From: Martin Pieuchot <mpi@grenadille.net>
Subject: ktrace vs KERNEL_LOCK
To: tech@openbsd.org
Date: Tue, 24 Dec 2024 12:21:24 +0100

Diff below is extract from my previous VFS syscalls unlocking diff.  It
ensures the KERNEL_LOCK() is taken around all ktrwrite{,2}() calls.

This should be enough to unlock remaining syscalls without having to
care about ktrace bits.

ok?

Index: kern/kern_ktrace.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_ktrace.c,v
diff -u -p -r1.114 kern_ktrace.c
--- kern/kern_ktrace.c	15 Dec 2023 15:12:08 -0000	1.114
+++ kern/kern_ktrace.c	24 Dec 2024 11:14:56 -0000
@@ -179,7 +179,9 @@ ktrsyscall(struct proc *p, register_t co
 		*argp++ = args[i];
 	if (nargs && copyin((void *)args[0], argp, nargs * sizeof(int)))
 		memset(argp, 0, nargs * sizeof(int));
+	KERNEL_LOCK();
 	ktrwrite(p, &kth, ktp, len);
+	KERNEL_UNLOCK();
 	free(ktp, M_TEMP, len);
 	atomic_clearbits_int(&p->p_flag, P_INKTR);
 }
@@ -203,7 +205,9 @@ ktrsysret(struct proc *p, register_t cod
 		len = sizeof(long long);
 	else
 		len = sizeof(register_t);
+	KERNEL_LOCK();
 	ktrwrite2(p, &kth, &ktp, sizeof(ktp), retval, len);
+	KERNEL_UNLOCK();
 	atomic_clearbits_int(&p->p_flag, P_INKTR);
 }
 
@@ -214,7 +218,9 @@ ktrnamei(struct proc *p, char *path)
 
 	atomic_setbits_int(&p->p_flag, P_INKTR);
 	ktrinitheader(&kth, p, KTR_NAMEI);
+	KERNEL_LOCK();
 	ktrwrite(p, &kth, path, strlen(path));
+	KERNEL_UNLOCK();
 	atomic_clearbits_int(&p->p_flag, P_INKTR);
 }
 
@@ -351,7 +357,7 @@ void
 ktrexec(struct proc *p, int type, const char *data, ssize_t len)
 {
 	struct ktr_header kth;
-	int count;
+	int count, error;
 	int buflen;
 
 	assert(type == KTR_EXECARGS || type == KTR_EXECENV);
@@ -373,7 +379,10 @@ ktrexec(struct proc *p, int type, const 
 		sched_pause(preempt);
 
 		count = lmin(len, buflen);
-		if (ktrwrite(p, &kth, data, count) != 0)
+		KERNEL_LOCK();
+		error = ktrwrite(p, &kth, data, count);
+		KERNEL_UNLOCK();
+		if (error != 0)
 			break;
 
 		len -= count;
Index: sys//syscall_mi.h
===================================================================
RCS file: /cvs/src/sys/sys/syscall_mi.h,v
diff -u -p -r1.36 syscall_mi.h
--- sys//syscall_mi.h	29 Oct 2024 12:40:17 -0000	1.36
+++ sys//syscall_mi.h	24 Dec 2024 11:13:18 -0000
@@ -151,9 +151,7 @@ mi_syscall(struct proc *p, register_t co
 #ifdef KTRACE
 	if (KTRPOINT(p, KTR_SYSCALL)) {
 		/* convert to mask, then include with code */
-		KERNEL_LOCK();
 		ktrsyscall(p, code, callp->sy_argsize, argp);
-		KERNEL_UNLOCK();
 	}
 #endif
 
@@ -203,9 +201,7 @@ mi_syscall_return(struct proc *p, regist
 
 #ifdef KTRACE
 	if (KTRPOINT(p, KTR_SYSRET)) {
-		KERNEL_LOCK();
 		ktrsysret(p, code, error, retval);
-		KERNEL_UNLOCK();
 	}
 #endif
 }
@@ -238,9 +234,7 @@ mi_child_return(struct proc *p)
 
 #ifdef KTRACE
 	if (KTRPOINT(p, KTR_SYSRET)) {
-		KERNEL_LOCK();
 		ktrsysret(p, code, 0, child_retval);
-		KERNEL_UNLOCK();
 	}
 #endif
 }