/pthreads.c)
   tobuild(pthreads.pthreads_exit pthreads/pthreads_exit.c)
   tobuild(pthreads.ptsig pthreads/ptsig.c)

suite/tests/client-interface/redirect_execution.dll.c

@@ -0,0 +1,77 @@
+/* **********************************************************
+ * Copyright (c) 2026 Google, Inc.  All rights reserved.
+ * **********************************************************/
+
+/*
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * * Neither the name of VMware, Inc. nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL VMWARE, INC. OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ */
+
+#include "dr_api.h"
+#include "client_tools.h"
+
+static bool redirect_execution = false;
+
+static void
+bb_event(void *pc)
+{
+    void *drcontext = dr_get_current_drcontext();
+    dr_mcontext_t mcontext;
+    mcontext.size = sizeof(mcontext);
+    mcontext.flags = DR_MC_ALL;
+    ASSERT(dr_get_mcontext(drcontext, &mcontext) == true);
+    mcontext.pc = dr_app_pc_as_jump_target(dr_get_isa_mode(drcontext), pc);
+    dr_redirect_execution(&mcontext);
+}
+
+static dr_emit_flags_t
+instrument_bb(void *drcontext, void *tag, instrlist_t *bb, bool for_trace,
+              bool translating)
+{
+    instr_t *instr, *next_instr;
+    for (instr = instrlist_first(bb); instr != NULL; instr = next_instr) {
+        next_instr = instr_get_next(instr);
+        if (next_instr == NULL) {
+            return DR_EMIT_DEFAULT;
+        }
+        // Insert a clean call after the two-consecutive NOP sentinel sequence.
+        // The clean call invokes dr_redirect_execution() to restore the saved application
+        // context and resume execution with the original register state.
+        if (instr_is_nop(instr) && instr_is_nop(next_instr)) {
+            dr_insert_clean_call_ex(
+                drcontext, bb, next_instr, (void *)bb_event,
+                DR_CLEANCALL_READS_APP_CONTEXT, 1,
+                OPND_CREATE_INTPTR((ptr_uint_t)instr_get_app_pc(next_instr)));
+        }
+    }
+    return DR_EMIT_DEFAULT;
+}
+
+DR_EXPORT void
+dr_init(client_id_t id)
+{
+    dr_register_bb_event(instrument_bb);
+}