Luna/kernel/src/sys/exec.cpp

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#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>
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#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 string_addr;
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while (true)
{
if (!MemoryManager::copy_from_user_typed(user_vector, &string_addr)) return err(EFAULT);
if (!string_addr) break;
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auto string = TRY(MemoryManager::strdup_from_user(string_addr));
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TRY(result.try_append(move(string)));
user_vector++;
}
return result;
}
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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]));
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auto argv = TRY(copy_string_vector_from_userspace(args[1]));
// 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();
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auto guard = make_scope_guard([current] { MMU::switch_page_directory(current->directory); });
auto image = TRY(ThreadImage::try_load_from_elf(inode));
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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");
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guard.deactivate();
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// 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);
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current->set_arguments(user_argc, user_argv, 0, 0);
memcpy(regs, &current->regs, sizeof(*regs));
kinfoln("exec: done");
return 0;
}