[DTrace-devel] [PATCH 1/3] Implement a 'state' BPF map to communicate tracing session state
Kris Van Hees
kris.van.hees at oracle.com
Thu Aug 27 11:53:47 PDT 2020
The is a need to communicate information about the tracing session
between the BPF programs we generate and the userspace consumer. The
current need covers:
- DT_STATE_ACTIVITY Records the activity state of the session
- DT_STATE_BEGANON Records the CPU the BEGIN probe ran on
- DT_STATE_ENDEDON Records the CPU the END probe ran on
Patches will be forthcoming that provide the implementation of these
features.
Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
libdtrace/dt_bpf.c | 73 +++++++++++++++++++++++++-------------------
libdtrace/dt_dlibs.c | 1 +
libdtrace/dt_impl.h | 1 +
libdtrace/dt_state.h | 27 ++++++++++++++++
4 files changed, 71 insertions(+), 31 deletions(-)
create mode 100644 libdtrace/dt_state.h
diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
index 0531a37e..a381a86e 100644
--- a/libdtrace/dt_bpf.c
+++ b/libdtrace/dt_bpf.c
@@ -14,6 +14,7 @@
#include <dtrace.h>
#include <dt_impl.h>
#include <dt_probe.h>
+#include <dt_state.h>
#include <dt_bpf.h>
#include <port.h>
@@ -51,6 +52,37 @@ dt_bpf_error(dtrace_hdl_t *dtp, const char *fmt, ...)
return dt_set_errno(dtp, EDT_BPF);
}
+/*
+ * Load the value for the given key in the map referenced by the given fd.
+ */
+int dt_bpf_map_lookup(int fd, const void *key, void *val)
+{
+ union bpf_attr attr;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.map_fd = fd;
+ attr.key = (uint64_t)(unsigned long)key;
+ attr.value = (uint64_t)(unsigned long)val;
+
+ return bpf(BPF_MAP_LOOKUP_ELEM, &attr);
+}
+
+/*
+ * Store the (key, value) pair in the map referenced by the given fd.
+ */
+int dt_bpf_map_update(int fd, const void *key, const void *val)
+{
+ union bpf_attr attr;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.map_fd = fd;
+ attr.key = (uint64_t)(unsigned long)key;
+ attr.value = (uint64_t)(unsigned long)val;
+ attr.flags = 0;
+
+ return bpf(BPF_MAP_UPDATE_ELEM, &attr);
+}
+
static int
create_gmap(dtrace_hdl_t *dtp, const char *name, enum bpf_map_type type,
int ksz, int vsz, int size)
@@ -86,6 +118,9 @@ create_gmap(dtrace_hdl_t *dtp, const char *name, enum bpf_map_type type,
* Create the global BPF maps that are shared between all BPF programs in a
* single tracing session:
*
+ * - state: DTrace session state, used to communicate state between BPF
+ * programs and userspace. The content of the map is defined in
+ * dt_state.h.
* - buffers: Perf event output buffer map, associating a perf event output
* buffer with each CPU. The map is indexed by CPU id.
* - cpuinfo: CPU information map, associating a cpuinfo_t structure with
@@ -149,6 +184,13 @@ dt_bpf_gmap_create(dtrace_hdl_t *dtp)
tvarc = dt_idhash_peekid(dtp->dt_tls) - DIF_VAR_OTHER_UBASE;
/* Create global maps as long as there are no errors. */
+ dtp->dt_stmap_fd = create_gmap(dtp, "state", BPF_MAP_TYPE_ARRAY,
+ sizeof(DT_STATE_KEY_TYPE),
+ sizeof(DT_STATE_VAL_TYPE),
+ DT_STATE_NUM_ELEMS);
+ if (dtp->dt_stmap_fd == -1)
+ return -1; /* dt_errno is set for us */
+
if (create_gmap(dtp, "buffers", BPF_MAP_TYPE_PERF_EVENT_ARRAY,
sizeof(uint32_t), sizeof(uint32_t),
dtp->dt_conf.num_online_cpus) == -1)
@@ -185,37 +227,6 @@ dt_bpf_gmap_create(dtrace_hdl_t *dtp)
return 0;
}
-/*
- * Load the value for the given key in the map referenced by the given fd.
