CPU: Handle breakpoint trap

Also, start working on the debugger app.

Applications/Debugger/Makefile

@@ -0,0 +1,8 @@
+OBJS = \
+    main.o
+
+PROGRAM = Debugger
+
+LIB_DEPS = Core
+
+include ../../Makefile.common

Applications/Debugger/main.cpp

@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. 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.
+ *
+ * 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 THE COPYRIGHT HOLDER 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 <AK/Assertions.h>
+#include <LibC/sys/arch/i386/regs.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static int usage()
+{
+    printf("usage: sdb [command...]\n");
+    return 1;
+}
+
+static int g_pid = -1;
+
+static void handle_sigint(int)
+{
+    if (g_pid == -1)
+        return;
+
+    if (ptrace(PT_DETACH, g_pid, 0, 0) == -1) {
+        perror("detach");
+    }
+}
+
+void run_child_and_attach(char** argv)
+{
+    int pid = fork();
+
+    if (!pid) {
+        if (ptrace(PT_TRACE_ME, 0, 0, 0) == -1) {
+            perror("traceme");
+            return exit(1);
+        }
+
+        int rc = execvp(argv[1], &argv[1]);
+        if (rc < 0) {
+            perror("execvp");
+            exit(1);
+        }
+        ASSERT_NOT_REACHED();
+    }
+
+    if (waitpid(pid, nullptr, WSTOPPED) != pid) {
+        perror("waitpid");
+        exit(1);
+    }
+    g_pid = pid;
+}
+
+int main(int argc, char** argv)
+{
+    if (argc == 1)
+        return usage();
+
+    run_child_and_attach(argv);
+
+    struct sigaction sa;
+    memset(&sa, 0, sizeof(struct sigaction));
+    sa.sa_handler = handle_sigint;
+    sigaction(SIGINT, &sa, nullptr);
+
+    if (ptrace(PT_ATTACH, g_pid, 0, 0) == -1) {
+        perror("attach");
+        return 1;
+    }
+    if (waitpid(g_pid, nullptr, WSTOPPED) != g_pid) {
+        perror("waitpid");
+        return 1;
+    }
+
+    if (ptrace(PT_CONTINUE, g_pid, 0, 0) == -1) {
+        perror("continue");
+    }
+
+    // wait for breakpoint
+    if (waitpid(g_pid, nullptr, WSTOPPED) != g_pid) {
+        perror("waitpid");
+        return 1;
+    }
+
+    printf("hit breakpoint\n");
+
+    sleep(1);
+
+    if (ptrace(PT_CONTINUE, g_pid, 0, 0) == -1) {
+        perror("continue");
+    }
+
+    if (waitpid(g_pid, nullptr, WSTOPPED) != g_pid) {
+        perror("waitpid");
+        return 1;
+    }
+}

Demos/Debugee/Makefile

@@ -0,0 +1,8 @@
+OBJS = \
+    main.o
+
+PROGRAM = Debugee
+
+# LIB_DEPS = Core
+
+include ../../Makefile.common

Demos/Debugee/main.cpp

@@ -0,0 +1,8 @@
+#include <cstdio>
+int main(int, char**)
+{
+    printf("before breakpoint\n");
+    asm("int3");
+    printf("after breakpoint\n");
+    return 0;
+}

Kernel/Arch/i386/CPU.cpp

@@ -297,6 +297,21 @@ void page_fault_handler(RegisterState regs)
     }
 }
 
+EH_ENTRY_NO_CODE(3, breakpoint);
+void breakpoint_handler(RegisterState regs)
+{
+    clac();
+    if (!Process::current || Process::current->is_ring0()) {
+        klog() << "Breakpoint Trap in Ring0";
+        hang();
+        return;
+    }
+    if (Thread::current->tracer()) {
+        Thread::current->tracer()->set_regs(regs);
+    }
+    Thread::current->send_urgent_signal_to_self(SIGTRAP);
+}
+
 #define EH(i, msg)                                                                                                                                                             \
     static void _exception##i()                                                                                                                                                \
     {                                                                                                                                                                          \
@@ -316,7 +331,6 @@ void page_fault_handler(RegisterState regs)
 
