Fix symbol resolution by name (SymbolCache.resolve_name)

The implementation of `ProcSyms::resolve_name` was only valid for
kernel symbols, when there is no module. When a module was provided,
it would segfault due to the module being null. Fixed by making
`bcc_symcache_resolve_name` take an additional module parameter,
which, for kernel symbols, is simply null (`None` from Python).

src/cc/bcc_syms.cc

@@ -226,10 +226,10 @@ int bcc_symcache_resolve(void *resolver, uint64_t addr,
  return cache->resolve_addr(addr, sym) ? 0 : -1;
 }
 
-int bcc_symcache_resolve_name(void *resolver, const char *name,
- uint64_t *addr) {
+int bcc_symcache_resolve_name(void *resolver, const char *module,
+ const char *name, uint64_t *addr) {
  SymbolCache *cache = static_cast<SymbolCache *>(resolver);
- return cache->resolve_name(nullptr, name, addr) ? 0 : -1;
+ return cache->resolve_name(module, name, addr) ? 0 : -1;
 }
 
 void bcc_symcache_refresh(void *resolver) {

src/cc/bcc_syms.h

@@ -35,7 +35,8 @@ void *bcc_symcache_new(int pid);
 void bcc_free_symcache(void *symcache, int pid);
 
 int bcc_symcache_resolve(void *symcache, uint64_t addr, struct bcc_symbol *sym);
-int bcc_symcache_resolve_name(void *resolver, const char *name, uint64_t *addr);
+int bcc_symcache_resolve_name(void *resolver, const char *module,
+ const char *name, uint64_t *addr);
 void bcc_symcache_refresh(void *resolver);
 
 int bcc_resolve_global_addr(int pid, const char *module, const uint64_t address,

src/python/bcc/__init__.py

@@ -68,9 +68,10 @@ def resolve(self, addr):
  return (sym.demangle_name.decode(), sym.offset,
  ct.cast(sym.module, ct.c_char_p).value.decode())
 
- def resolve_name(self, name):
+ def resolve_name(self, module, name):
  addr = ct.c_ulonglong()
- if lib.bcc_symcache_resolve_name(self.cache, name, ct.pointer(addr)) < 0:
+ if lib.bcc_symcache_resolve_name(
+ self.cache, module, name, ct.pointer(addr)) < 0:
  return -1
  return addr.value
 
@@ -1023,7 +1024,7 @@ def ksymname(name):
 
  Translate a kernel name into an address. This is the reverse of
  ksym. Returns -1 when the function name is unknown."""
- return BPF._sym_cache(-1).resolve_name(name)
+ return BPF._sym_cache(-1).resolve_name(None, name)
 
  def num_open_kprobes(self):
  """num_open_kprobes()

src/python/bcc/libbcc.py

@@ -154,7 +154,7 @@ class bcc_symbol(ct.Structure):
 
 lib.bcc_symcache_resolve_name.restype = ct.c_int
 lib.bcc_symcache_resolve_name.argtypes = [
- ct.c_void_p, ct.c_char_p, ct.POINTER(ct.c_ulonglong)]
+ ct.c_void_p, ct.c_char_p, ct.c_char_p, ct.POINTER(ct.c_ulonglong)]
 
 lib.bcc_symcache_refresh.restype = None
 lib.bcc_symcache_refresh.argtypes = [ct.c_void_p]