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Kernel: Improve ProcFS behavior in low memory conditions

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When ProcFS could no longer allocate KBuffer objects to serve calls to
read, it would just return 0, indicating EOF. This then triggered
parsing errors because code assumed it read the file.

Because read isn't supposed to return ENOMEM, change ProcFS to populate
the file data upon file open or seek to the beginning. This also means
that calls to open can now return ENOMEM if needed. This allows the
caller to either be able to successfully open the file and read it, or
fail to open it in the first place.
This commit is contained in:
Tom 2020-09-17 13:51:09 -06:00 • committed by Andreas Kling
parent b36f57e570
commit f98ca35b83
24 changed files with 398 additions and 243 deletions
Download patch file Download diff file Expand all files Collapse all files

34
Kernel/KBuffer.h
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@ -48,21 +48,21 @@ namespace Kernel {
class KBufferImpl : public RefCounted<KBufferImpl> {
public:
static RefPtr<KBufferImpl> try_create_with_size(size_t size, u8 access, const char* name, AllocationStrategy strategy = AllocationStrategy::Reserve)
static RefPtr<KBufferImpl> try_create_with_size(size_t size, u8 access, const char* name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
{
auto region = MM.allocate_kernel_region(PAGE_ROUND_UP(size), name, access, false, strategy);
if (!region)
return nullptr;
return adopt(*new KBufferImpl(region.release_nonnull(), size));
return adopt(*new KBufferImpl(region.release_nonnull(), size, strategy));
}
static RefPtr<KBufferImpl> try_create_with_bytes(ReadonlyBytes bytes, u8 access, const char* name, AllocationStrategy strategy = AllocationStrategy::Reserve)
static RefPtr<KBufferImpl> try_create_with_bytes(ReadonlyBytes bytes, u8 access, const char* name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
{
auto region = MM.allocate_kernel_region(PAGE_ROUND_UP(bytes.size()), name, access, false, strategy);
if (!region)
return nullptr;
memcpy(region->vaddr().as_ptr(), bytes.data(), bytes.size());
return adopt(*new KBufferImpl(region.release_nonnull(), bytes.size()));
return adopt(*new KBufferImpl(region.release_nonnull(), bytes.size(), strategy));
}
static RefPtr<KBufferImpl> create_with_size(size_t size, u8 access, const char* name, AllocationStrategy strategy = AllocationStrategy::Reserve)
@ -79,6 +79,17 @@ public:
return buffer;
}
bool expand(size_t new_capacity)
{
auto new_region = MM.allocate_kernel_region(PAGE_ROUND_UP(new_capacity), m_region->name(), m_region->access(), false, m_allocation_strategy);
if (!new_region)
return false;
if (m_region && m_size > 0)
memcpy(new_region->vaddr().as_ptr(), data(), min(m_region->size(), m_size));
m_region = new_region.release_nonnull();
return true;
}
u8* data() { return m_region->vaddr().as_ptr(); }
const u8* data() const { return m_region->vaddr().as_ptr(); }
size_t size() const { return m_size; }
@ -94,18 +105,25 @@ public:
Region& region() { return *m_region; }
private:
explicit KBufferImpl(NonnullOwnPtr<Region>&& region, size_t size)
explicit KBufferImpl(NonnullOwnPtr<Region>&& region, size_t size, AllocationStrategy strategy)
: m_size(size)
, m_allocation_strategy(strategy)
, m_region(move(region))
{
}
size_t m_size { 0 };
AllocationStrategy m_allocation_strategy { AllocationStrategy::Reserve };
NonnullOwnPtr<Region> m_region;
};
class KBuffer {
public:
explicit KBuffer(RefPtr<KBufferImpl>&& impl)
: m_impl(move(impl))
{
}
static OwnPtr<KBuffer> try_create_with_size(size_t size, u8 access = Region::Access::Read | Region::Access::Write, const char* name = "KBuffer", AllocationStrategy strategy = AllocationStrategy::Reserve)
{
auto impl = KBufferImpl::try_create_with_size(size, access, name, strategy);
@ -145,6 +163,7 @@ public:
void set_size(size_t size) { m_impl->set_size(size); }
const KBufferImpl& impl() const { return *m_impl; }
RefPtr<KBufferImpl> take_impl() { return move(m_impl); }
KBuffer(const ByteBuffer& buffer, u8 access = Region::Access::Read | Region::Access::Write, const char* name = "KBuffer")
: m_impl(KBufferImpl::copy(buffer.data(), buffer.size(), access, name))
@ -152,11 +171,6 @@ public:
}
private:
explicit KBuffer(RefPtr<KBufferImpl>&& impl)
: m_impl(move(impl))
{
}
RefPtr<KBufferImpl> m_impl;
};