Luna/kernel/src/sys/exec.cpp

#include "ELF.h"
#include "Log.h"
#include "fs/VFS.h"
#include "memory/MemoryManager.h"
#include "sys/Syscall.h"
#include "thread/Scheduler.h"
#include "thread/ThreadImage.h"
#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()));

    // Not executable
    if ((inode->mode() & S_IXUSR) != S_IXUSR) return err(EACCES);

    kinfoln("exec: attempting to replace current image with %s", path.chars());

    auto current = Scheduler::current();

    auto image = TRY(ThreadImage::try_load_from_elf(inode));

    // From now on, nothing should fail.

    kinfoln("exec: image load ok, will now replace existing process image");

    // 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);

    image->apply(current);

    MMU::switch_page_directory(current->directory);

    memcpy(regs, &current->regs, sizeof(*regs));

    kinfoln("exec: done");

    return 0;
}