rt0_linux_ppc64le.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#include "go_asm.h"
     6#include "textflag.h"
     7#include "asm_ppc64x.h"
     8
     9TEXT _rt0_ppc64le_linux(SB),NOSPLIT,$0
    10	XOR R0, R0	  // Make sure R0 is zero before _main
    11	BR _main<>(SB)
    12
    13TEXT _rt0_ppc64le_linux_lib(SB),NOSPLIT|NOFRAME,$0
    14	JMP _rt0_ppc64x_lib(SB)
    15
    16TEXT _main<>(SB),NOSPLIT,$-8
    17	// In a statically linked binary, the stack contains argc,
    18	// argv as argc string pointers followed by a NULL, envv as a
    19	// sequence of string pointers followed by a NULL, and auxv.
    20	// The TLS pointer should be initialized to 0.
    21	//
    22	// In an ELFv2 compliant dynamically linked binary, R3 contains argc,
    23	// R4 contains argv, R5 contains envp, R6 contains auxv, and R13
    24	// contains the TLS pointer.
    25	//
    26	// When loading via glibc, the first doubleword on the stack points
    27	// to NULL a value. (that is *(uintptr)(R1) == 0). This is used to
    28	// differentiate static vs dynamically linked binaries.
    29	//
    30	// If loading with the musl loader, it doesn't follow the ELFv2 ABI. It
    31	// passes argc/argv similar to the linux kernel, R13 (TLS) is
    32	// initialized, and R3/R4 are undefined.
    33	MOVD	(R1), R12
    34	CMP	R12, $0
    35	BEQ	tls_and_argcv_in_reg
    36
    37	// Arguments are passed via the stack (musl loader or a static binary)
    38	MOVD	0(R1), R3 // argc
    39	ADD	$8, R1, R4 // argv
    40
    41	// Did the TLS pointer get set? If so, don't change it (e.g musl).
    42	CMP	R13, $0
    43	BNE	tls_and_argcv_in_reg
    44
    45	MOVD	$runtime·m0+m_tls(SB), R13 // TLS
    46	ADD	$0x7000, R13
    47
    48tls_and_argcv_in_reg:
    49	BR	main(SB)
    50
    51TEXT main(SB),NOSPLIT,$-8
    52	MOVD	$runtime·rt0_go(SB), R12
    53	MOVD	R12, CTR
    54	BR	(CTR)
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