Implement userspace probe location extraction and registration
authorFrancis Deslauriers <francis.deslauriers@efficios.com>
Fri, 29 Jun 2018 18:33:37 +0000 (14:33 -0400)
committerJérémie Galarneau <jeremie.galarneau@efficios.com>
Fri, 24 Aug 2018 20:00:02 +0000 (16:00 -0400)
These functions use run_as commands to extract the offsets in the binary
where the instrumentation should be placed and pass these offsets
to the kernel tracer along with the FD to complete the registration of
userspace probe events using the two-step registration process.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
include/lttng/event.h
src/bin/lttng-sessiond/kernel.c
src/bin/lttng/commands/list.c

index 548ec2a4691b7900370c4795b55e04daa8e43eca..630d6c1188dd0255e71c11f4c487b4160df1a1ca 100644 (file)
@@ -37,6 +37,7 @@ enum lttng_event_type {
        LTTNG_EVENT_FUNCTION_ENTRY            = 3,
        LTTNG_EVENT_NOOP                      = 4,
        LTTNG_EVENT_SYSCALL                   = 5,
+       LTTNG_EVENT_USERSPACE_PROBE           = 6,
 };
 
 /*
index 8a4652aecf4f548658f716d63aa0a71b0e1e3661..e13925e27c715d2dc796184f105bdef759df3257 100644 (file)
@@ -41,6 +41,8 @@
  */
 static uint64_t next_kernel_channel_key;
 
+#include <lttng/userspace-probe.h>
+#include <lttng/userspace-probe-internal.h>
 /*
  * Add context on a kernel channel.
  *
@@ -191,6 +193,237 @@ error:
        return -1;
 }
 
