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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#include "pal/dbgmsg.h"
SET_DEFAULT_DEBUG_CHANNEL(EXCEPT); // some headers have code with asserts, so do this first
#include "pal/palinternal.h"
#include "pal/context.h"
#include "pal/signal.hpp"
#include "pal/utils.h"
#include <sys/ucontext.h>
/*++
Function :
signal_handler_worker
Handles signal on the original stack where the signal occured.
Invoked via setcontext.
Parameters :
POSIX signal handler parameter list ("man sigaction" for details)
returnPoint - context to which the function returns if the common_signal_handler returns
(no return value)
--*/
void ExecuteHandlerOnOriginalStack(int code, siginfo_t *siginfo, void *context, SignalHandlerWorkerReturnPoint* returnPoint)
{
ucontext_t *ucontext = (ucontext_t *)context;
size_t faultSp = (size_t)MCREG_Sp(ucontext->uc_mcontext);
_ASSERTE(IS_ALIGNED(faultSp, 4));
size_t fakeFrameReturnAddress;
if (IS_ALIGNED(faultSp, 8))
{
fakeFrameReturnAddress = (size_t)SignalHandlerWorkerReturnOffset0 + (size_t)CallSignalHandlerWrapper0;
}
else
{
fakeFrameReturnAddress = (size_t)SignalHandlerWorkerReturnOffset4 + (size_t)CallSignalHandlerWrapper4;
}
// preserve 8 bytes long red zone and align stack pointer
size_t* sp = (size_t*)ALIGN_DOWN(faultSp - 8, 8);
// Build fake stack frame to enable the stack unwinder to unwind from signal_handler_worker to the faulting instruction
// pushed LR
*--sp = (size_t)MCREG_Pc(ucontext->uc_mcontext);
// pushed frame pointer
*--sp = (size_t)MCREG_R7(ucontext->uc_mcontext);
// Switch the current context to the signal_handler_worker and the original stack
ucontext_t ucontext2;
getcontext(&ucontext2);
// We don't care about the other registers state since the stack unwinding restores
// them for the target frame directly from the signal context.
MCREG_Sp(ucontext2.uc_mcontext) = (size_t)sp;
MCREG_R7(ucontext2.uc_mcontext) = (size_t)sp; // Fp and Sp are the same
MCREG_Lr(ucontext2.uc_mcontext) = fakeFrameReturnAddress;
MCREG_Pc(ucontext2.uc_mcontext) = (size_t)signal_handler_worker;
MCREG_R0(ucontext2.uc_mcontext) = code;
MCREG_R1(ucontext2.uc_mcontext) = (size_t)siginfo;
MCREG_R2(ucontext2.uc_mcontext) = (size_t)context;
MCREG_R3(ucontext2.uc_mcontext) = (size_t)returnPoint;
setcontext(&ucontext2);
}
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