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Text file src/runtime/cgo/signal_darwin_arm64.s

Documentation: runtime/cgo

     1	// Copyright 2015 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	#include "textflag.h"
     6	
     7	// panicmem is the entrypoint for SIGSEGV as intercepted via a
     8	// mach thread port as EXC_BAD_ACCESS. As the segfault may have happened
     9	// in C code, we first need to load_g then call panicmem.
    10	//
    11	//	R1 - LR at moment of fault
    12	//	R2 - PC at moment of fault
    13	TEXT ·panicmem(SB),NOSPLIT,$-8
    14		// If in external C code, we need to load the g register.
    15		BL  runtime·load_g(SB)
    16		CMP $0, g
    17		BNE ongothread
    18	
    19		// On a foreign thread.
    20		// TODO(crawshaw): call badsignal
    21		MOVD.W $0, -16(RSP)
    22		MOVW $139, R1
    23		MOVW R1, 8(RSP)
    24		B    runtime·exit(SB)
    25	
    26	ongothread:
    27		// Trigger a SIGSEGV panic.
    28		//
    29		// The goal is to arrange the stack so it looks like the runtime
    30		// function sigpanic was called from the PC that faulted. It has
    31		// to be sigpanic, as the stack unwinding code in traceback.go
    32		// looks explicitly for it.
    33		//
    34		// To do this we call into runtime·setsigsegv, which sets the
    35		// appropriate state inside the g object. We give it the faulting
    36		// PC on the stack, then put it in the LR before calling sigpanic.
    37	
    38		// Build a 32-byte stack frame for us for this call.
    39		// Saved LR (none available) is at the bottom,
    40		// then the PC argument for setsigsegv, 
    41		// then a copy of the LR for us to restore.
    42		MOVD.W $0, -32(RSP)
    43		MOVD R1, 8(RSP)
    44		MOVD R2, 16(RSP)
    45		BL runtime·setsigsegv(SB)
    46		MOVD 8(RSP), R1
    47		MOVD 16(RSP), R2
    48	
    49		// Build a 16-byte stack frame for the simulated
    50		// call to sigpanic, by taking 16 bytes away from the
    51		// 32-byte stack frame above.
    52		// The saved LR in this frame is the LR at time of fault,
    53		// and the LR on entry to sigpanic is the PC at time of fault.
    54		MOVD.W R1, 16(RSP)
    55		MOVD R2, R30
    56		B runtime·sigpanic(SB)

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