rt0_linux_ppc64x.s

Documentation: runtime

     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
    19TEXT ENTRYPOINT(SB),NOSPLIT,$0
    20	XOR R0, R0	  // Make sure R0 is zero before _main
    21	BR _main<>(SB)
    22
    23TEXT ENTRYPOINT_LIB(SB),NOSPLIT|NOFRAME,$0
    24	JMP _rt0_ppc64x_lib(SB)
    25
    26TEXT _main<>(SB),NOSPLIT,$-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	$0x7000, R13
    57
    58tls_and_argcv_in_reg:
    59	BR	main(SB)
    60
    61TEXT main(SB),NOSPLIT,$-8
    62	MOVD	$runtime·rt0_go(SB), R12
    63	MOVD	R12, CTR
    64	BR	(CTR)
View as plain text