From 0a1427c5ab7b7524590dd98fa6ed822d6c9d6fa1 Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Mon, 3 Feb 2020 22:26:00 +0000
Subject: [PATCH] ktrace: provide ktrstat_error

This eliminates a branch from its consumers trading it for an extra call
if ktrace is enabled for curthread. Given that this is almost never true,
the tradeoff is worth it.
---
 sys/kern/kern_descrip.c | 14 ++++++--------
 sys/kern/kern_ktrace.c  |  8 ++++++++
 sys/kern/vfs_syscalls.c |  6 ++----
 sys/sys/ktrace.h        |  3 +++
 4 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 629366ac9ea2..84d86bf99b05 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -1445,16 +1445,14 @@ kern_fstat(struct thread *td, int fd, struct stat *sbp)
 	error = fo_stat(fp, sbp, td->td_ucred, td);
 	fdrop(fp, td);
 #ifdef __STAT_TIME_T_EXT
-	if (error == 0) {
-		sbp->st_atim_ext = 0;
-		sbp->st_mtim_ext = 0;
-		sbp->st_ctim_ext = 0;
-		sbp->st_btim_ext = 0;
-	}
+	sbp->st_atim_ext = 0;
+	sbp->st_mtim_ext = 0;
+	sbp->st_ctim_ext = 0;
+	sbp->st_btim_ext = 0;
 #endif
 #ifdef KTRACE
-	if (error == 0 && KTRPOINT(td, KTR_STRUCT))
-		ktrstat(sbp);
+	if (KTRPOINT(td, KTR_STRUCT))
+		ktrstat_error(sbp, error);
 #endif
 	return (error);
 }
diff --git a/sys/kern/kern_ktrace.c b/sys/kern/kern_ktrace.c
index a6788afad3b8..b4df404afe0c 100644
--- a/sys/kern/kern_ktrace.c
+++ b/sys/kern/kern_ktrace.c
@@ -778,6 +778,14 @@ ktrstruct(const char *name, const void *data, size_t datalen)
 	ktr_submitrequest(curthread, req);
 }
 
+void
+ktrstruct_error(const char *name, const void *data, size_t datalen, int error)
+{
+
+	if (error == 0)
+		ktrstruct(name, data, datalen);
+}
+
 void
 ktrstructarray(const char *name, enum uio_seg seg, const void *data,
     int num_items, size_t struct_size)
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 20ed0dc8f39d..c22cb8662eae 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -2349,8 +2349,6 @@ kern_statat(struct thread *td, int flag, int fd, const char *path,
 	}
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	vput(nd.ni_vp);
-	if (error != 0)
-		return (error);
 #ifdef __STAT_TIME_T_EXT
 	sbp->st_atim_ext = 0;
 	sbp->st_mtim_ext = 0;
@@ -2359,9 +2357,9 @@ kern_statat(struct thread *td, int flag, int fd, const char *path,
 #endif
 #ifdef KTRACE
 	if (KTRPOINT(td, KTR_STRUCT))
-		ktrstat(sbp);
+		ktrstat_error(sbp, error);
 #endif
-	return (0);
+	return (error);
 }
 
 #if defined(COMPAT_FREEBSD11)
diff --git a/sys/sys/ktrace.h b/sys/sys/ktrace.h
index 97fe82730315..0a37e1dea718 100644
--- a/sys/sys/ktrace.h
+++ b/sys/sys/ktrace.h
@@ -280,6 +280,7 @@ void	ktrprocexit(struct thread *);
 void	ktrprocfork(struct proc *, struct proc *);
 void	ktruserret(struct thread *);
 void	ktrstruct(const char *, const void *, size_t);
+void	ktrstruct_error(const char *, const void *, size_t, int);
 void	ktrstructarray(const char *, enum uio_seg, const void *, int, size_t);
 void	ktrcapfail(enum ktr_cap_fail_type, const cap_rights_t *,
 	    const cap_rights_t *);
@@ -291,6 +292,8 @@ void	ktrcapfail(enum ktr_cap_fail_type, const cap_rights_t *,
 	ktrstruct("sockaddr", (s), ((struct sockaddr *)(s))->sa_len)
 #define ktrstat(s) \
 	ktrstruct("stat", (s), sizeof(struct stat))
+#define ktrstat_error(s, error) \
+	ktrstruct_error("stat", (s), sizeof(struct stat), error)
 extern u_int ktr_geniosize;
 #else