ProcSyms: fix off-by-ones, use binary search to resolve addresses (io…

…visor#594)

* libbcc: fix off-by-one errors in resolving adjacent modules/symbols, add test

* libbcc: use binary search in ProcSyms::Module::find_addr()

src/cc/bcc_perf_map.c

@@ -93,7 +93,7 @@ int bcc_perf_map_foreach_sym(const char *path, bcc_perf_map_symcb callback,
  if (newline)
  newline[0] = '\0';
 
- callback(cursor, begin, len - 1, 0, payload);
+ callback(cursor, begin, len, 0, payload);
  }
 
  free(line);

src/cc/bcc_syms.cc

@@ -111,7 +111,7 @@ bool ProcSyms::resolve_addr(uint64_t addr, struct bcc_symbol *sym) {
  sym->offset = 0x0;
 
  for (Module &mod : modules_) {
- if (addr >= mod.start_ && addr <= mod.end_)
+ if (addr >= mod.start_ && addr < mod.end_)
  return mod.find_addr(addr, sym);
  }
  return false;
@@ -152,6 +152,8 @@ void ProcSyms::Module::load_sym_table() {
  bcc_perf_map_foreach_sym(name_.c_str(), _add_symbol, this);
  else
  bcc_elf_foreach_sym(name_.c_str(), _add_symbol, this);
+
+ std::sort(syms_.begin(), syms_.end());
 }
 
 bool ProcSyms::Module::find_name(const char *symname, uint64_t *addr) {
@@ -174,13 +176,19 @@ bool ProcSyms::Module::find_addr(uint64_t addr, struct bcc_symbol *sym) {
  sym->module = name_.c_str();
  sym->offset = offset;
 
- for (Symbol &s : syms_) {
- if (offset >= s.start && offset <= (s.start + s.size)) {
- sym->name = s.name.c_str();
- sym->offset = (offset - s.start);
- return true;
- }
+ auto it = std::upper_bound(syms_.begin(), syms_.end(), Symbol("", offset, 0));
+ if (it != syms_.begin())
+ --it;
+ else
+ it = syms_.end();
+
+ if (it != syms_.end()
+ && offset >= it->start && offset < it->start + it->size) {
+ sym->name = it->name.c_str();
+ sym->offset = (offset - it->start);
+ return true;
  }
+
  return false;
 }
 

src/cc/syms.h

@@ -69,6 +69,10 @@ class ProcSyms : SymbolCache {
  uint64_t start;
  uint64_t size;
  int flags;
+
+ bool operator<(const struct Symbol& rhs) const {
+ return start < rhs.start;
+ }
  };
 
  struct Module {

tests/cc/test_c_api.cc

@@ -129,6 +129,7 @@ static int child_func(void *arg) {
  return -1;
  }
  fprintf(file, "%llx 10 dummy_fn\n", map_addr);
+ fprintf(file, "%llx 10 right_next_door_fn\n", map_addr + 0x10);
  fclose(file);
 
  sleep(5);
@@ -172,6 +173,12 @@ TEST_CASE("resolve symbols using /tmp/perf-pid.map", "[c_api]") {
  REQUIRE(sym.module);
  REQUIRE(string(sym.module) == perf_map_path(child));
  REQUIRE(string("dummy_fn") == sym.name);
+
+ REQUIRE(bcc_symcache_resolve(resolver, (unsigned long long)map_addr + 0x10,
+ &sym) == 0);
+ REQUIRE(sym.module);
+ REQUIRE(string(sym.module) == perf_map_path(child));
+ REQUIRE(string("right_next_door_fn") == sym.name);
  }
 
  SECTION("separate namespace") {