+/*
+ * Compute the offset of the instrumentation byte in the binary based on the
+ * function probe location using the ELF lookup method.
+ *
+ * Returns 0 on success and set the offset out parameter to the offset of the
+ * elf symbol
+ * Returns -1 on error
+ */
+static
+int extract_userspace_probe_offset_function_elf(
+               struct lttng_userspace_probe_location *probe_location,
+               struct ltt_kernel_session *session, uint64_t *offset)
+{
+       int fd;
+       int ret = 0;
+       const char *symbol = NULL;
+       struct lttng_userspace_probe_location_lookup_method *lookup = NULL;
+       enum lttng_userspace_probe_location_lookup_method_type lookup_method_type;
+
+
+       assert(lttng_userspace_probe_location_get_type(probe_location) ==
+                       LTTNG_USERSPACE_PROBE_LOCATION_TYPE_FUNCTION);
+
+       lookup = lttng_userspace_probe_location_get_lookup_method(
+                       probe_location);
+       if (!lookup) {
+               ret = -1;
+               goto end;
+       }
+
+       lookup_method_type =
+                       lttng_userspace_probe_location_lookup_method_get_type(lookup);
+
+       assert(lookup_method_type ==
+                       LTTNG_USERSPACE_PROBE_LOCATION_LOOKUP_METHOD_TYPE_FUNCTION_ELF);
+
+       symbol = lttng_userspace_probe_location_function_get_function_name(
+                       probe_location);
+       if (!symbol) {
+               ret = -1;
+               goto end;
+       }
+
+       fd = lttng_userspace_probe_location_function_get_binary_fd(probe_location);
+       if (fd < 0) {
+               ret = -1;
+               goto end;
+       }
+
+       ret = run_as_extract_elf_symbol_offset(fd, symbol, session->uid,
+                       session->gid, offset);
+       if (ret < 0) {
+               DBG("userspace probe offset calculation failed for "
+                               "function %s", symbol);
+               goto end;
+       }
+
+       DBG("userspace probe elf offset for %s is 0x%jd", symbol, (intmax_t)(*offset));
+end:
+       return ret;
+}
+
+/*
+ * Compute the offsets of the instrumentation bytes in the binary based on the
+ * tracepoint probe location using the SDT lookup method. This function
+ * allocates the offsets buffer, the caller must free it.
+ *
+ * Returns 0 on success and set the offset out parameter to the offsets of the
+ * SDT tracepoint.
+ * Returns -1 on error.
+ */
+static
+int extract_userspace_probe_offset_tracepoint_sdt(
+               struct lttng_userspace_probe_location *probe_location,
+               struct ltt_kernel_session *session, uint64_t **offsets,
+               uint32_t *offsets_count)
+{
+       enum lttng_userspace_probe_location_lookup_method_type lookup_method_type;
+       struct lttng_userspace_probe_location_lookup_method *lookup = NULL;
+       const char *probe_name = NULL, *provider_name = NULL;
+       int ret = 0;
+       int fd, i;
+
+       assert(lttng_userspace_probe_location_get_type(probe_location) ==
+                       LTTNG_USERSPACE_PROBE_LOCATION_TYPE_TRACEPOINT);
+
+       lookup = lttng_userspace_probe_location_get_lookup_method(probe_location);
+       if (!lookup) {
+               ret = -1;
+               goto end;
+       }
+
+       lookup_method_type =
+                       lttng_userspace_probe_location_lookup_method_get_type(lookup);
+
+       assert(lookup_method_type ==
+                       LTTNG_USERSPACE_PROBE_LOCATION_LOOKUP_METHOD_TYPE_TRACEPOINT_SDT);
+
+
+       probe_name = lttng_userspace_probe_location_tracepoint_get_probe_name(
+                       probe_location);
+       if (!probe_name) {
+               ret = -1;
+               goto end;
+       }
+
+       provider_name = lttng_userspace_probe_location_tracepoint_get_provider_name(
+                       probe_location);
+       if (!provider_name) {
+               ret = -1;
+               goto end;
+       }
+
+       fd = lttng_userspace_probe_location_tracepoint_get_binary_fd(probe_location);
+       if (fd < 0) {
+               ret = -1;
+               goto end;
+       }
+
+       ret = run_as_extract_sdt_probe_offsets(fd, provider_name, probe_name,
+                       session->uid, session->gid, offsets, offsets_count);
+       if (ret < 0) {
+               DBG("userspace probe offset calculation failed for sdt "
+                               "probe %s:%s", provider_name, probe_name);
+               goto end;
+       }
+
+       if (*offsets_count == 0) {
+               DBG("no userspace probe offset found");
+               goto end;
+       }
+
+       DBG("%u userspace probe SDT offsets found for %s:%s at:",
+                       *offsets_count, provider_name, probe_name);
+       for (i = 0; i < *offsets_count; i++) {
+               DBG("\t0x%jd", (intmax_t)((*offsets)[i]));
+       }
+end:
+       return ret;
+}
+
+/*
+ * Extract the offsets of the instrumentation point for the different lookup
+ * methods.
+ */
+static
+int userspace_probe_add_callsites(struct lttng_event *ev,
+                       struct ltt_kernel_session *session, int fd)
+{
+       struct lttng_userspace_probe_location_lookup_method *lookup_method = NULL;
+       enum lttng_userspace_probe_location_lookup_method_type type;
+       struct lttng_userspace_probe_location *location = NULL;
+       int ret;
+
+       assert(ev);
+       assert(ev->type == LTTNG_EVENT_USERSPACE_PROBE);
+
+       location = lttng_event_get_userspace_probe_location(ev);
+       if (!location) {
+               ret = -1;
+               goto end;
+       }
+       lookup_method =
+                       lttng_userspace_probe_location_get_lookup_method(location);
+       if (!lookup_method) {
+               ret = -1;
+               goto end;
+       }
+
+       type = lttng_userspace_probe_location_lookup_method_get_type(lookup_method);
+       switch (type) {
+       case LTTNG_USERSPACE_PROBE_LOCATION_LOOKUP_METHOD_TYPE_FUNCTION_ELF:
+       {
+               struct lttng_kernel_event_callsite callsite;
+               uint64_t offset;
+
+               ret = extract_userspace_probe_offset_function_elf(location, session, &offset);
+               if (ret) {
+                       ret = LTTNG_ERR_PROBE_LOCATION_INVAL;
+                       goto end;
+               }
+
+               callsite.u.uprobe.offset = offset;
+               ret = kernctl_add_callsite(fd, &callsite);
+               if (ret) {
+                       WARN("Adding callsite to userspace probe "
+                                       "event %s failed.", ev->name);
+                       ret = LTTNG_ERR_KERN_ENABLE_FAIL;
+                       goto end;
+               }
+               break;
+       }
+       case LTTNG_USERSPACE_PROBE_LOCATION_LOOKUP_METHOD_TYPE_TRACEPOINT_SDT:
+       {
+               int i;
+               uint64_t *offsets = NULL;
+               uint32_t offsets_count;
+               struct lttng_kernel_event_callsite callsite;
+
+               /*
+                * This call allocates the offsets buffer. This buffer must be freed
+                * by the caller
+                */
+               ret = extract_userspace_probe_offset_tracepoint_sdt(location, session,
+                               &offsets, &offsets_count);
+               if (ret) {
+                       ret = LTTNG_ERR_PROBE_LOCATION_INVAL;
+                       goto end;
+               }
+               for (i = 0; i < offsets_count; i++) {
+                       callsite.u.uprobe.offset = offsets[i];
+                       ret = kernctl_add_callsite(fd, &callsite);
+                       if (ret) {
+                               WARN("Adding callsite to userspace probe "
+                                               "event %s failed.", ev->name);
+                               ret = LTTNG_ERR_KERN_ENABLE_FAIL;
+                               free(offsets);
+                               goto end;
+                       }
+               }
+               free(offsets);
+               break;
+       }
+       default:
+               ret = LTTNG_ERR_PROBE_LOCATION_INVAL;
+               goto end;
+       }
+end:
+       return ret;
+}
+
 /*
  * Create a kernel event, enable it to the kernel tracer and add it to the
  * channel event list of the kernel session.
index 5816a05de36783f7250ed992244c20ce69399081..4a94690b038b4ca20fe9839a01c51637bc457ceb 100644 (file)
@@ -343,6 +343,8 @@ static void print_events(struct lttng_event *event)
                                safe_string(filter_msg));
                break;
        case LTTNG_EVENT_ALL:
+               /* Fall-through. */
+       default:
                /* We should never have "all" events in list. */
                assert(0);
                break;
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