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Teach Process::exec() about the magic of file-backed VMO's.

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This is really sweet! :^) The four instances of /bin/sh spawned at
startup now share their read-only text pages.

There are problems and limitations here, and plenty of room for
improvement. But it kinda works.
This commit is contained in:
Andreas Kling 2018-11-08 21:20:09 +01:00
parent 992769c9d4
commit cd1e7419f0
10 changed files with 159 additions and 70 deletions
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64
Kernel/Process.cpp
View file

@ -94,12 +94,7 @@ Region* Process::allocate_region(LinearAddress laddr, size_t size, String&& name
laddr = m_nextRegion;
m_nextRegion = m_nextRegion.offset(size).offset(PAGE_SIZE);
}
laddr.mask(0xfffff000);
unsigned page_count = ceilDiv(size, PAGE_SIZE);
auto physical_pages = MM.allocate_physical_pages(page_count);
ASSERT(physical_pages.size() == page_count);
m_regions.append(adopt(*new Region(laddr, size, move(name), is_readable, is_writable)));
m_regions.last()->commit(*this);
MM.mapRegion(*this, *m_regions.last());
@ -115,18 +110,29 @@ Region* Process::allocate_file_backed_region(LinearAddress laddr, size_t size, R
laddr = m_nextRegion;
m_nextRegion = m_nextRegion.offset(size).offset(PAGE_SIZE);
}
laddr.mask(0xfffff000);
unsigned page_count = ceilDiv(size, PAGE_SIZE);
Vector<RetainPtr<PhysicalPage>> physical_pages;
physical_pages.resize(page_count); // Start out with no physical pages!
m_regions.append(adopt(*new Region(laddr, size, move(vnode), move(name), is_readable, is_writable)));
MM.mapRegion(*this, *m_regions.last());
return m_regions.last().ptr();
}
Region* Process::allocate_region_with_vmo(LinearAddress laddr, size_t size, RetainPtr<VMObject>&& vmo, size_t offset_in_vmo, String&& name, bool is_readable, bool is_writable)
{
ASSERT(vmo);
// FIXME: This needs sanity checks. What if this overlaps existing regions?
if (laddr.is_null()) {
laddr = m_nextRegion;
m_nextRegion = m_nextRegion.offset(size).offset(PAGE_SIZE);
}
laddr.mask(0xfffff000);
offset_in_vmo &= PAGE_MASK;
size = ceilDiv(size, PAGE_SIZE) * PAGE_SIZE;
m_regions.append(adopt(*new Region(laddr, size, move(vmo), offset_in_vmo, move(name), is_readable, is_writable)));
MM.mapRegion(*this, *m_regions.last());
return m_regions.last().ptr();
}
bool Process::deallocate_region(Region& region)
{
InterruptDisabler disabler;
@ -296,23 +302,42 @@ int Process::exec(const String& path, Vector<String>&& arguments, Vector<String>
if (!descriptor->metadata().mayExecute(m_euid, m_gids))
return -EACCES;
if (!descriptor->metadata().size) {
kprintf("exec() of 0-length binaries not supported\n");
return -ENOTIMPL;
}
auto vmo = VMObject::create_file_backed(descriptor->vnode(), descriptor->metadata().size);
auto* region = allocate_region_with_vmo(LinearAddress(), descriptor->metadata().size, vmo.copyRef(), 0, "helper", true, false);
#if 0
auto elfData = descriptor->readEntireFile();
if (!elfData)
return -EIO; // FIXME: Get a more detailed error from VFS.
#endif
dword entry_eip = 0;
PageDirectory* old_page_directory;
PageDirectory* new_page_directory;
PageDirectory* old_page_directory = m_page_directory;
PageDirectory* new_page_directory = reinterpret_cast<PageDirectory*>(kmalloc_page_aligned(sizeof(PageDirectory)));
dbgprintf("Process exec: PD=%x created\n", new_page_directory);
MM.populate_page_directory(*new_page_directory);
m_page_directory = new_page_directory;
MM.enter_process_paging_scope(*this);
bool success = region->page_in(*new_page_directory);
ASSERT(success);
{
InterruptDisabler disabler;
// Okay, here comes the sleight of hand, pay close attention..
auto old_regions = move(m_regions);
old_page_directory = m_page_directory;
new_page_directory = reinterpret_cast<PageDirectory*>(kmalloc_page_aligned(sizeof(PageDirectory)));
MM.populate_page_directory(*new_page_directory);
m_page_directory = new_page_directory;
MM.enter_process_paging_scope(*this);
ELFLoader loader(move(elfData));
ELFLoader loader(region->linearAddress.asPtr());
loader.map_section_hook = [&] (LinearAddress laddr, size_t size, size_t alignment, size_t offset_in_image, bool is_readable, bool is_writable, const String& name) {
ASSERT(size);
size = ((size / 4096) + 1) * 4096; // FIXME: Use ceil_div?
(void) allocate_region_with_vmo(laddr, size, vmo.copyRef(), offset_in_image, String(name), is_readable, is_writable);
return laddr.asPtr();
};
loader.alloc_section_hook = [&] (LinearAddress laddr, size_t size, size_t alignment, bool is_readable, bool is_writable, const String& name) {
ASSERT(size);
size = ((size / 4096) + 1) * 4096; // FIXME: Use ceil_div?
@ -580,6 +605,7 @@ Process::Process(String&& name, uid_t uid, gid_t gid, pid_t ppid, RingLevel ring
}
m_page_directory = (PageDirectory*)kmalloc_page_aligned(sizeof(PageDirectory));
dbgprintf("Process ctor: PD=%x created\n", m_page_directory);
MM.populate_page_directory(*m_page_directory);
if (fork_parent) {
@ -1326,7 +1352,7 @@ pid_t Process::sys$setsid()
{
InterruptDisabler disabler;
bool found_process_with_same_pgid_as_my_pid = false;
Process::for_each_in_pgrp(pid(), [&] (auto& process) {
Process::for_each_in_pgrp(pid(), [&] (auto&) {
found_process_with_same_pgid_as_my_pid = true;
return false;
});