 EH(1, "Debug exception")
 EH(2, "Unknown error")
-EH(3, "Breakpoint")
 EH(4, "Overflow")
 EH(5, "Bounds check")
 EH(8, "Double fault")
@@ -486,7 +500,7 @@ void idt_init()
     register_interrupt_handler(0x00, divide_error_asm_entry);
     register_interrupt_handler(0x01, _exception1);
     register_interrupt_handler(0x02, _exception2);
-    register_interrupt_handler(0x03, _exception3);
+    register_user_callable_interrupt_handler(0x03, breakpoint_asm_entry);
     register_interrupt_handler(0x04, _exception4);
     register_interrupt_handler(0x05, _exception5);
     register_interrupt_handler(0x06, illegal_instruction_asm_entry);

Kernel/Thread.h

@@ -36,6 +36,7 @@
 #include <Kernel/Forward.h>
 #include <Kernel/KResult.h>
 #include <Kernel/Scheduler.h>
+#include <Kernel/ThreadTracer.h>
 #include <Kernel/UnixTypes.h>
 #include <LibC/fd_set.h>
 

Kernel/ThreadTracer.cpp

@@ -25,6 +25,7 @@
  */
 
 #include <AK/Memory.h>
+#include <AK/kmalloc.h>
 #include <Kernel/ThreadTracer.h>
 
 namespace Kernel {

Kernel/ThreadTracer.h

@@ -26,11 +26,8 @@
 
 #pragma once
 
-#include <AK/CircularDeque.h>
 #include <AK/NonnullOwnPtr.h>
 #include <AK/Optional.h>
-#include <AK/RefCounted.h>
-#include <Kernel/Arch/i386/CPU.h>
 #include <Kernel/UnixTypes.h>
 #include <LibC/sys/arch/i386/regs.h>
 

Kernel/build-root-filesystem.sh

@@ -143,8 +143,10 @@ cp ../Applications/DisplayProperties/DisplayProperties mnt/bin/DisplayProperties
 cp ../Applications/Welcome/Welcome mnt/bin/Welcome
 cp ../Applications/Help/Help mnt/bin/Help
 cp ../Applications/Browser/Browser mnt/bin/Browser
+cp ../Applications/Debugger/Debugger mnt/bin/sdb
 cp ../Games/Solitaire/Solitaire mnt/bin/Solitaire
 cp ../Demos/HelloWorld/HelloWorld mnt/bin/HelloWorld
+cp ../Demos/Debugee/Debugee mnt/bin/Debugee
 cp ../Demos/WidgetGallery/WidgetGallery mnt/bin/WidgetGallery
 cp ../Demos/Fire/Fire mnt/bin/Fire
 cp ../Demos/DynamicLink/LinkDemo/LinkDemo mnt/bin/LinkDemo

Libraries/LibC/sys/arch/i386/regs.h

@@ -25,25 +25,24 @@
  */
 
 #pragma once
-#include <AK/kmalloc.h>
-#include <bits/stdint.h>
+#include <AK/Types.h>
 
 struct [[gnu::packed]] PtraceRegisters
 {
-    uint32_t eax;
-    uint32_t ecx;
-    uint32_t edx;
-    uint32_t ebx;
-    uint32_t esp;
-    uint32_t ebp;
-    uint32_t esi;
-    uint32_t edi;
-    uint32_t eip;
-    uint32_t eflags;
-    uint32_t cs;
-    uint32_t ss;
-    uint32_t ds;
-    uint32_t es;
-    uint32_t fs;
-    uint32_t gs;
+    u32 eax;
+    u32 ecx;
+    u32 edx;
+    u32 ebx;
+    u32 esp;
+    u32 ebp;
+    u32 esi;
+    u32 edi;
+    u32 eip;
+    u32 eflags;
+    u32 cs;
+    u32 ss;
+    u32 ds;
+    u32 es;
+    u32 fs;
+    u32 gs;
 };