From b63b6b847122e058977934c5af7841f47485177d Mon Sep 17 00:00:00 2001
From: Ed Schouten <eschouten@apple.com>
Date: Tue, 25 Jul 2023 08:52:39 +0200
Subject: [PATCH] unix: retry fetching of lists through sysctl if the size
 changes

On macOS, the SysctlKinfoProcSlice() function may be used to fetch the
contents of the process table. As the process table may grow between the
first and second call to sysctl(), the second call may fail with ENOMEM.
In that case we simply need to retry.
---
 unix/syscall_darwin.go | 50 +++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 22 deletions(-)

diff --git a/unix/syscall_darwin.go b/unix/syscall_darwin.go
index 206921504..135cc3cd7 100644
--- a/unix/syscall_darwin.go
+++ b/unix/syscall_darwin.go
@@ -510,30 +510,36 @@ func SysctlKinfoProcSlice(name string, args ...int) ([]KinfoProc, error) {
 		return nil, err
 	}
 
-	// Find size.
-	n := uintptr(0)
-	if err := sysctl(mib, nil, &n, nil, 0); err != nil {
-		return nil, err
-	}
-	if n == 0 {
-		return nil, nil
-	}
-	if n%SizeofKinfoProc != 0 {
-		return nil, fmt.Errorf("sysctl() returned a size of %d, which is not a multiple of %d", n, SizeofKinfoProc)
-	}
+	for {
+		// Find size.
+		n := uintptr(0)
+		if err := sysctl(mib, nil, &n, nil, 0); err != nil {
+			return nil, err
+		}
+		if n == 0 {
+			return nil, nil
+		}
+		if n%SizeofKinfoProc != 0 {
+			return nil, fmt.Errorf("sysctl() returned a size of %d, which is not a multiple of %d", n, SizeofKinfoProc)
+		}
 
-	// Read into buffer of that size.
-	buf := make([]KinfoProc, n/SizeofKinfoProc)
-	if err := sysctl(mib, (*byte)(unsafe.Pointer(&buf[0])), &n, nil, 0); err != nil {
-		return nil, err
-	}
-	if n%SizeofKinfoProc != 0 {
-		return nil, fmt.Errorf("sysctl() returned a size of %d, which is not a multiple of %d", n, SizeofKinfoProc)
-	}
+		// Read into buffer of that size.
+		buf := make([]KinfoProc, n/SizeofKinfoProc)
+		if err := sysctl(mib, (*byte)(unsafe.Pointer(&buf[0])), &n, nil, 0); err != nil {
+			if err == ENOMEM {
+				// Process table grew. Try again.
+				continue
+			}
+			return nil, err
+		}
+		if n%SizeofKinfoProc != 0 {
+			return nil, fmt.Errorf("sysctl() returned a size of %d, which is not a multiple of %d", n, SizeofKinfoProc)
+		}
 
-	// The actual call may return less than the original reported required
-	// size so ensure we deal with that.
-	return buf[:n/SizeofKinfoProc], nil
+		// The actual call may return less than the original reported required
+		// size so ensure we deal with that.
+		return buf[:n/SizeofKinfoProc], nil
+	}
 }
 
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