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unix: fix last argument of pselect6 on linux

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On Linux, the last argument of pselect6 system call is **not** a
sigseg_t * pointer, but instead it is a structure of the form:

    struct {
        const sigset_t *ss;     /* Pointer to signal set */
        size_t          ss_len; /* Size (in bytes) of object pointed
    };

See man 2 pselect6.

Fixes #61251

Change-Id: Id0aa122a77796713bc6d624dc395d396fbc0c5e2
GitHub-Last-Rev: cb3c6d7da9b846843a4a81898ebfdcf2e449942a
GitHub-Pull-Request: golang/sys#167
Reviewed-on: https://go-review.googlesource.com/c/sys/+/510195
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
This commit is contained in:
Mauri de Souza Meneguzzo
2023-07-19 00:01:56 +00:00
committed by Gopher Robot
parent 706fa9866a
commit 25d0004552
10 changed files with 67 additions and 7 deletions
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unix/syscall_linux.go
+34 -1
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@@ -1885,7 +1885,7 @@ func Getpgrp() (pid int) {
//sys PerfEventOpen(attr *PerfEventAttr, pid int, cpu int, groupFd int, flags int) (fd int, err error)
//sys PivotRoot(newroot string, putold string) (err error) = SYS_PIVOT_ROOT
//sys Prctl(option int, arg2 uintptr, arg3 uintptr, arg4 uintptr, arg5 uintptr) (err error)
//sys Pselect(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timespec, sigmask *Sigset_t) (n int, err error) = SYS_PSELECT6
//sys pselect6(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timespec, sigmask *sigset_argpack) (n int, err error)
//sys read(fd int, p []byte) (n int, err error)
//sys Removexattr(path string, attr string) (err error)
//sys Renameat2(olddirfd int, oldpath string, newdirfd int, newpath string, flags uint) (err error)
@@ -2438,6 +2438,39 @@ func Getresgid() (rgid, egid, sgid int) {
return int(r), int(e), int(s)
}
// Pselect is a wrapper around the Linux pselect6 system call.
// This version does not modify the timeout argument.
func Pselect(nfd int, r *FdSet, w *FdSet, e *FdSet, timeout *Timespec, sigmask *Sigset_t) (n int, err error) {
// Per https://man7.org/linux/man-pages/man2/select.2.html#NOTES,
// The Linux pselect6() system call modifies its timeout argument.
// [Not modifying the argument] is the behavior required by POSIX.1-2001.
var mutableTimeout *Timespec
if timeout != nil {
mutableTimeout = new(Timespec)
*mutableTimeout = *timeout
}
// The final argument of the pselect6() system call is not a
// sigset_t * pointer, but is instead a structure
var kernelMask *sigset_argpack
if sigmask != nil {
wordBits := 32 << (^uintptr(0) >> 63) // see math.intSize
// A sigset stores one bit per signal,
// offset by 1 (because signal 0 does not exist).
// So the number of words needed is ⌈__C_NSIG - 1 / wordBits⌉.
sigsetWords := (_C__NSIG - 1 + wordBits - 1) / (wordBits)
sigsetBytes := uintptr(sigsetWords * (wordBits / 8))
kernelMask = &sigset_argpack{
ss: sigmask,
ssLen: sigsetBytes,
}
}
return pselect6(nfd, r, w, e, mutableTimeout, kernelMask)
}
/*
* Unimplemented
*/