Revert "os: make use of pidfd on linux"

This reverts CL 528438.

Reason for revert: Implicated in "bad FD" test failures. Full extent of
issue still unclear.

For #62654.
Fixes #65857.

Change-Id: I066e38040544c506917e90255bd0e330964a0276
Reviewed-on: https://go-review.googlesource.com/c/go/+/566477
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

13 files changed, 0 insertions, 163 deletions

diff --git a/src/internal/syscall/unix/pidfd_linux.go b/src/internal/syscall/unix/pidfd_linux.go
index e9417623db..02cfaa062c 100644
--- a/src/internal/syscall/unix/pidfd_linux.go
+++ b/src/internal/syscall/unix/pidfd_linux.go
@@ -13,11 +13,3 @@ func PidFDSendSignal(pidfd uintptr, s syscall.Signal) error {
 	}
 	return nil
 }
-
-func PidFDOpen(pid, flags int) (uintptr, error) {
-	pidfd, _, errno := syscall.Syscall(pidfdOpenTrap, uintptr(pid), uintptr(flags), 0)
-	if errno != 0 {
-		return ^uintptr(0), errno
-	}
-	return uintptr(pidfd), nil
-}
diff --git a/src/internal/syscall/unix/siginfo_linux.go b/src/internal/syscall/unix/siginfo_linux.go
deleted file mode 100644
index 9f83114e45..0000000000
--- a/src/internal/syscall/unix/siginfo_linux.go
+++ /dev/null
@@ -1,64 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package unix
-
-import (
-	"syscall"
-)
-
-const is64bit = ^uint(0) >> 63 // 0 for 32-bit hosts, 1 for 64-bit ones.
-
-// SiginfoChild is a struct filled in by Linux waitid syscall.
-// In C, siginfo_t contains a union with multiple members;
-// this struct corresponds to one used when Signo is SIGCHLD.
-//
-// NOTE fields are exported to be used by TestSiginfoChildLayout.
-type SiginfoChild struct {
-	Signo       int32
-	siErrnoCode                // Two int32 fields, swapped on MIPS.
-	_           [is64bit]int32 // Extra padding for 64-bit hosts only.
-
-	// End of common part. Beginning of signal-specific part.
-
-	Pid    int32
-	Uid    uint32
-	Status int32
-
-	// Pad to 128 bytes.
-	_ [128 - (6+is64bit)*4]byte
-}
-
-const (
-	// Possible values for SiginfoChild.Code field.
-	_CLD_EXITED    int32 = 1
-	_CLD_KILLED          = 2
-	_CLD_DUMPED          = 3
-	_CLD_TRAPPED         = 4
-	_CLD_STOPPED         = 5
-	_CLD_CONTINUED       = 6
-
-	// These are the same as in syscall/syscall_linux.go.
-	core      = 0x80
-	stopped   = 0x7f
-	continued = 0xffff
-)
-
-// WaitStatus converts SiginfoChild, as filled in by the waitid syscall,
-// to syscall.WaitStatus.
-func (s *SiginfoChild) WaitStatus() (ws syscall.WaitStatus) {
-	switch s.Code {
-	case _CLD_EXITED:
-		ws = syscall.WaitStatus(s.Status << 8)
-	case _CLD_DUMPED:
-		ws = syscall.WaitStatus(s.Status) | core
-	case _CLD_KILLED:
-		ws = syscall.WaitStatus(s.Status)
-	case _CLD_TRAPPED, _CLD_STOPPED:
-		ws = syscall.WaitStatus(s.Status<<8) | stopped
-	case _CLD_CONTINUED:
-		ws = continued
-	}
-	return
-}
diff --git a/src/internal/syscall/unix/siginfo_linux_mipsx.go b/src/internal/syscall/unix/siginfo_linux_mipsx.go
