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UserspaceEmulator: Add a fast path for forward REP STOSD

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Same as REP STOSB, except for 32-bit fills instead.
This commit is contained in:
Andreas Kling 2020-11-15 18:07:22 +01:00
parent 102e1d330c
commit 6dab0af9af
Notes: sideshowbarker 2024-07-19 01:22:43 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/6dab0af9aff
3 changed files with 43 additions and 1 deletions
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16
DevTools/UserspaceEmulator/SoftCPU.cpp
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@ -3072,6 +3072,22 @@ void SoftCPU::STOSB(const X86::Instruction& insn)
void SoftCPU::STOSD(const X86::Instruction& insn)
{
if (insn.has_rep_prefix() && !df()) {
// Fast path for 32-bit forward memory fill.
if (m_emulator.mmu().fast_fill_memory32({ es(), destination_index(insn.a32()).value() }, ecx().value(), eax())) {
if (insn.a32()) {
// FIXME: Should an uninitialized ECX taint EDI here?
set_edi({ (u32)(edi().value() + (ecx().value() * sizeof(u32))), edi().shadow() });
set_ecx(shadow_wrap_as_initialized<u32>(0));
} else {
// FIXME: Should an uninitialized CX taint DI here?
set_di({ (u16)(di().value() + (cx().value() * sizeof(u32))), di().shadow() });
set_cx(shadow_wrap_as_initialized<u16>(0));
}
return;
}
}
do_once_or_repeat<false>(insn, [&] {
write_memory32({ es(), destination_index(insn.a32()).value() }, eax());
step_destination_index(insn.a32(), 4);

27
DevTools/UserspaceEmulator/SoftMMU.cpp
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@ -259,7 +259,7 @@ bool SoftMMU::fast_fill_memory8(X86::LogicalAddress address, size_t size, ValueW
if (region->is_mmap() && static_cast<const MmapRegion&>(*region).is_malloc_block()) {
if (auto* tracer = Emulator::the().malloc_tracer()) {
// FIXME: Add a way to audit an entire range of memory instead of looping here!
for (size_t i = 0; i < size; i += sizeof(u8)) {
for (size_t i = 0; i < size; ++i) {
tracer->audit_write(address.offset() + (i * sizeof(u8)), sizeof(u8));
}
}
@ -271,4 +271,29 @@ bool SoftMMU::fast_fill_memory8(X86::LogicalAddress address, size_t size, ValueW
return true;
}
bool SoftMMU::fast_fill_memory32(X86::LogicalAddress address, size_t count, ValueWithShadow<u32> value)
{
if (!count)
return true;
auto* region = find_region(address);
if (!region)
return false;
if (!region->contains(address.offset() + (count * sizeof(u32)) - 1))
return false;
if (region->is_mmap() && static_cast<const MmapRegion&>(*region).is_malloc_block()) {
if (auto* tracer = Emulator::the().malloc_tracer()) {
// FIXME: Add a way to audit an entire range of memory instead of looping here!
for (size_t i = 0; i < count; ++i) {
tracer->audit_write(address.offset() + (i * sizeof(u32)), sizeof(u32));
}
}
}
size_t offset_in_region = address.offset() - region->base();
fast_u32_fill((u32*)(region->data() + offset_in_region), value.value(), count);
fast_u32_fill((u32*)(region->shadow_data() + offset_in_region), value.shadow(), count);
return true;
}
}

1
DevTools/UserspaceEmulator/SoftMMU.h
View File

@ -109,6 +109,7 @@ public:
void set_tls_region(NonnullOwnPtr<Region>);
bool fast_fill_memory8(X86::LogicalAddress, size_t size, ValueWithShadow<u8>);
bool fast_fill_memory32(X86::LogicalAddress, size_t size, ValueWithShadow<u32>);
void copy_to_vm(FlatPtr destination, const void* source, size_t);
void copy_from_vm(void* destination, const FlatPtr source, size_t);