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Kernel: Implement proper memory region splitting

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Memory regions are now splitted when they get munmapped, mprotected, or
mmapped with MAP_FIXED. This is used by couple of ports, and without
this we were just leaking up memory or straight up crashing programs.
This commit is contained in:
Bananymous
2025-11-10 19:57:26 +02:00
parent a39aa73e21
commit 9537922acc
10 changed files with 145 additions and 46 deletions
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126
kernel/kernel/Process.cpp
View File

@@ -2189,6 +2189,38 @@ namespace Kernel
return 0;
}
BAN::ErrorOr<BAN::Vector<BAN::UniqPtr<MemoryRegion>>> Process::split_memory_region(BAN::UniqPtr<MemoryRegion>&& region, vaddr_t base, size_t length)
{
ASSERT(base % PAGE_SIZE == 0);
ASSERT(base < region->vaddr() + region->size());
if (auto rem = length % PAGE_SIZE)
length += PAGE_SIZE - rem;
if (base + length > region->vaddr() + region->size())
length = region->vaddr() + region->size() - base;
BAN::Vector<BAN::UniqPtr<MemoryRegion>> result;
TRY(result.reserve(3));
if (region->vaddr() < base)
{
auto temp = TRY(region->split(base - region->vaddr()));
MUST(result.push_back(BAN::move(region)));
region = BAN::move(temp);
}
if (base + length < region->vaddr() + region->size())
{
auto temp = TRY(region->split(base + length - region->vaddr()));
MUST(result.push_back(BAN::move(region)));
region = BAN::move(temp);
}
MUST(result.push_back(BAN::move(region)));
return result;
}
BAN::ErrorOr<long> Process::sys_mmap(const sys_mmap_t* user_args)
{
sys_mmap_t args;
@@ -2201,6 +2233,9 @@ namespace Kernel
if (args.prot != PROT_NONE && (args.prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC)))
return BAN::Error::from_errno(EINVAL);
if (!(args.flags & MAP_ANONYMOUS) && (args.off % PAGE_SIZE))
return BAN::Error::from_errno(EINVAL);
if (!(args.flags & MAP_PRIVATE) == !(args.flags & MAP_SHARED))
return BAN::Error::from_errno(EINVAL);
auto region_type = (args.flags & MAP_PRIVATE) ? MemoryRegion::Type::PRIVATE : MemoryRegion::Type::SHARED;
@@ -2241,10 +2276,18 @@ namespace Kernel
{
if (!m_mapped_regions[i]->overlaps(vaddr, args.len))
continue;
if (!m_mapped_regions[i]->is_contained_by(vaddr, args.len))
derrorln("VERY BROKEN MAP_FIXED UNMAP");
m_mapped_regions[i]->wait_not_pinned();
auto temp = BAN::move(m_mapped_regions[i]);
m_mapped_regions.remove(i--);
if (!temp->is_contained_by(vaddr, args.len))
{
auto new_regions = TRY(split_memory_region(BAN::move(temp), vaddr, args.len));
for (auto& new_region : new_regions)
if (!new_region->overlaps(vaddr, args.len))
TRY(m_mapped_regions.push_back(BAN::move(new_region)));
}
}
}
else if (const vaddr_t vaddr = reinterpret_cast<vaddr_t>(args.addr); vaddr == 0)
@@ -2267,9 +2310,6 @@ namespace Kernel
if (args.flags & MAP_ANONYMOUS)
{
if (args.off != 0)
return BAN::Error::from_errno(EINVAL);
auto region = TRY(MemoryBackedRegion::create(
page_table(),
args.len,
@@ -2330,7 +2370,7 @@ namespace Kernel
if (auto rem = vaddr % PAGE_SIZE)
{
vaddr -= rem;
len += PAGE_SIZE - rem;
len += rem;
}
if (auto rem = len % PAGE_SIZE)
@@ -2338,22 +2378,22 @@ namespace Kernel
LockGuard _(m_process_lock);
// FIXME: We should unmap partial regions.
// This is a hack to only unmap if the whole mmap region
// is contained within [addr, addr + len]
for (size_t i = 0; i < m_mapped_regions.size(); i++)
{
auto& region = m_mapped_regions[i];
if (!m_mapped_regions[i]->overlaps(vaddr, len))
continue;
const vaddr_t region_s = region->vaddr();
const vaddr_t region_e = region->vaddr() + region->size();
if (vaddr <= region_s && region_e <= vaddr + len)
m_mapped_regions[i]->wait_not_pinned();
auto temp = BAN::move(m_mapped_regions[i]);
m_mapped_regions.remove(i--);
if (!temp->is_contained_by(vaddr, len))
{
region->wait_not_pinned();
m_mapped_regions.remove(i--);
auto new_regions = TRY(split_memory_region(BAN::move(temp), vaddr, len));
for (auto& new_region : new_regions)
if (!new_region->overlaps(vaddr, len))
TRY(m_mapped_regions.push_back(BAN::move(new_region)));
}
else if (region->overlaps(vaddr, len))
dwarnln("TODO: partial region munmap");
}
return 0;
@@ -2386,38 +2426,34 @@ namespace Kernel
LockGuard _(m_process_lock);
// FIXME: We should protect partial regions.
// This is a hack to only protect if the whole mmap region
// is contained within [addr, addr + len]
for (size_t i = 0; i < m_mapped_regions.size(); i++)
{
if (!m_mapped_regions[i]->overlaps(vaddr, len))
continue;
if (!m_mapped_regions[i]->is_contained_by(vaddr, len))
{
m_mapped_regions[i]->wait_not_pinned();
auto temp = BAN::move(m_mapped_regions[i]);
m_mapped_regions.remove(i--);
auto new_regions = TRY(split_memory_region(BAN::move(temp), vaddr, len));
for (auto& new_region : new_regions)
TRY(m_mapped_regions.push_back(BAN::move(new_region)));
continue;
}
auto& region = m_mapped_regions[i];
const bool is_shared = (region->type() == MemoryRegion::Type::SHARED);
const bool is_writable = (region->status_flags() & O_WRONLY);
const bool want_write = (prot & PROT_WRITE);
if (is_shared && want_write && !is_writable)
return BAN::Error::from_errno(EACCES);
const vaddr_t region_s = region->vaddr();
const vaddr_t region_e = region->vaddr() + region->size();
if (vaddr <= region_s && region_e <= vaddr + len)
{
const bool is_shared = (region->type() == MemoryRegion::Type::SHARED);
const bool is_writable = (region->status_flags() & O_WRONLY);
const bool want_write = (prot & PROT_WRITE);
if (is_shared && want_write && !is_writable)
return BAN::Error::from_errno(EACCES);
// FIXME: if the region is pinned writable, this may
// cause some problems :D
TRY(region->mprotect(flags));
}
else if (region->overlaps(vaddr, len))
{
const bool is_shared = (region->type() == MemoryRegion::Type::SHARED);
const bool is_writable = (region->status_flags() & O_WRONLY);
const bool want_write = (prot & PROT_WRITE);
if (is_shared && want_write && !is_writable)
return BAN::Error::from_errno(EACCES);
dwarnln("TODO: partial region mprotect");
TRY(region->mprotect(flags | region->flags()));
}
// NOTE: don't change protection of regions in use
region->wait_not_pinned();
TRY(region->mprotect(flags));
}
return 0;