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Merge pull request #10005 from liamwhite/kernel-atomics

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kernel: fix unbounded stack usage in atomics
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bunnei 2023-04-01 01:54:36 -07:00 committed by GitHub
commit 0730dc6c44
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2 changed files with 54 additions and 37 deletions
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64
src/core/hle/kernel/k_address_arbiter.cpp
View file

@ -35,24 +35,30 @@ bool DecrementIfLessThan(Core::System& system, s32* out, KProcessAddress address
// TODO(bunnei): We should call CanAccessAtomic(..) here.
// Load the value from the address.
const s32 current_value =
static_cast<s32>(monitor.ExclusiveRead32(current_core, GetInteger(address)));
s32 current_value{};
// Compare it to the desired one.
if (current_value < value) {
// If less than, we want to try to decrement.
const s32 decrement_value = current_value - 1;
while (true) {
// Load the value from the address.
current_value =
static_cast<s32>(monitor.ExclusiveRead32(current_core, GetInteger(address)));
// Compare it to the desired one.
if (current_value < value) {
// If less than, we want to try to decrement.
const s32 decrement_value = current_value - 1;
// Decrement and try to store.
if (monitor.ExclusiveWrite32(current_core, GetInteger(address),
static_cast<u32>(decrement_value))) {
break;
}
// Decrement and try to store.
if (!monitor.ExclusiveWrite32(current_core, GetInteger(address),
static_cast<u32>(decrement_value))) {
// If we failed to store, try again.
DecrementIfLessThan(system, out, address, value);
} else {
// Otherwise, clear our exclusive hold and finish
monitor.ClearExclusive(current_core);
break;
}
} else {
// Otherwise, clear our exclusive hold and finish
monitor.ClearExclusive(current_core);
}
// We're done.
@ -70,23 +76,29 @@ bool UpdateIfEqual(Core::System& system, s32* out, KProcessAddress address, s32
// TODO(bunnei): We should call CanAccessAtomic(..) here.
s32 current_value{};
// Load the value from the address.
const s32 current_value =
static_cast<s32>(monitor.ExclusiveRead32(current_core, GetInteger(address)));
while (true) {
current_value =
static_cast<s32>(monitor.ExclusiveRead32(current_core, GetInteger(address)));
// Compare it to the desired one.
if (current_value == value) {
// If equal, we want to try to write the new value.
// Compare it to the desired one.
if (current_value == value) {
// If equal, we want to try to write the new value.
// Try to store.
if (monitor.ExclusiveWrite32(current_core, GetInteger(address),
static_cast<u32>(new_value))) {
break;
}
// Try to store.
if (!monitor.ExclusiveWrite32(current_core, GetInteger(address),
static_cast<u32>(new_value))) {
// If we failed to store, try again.
UpdateIfEqual(system, out, address, value, new_value);
} else {
// Otherwise, clear our exclusive hold and finish.
monitor.ClearExclusive(current_core);
break;
}
} else {
// Otherwise, clear our exclusive hold and finish.
monitor.ClearExclusive(current_core);
}
// We're done.

27
src/core/hle/kernel/k_condition_variable.cpp
View file

@ -33,21 +33,26 @@ bool UpdateLockAtomic(Core::System& system, u32* out, KProcessAddress address, u
auto& monitor = system.Monitor();
const auto current_core = system.Kernel().CurrentPhysicalCoreIndex();
// Load the value from the address.
const auto expected = monitor.ExclusiveRead32(current_core, GetInteger(address));
u32 expected{};
// Orr in the new mask.
u32 value = expected | new_orr_mask;
while (true) {
// Load the value from the address.
expected = monitor.ExclusiveRead32(current_core, GetInteger(address));
// If the value is zero, use the if_zero value, otherwise use the newly orr'd value.
if (!expected) {
value = if_zero;
}
// Orr in the new mask.
u32 value = expected | new_orr_mask;
// If the value is zero, use the if_zero value, otherwise use the newly orr'd value.
if (!expected) {
value = if_zero;
}
// Try to store.
if (monitor.ExclusiveWrite32(current_core, GetInteger(address), value)) {
break;
}
// Try to store.
if (!monitor.ExclusiveWrite32(current_core, GetInteger(address), value)) {
// If we failed to store, try again.
return UpdateLockAtomic(system, out, address, if_zero, new_orr_mask);
}
// We're done.