From 07cb63aae5629213a0f5c484a8d79ae4bc1026e6 Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Thu, 23 Apr 2020 21:15:03 -0700 Subject: [PATCH] syscall: document exact meaning of Ctty field The Ctty field is a child descriptor number when Setctty is set, but a parent descriptor when Foreground is set. This is absurd but changing either behavior breaks existing programs. With this change we at least document how it works. For #29458 Change-Id: If9cf0a1a1e6ed0d4a4edae5043016d5b4ee3308b Reviewed-on: https://go-review.googlesource.com/c/go/+/229768 Run-TryBot: Ian Lance Taylor TryBot-Result: Gobot Gobot Reviewed-by: Damien Neil --- src/syscall/exec_bsd.go | 23 +++++++++++++++++------ src/syscall/exec_darwin.go | 23 +++++++++++++++++------ src/syscall/exec_libc.go | 23 +++++++++++++++++------ src/syscall/exec_linux.go | 25 ++++++++++++++++++------- 4 files changed, 69 insertions(+), 25 deletions(-) diff --git a/src/syscall/exec_bsd.go b/src/syscall/exec_bsd.go index 30b88eba7a..af6c836961 100644 --- a/src/syscall/exec_bsd.go +++ b/src/syscall/exec_bsd.go @@ -15,12 +15,23 @@ type SysProcAttr struct { Credential *Credential // Credential. Ptrace bool // Enable tracing. Setsid bool // Create session. - Setpgid bool // Set process group ID to Pgid, or, if Pgid == 0, to new pid. - Setctty bool // Set controlling terminal to fd Ctty - Noctty bool // Detach fd 0 from controlling terminal - Ctty int // Controlling TTY fd - Foreground bool // Place child's process group in foreground. (Implies Setpgid. Uses Ctty as fd of controlling TTY) - Pgid int // Child's process group ID if Setpgid. + // Setpgid sets the process group ID of the child to Pgid, + // or, if Pgid == 0, to the new child's process ID. + Setpgid bool + // Setctty sets the controlling terminal of the child to + // file descriptor Ctty. Ctty must be a descriptor number + // in the child process: an index into ProcAttr.Files. + // This is only meaningful if Setsid is true. + Setctty bool + Noctty bool // Detach fd 0 from controlling terminal + Ctty int // Controlling TTY fd + // Foreground places the child process group in the foreground. + // This implies Setpgid. The Ctty field must be set to + // the descriptor of the controlling TTY. + // Unlike Setctty, in this case Ctty must be a descriptor + // number in the parent process. + Foreground bool + Pgid int // Child's process group ID if Setpgid. } // Implemented in runtime package. diff --git a/src/syscall/exec_darwin.go b/src/syscall/exec_darwin.go index ac1ead3a2b..f035d55553 100644 --- a/src/syscall/exec_darwin.go +++ b/src/syscall/exec_darwin.go @@ -13,12 +13,23 @@ type SysProcAttr struct { Credential *Credential // Credential. Ptrace bool // Enable tracing. Setsid bool // Create session. - Setpgid bool // Set process group ID to Pgid, or, if Pgid == 0, to new pid. - Setctty bool // Set controlling terminal to fd Ctty - Noctty bool // Detach fd 0 from controlling terminal - Ctty int // Controlling TTY fd - Foreground bool // Place child's process group in foreground. (Implies Setpgid. Uses Ctty as fd of controlling TTY) - Pgid int // Child's process group ID if Setpgid. + // Setpgid sets the process group ID of the child to Pgid, + // or, if Pgid == 0, to the new child's process ID. + Setpgid bool + // Setctty sets the controlling terminal of the child to + // file descriptor Ctty. Ctty must be a descriptor number + // in the child process: an index into ProcAttr.Files. + // This is only meaningful if Setsid is true. + Setctty bool + Noctty bool // Detach fd 0 from controlling terminal + Ctty int // Controlling TTY fd + // Foreground places the child process group in the foreground. + // This implies Setpgid. The Ctty field must be set to + // the descriptor of the controlling TTY. + // Unlike Setctty, in this case Ctty must be a descriptor + // number in the parent process. + Foreground bool + Pgid int // Child's process group ID if Setpgid. } // Implemented in runtime package. diff --git a/src/syscall/exec_libc.go b/src/syscall/exec_libc.go index 0133139000..3722858325 100644 --- a/src/syscall/exec_libc.go +++ b/src/syscall/exec_libc.go @@ -16,12 +16,23 @@ type SysProcAttr struct { Chroot string // Chroot. Credential *Credential // Credential. Setsid bool // Create session. - Setpgid bool // Set process group ID to Pgid, or, if Pgid == 0, to new pid. - Setctty bool // Set controlling terminal to fd Ctty - Noctty bool // Detach fd 0 from controlling terminal - Ctty int // Controlling TTY fd - Foreground bool // Place child's process group in foreground. (Implies Setpgid. Uses Ctty as fd of controlling TTY) - Pgid int // Child's process group ID if Setpgid. + // Setpgid sets the process group ID of the child to Pgid, + // or, if Pgid == 0, to the new child's process ID. + Setpgid bool + // Setctty sets the controlling terminal of the child to + // file descriptor Ctty. Ctty must be a descriptor number + // in the child process: an index into ProcAttr.Files. + // This is only meaningful if Setsid is true. + Setctty bool + Noctty bool // Detach fd 0 from controlling terminal + Ctty int // Controlling TTY fd + // Foreground places the child process group in the foreground. + // This implies Setpgid. The Ctty field must be set to + // the descriptor of the controlling TTY. + // Unlike Setctty, in this case Ctty must be a descriptor + // number in the parent process. + Foreground bool + Pgid int // Child's process group ID if Setpgid. } // Implemented in runtime package. diff --git a/src/syscall/exec_linux.go b/src/syscall/exec_linux.go index f32d682493..23d7343d3a 100644 --- a/src/syscall/exec_linux.go +++ b/src/syscall/exec_linux.go @@ -25,13 +25,24 @@ type SysProcAttr struct { // Ptrace tells the child to call ptrace(PTRACE_TRACEME). // Call runtime.LockOSThread before starting a process with this set, // and don't call UnlockOSThread until done with PtraceSyscall calls. - Ptrace bool - Setsid bool // Create session. - Setpgid bool // Set process group ID to Pgid, or, if Pgid == 0, to new pid. - Setctty bool // Set controlling terminal to fd Ctty (only meaningful if Setsid is set) - Noctty bool // Detach fd 0 from controlling terminal - Ctty int // Controlling TTY fd - Foreground bool // Place child's process group in foreground. (Implies Setpgid. Uses Ctty as fd of controlling TTY) + Ptrace bool + Setsid bool // Create session. + // Setpgid sets the process group ID of the child to Pgid, + // or, if Pgid == 0, to the new child's process ID. + Setpgid bool + // Setctty sets the controlling terminal of the child to + // file descriptor Ctty. Ctty must be a descriptor number + // in the child process: an index into ProcAttr.Files. + // This is only meaningful if Setsid is true. + Setctty bool + Noctty bool // Detach fd 0 from controlling terminal + Ctty int // Controlling TTY fd + // Foreground places the child process group in the foreground. + // This implies Setpgid. The Ctty field must be set to + // the descriptor of the controlling TTY. + // Unlike Setctty, in this case Ctty must be a descriptor + // number in the parent process. + Foreground bool Pgid int // Child's process group ID if Setpgid. Pdeathsig Signal // Signal that the process will get when its parent dies (Linux only) Cloneflags uintptr // Flags for clone calls (Linux only) -- 2.48.1