syscall: split out env logic so wasip2 can do non-libc version

Author: dgryski

compiler/symbol.go

@@ -346,7 +346,7 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
 // The list of allowed types is based on this proposal:
 // https://github.com/golang/go/issues/59149
 func (c *compilerContext) checkWasmImport(f *ssa.Function, pragma string) {
-	if c.pkg.Path() == "runtime" || c.pkg.Path() == "syscall/js" {
+	if c.pkg.Path() == "runtime" || c.pkg.Path() == "syscall/js" || c.pkg.Path() == "syscall" {
 		// The runtime is a special case. Allow all kinds of parameters
 		// (importantly, including pointers).
 		return

src/syscall/env_libc.go

@@ -0,0 +1,59 @@
+//go:build (darwin || nintendoswitch || wasi || wasip1) && !wasip2
+
+package syscall
+
+import (
+	"unsafe"
+)
+
+func Environ() []string {
+
+	// This function combines all the environment into a single allocation.
+	// While this optimizes for memory usage and garbage collector
+	// overhead, it does run the risk of potentially pinning a "large"
+	// allocation if a user holds onto a single environment variable or
+	// value.  Having each variable be its own allocation would make the
+	// trade-off in the other direction.
+
+	// calculate total memory required
+	var length uintptr
+	var vars int
+	for environ := libc_environ; *environ != nil; {
+		length += libc_strlen(*environ)
+		vars++
+		environ = (*unsafe.Pointer)(unsafe.Add(unsafe.Pointer(environ), unsafe.Sizeof(environ)))
+	}
+
+	// allocate our backing slice for the strings
+	b := make([]byte, length)
+	// and the slice we're going to return
+	envs := make([]string, 0, vars)
+
+	// loop over the environment again, this time copying over the data to the backing slice
+	for environ := libc_environ; *environ != nil; {
+		length = libc_strlen(*environ)
+		// construct a Go string pointing at the libc-allocated environment variable data
+		var envVar string
+		rawEnvVar := (*struct {
+			ptr    unsafe.Pointer
+			length uintptr
+		})(unsafe.Pointer(&envVar))
+		rawEnvVar.ptr = *environ
+		rawEnvVar.length = length
+		// pull off the number of bytes we need for this environment variable
+		var bs []byte
+		bs, b = b[:length], b[length:]
+		// copy over the bytes to the Go heap
+		copy(bs, envVar)
+		// convert trimmed slice to string
+		s := *(*string)(unsafe.Pointer(&bs))
+		// add s to our list of environment variables
+		envs = append(envs, s)
+		// environ++
+		environ = (*unsafe.Pointer)(unsafe.Add(unsafe.Pointer(environ), unsafe.Sizeof(environ)))
+	}
+	return envs
+}
+
+//go:extern environ
+var libc_environ *unsafe.Pointer

src/syscall/env_wasip2.go

@@ -0,0 +1,51 @@
+//go:build wasip2
+
+package syscall
+
+import (
+	"unsafe"
+)
+
+type __wasi_list_tuple struct {
+	ptr unsafe.Pointer
+	len uint32
+}
+
+type __wasi_tuple_string_string struct {
+	first  __wasi_string
+	second __wasi_string
+}
+
+type __wasi_string struct {
+	data unsafe.Pointer
+	len  uint32
+}
+
+type _string struct {
+	ptr    *byte
+	length uintptr
+}
+
+//go:wasmimport wasi:cli/[email protected] get-environment
+func __wasi_cli_environment_get_environment() __wasi_list_tuple
+
+func Environ() []string {
+	var envs []string
+	list_tuple := __wasi_cli_environment_get_environment()
+	envs = make([]string, list_tuple.len)
+	ptr := list_tuple.ptr
+	for i := uint32(0); i < list_tuple.len; i++ {
+		tuple := *(*__wasi_tuple_string_string)(ptr)
+		first, second := tuple.first, tuple.second
+		envKey := _string{
+			(*byte)(first.data), uintptr(first.len),
+		}
+		envValue := _string{
+			(*byte)(second.data), uintptr(second.len),
+		}
+		envs[i] = *(*string)(unsafe.Pointer(&envKey)) + "=" + *(*string)(unsafe.Pointer(&envValue))
+		ptr = unsafe.Add(ptr, unsafe.Sizeof(__wasi_tuple_string_string{}))
+	}
+
+	return envs
+}

src/syscall/libc_wasip2.go

@@ -152,9 +152,6 @@ func unlink(pathname *byte) int32 {
 	return 0
 }
 
-//go:export environ
-var environ *unsafe.Pointer
-
 // int getpagesize(void);
 //
 //go:export getpagesize

src/syscall/syscall_libc.go

@@ -250,55 +250,6 @@ func Mprotect(b []byte, prot int) (err error) {
 	return
 }
 
-func Environ() []string {
-
-	// This function combines all the environment into a single allocation.
-	// While this optimizes for memory usage and garbage collector
-	// overhead, it does run the risk of potentially pinning a "large"
-	// allocation if a user holds onto a single environment variable or
-	// value.  Having each variable be its own allocation would make the
-	// trade-off in the other direction.
-
-	// calculate total memory required
-	var length uintptr
-	var vars int
-	for environ := libc_environ; *environ != nil; {
-		length += libc_strlen(*environ)
-		vars++
-		environ = (*unsafe.Pointer)(unsafe.Add(unsafe.Pointer(environ), unsafe.Sizeof(environ)))
-	}
-
-	// allocate our backing slice for the strings
-	b := make([]byte, length)
-	// and the slice we're going to return
-	envs := make([]string, 0, vars)
-
-	// loop over the environment again, this time copying over the data to the backing slice
-	for environ := libc_environ; *environ != nil; {
-		length = libc_strlen(*environ)
-		// construct a Go string pointing at the libc-allocated environment variable data
-		var envVar string
-		rawEnvVar := (*struct {
-			ptr    unsafe.Pointer
-			length uintptr
-		})(unsafe.Pointer(&envVar))
-		rawEnvVar.ptr = *environ
-		rawEnvVar.length = length
-		// pull off the number of bytes we need for this environment variable
-		var bs []byte
-		bs, b = b[:length], b[length:]
-		// copy over the bytes to the Go heap
-		copy(bs, envVar)
-		// convert trimmed slice to string
-		s := *(*string)(unsafe.Pointer(&bs))
-		// add s to our list of environment variables
-		envs = append(envs, s)
-		// environ++
-		environ = (*unsafe.Pointer)(unsafe.Add(unsafe.Pointer(environ), unsafe.Sizeof(environ)))
-	}
-	return envs
-}
-
 // BytePtrFromString returns a pointer to a NUL-terminated array of
 // bytes containing the text of s. If s contains a NUL byte at any
 // location, it returns (nil, EINVAL).
@@ -430,6 +381,3 @@ func libc_readlink(path *byte, buf *byte, count uint) int
 //
 //export unlink
 func libc_unlink(pathname *byte) int32
-
-//go:extern environ
-var libc_environ *unsafe.Pointer