kernel+libc: Copy argv to userspace

apps/hello.c

@@ -1,24 +1,6 @@
 #include <stdio.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/syscall.h>
-#include <sys/sysmacros.h>
-#include <unistd.h>
 
-int main()
+int main(int argc, char** argv)
 {
-    printf("Hello world!\n");
-
-    mkdir("/dev", 0755);
-    if (mknod("/dev/console", 0666, makedev(1, 0)) < 0)
-    {
-        perror("mknod");
-        return 1;
-    }
-
-    const char* str = "Hello from /dev!";
-
-    FILE* f = fopen("/dev/console", "r+");
-    if (f) fwrite(str, 1, strlen(str), f);
-    if (f) fclose(f);
+    printf("Hello world! argc=%d, argv[0]=%s, argv[1]=%s, argv[2]=%s\n", argc, argv[0], argv[1], argv[2]);
 }

kernel/src/sys/exec.cpp

@@ -30,14 +30,26 @@ static Result<Vector<OwnedStringView>> copy_string_vector_from_userspace(u64 add
     return result;
 }
 
+static Result<u64> copy_string_vector_to_userspace(const Vector<OwnedStringView>& vec, ThreadImage& image)
+{
+    Vector<u64> user_vec;
+    for (const auto& item : vec)
+    {
+        // Copy each individual string and retrieve a userspace pointer to said copy
+        u64 addr = TRY(image.push_mem_on_stack((const u8*)item.chars(), item.length() + 1));
+        TRY(user_vec.try_append(addr));
+    }
+
+    TRY(user_vec.try_append((u64) nullptr));
+    // Copy the actual vector of userspace pointers to the stack
+    return TRY(image.push_mem_on_stack((u8*)user_vec.data(), user_vec.size() * sizeof(u64)));
+}
+
 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()));
@@ -49,12 +61,21 @@ Result<u64> sys_exec(Registers* regs, SyscallArgs args)
 
     auto current = Scheduler::current();
 
+    auto guard = make_scope_guard([current] { MMU::switch_page_directory(current->directory); });
+
     auto image = TRY(ThreadImage::try_load_from_elf(inode));
 
+    kdbgln("exec: copying argv to image memory (argc = %zu)", argv.size());
+
+    u64 user_argv = TRY(copy_string_vector_to_userspace(argv, *image));
+    usize user_argc = argv.size();
+
     // From now on, nothing should fail.
 
     kinfoln("exec: image load ok, will now replace existing process image");
 
+    guard.deactivate();
+
     // FIXME: Close O_CLOEXEC file descriptors.
     // for (int i = 0; i < FD_MAX; i++) { current->fd_table[i] = {}; }
 
@@ -64,6 +85,8 @@ Result<u64> sys_exec(Registers* regs, SyscallArgs args)
 
     MMU::switch_page_directory(current->directory);
 
+    current->set_arguments(user_argc, user_argv, 0, 0);
+
     memcpy(regs, &current->regs, sizeof(*regs));
 
     kinfoln("exec: done");

kernel/src/thread/ThreadImage.cpp

@@ -1,6 +1,7 @@
 #include "thread/ThreadImage.h"
 #include "memory/MemoryManager.h"
 #include "thread/Thread.h"
+#include <luna/CString.h>
 
 static Result<void> create_stacks(Stack& user_stack, Stack& kernel_stack)
 {
@@ -50,10 +51,24 @@ Result<OwnedPtr<ThreadImage>> ThreadImage::try_load_from_elf(SharedPtr<VFS::Inod
     image->m_user_stack = user_stack;
     image->m_loaded_image_data = data;
     image->m_vm_allocator = move(vm_allocator);
+    image->m_sp = user_stack.top();
 
     return image;
 }
 
+Result<u64> ThreadImage::push_mem_on_stack(const u8* mem, usize size)
+{
+    if ((m_sp - size) < m_user_stack.bottom()) return err(E2BIG);
+
+    if (!MemoryManager::validate_user_write((void*)(m_sp - size), size)) return err(EFAULT);
+
+    m_sp -= size;
+
+    memcpy((void*)m_sp, mem, size);
+
+    return m_sp;
+}
+
 void ThreadImage::apply(Thread* thread)
 {
     thread->init_regs_user();
@@ -62,7 +77,7 @@ void ThreadImage::apply(Thread* thread)
 
     thread->kernel_stack = m_kernel_stack;
     thread->stack = m_user_stack;
-    thread->set_sp(m_user_stack.top());
+    thread->set_sp(m_sp);
 
     thread->directory = m_directory;
 

kernel/src/thread/ThreadImage.h

@@ -17,6 +17,8 @@ class ThreadImage
   public:
     static Result<OwnedPtr<ThreadImage>> try_load_from_elf(SharedPtr<VFS::Inode> inode);
 
+    Result<u64> push_mem_on_stack(const u8* mem, usize size);
+
     void apply(Thread* thread);
 
   private:
@@ -25,4 +27,5 @@ class ThreadImage
     Stack m_user_stack;
     Stack m_kernel_stack;
     ELFData m_loaded_image_data;
+    u64 m_sp;
 };

libc/src/arch/x86_64/crt0.S

@@ -10,11 +10,17 @@ _start:
 	pushq %rbp # rbp=0
 	movq %rsp, %rbp
 
+	pushq %rsi
+	pushq %rdi
+
 	call libc_init
 
 	# Run the global constructors.
 	call _init
 
+	popq %rdi
+	popq %rsi
+
 	# Run main
 	call main