git: 9c80ad6839cd - main - kinst: add kinst_excluded()

The branch main has been updated by christos:

URL: https://cgit.FreeBSD.org/src/commit/?id=9c80ad6839cd30ecfeff2fb946d86888815da600

commit 9c80ad6839cd30ecfeff2fb946d86888815da600
Author:     Christos Margiolis <christos@FreeBSD.org>
AuthorDate: 2023-05-26 13:54:08 +0000
Commit:     Christos Margiolis <christos@FreeBSD.org>
CommitDate: 2023-05-26 13:54:08 +0000

    kinst: add kinst_excluded()
    
    Exclude functions that are not safe-to-trace.
    
    Reviewed by:    markj
    Approved by:    markj (mentor)
    Sponsored by:   The FreeBSD Foundation
    ifferential Revision:   https://reviews.freebsd.org/D39229
---
 sys/cddl/dev/kinst/amd64/kinst_isa.c | 13 +++++++++-
 sys/cddl/dev/kinst/kinst.c           | 50 ++++++++++++++++++++++++++++++++++++
 sys/cddl/dev/kinst/kinst.h           |  2 ++
 3 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/sys/cddl/dev/kinst/amd64/kinst_isa.c b/sys/cddl/dev/kinst/amd64/kinst_isa.c
index 5035f43be440..7aba79c1d481 100644
--- a/sys/cddl/dev/kinst/amd64/kinst_isa.c
+++ b/sys/cddl/dev/kinst/amd64/kinst_isa.c
@@ -500,7 +500,9 @@ kinst_make_probe(linker_file_t lf, int symindx, linker_symval_t *symval,
 
 	pd = opaque;
 	func = symval->name;
-	if (strcmp(func, pd->kpd_func) != 0 || strcmp(func, "trap_check") == 0)
+	if (kinst_excluded(func))
+		return (0);
+	if (strcmp(func, pd->kpd_func) != 0)
 		return (0);
 
 	instr = (uint8_t *)symval->value;
@@ -605,3 +607,12 @@ kinst_md_deinit(void)
 		}
 	}
 }
+
+/*
+ * Exclude machine-dependent functions that are not safe-to-trace.
+ */
+int
+kinst_md_excluded(const char *name)
+{
+	return (0);
+}
diff --git a/sys/cddl/dev/kinst/kinst.c b/sys/cddl/dev/kinst/kinst.c
index 8c9872ba86c8..46b9bf2f41e8 100644
--- a/sys/cddl/dev/kinst/kinst.c
+++ b/sys/cddl/dev/kinst/kinst.c
@@ -65,6 +65,56 @@ static dtrace_provider_id_t	kinst_id;
 struct kinst_probe_list	*kinst_probetab;
 static struct cdev	*kinst_cdev;
 
+int
+kinst_excluded(const char *name)
+{
+	if (kinst_md_excluded(name))
+		return (1);
+
+	/*
+	 * Anything beginning with "dtrace_" may be called from probe context
+	 * unless it explicitly indicates that it won't be called from probe
+	 * context by using the prefix "dtrace_safe_".
+	 */
+	if (strncmp(name, "dtrace_", strlen("dtrace_")) == 0 &&
+	    strncmp(name, "dtrace_safe_", strlen("dtrace_safe_")) != 0)
+		return (1);
+
+	/*
+	 * Omit instrumentation of functions that are probably in DDB.  It
+	 * makes it too hard to debug broken kinst.
+	 *
+	 * NB: kdb_enter() can be excluded, but its call to printf() can't be.
+	 * This is generally OK since we're not yet in debugging context.
+	 */
+	if (strncmp(name, "db_", strlen("db_")) == 0 ||
+	    strncmp(name, "kdb_", strlen("kdb_")) == 0)
+		return (1);
+
+	/*
+	 * Lock owner methods may be called from probe context.
+	 */
+	if (strcmp(name, "owner_mtx") == 0 ||
+	    strcmp(name, "owner_rm") == 0 ||
+	    strcmp(name, "owner_rw") == 0 ||
+	    strcmp(name, "owner_sx") == 0)
+		return (1);
+
+	/*
+	 * When DTrace is built into the kernel we need to exclude the kinst
+	 * functions from instrumentation.
+	 */
+#ifndef _KLD_MODULE
+	if (strncmp(name, "kinst_", strlen("kinst_")) == 0)
+		return (1);
+#endif
+
+	if (strcmp(name, "trap_check") == 0)
+		return (1);
+
+	return (0);
+}
+
 void
 kinst_probe_create(struct kinst_probe *kp, linker_file_t lf)
 {
diff --git a/sys/cddl/dev/kinst/kinst.h b/sys/cddl/dev/kinst/kinst.h
index b7abfd1e61e0..ee756dc87d09 100644
--- a/sys/cddl/dev/kinst/kinst.h
+++ b/sys/cddl/dev/kinst/kinst.h
@@ -46,6 +46,8 @@ extern struct kinst_probe_list	*kinst_probetab;
 struct linker_file;
 struct linker_symval;
 
+int	kinst_excluded(const char *);
+int	kinst_md_excluded(const char *);
 int	kinst_invop(uintptr_t, struct trapframe *, uintptr_t);
 int	kinst_make_probe(struct linker_file *, int, struct linker_symval *,
 	    void *);