hw debug API: aarch64 sw break, single step tests

Ported software breakpoint test to aarch64 and moved single
stepping test from x86-only to arch-independent.

Signed-off-by: Alwin Joshy <[email protected]>

apps/sel4test-tests/arch/arm/arch/debug.h

@@ -5,12 +5,21 @@
  */
 #pragma once
 
+#ifdef CONFIG_ARCH_AARCH32
 #define TEST_SOFTWARE_BREAK_ASM() \
     asm volatile( \
         ".global sbreak, post_sbreak\n\t" \
         ".type post_sbreak, function\n\t" \
         "sbreak:\n\t" \
         "bkpt\n\t")
+#else
+#define TEST_SOFTWARE_BREAK_ASM() \
+    asm volatile( \
+        ".global sbreak, post_sbreak\n\t" \
+        ".type post_sbreak, function\n\t" \
+        "sbreak:\n\t" \
+        "brk #0\n\t")
+#endif
 
 /* Tell C about the symbols exported by the ASM above. */
 extern char sbreak;

apps/sel4test-tests/src/tests/breakpoints.c

@@ -449,6 +449,8 @@ DEFINE_TEST(BREAKPOINT_007, "Attempt to pass various invalid values to the "
             "invocations, and expect error return values.",
             test_debug_api_setbp_invalid_values, config_set(CONFIG_HARDWARE_DEBUG_API))
 
+/* Test software breakpoints */
+
 static int
 test_debug_api_software_break_request(struct env *env)
 {
@@ -482,4 +484,158 @@ DEFINE_TEST(BREAK_REQUEST_001, "Use an INT3/BKPT instruction to trigger a "
             "listening handler.",
             test_debug_api_software_break_request, config_set(CONFIG_HARDWARE_DEBUG_API))
 
