Fix: race between lttng-ust getenv() and application setenv()
[lttng-ust.git] / liblttng-ust / lttng-ust-statedump.c
index 93a035b35a0ead7032e2ae121d8168f5c624c6da..ea80817bd9807fd99cdfdabb8d12a2e58c4015c3 100644 (file)
@@ -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
@@ -42,7 +43,7 @@ struct dl_iterate_data {
        int exec_found;
 };
 
-struct soinfo_data {
+struct bin_info_data {
        void *owner;
        void *base_addr_ptr;
        const char *resolved_path;
@@ -52,6 +53,9 @@ struct soinfo_data {
        size_t build_id_len;
        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);
@@ -78,33 +82,35 @@ int trace_statedump_event(tracepoint_cb tp_cb, void *owner, void *priv)
 }
 
 static
-void trace_soinfo_cb(struct lttng_session *session, void *priv)
+void trace_bin_info_cb(struct lttng_session *session, void *priv)
 {
-       struct soinfo_data *so_data = (struct soinfo_data *) priv;
+       struct bin_info_data *bin_data = (struct bin_info_data *) priv;
 
-       tracepoint(lttng_ust_statedump, soinfo,
-               session, so_data->base_addr_ptr,
-               so_data->resolved_path, so_data->memsz);
+       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->has_build_id,
+               bin_data->has_debug_link);
 }
 
 static
 void trace_build_id_cb(struct lttng_session *session, void *priv)
 {
-       struct soinfo_data *so_data = (struct soinfo_data *) priv;
+       struct bin_info_data *bin_data = (struct bin_info_data *) priv;
 
        tracepoint(lttng_ust_statedump, build_id,
-               session, so_data->base_addr_ptr,
-               so_data->build_id, so_data->build_id_len);
+               session, bin_data->base_addr_ptr,
+               bin_data->build_id, bin_data->build_id_len);
 }
 
 static
 void trace_debug_link_cb(struct lttng_session *session, void *priv)
 {
-       struct soinfo_data *so_data = (struct soinfo_data *) priv;
+       struct bin_info_data *bin_data = (struct bin_info_data *) priv;
 
        tracepoint(lttng_ust_statedump, debug_link,
-               session, so_data->base_addr_ptr,
-               so_data->dbg_file, so_data->crc);
+               session, bin_data->base_addr_ptr,
+               bin_data->dbg_file, bin_data->crc);
 }
 
 static
@@ -120,32 +126,40 @@ void trace_end_cb(struct lttng_session *session, void *priv)
 }
 
 static
-int get_elf_info(struct soinfo_data *so_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(so_data->resolved_path);
+       elf = lttng_ust_elf_create(bin_data->resolved_path);
        if (!elf) {
                ret = -1;
                goto end;
        }
 
-       ret = lttng_ust_elf_get_memsz(elf, &so_data->memsz);
+       ret = lttng_ust_elf_get_memsz(elf, &bin_data->memsz);
        if (ret) {
                goto end;
        }
 
-       ret = lttng_ust_elf_get_build_id(elf, &so_data->build_id,
-                                       &so_data->build_id_len, has_build_id);
+       found = 0;
+       ret = lttng_ust_elf_get_build_id(elf, &bin_data->build_id,
+                                       &bin_data->build_id_len,
+                                       &found);
        if (ret) {
                goto end;
        }
-       ret = lttng_ust_elf_get_debug_link(elf, &so_data->dbg_file,
-                                       &so_data->crc, has_debug_link);
+       bin_data->has_build_id = !!found;
+       found = 0;
+       ret = lttng_ust_elf_get_debug_link(elf, &bin_data->dbg_file,
+                                       &bin_data->crc,
+                                       &found);
        if (ret) {
                goto end;
        }
+       bin_data->has_debug_link = !!found;
+
+       bin_data->is_pic = lttng_ust_elf_is_pic(elf);
 
 end:
        lttng_ust_elf_destroy(elf);
@@ -153,37 +167,40 @@ end:
 }
 
 static
-int trace_baddr(struct soinfo_data *so_data)
+int trace_baddr(struct bin_info_data *bin_data)
 {
-       int ret = 0, has_build_id = 0, has_debug_link = 0;
+       int ret = 0;
 
