From e672f3994bfd4f903fc7ee05be307c800ff9db91 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 15 Oct 2022 18:19:47 +0200
Subject: [PATCH] libc: Add support for fork()

That doesn't mean it works.
Why doesn't it work??

Oh well...
---
 apps/src/init.c                  | 12 ++++++++----
 kernel/src/trace/StackTracer.cpp |  7 +++++++
 libs/libc/include/luna/syscall.h |  1 +
 libs/libc/include/unistd.h       |  3 ++-
 libs/libc/src/unistd.cpp         |  4 +++-
 5 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/apps/src/init.c b/apps/src/init.c
index f83fd1f7..29f51333 100644
--- a/apps/src/init.c
+++ b/apps/src/init.c
@@ -141,9 +141,13 @@ int main()
 
     fclose(new_stderr);
 
-    execv("/bin/sym", NULL);
+    pid_t child = fork();
+    if (child == 0)
+    {
+        msleep(500);
+        printf("I am the child, who is my parent?\n");
+    }
+    else { printf("My child is %ld!", child); }
 
-    perror("execv"); // If we're here, execv failed
-
-    return 1;
+    return 0;
 }
diff --git a/kernel/src/trace/StackTracer.cpp b/kernel/src/trace/StackTracer.cpp
index ea305c52..39a38e7f 100644
--- a/kernel/src/trace/StackTracer.cpp
+++ b/kernel/src/trace/StackTracer.cpp
@@ -1,5 +1,6 @@
 #include "trace/StackTracer.h"
 #include "memory/Memory.h"
+#include "memory/VMM.h"
 #include "std/stdio.h"
 #include "trace/Resolve.h"
 
@@ -20,6 +21,11 @@ typedef struct stackframe
 
 void StackTracer::trace()
 {
+    if (!VMM::is_using_kernel_address_space())
+    {
+        VMM::switch_back_to_kernel_address_space();
+        VMM::apply_address_space();
+    }
     stackframe* frame = (stackframe*)m_base_pointer;
     while (frame && frame->instruction)
     {
@@ -27,6 +33,7 @@ void StackTracer::trace()
         get_symbol_name(frame->instruction, symbol_name, sizeof(symbol_name));
         printf("%lx: %s\n", frame->instruction, symbol_name);
         frame = frame->next;
+        if (VMM::get_physical((uint64_t)frame) == (uint64_t)-1) return;
     }
 }
 
diff --git a/libs/libc/include/luna/syscall.h b/libs/libc/include/luna/syscall.h
index 6d92d320..b706db8d 100644
--- a/libs/libc/include/luna/syscall.h
+++ b/libs/libc/include/luna/syscall.h
@@ -17,6 +17,7 @@
 #define SYS_fcntl 13
 #define SYS_mprotect 14
 #define SYS_clock 15
+#define SYS_fork 16
 
 #ifndef __want_syscalls
 #ifdef __cplusplus
diff --git a/libs/libc/include/unistd.h b/libs/libc/include/unistd.h
index 80add4cb..3e5a00a0 100644
--- a/libs/libc/include/unistd.h
+++ b/libs/libc/include/unistd.h
@@ -22,7 +22,8 @@ extern "C"
     int execve(const char*, char* const[], char* const[]);
     /* Not implemented. */
     int execvp(const char*, char* const[]);
-    /* Not implemented. */
+
+    /* Creates an identical copy of the current process and returns its process ID. */
     pid_t fork(void);
 
     /* Terminates the program with the status code status. */
diff --git a/libs/libc/src/unistd.cpp b/libs/libc/src/unistd.cpp
index 86ac5df3..1c4577f0 100644
--- a/libs/libc/src/unistd.cpp
+++ b/libs/libc/src/unistd.cpp
@@ -19,9 +19,10 @@ extern "C"
     {
         NOT_IMPLEMENTED("execvp");
     }
+
     pid_t fork(void)
     {
-        NOT_IMPLEMENTED("fork");
+        return syscall(SYS_fork);
     }
 
     long syscall(long number, ...)
@@ -34,6 +35,7 @@ extern "C"
         {
         case SYS_clock:
         case SYS_yield:
+        case SYS_fork:
         case SYS_gettid: result = __luna_syscall0(number); break;
         case SYS_exit:
         case SYS_close: