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Kernel: Encapsulate the Region's COW map a bit better.

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This commit is contained in:
Andreas Kling 2019-05-14 17:31:57 +02:00
parent 2fa5e2b66b
commit 01ffcdfa31
Notes: sideshowbarker 2024-07-19 14:08:51 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/01ffcdfa31b
5 changed files with 19 additions and 13 deletions
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12
AK/Bitmap.h
View File

@ -45,15 +45,19 @@ public:
byte* data() { return m_data; }
const byte* data() const { return m_data; }
void fill(bool value)
{
memset(m_data, value ? 0xff : 0x00, size_in_bytes());
}
private:
explicit Bitmap(int size, bool default_value)
: m_size(size)
, m_owned(true)
{
ASSERT(m_size != 0);
int size_to_allocate = ceil_div(size, 8);
m_data = reinterpret_cast<byte*>(kmalloc(size_to_allocate));
memset(m_data, default_value ? 0xff : 0x00, size_to_allocate);
m_data = reinterpret_cast<byte*>(kmalloc(size_in_bytes()));
fill(default_value);
}
Bitmap(byte* data, int size)
@ -63,6 +67,8 @@ private:
{
}
int size_in_bytes() const { return ceil_div(m_size, 8); }
byte* m_data { nullptr };
int m_size { 0 };
bool m_owned { false };

2
Kernel/FileSystem/ProcFS.cpp
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@ -279,7 +279,7 @@ ByteBuffer procfs$pid_vmo(InodeIdentifier identifier)
auto& physical_page = region->vmo().physical_pages()[i];
builder.appendf("P%x%s(%u) ",
physical_page ? physical_page->paddr().get() : 0,
region->cow_map().get(i) ? "!" : "",
region->should_cow(i) ? "!" : "",
physical_page ? physical_page->retain_count() : 0
);
}

12
Kernel/VM/MemoryManager.cpp
View File

@ -264,7 +264,7 @@ bool MemoryManager::zero_page(Region& region, unsigned page_index_in_region)
#ifdef PAGE_FAULT_DEBUG
dbgprintf(" >> ZERO P%x\n", physical_page->paddr().get());
#endif
region.m_cow_map.set(page_index_in_region, false);
region.set_should_cow(page_index_in_region, false);
vmo.physical_pages()[page_index_in_region] = move(physical_page);
remap_region_page(region, page_index_in_region, true);
return true;
@ -278,7 +278,7 @@ bool MemoryManager::copy_on_write(Region& region, unsigned page_index_in_region)
#ifdef PAGE_FAULT_DEBUG
dbgprintf(" >> It's a COW page but nobody is sharing it anymore. Remap r/w\n");
#endif
region.m_cow_map.set(page_index_in_region, false);
region.set_should_cow(page_index_in_region, false);
remap_region_page(region, page_index_in_region, true);
return true;
}
@ -296,7 +296,7 @@ bool MemoryManager::copy_on_write(Region& region, unsigned page_index_in_region)
memcpy(dest_ptr, src_ptr, PAGE_SIZE);
vmo.physical_pages()[page_index_in_region] = move(physical_page);
unquickmap_page();
region.m_cow_map.set(page_index_in_region, false);
region.set_should_cow(page_index_in_region, false);
remap_region_page(region, page_index_in_region, true);
return true;
}
@ -379,7 +379,7 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
return PageFaultResponse::Continue;
}
} else if (fault.is_protection_violation()) {
if (region->m_cow_map.get(page_index_in_region)) {
if (region->should_cow(page_index_in_region)) {
#ifdef PAGE_FAULT_DEBUG
dbgprintf("PV(cow) fault in Region{%p}[%u]\n", region, page_index_in_region);
#endif
@ -534,7 +534,7 @@ void MemoryManager::remap_region_page(Region& region, unsigned page_index_in_reg
ASSERT(physical_page);
pte.set_physical_page_base(physical_page->paddr().get());
pte.set_present(true); // FIXME: Maybe we should use the is_readable flag here?
if (region.m_cow_map.get(page_index_in_region))
if (region.should_cow(page_index_in_region))
pte.set_writable(false);
else
pte.set_writable(region.is_writable());
@ -570,7 +570,7 @@ void MemoryManager::map_region_at_address(PageDirectory& page_directory, Region&
pte.set_physical_page_base(physical_page->paddr().get());
pte.set_present(true); // FIXME: Maybe we should use the is_readable flag here?
// FIXME: It seems wrong that the *region* cow map is essentially using *VMO* relative indices.
if (region.m_cow_map.get(region.first_page_index() + i))
if (region.should_cow(region.first_page_index() + i))
pte.set_writable(false);
else
pte.set_writable(region.is_writable());

3
Kernel/VM/Region.cpp
View File

@ -94,8 +94,7 @@ Retained<Region> Region::clone()
laddr().get());
#endif
// Set up a COW region. The parent (this) region becomes COW as well!
for (size_t i = 0; i < page_count(); ++i)
m_cow_map.set(i, true);
m_cow_map.fill(true);
MM.remap_region(current->process().page_directory(), *this);
return adopt(*new Region(laddr(), size(), m_vmo->clone(), m_offset_in_vmo, String(m_name), m_readable, m_writable, true));
}

3
Kernel/VM/Region.h
View File

@ -75,7 +75,8 @@ public:
m_page_directory.clear();
}
const Bitmap& cow_map() const { return m_cow_map; }
bool should_cow(size_t page_index) const { return m_cow_map.get(page_index); }
void set_should_cow(size_t page_index, bool cow) { m_cow_map.set(page_index, cow); }
void set_writable(bool b) { m_writable = b; }