deleted file mode 100644
index 2fca0c5505..0000000000
--- a/src/internal/syscall/unix/siginfo_linux_mipsx.go
+++ /dev/null
@@ -1,12 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build linux && (mips || mipsle || mips64 || mips64le)
-
-package unix
-
-type siErrnoCode struct {
-	Code  int32
-	Errno int32
-}
diff --git a/src/internal/syscall/unix/siginfo_linux_other.go b/src/internal/syscall/unix/siginfo_linux_other.go
deleted file mode 100644
index cfdc4ddf51..0000000000
--- a/src/internal/syscall/unix/siginfo_linux_other.go
+++ /dev/null
@@ -1,12 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build linux && !(mips || mipsle || mips64 || mips64le)
-
-package unix
-
-type siErrnoCode struct {
-	Errno int32
-	Code  int32
-}
diff --git a/src/internal/syscall/unix/siginfo_linux_test.go b/src/internal/syscall/unix/siginfo_linux_test.go
deleted file mode 100644
index 596c2ebee3..0000000000
--- a/src/internal/syscall/unix/siginfo_linux_test.go
+++ /dev/null
@@ -1,59 +0,0 @@
-// Copyright 2023 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package unix_test
-
-import (
-	"internal/goarch"
-	"internal/syscall/unix"
-	"runtime"
-	"strings"
-	"testing"
-	"unsafe"
-)
-
-// TestSiginfoChildLayout validates SiginfoChild layout. Modelled after
-// static assertions in linux kernel's arch/*/kernel/signal*.c.
-func TestSiginfoChildLayout(t *testing.T) {
-	var si unix.SiginfoChild
-
-	const host64bit = goarch.PtrSize == 8
-
-	if v := unsafe.Sizeof(si); v != 128 {
-		t.Fatalf("sizeof: got %d, want 128", v)
-	}
-
-	ofSigno := 0
-	ofErrno := 4
-	ofCode := 8
-	if strings.HasPrefix(runtime.GOARCH, "mips") {
-		// These two fields are swapped on MIPS platforms.
-		ofErrno, ofCode = ofCode, ofErrno
-	}
-	ofPid := 12
-	if host64bit {
-		ofPid = 16
-	}
-	ofUid := ofPid + 4
-	ofStatus := ofPid + 8
-
-	offsets := []struct {
-		name string
-		got  uintptr
-		want int
-	}{
-		{"Signo", unsafe.Offsetof(si.Signo), ofSigno},
-		{"Errno", unsafe.Offsetof(si.Errno), ofErrno},
-		{"Code", unsafe.Offsetof(si.Code), ofCode},
-		{"Pid", unsafe.Offsetof(si.Pid), ofPid},
-		{"Uid", unsafe.Offsetof(si.Uid), ofUid},
-		{"Status", unsafe.Offsetof(si.Status), ofStatus},
-	}
-
-	for _, tc := range offsets {
-		if int(tc.got) != tc.want {
-			t.Errorf("offsetof %s: got %d, want %d", tc.name, tc.got, tc.want)
-		}
-	}
-}
diff --git a/src/internal/syscall/unix/sysnum_linux_386.go b/src/internal/syscall/unix/sysnum_linux_386.go
index be048bcf73..9f750a1c03 100644
--- a/src/internal/syscall/unix/sysnum_linux_386.go
+++ b/src/internal/syscall/unix/sysnum_linux_386.go
@@ -8,5 +8,4 @@ const (
 	getrandomTrap       uintptr = 355
 	copyFileRangeTrap   uintptr = 377
 	pidfdSendSignalTrap uintptr = 424
-	pidfdOpenTrap       uintptr = 434
 )
diff --git a/src/internal/syscall/unix/sysnum_linux_amd64.go b/src/internal/syscall/unix/sysnum_linux_amd64.go
