Fix: race between lttng-ust getenv() and application setenv()

[lttng-ust.git] / liblttng-ust / lttng-ust-statedump.c

diff --git a/liblttng-ust/lttng-ust-statedump.c b/liblttng-ust/lttng-ust-statedump.c
index c676a3451e24698671413658add89dea9e18b6e0..ea80817bd9807fd99cdfdabb8d12a2e58c4015c3 100644 (file)
--- a/liblttng-ust/lttng-ust-statedump.c
+++ b/liblttng-ust/lttng-ust-statedump.c
@@ -31,6 +31,7 @@
 #include <lttng/ust-elf.h>
 #include "lttng-tracer-core.h"
 #include "lttng-ust-statedump.h"
+#include "getenv.h"
 
 #define TRACEPOINT_DEFINE
 #define TRACEPOINT_CREATE_PROBES
@@ -53,6 +54,8 @@ struct bin_info_data {
        int vdso;
        uint32_t crc;
        uint8_t is_pic;
+       uint8_t has_build_id;
+       uint8_t has_debug_link;
 };
 
 typedef void (*tracepoint_cb)(struct lttng_session *session, void *priv);
@@ -85,7 +88,9 @@ void trace_bin_info_cb(struct lttng_session *session, void *priv)
 
        tracepoint(lttng_ust_statedump, bin_info,
                session, bin_data->base_addr_ptr,
-               bin_data->resolved_path, bin_data->memsz, bin_data->is_pic);
+               bin_data->resolved_path, bin_data->memsz,
+               bin_data->is_pic, bin_data->has_build_id,
+               bin_data->has_debug_link);
 }
 
 static
@@ -121,10 +126,10 @@ void trace_end_cb(struct lttng_session *session, void *priv)
 }
 
 static
-int get_elf_info(struct bin_info_data *bin_data, int *has_build_id,
-               int *has_debug_link) {
+int get_elf_info(struct bin_info_data *bin_data)
+{
        struct lttng_ust_elf *elf;
-       int ret = 0;
+       int ret = 0, found;
 
        elf = lttng_ust_elf_create(bin_data->resolved_path);
        if (!elf) {
@@ -137,16 +142,22 @@ int get_elf_info(struct bin_info_data *bin_data, int *has_build_id,
                goto end;
        }
 
+       found = 0;
        ret = lttng_ust_elf_get_build_id(elf, &bin_data->build_id,
-                                       &bin_data->build_id_len, has_build_id);
+                                       &bin_data->build_id_len,
+                                       &found);
        if (ret) {
                goto end;
        }
+       bin_data->has_build_id = !!found;
+       found = 0;
        ret = lttng_ust_elf_get_debug_link(elf, &bin_data->dbg_file,
-                                       &bin_data->crc, has_debug_link);
+                                       &bin_data->crc,
+                                       &found);
        if (ret) {
                goto end;
        }
+       bin_data->has_debug_link = !!found;
 
        bin_data->is_pic = lttng_ust_elf_is_pic(elf);
 
@@ -158,10 +169,10 @@ end:
 static
 int trace_baddr(struct bin_info_data *bin_data)
 {
-       int ret = 0, has_build_id = 0, has_debug_link = 0;
+       int ret = 0;
 
        if (!bin_data->vdso) {
-               ret = get_elf_info(bin_data, &has_build_id, &has_debug_link);
+               ret = get_elf_info(bin_data);
                if (ret) {
                        goto end;
                }
@@ -177,7 +188,7 @@ int trace_baddr(struct bin_info_data *bin_data)
                goto end;
        }
 
-       if (has_build_id) {
+       if (bin_data->has_build_id) {
                ret = trace_statedump_event(
                        trace_build_id_cb, bin_data->owner, bin_data);
                free(bin_data->build_id);
@@ -186,7 +197,7 @@ int trace_baddr(struct bin_info_data *bin_data)
                }
        }
 
-       if (has_debug_link) {
+       if (bin_data->has_debug_link) {
                ret = trace_statedump_event(
                        trace_debug_link_cb, bin_data->owner, bin_data);
                free(bin_data->dbg_file);
@@ -302,9 +313,15 @@ int do_baddr_statedump(void *owner)
 {
        struct dl_iterate_data data;
 
-       if (getenv("LTTNG_UST_WITHOUT_BADDR_STATEDUMP"))
+       if (lttng_getenv("LTTNG_UST_WITHOUT_BADDR_STATEDUMP"))
                return 0;
 
+       /*
+        * Fixup lttng-ust TLS when called from dlopen/dlclose
+        * instrumentation.
+        */
+       lttng_ust_fixup_tls();
+
        data.owner = owner;
        data.exec_found = 0;
        /*
@@ -324,12 +341,22 @@ int do_baddr_statedump(void *owner)
  * session, statedumps from different processes may be
  * interleaved. The vpid context should be used to identify which
  * events belong to which process.
+ *
+ * Grab the ust_lock outside of the RCU read-side lock because we
+ * perform synchronize_rcu with the ust_lock held, which can trigger
+ * deadlocks otherwise.
  */
 int do_lttng_ust_statedump(void *owner)
 {
+       ust_lock_nocheck();
        trace_statedump_start(owner);
+       ust_unlock();
+
        do_baddr_statedump(owner);
+
+       ust_lock_nocheck();
        trace_statedump_end(owner);
+       ust_unlock();
 
        return 0;
 }