- */
-int dt_bpf_map_lookup(int fd, const void *key, void *val)
-{
- union bpf_attr attr;
-
- memset(&attr, 0, sizeof(attr));
- attr.map_fd = fd;
- attr.key = (uint64_t)(unsigned long)key;
- attr.value = (uint64_t)(unsigned long)val;
-
- return bpf(BPF_MAP_LOOKUP_ELEM, &attr);
-}
-
-/*
- * Store the (key, value) pair in the map referenced by the given fd.
- */
-int dt_bpf_map_update(int fd, const void *key, const void *val)
-{
- union bpf_attr attr;
-
- memset(&attr, 0, sizeof(attr));
- attr.map_fd = fd;
- attr.key = (uint64_t)(unsigned long)key;
- attr.value = (uint64_t)(unsigned long)val;
- attr.flags = 0;
-
- return bpf(BPF_MAP_UPDATE_ELEM, &attr);
-}
-
/*
* Perform relocation processing on a program.
*/
diff --git a/libdtrace/dt_dlibs.c b/libdtrace/dt_dlibs.c
index 83eb4a10..15b8525a 100644
--- a/libdtrace/dt_dlibs.c
+++ b/libdtrace/dt_dlibs.c
@@ -65,6 +65,7 @@ static const dt_ident_t dt_bpf_symbols[] = {
DT_BPF_SYMBOL(cpuinfo, DT_IDENT_PTR),
DT_BPF_SYMBOL(gvars, DT_IDENT_PTR),
DT_BPF_SYMBOL(mem, DT_IDENT_PTR),
+ DT_BPF_SYMBOL(state, DT_IDENT_PTR),
DT_BPF_SYMBOL(strtab, DT_IDENT_PTR),
DT_BPF_SYMBOL(tvars, DT_IDENT_PTR),
/* BPF internal identifiers */
diff --git a/libdtrace/dt_impl.h b/libdtrace/dt_impl.h
index 0f79b45f..60095a80 100644
--- a/libdtrace/dt_impl.h
+++ b/libdtrace/dt_impl.h
@@ -339,6 +339,7 @@ struct dtrace_hdl {
int dt_ddefs_fd; /* file descriptor for D CTF debugging cache */
int dt_stdout_fd; /* file descriptor for saved stdout */
int dt_poll_fd; /* file descriptor for event polling */
+ int dt_stmap_fd; /* file descriptor for the 'state' BPF map */
dtrace_handle_err_f *dt_errhdlr; /* error handler, if any */
void *dt_errarg; /* error handler argument */
dtrace_prog_t *dt_errprog; /* error handler program, if any */
diff --git a/libdtrace/dt_state.h b/libdtrace/dt_state.h
new file mode 100644
index 00000000..9acb66b2
--- /dev/null
+++ b/libdtrace/dt_state.h
@@ -0,0 +1,27 @@
+/*
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ *
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ */
+
+#ifndef _DT_STATE_H
+#define _DT_STATE_H
+
+/*
+ * DTrace 'state' BPF map.
+ *
+ * The keys are uint32_t values corresponding to dt_state_elem_t values.
+ * The values are uint32_t values.
+ */
+#define DT_STATE_KEY_TYPE uint32_t
+#define DT_STATE_VAL_TYPE uint32_t
+
+typedef enum dt_state_elem {
+ DT_STATE_ACTIVITY = 0, /* activity state of the seesion */
+ DT_STATE_BEGANON, /* cpu BEGIN probe executed on */
+ DT_STATE_ENDEDON, /* cpu END probe executed on */
+ DT_STATE_NUM_ELEMS
+} dt_state_elem_t;
+
+#endif /* _DT_STATE_H */
--
2.28.0
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