-       if (!so_data->vdso) {
-               ret = get_elf_info(so_data, &has_build_id, &has_debug_link);
+       if (!bin_data->vdso) {
+               ret = get_elf_info(bin_data);
                if (ret) {
                        goto end;
                }
        } else {
-               so_data->memsz = 0;
+               bin_data->memsz = 0;
+               bin_data->has_build_id = 0;
+               bin_data->has_debug_link = 0;
        }
 
-       ret = trace_statedump_event(trace_soinfo_cb, so_data->owner, so_data);
+       ret = trace_statedump_event(trace_bin_info_cb, bin_data->owner,
+                       bin_data);
        if (ret) {
                goto end;
        }
 
-       if (has_build_id) {
+       if (bin_data->has_build_id) {
                ret = trace_statedump_event(
-                       trace_build_id_cb, so_data->owner, so_data);
-               free(so_data->build_id);
+                       trace_build_id_cb, bin_data->owner, bin_data);
+               free(bin_data->build_id);
                if (ret) {
                        goto end;
                }
        }
 
-       if (has_debug_link) {
+       if (bin_data->has_debug_link) {
                ret = trace_statedump_event(
-                       trace_debug_link_cb, so_data->owner, so_data);
-               free(so_data->dbg_file);
+                       trace_debug_link_cb, bin_data->owner, bin_data);
+               free(bin_data->dbg_file);
                if (ret) {
                        goto end;
                }
@@ -206,7 +223,7 @@ int trace_statedump_end(void *owner)
 }
 
 static
-int extract_soinfo_events(struct dl_phdr_info *info, size_t size, void *_data)
+int extract_bin_info_events(struct dl_phdr_info *info, size_t size, void *_data)
 {
        int j, ret = 0;
        struct dl_iterate_data *data = _data;
@@ -223,7 +240,7 @@ int extract_soinfo_events(struct dl_phdr_info *info, size_t size, void *_data)
        }
 
        for (j = 0; j < info->dlpi_phnum; j++) {
-               struct soinfo_data so_data;
+               struct bin_info_data bin_data;
                char resolved_path[PATH_MAX];
                void *base_addr_ptr;
 
@@ -255,30 +272,30 @@ int extract_soinfo_events(struct dl_phdr_info *info, size_t size, void *_data)
                                        break;
 
                                resolved_path[path_len] = '\0';
-                               so_data.vdso = 0;
+                               bin_data.vdso = 0;
                        } else {
                                snprintf(resolved_path, PATH_MAX - 1, "[vdso]");
-                               so_data.vdso = 1;
+                               bin_data.vdso = 1;
                        }
                } else {
                        /*
                         * For regular dl_phdr_info entries check if
-                        * the path to the SO really exists. If not,
+                        * the path to the binary really exists. If not,
                         * treat as vdso and use dlpi_name as 'path'.
                         */
                        if (!realpath(info->dlpi_name, resolved_path)) {
                                snprintf(resolved_path, PATH_MAX - 1, "[%s]",
                                        info->dlpi_name);
-                               so_data.vdso = 1;
+                               bin_data.vdso = 1;
                        } else {
-                               so_data.vdso = 0;
+                               bin_data.vdso = 0;
                        }
                }
 
-               so_data.owner = data->owner;
-               so_data.base_addr_ptr = base_addr_ptr;
-               so_data.resolved_path = resolved_path;
-               ret = trace_baddr(&so_data);
+               bin_data.owner = data->owner;
+               bin_data.base_addr_ptr = base_addr_ptr;
+               bin_data.resolved_path = resolved_path;
+               ret = trace_baddr(&bin_data);
                break;
        }
 end:
@@ -296,17 +313,23 @@ 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;
        /*
         * Iterate through the list of currently loaded shared objects and
         * generate events for loadable segments using
-        * extract_soinfo_events.
+        * extract_bin_info_events.
         */
-       dl_iterate_phdr(extract_soinfo_events, &data);
+       dl_iterate_phdr(extract_bin_info_events, &data);
 
        return 0;
 }
@@ -318,12 +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;
 }
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