From ac81156bce3ff4bfdcf983cf21acb6830a450a4b Mon Sep 17 00:00:00 2001 From: Cherry Mui Date: Thu, 8 Jun 2023 12:19:54 -0400 Subject: cmd/link: handle dynamic import variables on Darwin Currently, on darwin, we only support cgo_dynamic_import for functions, but not variables, as we don't need it before. mach_task_self_ is a variable defined in the system library, which can be used to e.g. access the process's memory mappings via the mach API. The C header defines a macro mach_task_self(), which refers to the variable. To use mach_task_self_ (in pure-Go programs) we need to access it in Go. This CL handles cgo_dynamic_import for variables in the linker, loading its address via the GOT. (Currently only on Darwin, as we only need it there.) For #50891. Change-Id: Idf64fa88ba2f2381443a1ed0b42b14b581843493 Reviewed-on: https://go-review.googlesource.com/c/go/+/501855 Run-TryBot: Cherry Mui TryBot-Result: Gopher Robot Reviewed-by: Than McIntosh --- src/cmd/link/testdata/dynimportvar/asm/a.go | 15 +++++++++++ src/cmd/link/testdata/dynimportvar/asm/a_amd64.s | 11 ++++++++ src/cmd/link/testdata/dynimportvar/asm/a_arm64.s | 11 ++++++++ src/cmd/link/testdata/dynimportvar/main.go | 32 ++++++++++++++++++++++++ 4 files changed, 69 insertions(+) create mode 100644 src/cmd/link/testdata/dynimportvar/asm/a.go create mode 100644 src/cmd/link/testdata/dynimportvar/asm/a_amd64.s create mode 100644 src/cmd/link/testdata/dynimportvar/asm/a_arm64.s create mode 100644 src/cmd/link/testdata/dynimportvar/main.go (limited to 'src/cmd/link/testdata') diff --git a/src/cmd/link/testdata/dynimportvar/asm/a.go b/src/cmd/link/testdata/dynimportvar/asm/a.go new file mode 100644 index 0000000000..8d9299972b --- /dev/null +++ b/src/cmd/link/testdata/dynimportvar/asm/a.go @@ -0,0 +1,15 @@ +// Copyright 2023 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// This is a separate package because we cannot have Go +// assembly code and cgo code in the same package. + +//go:build darwin + +package asm + +//go:cgo_import_dynamic libc_mach_task_self_ mach_task_self_ "/usr/lib/libSystem.B.dylib" + +// load mach_task_self_ from assembly code +func Mach_task_self() uint32 diff --git a/src/cmd/link/testdata/dynimportvar/asm/a_amd64.s b/src/cmd/link/testdata/dynimportvar/asm/a_amd64.s new file mode 100644 index 0000000000..93547e32f1 --- /dev/null +++ b/src/cmd/link/testdata/dynimportvar/asm/a_amd64.s @@ -0,0 +1,11 @@ +// Copyright 2023 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build darwin + +TEXT ·Mach_task_self(SB),0,$0-4 + MOVQ $libc_mach_task_self_(SB), AX + MOVQ (AX), AX + MOVL AX, ret+0(FP) + RET diff --git a/src/cmd/link/testdata/dynimportvar/asm/a_arm64.s b/src/cmd/link/testdata/dynimportvar/asm/a_arm64.s new file mode 100644 index 0000000000..bd3c9d71f5 --- /dev/null +++ b/src/cmd/link/testdata/dynimportvar/asm/a_arm64.s @@ -0,0 +1,11 @@ +// Copyright 2023 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +//go:build darwin + +TEXT ·Mach_task_self(SB),0,$0-4 + MOVD $libc_mach_task_self_(SB), R0 + MOVD (R0), R0 + MOVW R0, ret+0(FP) + RET diff --git a/src/cmd/link/testdata/dynimportvar/main.go b/src/cmd/link/testdata/dynimportvar/main.go new file mode 100644 index 0000000000..658d340532 --- /dev/null +++ b/src/cmd/link/testdata/dynimportvar/main.go @@ -0,0 +1,32 @@ +// Copyright 2023 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Test that we can access dynamically imported variables. +// We ues mach_task_self_ from darwin's system library. +// Check that loading the variable from C and Go gets the +// same result. + +//go:build darwin + +package main + +/* +#include + +unsigned int Mach_task_self(void) { + return mach_task_self(); +} +*/ +import "C" + +import "cmd/link/testdata/dynimportvar/asm" + +func main() { + c := uint32(C.Mach_task_self()) + a := asm.Mach_task_self() + if a != c { + println("got", a, "want", c) + panic("FAIL") + } +} -- cgit v1.3