rt0_linux_ppc64x.s

     1  // Copyright 2016 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  //go:build (ppc64 || ppc64le) && linux
     6  
     7  #include "go_asm.h"
     8  #include "textflag.h"
     9  #include "asm_ppc64x.h"
    10  
    11  #ifdef GOARCH_ppc64
    12  #define ENTRYPOINT	_rt0_ppc64_linux
    13  #define ENTRYPOINT_LIB	_rt0_ppc64_linux_lib
    14  #else
    15  #define ENTRYPOINT	_rt0_ppc64le_linux
    16  #define ENTRYPOINT_LIB	_rt0_ppc64le_linux_lib
    17  #endif
    18  
    19  TEXT ENTRYPOINT(SB),NOSPLIT,$0
    20  	XOR R0, R0	  // Make sure R0 is zero before _main
    21  	BR _main<>(SB)
    22  
    23  TEXT ENTRYPOINT_LIB(SB),NOSPLIT|NOFRAME,$0
    24  	JMP _rt0_ppc64x_lib(SB)
    25  
    26  TEXT _main<>(SB),NOSPLIT,$-8
    27  	// In a statically linked binary, the stack contains argc,
    28  	// argv as argc string pointers followed by a NULL, envv as a
    29  	// sequence of string pointers followed by a NULL, and auxv.
    30  	// The TLS pointer should be initialized to 0.
    31  	//
    32  	// In an ELFv2 compliant dynamically linked binary, R3 contains argc,
    33  	// R4 contains argv, R5 contains envp, R6 contains auxv, and R13
    34  	// contains the TLS pointer.
    35  	//
    36  	// When loading via glibc, the first doubleword on the stack points
    37  	// to NULL a value. (that is *(uintptr)(R1) == 0). This is used to
    38  	// differentiate static vs dynamically linked binaries.
    39  	//
    40  	// If loading with the musl loader, it doesn't follow the ELFv2 ABI. It
    41  	// passes argc/argv similar to the linux kernel, R13 (TLS) is
    42  	// initialized, and R3/R4 are undefined.
    43  	MOVD	(R1), R12
    44  	CMP	R12, $0
    45  	BEQ	tls_and_argcv_in_reg
    46  
    47  	// Arguments are passed via the stack (musl loader or a static binary)
    48  	MOVD	0(R1), R3 // argc
    49  	ADD	$8, R1, R4 // argv
    50  
    51  	// Did the TLS pointer get set? If so, don't change it (e.g musl).
    52  	CMP	R13, $0
    53  	BNE	tls_and_argcv_in_reg
    54  
    55  	MOVD	$runtime·m0+m_tls(SB), R13 // TLS
    56  	ADD	$0x7000, R13
    57  
    58  tls_and_argcv_in_reg:
    59  	BR	main(SB)
    60  
    61  TEXT main(SB),NOSPLIT,$-8
    62  	MOVD	$runtime·rt0_go(SB), R12
    63  	MOVD	R12, CTR
    64  	BR	(CTR)
    65
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