github.com/moontrade/unsafe@v0.9.1/cgo/call_amd64.s (about)

     1  // Copyright 2019 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 "go_asm.h"
     6  #include "go_tls.h"
     7  #include "textflag.h"
     8  
     9  // Based on race_amd64.s; see commentary there.
    10  
    11  #ifdef GOOS_windows
    12  #define RARG0 CX
    13  #define RARG1 DX
    14  #else
    15  #define RARG0 DI
    16  #define RARG1 SI
    17  #endif
    18  
    19  // WARNING!!!
    20  // Go doesn't allow packages outside of runtime to include "go_asm.h" so the below
    21  // defines required were pulled from generated "go_asm.h" by running make in the
    22  // cmd sub-directory of this package. Navigate into the build (WORK) directory and
    23  // look for a go_asm.h file that's big (>10kb). The below defines will be in there.
    24  // The below defines have been observed to be the same across both linux and darwin
    25  // given it appears to be CPU arch based (amd64) only. The below defines are also
    26  // the same for arm64.
    27  //
    28  // Safer to add build tag "libfuzzer" to hook into the auto-generated "go_asm.h".
    29  // However, it's about ~1ns slower per call because of linking overhead somehow.
    30  
    31  #define g_m 48
    32  #define g_sched 56
    33  #define gobuf_sp 0
    34  #define m_g0 0
    35  
    36  // void runtime·libfuzzerCall(fn, arg0, arg1 uintptr)
    37  // Calls C function fn from libFuzzer and passes 2 arguments to it.
    38  TEXT ·NonBlocking(SB), NOSPLIT, $0-24
    39  	MOVQ	fn+0(FP), AX
    40  	MOVQ	arg0+8(FP), RARG0
    41  	MOVQ	arg1+16(FP), RARG1
    42  
    43  	get_tls(R12)
    44  	MOVQ	g(R12), R14
    45  	MOVQ	g_m(R14), R13
    46  
    47  	// Switch to g0 stack.
    48  	MOVQ	SP, R12		// callee-saved, preserved across the CALL
    49  	MOVQ	m_g0(R13), R10
    50  	CMPQ	R10, R14
    51  	JE	call	// already on g0
    52  	MOVQ	(g_sched+gobuf_sp)(R10), SP
    53  call:
    54  	ANDQ	$~15, SP	// alignment for gcc ABI
    55  	CALL	AX
    56  	MOVQ	R12, SP
    57  	// Back to Go world, set special registers.
    58      // The g register (R14) is preserved in C.
    59      //XORPS	X15, X15
    60  	RET