+
+/* Test single stepping */
+
+static volatile int counter;
+
+NO_INLINE static void stop_point(void)
+{
+    /* Counter is volatile so the compiler cannot optimize this away */
+    counter = counter;
+}
+
+NO_INLINE static void single_step_guinea_pig(void)
+{
+    for (; counter < SINGLESTEP_TEST_MAX_LOOP_ITERATIONS; counter++) {
+        /* This syscall is inserted here to ensure that syscalls are being
+         * stepped over successfully on x86.
+         */
+        seL4_Yield();
+    }
+    stop_point();
+}
+
+int debugger_main(seL4_Word a0, seL4_Word reply, seL4_Word a2, seL4_Word a3)
+{
+    seL4_CPtr debuggee_tcb_cap = a0;
+    seL4_Word badge;
+    seL4_MessageInfo_t tag;
+    seL4_TCB_ConfigureSingleStepping_t result;
+
+    /* The main thread sets a breakpoint in the debuggee thread, and this thread
+     * will get a fault on the fault EP. At that point we can enable
+     * single-stepping on the debuggee thread.
+     */
+    tag = api_wait(fault_ep_cspath.capPtr, &badge);
+
+    if (seL4_MessageInfo_get_label(tag) != seL4_Fault_DebugException) {
+        ZF_LOGE("debugger: Got unexpected fault %zd.\n",
+                seL4_MessageInfo_get_label(tag));
+        return -1;
+    }
+
+    fault_data.vaddr = seL4_GetMR(seL4_DebugException_FaultIP);
+    fault_data.reason = seL4_GetMR(seL4_DebugException_ExceptionReason);
+    fault_data.bp_num = seL4_GetMR(seL4_DebugException_BreakpointNumber);
+    if (fault_data.reason != seL4_InstructionBreakpoint
+        || fault_data.vaddr != (seL4_Word)&single_step_guinea_pig) {
+        ZF_LOGE("debugger: debug exception not triggered by expected conditions.\n");
+        return -1;
+    }
+
+    /* So now we can set the single stepping going. */
+    ZF_LOGV("debugger: Instruction BP triggered: beginning single-stepping.\n");
+    seL4_TCB_UnsetBreakpoint(debuggee_tcb_cap, TEST_FIRST_INSTR_BP);
+    result = seL4_TCB_ConfigureSingleStepping(debuggee_tcb_cap, TEST_FIRST_INSTR_BP + 1, 1);
+
+    test_eq((int)result.bp_was_consumed, SINGLESTEP_EXPECTED_BP_CONSUMPTION_VALUE);
+    test_eq(result.error, seL4_NoError);
+
+    /* Resume() the debuggee thread, and keep stepping until it reaches the
+     * stop point (when it calls stop_point()).
+     *
+     * Set the counter to 0. The debuggee thread will be incrementing this.
+     * We will check its value afterward to verify that the debuggee ran as
+     * expected.
+     */
+    counter = 0;
+    seL4_TCB_Resume(debuggee_tcb_cap);
+
+    for (;;) {
+        tag = api_recv(fault_ep_cspath.capPtr, &badge, reply);
+
+        if (seL4_MessageInfo_get_label(tag) != seL4_Fault_DebugException) {
+            ZF_LOGE("Debugger: while single stepping, got unexpected fault.\n");
+            return -1;
+        }
+
+        fault_data.vaddr = seL4_GetMR(seL4_DebugException_FaultIP);
+        fault_data.reason = seL4_GetMR(seL4_DebugException_ExceptionReason);
+        fault_data.bp_num = seL4_GetMR(seL4_DebugException_TriggerAddress);
+        if (fault_data.reason != seL4_SingleStep) {
+            ZF_LOGE("Debugger: while single stepping, got debug exception, but "
+                    "for the wrong reason (reason %zd).\n",
+                    fault_data.reason);
+            return -1;
+        }
+
+        if (fault_data.vaddr == (seL4_Word)&stop_point) {
+            /* We're done: disable single-stepping */
+            ZF_LOGV("About to disable stepping and resume debuggee.\n");
+            tag = seL4_MessageInfo_set_label(tag, 0);
+            seL4_SetMR(0, 0);
+            api_reply(reply, tag);
+            break;
+        }
+
+        tag = seL4_MessageInfo_set_label(tag, 0);
+        seL4_SetMR(0, 1);
+        api_reply(reply, tag);
+    }
+
+    if (fault_data.vaddr != (seL4_Word)&stop_point) {
+        ZF_LOGE("Exited loop, but the debuggee thread did not get where we "
+                "expected it to.\n");
+        return -1;
+    }
+
+    /* Test the value of "counter", which the debuggee thread was incrementing. */
+    if (counter <= 0 || counter != SINGLESTEP_TEST_MAX_LOOP_ITERATIONS) {
+        return -1;
+    }
+
+    return 0;
+}
+
+int debuggee_main(seL4_Word a0, seL4_Word a1, seL4_Word a2, seL4_Word a3)
+{
+    ZF_LOGV("Debuggee: about to execute guinea_pig.\n");
+    single_step_guinea_pig();
+    return 0;
+}
+
+static int test_debug_api_single_step(struct env *env)
+{
+    helper_thread_t debugger, debuggee;
+    int error;
+
+    test_eq(setup_caps_for_test(env), 0);
+
+    create_helper_thread(env, &debugger);
+    set_helper_priority(env, &debugger, BREAKPOINT_TEST_HANDLER_PRIO);
+
+    error = setup_faulter_thread_for_test(env, &debuggee);
+    test_eq(error, seL4_NoError);
+    error = seL4_TCB_SetBreakpoint(get_helper_tcb(&debuggee),
+                                   TEST_FIRST_INSTR_BP, (seL4_Word)&single_step_guinea_pig,
+                                   seL4_InstructionBreakpoint, 0, seL4_BreakOnRead);
+    test_eq(error, seL4_NoError);
+
+    start_helper(env, &debugger, &debugger_main,
+                 get_helper_tcb(&debuggee),
+                 get_helper_reply(&debuggee), 0, 0);
+    start_helper(env, &debuggee, &debuggee_main, 0, 0, 0, 0);
+
+    wait_for_helper(&debugger);
+    wait_for_helper(&debuggee);
+
+    cleanup_helper(env, &debuggee);
+    cleanup_helper(env, &debugger);
+    return sel4test_get_result();
+}
+DEFINE_TEST(SINGLESTEP_001, "Attempt to step through a function",
+            test_debug_api_single_step, config_set(CONFIG_HARDWARE_DEBUG_API));
+
+
 #endif /* CONFIG_HARDWARE_DEBUG_API */