Fix symbol resolution for shared libraries with multiple load sections

src/cc/bcc_syms.cc

@@ -14,7 +14,6 @@
  * limitations under the License.
  */
 
-#include <algorithm>
 #include <cxxabi.h>
 #include <cstring>
 #include <fcntl.h>
@@ -114,7 +113,7 @@ ProcSyms::ProcSyms(int pid, struct bcc_symbol_option *option)
 int ProcSyms::_add_load_sections(uint64_t v_addr, uint64_t mem_sz,
                                  uint64_t file_offset, void *payload) {
   auto module = static_cast<Module *>(payload);
-  module->add_range(v_addr, v_addr + mem_sz);
+  module->ranges_.emplace_back(v_addr, v_addr + mem_sz, file_offset);
   return 0;
 }
 
@@ -162,7 +161,11 @@ int ProcSyms::_add_module(const char *modname, uint64_t start, uint64_t end,
     else
       return 0;
   }
-  it->add_range(start, end);
+  it->ranges_.emplace_back(start, end, offset);
+  // perf-PID map is added last. We try both inside the Process's mount
+  // namespace + chroot, and in global /tmp. Make sure we only add one.
+  if (it->type_ == ModuleType::PERF_MAP)
+    return -1;
 
   return 0;
 }
@@ -275,21 +278,12 @@ void ProcSyms::Module::load_sym_table() {
   std::sort(syms_.begin(), syms_.end());
 }
 
-void ProcSyms::Module::add_range(uint64_t st, uint64_t en) {
-  if (!ranges_.empty()) {
-    Range &last = ranges_.back();
-    if (st >= last.start && st <= last.end) {
-      last.end = std::max(en, last.end);
-      return;
-    }
-  }
-  ranges_.emplace_back(st, en);
-}
-
 bool ProcSyms::Module::contains(uint64_t addr, uint64_t &offset) const {
   for (const auto &range : ranges_)
     if (addr >= range.start && addr < range.end) {
-      offset = type_ == ModuleType::SO ? addr - range.start : addr;
+      offset = (type_ == ModuleType::SO)
+                   ? (addr - range.start + range.file_offset)
+                   : addr;
       return true;
     }
   return false;

src/cc/syms.h

@@ -92,10 +92,12 @@ class ProcSyms : SymbolCache {
     struct Range {
       uint64_t start;
       uint64_t end;
-      Range(uint64_t s, uint64_t e) : start(s), end(e) {}
+      uint64_t file_offset;
+      Range(uint64_t s, uint64_t e, uint64_t f)
+          : start(s), end(e), file_offset(f) {}
     };
 
-    Module(const char *name, ProcMountNS* mount_ns,
+    Module(const char *name, ProcMountNS *mount_ns,
            struct bcc_symbol_option *option);
     bool init();
 
@@ -111,7 +113,6 @@ class ProcSyms : SymbolCache {
 
     void load_sym_table();
 
-    void add_range(uint64_t st, uint64_t en);
     bool contains(uint64_t addr, uint64_t &offset) const;
     uint64_t start() const { return ranges_.begin()->start; }