index 525de9cbd8..706898d41e 100644
--- a/src/internal/syscall/unix/sysnum_linux_amd64.go
+++ b/src/internal/syscall/unix/sysnum_linux_amd64.go
@@ -8,5 +8,4 @@ const (
 	getrandomTrap       uintptr = 318
 	copyFileRangeTrap   uintptr = 326
 	pidfdSendSignalTrap uintptr = 424
-	pidfdOpenTrap       uintptr = 434
 )
diff --git a/src/internal/syscall/unix/sysnum_linux_arm.go b/src/internal/syscall/unix/sysnum_linux_arm.go
index b803892278..c00644b552 100644
--- a/src/internal/syscall/unix/sysnum_linux_arm.go
+++ b/src/internal/syscall/unix/sysnum_linux_arm.go
@@ -8,5 +8,4 @@ const (
 	getrandomTrap       uintptr = 384
 	copyFileRangeTrap   uintptr = 391
 	pidfdSendSignalTrap uintptr = 424
-	pidfdOpenTrap       uintptr = 434
 )
diff --git a/src/internal/syscall/unix/sysnum_linux_generic.go b/src/internal/syscall/unix/sysnum_linux_generic.go
index b06bf69273..bf25428e7e 100644
--- a/src/internal/syscall/unix/sysnum_linux_generic.go
+++ b/src/internal/syscall/unix/sysnum_linux_generic.go
@@ -14,5 +14,4 @@ const (
 	getrandomTrap       uintptr = 278
 	copyFileRangeTrap   uintptr = 285
 	pidfdSendSignalTrap uintptr = 424
-	pidfdOpenTrap       uintptr = 434
 )
diff --git a/src/internal/syscall/unix/sysnum_linux_mips64x.go b/src/internal/syscall/unix/sysnum_linux_mips64x.go
index 8764f5dc8f..6a9e238ce3 100644
--- a/src/internal/syscall/unix/sysnum_linux_mips64x.go
+++ b/src/internal/syscall/unix/sysnum_linux_mips64x.go
@@ -10,5 +10,4 @@ const (
 	getrandomTrap       uintptr = 5313
 	copyFileRangeTrap   uintptr = 5320
 	pidfdSendSignalTrap uintptr = 5424
-	pidfdOpenTrap       uintptr = 5434
 )
diff --git a/src/internal/syscall/unix/sysnum_linux_mipsx.go b/src/internal/syscall/unix/sysnum_linux_mipsx.go
index 9b2e587ba5..22d38f148e 100644
--- a/src/internal/syscall/unix/sysnum_linux_mipsx.go
+++ b/src/internal/syscall/unix/sysnum_linux_mipsx.go
@@ -10,5 +10,4 @@ const (
 	getrandomTrap       uintptr = 4353
 	copyFileRangeTrap   uintptr = 4360
 	pidfdSendSignalTrap uintptr = 4424
-	pidfdOpenTrap       uintptr = 4434
 )
diff --git a/src/internal/syscall/unix/sysnum_linux_ppc64x.go b/src/internal/syscall/unix/sysnum_linux_ppc64x.go
index 03e9c19743..945ec28c2a 100644
--- a/src/internal/syscall/unix/sysnum_linux_ppc64x.go
+++ b/src/internal/syscall/unix/sysnum_linux_ppc64x.go
@@ -10,5 +10,4 @@ const (
 	getrandomTrap       uintptr = 359
 	copyFileRangeTrap   uintptr = 379
 	pidfdSendSignalTrap uintptr = 424
-	pidfdOpenTrap       uintptr = 434
 )
diff --git a/src/internal/syscall/unix/sysnum_linux_s390x.go b/src/internal/syscall/unix/sysnum_linux_s390x.go
index c6e3e02e46..2c74343820 100644
--- a/src/internal/syscall/unix/sysnum_linux_s390x.go
+++ b/src/internal/syscall/unix/sysnum_linux_s390x.go
@@ -8,5 +8,4 @@ const (
 	getrandomTrap       uintptr = 349
 	copyFileRangeTrap   uintptr = 375
 	pidfdSendSignalTrap uintptr = 424
-	pidfdOpenTrap       uintptr = 434
 )