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UserspaceEmulator: Convert backing storage from malloc to mmap

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This saves a few bytes for each guest-mmaped region, especially since these are likely to be page-aligned.
This commit is contained in:
Ben Wiederhake 2021-03-07 21:39:06 +01:00 • committed by Andreas Kling
parent 968ad0f8d1
commit 7cc8f20a30
3 changed files with 28 additions and 16 deletions
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40
Userland/DevTools/UserspaceEmulator/MmapRegion.cpp
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@ -31,42 +31,54 @@
namespace UserspaceEmulator {
static void* mmap_initialized(size_t bytes, char initial_value, const char* name)
{
auto* ptr = mmap_with_name(nullptr, bytes, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0, name);
VERIFY(ptr != MAP_FAILED);
memset(ptr, initial_value, bytes);
return ptr;
}
static void free_pages(void* ptr, size_t bytes)
{
int rc = munmap(ptr, bytes);
VERIFY(rc == 0);
}
NonnullOwnPtr<MmapRegion> MmapRegion::create_anonymous(u32 base, u32 size, u32 prot)
{
auto region = adopt_own(*new MmapRegion(base, size, prot));
region->m_file_backed = false;
region->m_data = (u8*)calloc(1, size);
auto data = (u8*)mmap_initialized(size, 0, nullptr);
auto shadow_data = (u8*)mmap_initialized(size, 1, "MmapRegion ShadowData");
auto region = adopt_own(*new MmapRegion(base, size, prot, data, shadow_data));
return region;
}
NonnullOwnPtr<MmapRegion> MmapRegion::create_file_backed(u32 base, u32 size, u32 prot, int flags, int fd, off_t offset, String name)
{
auto region = adopt_own(*new MmapRegion(base, size, prot));
auto data = (u8*)mmap_with_name(nullptr, size, prot, flags, fd, offset, name.is_empty() ? nullptr : name.characters());
VERIFY(data != MAP_FAILED);
auto shadow_data = (u8*)mmap_initialized(size, 1, "MmapRegion ShadowData");
auto region = adopt_own(*new MmapRegion(base, size, prot, data, shadow_data));
region->m_file_backed = true;
if (!name.is_empty()) {
name = String::formatted("{} (Emulated)", name);
region->m_name = name;
}
region->m_data = (u8*)mmap_with_name(nullptr, size, prot, flags, fd, offset, name.is_empty() ? nullptr : name.characters());
VERIFY(region->m_data != MAP_FAILED);
return region;
}
MmapRegion::MmapRegion(u32 base, u32 size, int prot)
MmapRegion::MmapRegion(u32 base, u32 size, int prot, u8* data, u8* shadow_data)
: Region(base, size)
, m_data(data)
, m_shadow_data(shadow_data)
{
set_prot(prot);
m_shadow_data = (u8*)malloc(size);
memset(m_shadow_data, 1, size);
}
MmapRegion::~MmapRegion()
{
free(m_shadow_data);
if (m_file_backed)
munmap(m_data, size());
else
free(m_data);
free_pages(m_data, size());
free_pages(m_shadow_data, size());
}
ValueWithShadow<u8> MmapRegion::read8(FlatPtr offset)