[DTrace-devel] [PATCH] Add support for built-in variable execname

[Kris Van Hees]

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
 bpf/get_bvar.c                              | 21 +++++++++++++++++++++
 libdtrace/dt_bpf.c                          |  4 ++++
 libdtrace/dt_state.h                        |  2 ++
 test/unittest/variables/bvar/tst.execname.d |  3 +--
 test/unittest/variables/bvar/tst.execname.r |  1 +
 5 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 test/unittest/variables/bvar/tst.execname.r

diff --git a/bpf/get_bvar.c b/bpf/get_bvar.c
index 67346014..f8b03487 100644
--- a/bpf/get_bvar.c
+++ b/bpf/get_bvar.c
@@ -133,6 +133,27 @@ noinline uint64_t dt_get_bvar(const dt_dctx_t *dctx, uint32_t id)
 
 		return val & 0x00000000ffffffffUL;
 	}
+	case DIF_VAR_EXECNAME: {
+		uint64_t	ptr;
+		uint32_t	key;
+		uint32_t	*comm_off;
+
+		/*
+		 * In the "state" map, look up the "struct task_struct" offset
+		 * of "comm".
+		 */
+		key = DT_STATE_TASK_COMM_OFF;
+		comm_off = bpf_map_lookup_elem(&state, &key);
+		if (comm_off == NULL)
+			return 0;
+
+		/* &(current->comm) */
+		ptr = bpf_get_current_task();
+		if (ptr == 0)
+			return error(dctx, DTRACEFLT_BADADDR, ptr);
+
+		return (uint64_t)ptr + *comm_off;
+	}
 	case DIF_VAR_WALLTIMESTAMP:
 		return bpf_ktime_get_ns() + ((uint64_t)&BOOTTM);
 	case DIF_VAR_PPID: {
diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index 4fa447da..8b551354 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -153,6 +153,10 @@ set_task_offsets(dtrace_hdl_t *dtp)
 		return -1;
 	dt_state_set_offtgid(dtp, ctm.ctm_offset / NBBY);
 
+	if (ctf_member_info(cfp, type, "comm", &ctm) == CTF_ERR)
+		return -1;
+	dt_state_set_offcomm(dtp, ctm.ctm_offset / NBBY);
+
 	return 0;
 }
 
diff --git a/libdtrace/dt_state.h b/libdtrace/dt_state.h
index 68ea6337..d48082e9 100644
--- a/libdtrace/dt_state.h
+++ b/libdtrace/dt_state.h
@@ -23,6 +23,7 @@ typedef enum dt_state_elem {
 	DT_STATE_ENDEDON,		/* cpu END probe executed on */
 	DT_STATE_TASK_PARENT_OFF,	/* offsetof(struct task_struct, real_parent) */
 	DT_STATE_TASK_TGID_OFF,		/* offsetof(struct task_struct, tgid) */
+	DT_STATE_TASK_COMM_OFF,		/* offsetof(struct task_struct, comm) */
 	DT_STATE_NUM_ELEMS
 } dt_state_elem_t;
 
@@ -66,6 +67,7 @@ dt_state_set(dtrace_hdl_t *dtp, uint32_t key, uint32_t val)
 
 # define dt_state_set_offparent(dtp, x)	dt_state_set(dtp, DT_STATE_TASK_PARENT_OFF, (x))
 # define dt_state_set_offtgid(dtp, x)	dt_state_set(dtp, DT_STATE_TASK_TGID_OFF, (x))
+# define dt_state_set_offcomm(dtp, x)	dt_state_set(dtp, DT_STATE_TASK_COMM_OFF, (x))
 #endif
 
 #endif /* _DT_STATE_H */
diff --git a/test/unittest/variables/bvar/tst.execname.d b/test/unittest/variables/bvar/tst.execname.d
index 8bb89b54..d0b1853d 100644
--- a/test/unittest/variables/bvar/tst.execname.d
+++ b/test/unittest/variables/bvar/tst.execname.d
@@ -4,7 +4,6 @@
  * Licensed under the Universal Permissive License v 1.0 as shown at
  * http://oss.oracle.com/licenses/upl.
  */
-/* @@xfail: dtv2 */
 
 /*
  * ASSERTION: The 'execname' variable can be accessed and is not -1.
@@ -16,7 +15,7 @@
 
 BEGIN {
 	trace(execname);
-	exit(execname != -1 ? 0 : 1);
+	exit(0);
 }
 
 ERROR {
diff --git a/test/unittest/variables/bvar/tst.execname.r b/test/unittest/variables/bvar/tst.execname.r
new file mode 100644
index 00000000..d60e7352
--- /dev/null
+++ b/test/unittest/variables/bvar/tst.execname.r
@@ -0,0 +1 @@
+dtrace
-- 
2.34.1