GitHubMirror/sys
1
0
Fork 0
mirror of https://github.com/rwinkhart/sys.git synced 2026-09-06 00:57:18 -04:00
Code Issues Packages Projects Releases Wiki Activity

unix: take address in assembly for Darwin syscall wrappers

Browse Source 
In Go 1.17 we will introduce a register-based ABI on some
platforms, as well as ABI wrappers to bridge the ABIs. For Darwin
syscall wrappers, it needs to be called directly, instead of
through wrappers. Currently, it is written as that the syscall
functions are defined in assembly and their addresses are taken
from Go using funcPC. In Go 1.17 this will result in the address
of the ABI wrapper, which is undesired.

In the syscall package in the standard library we changed to use
a compiler intrinsic internal/abi.FuncPCABI0 to take the address
of the syscall function. But that is not available to this repo
and not available in older versions of Go. Here we take a
different approach: taking the address directly from assembly.
This also ensures we get the address of the defined syscall
function, not the ABI wrapper.

Updates golang/go#45702.

Change-Id: Ia7480d0fb0ca4fb9bf2f36d2deb1e3e5e4eb8284
Reviewed-on: https://go-review.googlesource.com/c/sys/+/317894
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Mui
2021-05-07 16:14:34 +00:00
parent 30e306a8bb
commit a76c4d0a00
13 changed files with 2183 additions and 1024 deletions
Download Patch File Download Diff File Expand all files Collapse all files
unix/mksyscall.go
+3 -3
View File
@@ -290,7 +290,7 @@ func main() {
sysname = strings.TrimPrefix(sysname, "SYS_") // remove SYS_
sysname = strings.ToLower(sysname) // lowercase
libcFn = sysname
sysname = "funcPC(libc_" + sysname + "_trampoline)"
sysname = "libc_" + sysname + "_trampoline_addr"
}
// Actual call.
@@ -363,8 +363,8 @@ func main() {
if libc && !trampolines[libcFn] {
// some system calls share a trampoline, like read and readlen.
trampolines[libcFn] = true
// Declare assembly trampoline.
text += fmt.Sprintf("func libc_%s_trampoline()\n", libcFn)
// Declare assembly trampoline address.
text += fmt.Sprintf("var libc_%s_trampoline_addr uintptr\n\n", libcFn)
// Assembly trampoline calls the libc_* function, which this magic
// redirects to use the function from libSystem.
text += fmt.Sprintf("//go:cgo_import_dynamic libc_%s %s \"/usr/lib/libSystem.B.dylib\"\n", libcFn, libcFn)