kernel/exec: Copy argv from userspace

apps/init.c

@@ -3,6 +3,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/stat.h>
+#include <sys/syscall.h>
 #include <sys/sysmacros.h>
 #include <unistd.h>
 
@@ -35,4 +36,7 @@ int main()
     stderr = fopen("/dev/console", "w");
 
     fprintf(stderr, "init is running as PID %d\n", getpid());
+
+    char* argv[] = { "/bin/hello", "--help", NULL };
+    syscall(SYS_exec, "/bin/hello", argv);
 }

kernel/src/sys/exec.cpp

@@ -8,10 +8,37 @@
 #include <bits/modes.h>
 #include <luna/CString.h>
 #include <luna/ScopeGuard.h>
+#include <luna/Vector.h>
+
+static Result<Vector<OwnedStringView>> copy_string_vector_from_userspace(u64 address)
+{
+    Vector<OwnedStringView> result;
+
+    const u64* user_vector = (const u64*)address;
+
+    u64 item;
+    while (true)
+    {
+        if (!MemoryManager::copy_from_user_typed(user_vector, &item)) return err(EFAULT);
+        if (!item) break;
+
+        auto string = TRY(MemoryManager::strdup_from_user(item));
+        TRY(result.try_append(move(string)));
+        user_vector++;
+    }
+
+    return result;
+}
 
 Result<u64> sys_exec(Registers* regs, SyscallArgs args)
 {
     auto path = TRY(MemoryManager::strdup_from_user(args[0]));
+    auto argv = TRY(copy_string_vector_from_userspace(args[1]));
+
+    kdbgln("exec: printing out argv (argc = %zu)", argv.size());
+    for (const auto& arg : argv) { kdbgln("* %s", arg.chars()); }
+
+    // FIXME: Make sure argv is not too big.
 
     auto inode = TRY(VFS::resolve_path(path.chars()));
 
@@ -28,8 +55,8 @@ Result<u64> sys_exec(Registers* regs, SyscallArgs args)
 
     kinfoln("exec: image load ok, will now replace existing process image");
 
-    // FIXME: Close only O_CLOEXEC file descriptors.
-    for (int i = 0; i < FD_MAX; i++) { current->fd_table[i] = {}; }
+    // FIXME: Close O_CLOEXEC file descriptors.
+    // for (int i = 0; i < FD_MAX; i++) { current->fd_table[i] = {}; }
 
     MMU::delete_userspace_page_directory(current->directory);