From d1b1145cace8b968307f9311ff611e4bb810710c Mon Sep 17 00:00:00 2001 From: "Andrew G. Morgan" Date: Mon, 9 Dec 2019 21:50:16 -0800 Subject: syscall: support POSIX semantics for Linux syscalls This change adds two new methods for invoking system calls under Linux: syscall.AllThreadsSyscall() and syscall.AllThreadsSyscall6(). These system call wrappers ensure that all OSThreads mirror a common system call. The wrappers serialize execution of the runtime to ensure no race conditions where any Go code observes a non-atomic OS state change. As such, the syscalls have higher runtime overhead than regular system calls, and only need to be used where such thread (or 'm' in the parlance of the runtime sources) consistency is required. The new support is used to enable these functions under Linux: syscall.Setegid(), syscall.Seteuid(), syscall.Setgroups(), syscall.Setgid(), syscall.Setregid(), syscall.Setreuid(), syscall.Setresgid(), syscall.Setresuid() and syscall.Setuid(). They work identically to their glibc counterparts. Extensive discussion of the background issue addressed in this patch can be found here: https://github.com/golang/go/issues/1435 In the case where cgo is used, the C runtime can launch pthreads that are not managed by the Go runtime. As such, the added syscall.AllThreadsSyscall*() return ENOTSUP when cgo is enabled. However, for the 9 syscall.Set*() functions listed above, when cgo is active, these functions redirect to invoke their C.set*() equivalents in glibc, which wraps the raw system calls with a nptl:setxid fixup mechanism. This achieves POSIX semantics for these functions in the combined Go and C runtime. As a side note, the glibc/nptl:setxid support (2019-11-30) does not extend to all security related system calls under Linux so using native Go (CGO_ENABLED=0) and these AllThreadsSyscall*()s, where needed, will yield more well defined/consistent behavior over all threads of a Go program. That is, using the syscall.AllThreadsSyscall*() wrappers for things like setting state through SYS_PRCTL and SYS_CAPSET etc. Fixes #1435 Change-Id: Ib1a3e16b9180f64223196a32fc0f9dce14d9105c Reviewed-on: https://go-review.googlesource.com/c/go/+/210639 Trust: Emmanuel Odeke Trust: Ian Lance Taylor Trust: Michael Pratt Run-TryBot: Emmanuel Odeke Reviewed-by: Michael Pratt Reviewed-by: Austin Clements --- src/syscall/syscall_linux_arm.go | 5 ----- 1 file changed, 5 deletions(-) (limited to 'src/syscall/syscall_linux_arm.go') diff --git a/src/syscall/syscall_linux_arm.go b/src/syscall/syscall_linux_arm.go index c4c403a400..61133a59fb 100644 --- a/src/syscall/syscall_linux_arm.go +++ b/src/syscall/syscall_linux_arm.go @@ -63,7 +63,6 @@ func Seek(fd int, offset int64, whence int) (newoffset int64, err error) { //sys bind(s int, addr unsafe.Pointer, addrlen _Socklen) (err error) //sys connect(s int, addr unsafe.Pointer, addrlen _Socklen) (err error) //sysnb getgroups(n int, list *_Gid_t) (nn int, err error) = SYS_GETGROUPS32 -//sysnb setgroups(n int, list *_Gid_t) (err error) = SYS_SETGROUPS32 //sys getsockopt(s int, level int, name int, val unsafe.Pointer, vallen *_Socklen) (err error) //sys setsockopt(s int, level int, name int, val unsafe.Pointer, vallen uintptr) (err error) //sysnb socket(domain int, typ int, proto int) (fd int, err error) @@ -94,10 +93,6 @@ func Seek(fd int, offset int64, whence int) (newoffset int64, err error) { //sys Select(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timeval) (n int, err error) = SYS__NEWSELECT //sys Setfsgid(gid int) (err error) = SYS_SETFSGID32 //sys Setfsuid(uid int) (err error) = SYS_SETFSUID32 -//sysnb Setregid(rgid int, egid int) (err error) = SYS_SETREGID32 -//sysnb Setresgid(rgid int, egid int, sgid int) (err error) = SYS_SETRESGID32 -//sysnb Setresuid(ruid int, euid int, suid int) (err error) = SYS_SETRESUID32 -//sysnb Setreuid(ruid int, euid int) (err error) = SYS_SETREUID32 //sys Shutdown(fd int, how int) (err error) //sys Splice(rfd int, roff *int64, wfd int, woff *int64, len int, flags int) (n int, err error) //sys Ustat(dev int, ubuf *Ustat_t) (err error) -- cgit v1.2.1