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Fix mach hardware exception forwarding #105003

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merged 3 commits into from
Jul 17, 2024
Merged

Fix mach hardware exception forwarding #105003

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568b3b2
Fix mach hardware exception forwarding
janvorli Jul 17, 2024
fee489b
Simplify the RestoreState
janvorli Jul 17, 2024
9f38c18
Set the message buffer to the size of the mach_msg_t plus trailer size
janvorli Jul 17, 2024
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2 changes: 1 addition & 1 deletion src/coreclr/pal/src/exception/machexception.cpp
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Expand Up @@ -1325,7 +1325,7 @@ void MachExceptionInfo::RestoreState(mach_port_t thread)
kern_return_t machret = thread_set_state(thread, x86_THREAD_STATE, (thread_state_t)&ThreadState, x86_THREAD_STATE_COUNT);
CHECK_MACH("thread_set_state(thread)", machret);

machret = thread_set_state(thread, x86_FLOAT_STATE, (thread_state_t)&FloatState, x86_FLOAT_STATE_COUNT);
machret = thread_set_state(thread, FloatState.ash.flavor, (thread_state_t)&FloatState, FloatState.ash.count);
CHECK_MACH("thread_set_state(float)", machret);

machret = thread_set_state(thread, x86_DEBUG_STATE, (thread_state_t)&DebugState, x86_DEBUG_STATE_COUNT);
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5 changes: 4 additions & 1 deletion src/coreclr/pal/src/exception/machmessage.h
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Expand Up @@ -189,7 +189,7 @@ class MachMessage
// The maximum size in bytes of any Mach message we can send or receive. Calculating an exact size for
// this is non trivial (basically because of the security trailers that Mach appends) but the current
// value has proven to be more than enough so far.
static const size_t kcbMaxMessageSize = 1500;
static const size_t kcbMaxMessageSize = 0x1500;
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Would it be better to define this as sizeof(mach_message_t) plus some extra space?

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I've actually found a constant in the headers representing the maximum trailer size, so we can define it as sizeof(mach_message_t) + MAX_TRAILER_SIZE and be safe.

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Added a commit with that change.

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Is the MAX_TRAILER_SIZE in a mach source file header? And I am guessing it refers to the security trailers that are mentioned in the comment above?

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Yes, it is in the Apple headers and it refers to those trailers.


// The following are structures describing the formats of the Mach messages we understand.

Expand Down Expand Up @@ -298,6 +298,9 @@ class MachMessage
} data;
} __attribute__((packed));;


static_assert_no_msg(sizeof(mach_message_t) <= MachMessage::kcbMaxMessageSize);

// Re-initializes this data structure (to the same state as default construction, containing no message).
void ResetMessage();

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