The branch main has been updated by mjg:
URL:
https://cgit.FreeBSD.org/src/commit/?id=d81aefa8b7dd8cbeffeda541fca9962802404983
commit d81aefa8b7dd8cbeffeda541fca9962802404983
Author: Mateusz Guzik <m...@freebsd.org>
AuthorDate: 2021-05-25 17:34:26 +0000
Commit: Mateusz Guzik <m...@freebsd.org>
CommitDate: 2021-05-29 22:04:09 +0000
vfs: use the sentinel trick in locked lookup path parsing
---
sys/kern/vfs_lookup.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index 5336bf87ec68..e0b98c9f5661 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -850,6 +850,7 @@ lookup(struct nameidata *ndp)
{
char *cp; /* pointer into pathname argument */
char *prev_ni_next; /* saved ndp->ni_next */
+ char *nulchar; /* location of '\0' in cn_pnbuf */
struct vnode *dp = NULL; /* the directory we are searching */
struct vnode *tdp; /* saved dp */
struct mount *mp; /* mount table entry */
@@ -909,9 +910,23 @@ dirloop:
* cnp->cn_nameptr for callers that need the name. Callers needing
* the name set the SAVENAME flag. When done, they assume
* responsibility for freeing the pathname buffer.
+ *
+ * Store / as a temporary sentinel so that we only have one character
+ * to test for. Pathnames tend to be short so this should not be
+ * resulting in cache misses.
*/
- for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
+ nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
+ KASSERT(*nulchar == '\0',
+ ("%s: expected nul at %p; string [%s]\n", __func__, nulchar,
+ cnp->cn_pnbuf));
+ *nulchar = '/';
+ for (cp = cnp->cn_nameptr; *cp != '/'; cp++) {
+ KASSERT(*cp != '\0',
+ ("%s: encountered unexpected nul; string [%s]\n", __func__,
+ cnp->cn_nameptr));
continue;
+ }
+ *nulchar = '\0';
cnp->cn_namelen = cp - cnp->cn_nameptr;
if (cnp->cn_namelen > NAME_MAX) {
error = ENAMETOOLONG;
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