libdwfl: Minimize stack usage in dwfl_linux_kernel_report_offline.

Don't stack allocate module name. Also fixes a latent bug (if the module
file didn't have a suffix - which is very unlikely) and an inefficiency.
We only need to substitue chars up to the suffix.

Signed-off-by: Mark Wielaard <mjw@redhat.com>

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 7fbb914..d06d34d 100644 (file)
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-19  Mark Wielaard  <mjw@redhat.com>
+
+       * linux-kernel-modules.c (dwfl_linux_kernel_report_offline): Don't
+       stack allocate name. Only change chars up to suffix.
+
 2015-05-18  Mark Wielaard  <mjw@redhat.com>
 
        * dwfl_module_getdwarf.c (find_prelink_address_sync): Allocate

diff --git a/libdwfl/linux-kernel-modules.c b/libdwfl/linux-kernel-modules.c
index e4065d8..cb56868 100644 (file)
--- a/libdwfl/linux-kernel-modules.c
+++ b/libdwfl/linux-kernel-modules.c
@@ -1,5 +1,5 @@
 /* Standard libdwfl callbacks for debugging the running Linux kernel.
-   Copyright (C) 2005-2011, 2013, 2014 Red Hat, Inc.
+   Copyright (C) 2005-2011, 2013, 2014, 2015 Red Hat, Inc.
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -379,13 +379,16 @@ dwfl_linux_kernel_report_offline (Dwfl *dwfl, const char *release,
                     names.  To handle that, we would have to look at the
                     __this_module.name contents in the module's text.  */
 
-                 char name[f->fts_namelen - suffix + 1];
-                 for (size_t i = 0; i < f->fts_namelen - 3U; ++i)
-                   if (f->fts_name[i] == '-' || f->fts_name[i] == ',')
+                 char *name = strndup (f->fts_name, f->fts_namelen - suffix);
+                 if (unlikely (name == NULL))
+                   {
+                     __libdwfl_seterrno (DWFL_E_NOMEM);
+                     result = -1;
+                     break;
+                   }
+                 for (size_t i = 0; i < f->fts_namelen - suffix; ++i)
+                   if (name[i] == '-' || name[i] == ',')
                      name[i] = '_';
-                   else
-                     name[i] = f->fts_name[i];
-                 name[f->fts_namelen - suffix] = '\0';
 
                  if (predicate != NULL)
                    {
@@ -394,17 +397,23 @@ dwfl_linux_kernel_report_offline (Dwfl *dwfl, const char *release,
                      if (want < 0)
                        {
                          result = -1;
+                         free (name);
                          break;
                        }
                      if (!want)
-                       continue;
+                       {
+                         free (name);
+                         continue;
+                       }
                    }
 
                  if (dwfl_report_offline (dwfl, name, f->fts_path, -1) == NULL)
                    {
+                     free (name);
                      result = -1;
                      break;
                    }
+                 free (name);
                }
              continue;