Fix and improve dynamic loader

This patch fixes some issues found by Mark Stevens and
improve the dynamic loader.

include/elf.h

@@ -175,6 +175,9 @@
 #define SHT_REL            9
 #define SHT_SHLIB          10
 #define SHT_DYNSYM         11
+#define SHT_INIT_ARRAY     14
+#define SHT_FINI_ARRAY     15
+#define SHT_PREINIT_ARRAY  16
 #define SHT_LOPROC         0x70000000
 #define SHT_HIPROC         0x7fffffff
 #define SHT_LOUSER         0x80000000

include/elf32.h

@@ -40,6 +40,11 @@
 #define ELF32_ST_TYPE(i)   ((i) & 0xf)
 #define ELF32_ST_INFO(b,t) (((b) << 4) | ((t) & 0xf))
 
+/* Generic macro to abstract ELF32/ELF64 type/bind */
+
+#define ELF_ST_TYPE(a)     ELF32_ST_TYPE(a)
+#define ELF_ST_BIND(a)     ELF32_ST_BIND(a)
+
 /* Definitions for Elf32_Rel*::r_info */
 
 #define ELF32_R_SYM(i)     ((i) >> 8)

include/elf64.h

@@ -38,6 +38,15 @@
 
 /* See ELF-64 Object File Format: Version 1.5 Draft 2 */
 
+#define ELF64_ST_BIND(i)     ((i) >> 4)
+#define ELF64_ST_TYPE(i)     ((i) & 0xf)
+#define ELF64_ST_INFO(b,t)   (((b) << 4) | ((t) & 0xf))
+
+/* Generic macro to abstract ELF32/ELF64 type/bind */
+
+#define ELF_ST_TYPE(a)       ELF64_ST_TYPE(a)
+#define ELF_ST_BIND(a)       ELF64_ST_BIND(a)
+
 /* Definitions for Elf64_Rel*::r_info */
 
 #define ELF64_R_SYM(i)       ((i) >> 32)

include/nuttx/lib/modlib.h

@@ -173,6 +173,8 @@ struct module_s
 
   FAR struct module_s *dependencies[CONFIG_MODLIB_MAXDEPEND];
 #endif
+  uintptr_t finiarr;                     /* .fini_array */
+  uint16_t  nfini;                       /* Number of entries in .fini_array */
 };
 
 /* This struct provides a description of the currently loaded instantiation
@@ -202,6 +204,12 @@ struct mod_loadinfo_s
   uint8_t      *iobuffer;    /* File I/O buffer */
   uintptr_t     datasec;     /* ET_DYN - data area start from Phdr */
   uintptr_t     segpad;      /* Padding between text and data */
+  uintptr_t     initarr;     /* .init_array */
+  uintptr_t     finiarr;     /* .fini_array */
+  uintptr_t     preiarr;     /* .preinit_array */
+  uint16_t      ninit;       /* Number of .init_array entries */
+  uint16_t      nfini;       /* Number of .fini_array entries */
+  uint16_t      nprei;       /* Number of .preinit_array entries */
   uint16_t      symtabidx;   /* Symbol table section index */
   uint16_t      strtabidx;   /* String table section index */
   uint16_t      dsymtabidx;  /* Dynamic symbol table section index */

libs/libc/dlfcn/lib_dlclose.c

@@ -57,7 +57,9 @@
 static inline int dlremove(FAR void *handle)
 {
   FAR struct module_s *modp = (FAR struct module_s *)handle;
+  void (**array)(void);
   int ret;
+  int i;
 
   DEBUGASSERT(modp != NULL);
 
@@ -104,6 +106,15 @@ static inline int dlremove(FAR void *handle)
       /* Nullify so that the uninitializer cannot be called again */
 
       modp->modinfo.uninitializer = NULL;
+
+  /* Call any .fini_array entries in reverse order */
+
+  array = (void (**)(void)) modp->finiarr;
+  for (i = (modp->nfini - 1); i >= 0; i--)
+    {
+      array[i]();
+    }
+
 #if defined(CONFIG_FS_PROCFS) && !defined(CONFIG_FS_PROCFS_EXCLUDE_MODULE)
       modp->initializer           = NULL;
       modp->modinfo.arg           = NULL;

libs/libc/dlfcn/lib_dlopen.c

@@ -181,7 +181,9 @@ static inline FAR void *dlinsert(FAR const char *filename)
   struct mod_loadinfo_s loadinfo;
   FAR struct module_s *modp;
   mod_initializer_t initializer;
+  void (**array)(void);
   int ret;
+  int i;
 
   binfo("Loading file: %s\n", filename);
 
@@ -249,14 +251,37 @@ static inline FAR void *dlinsert(FAR const char *filename)
 
   /* Call the module initializer */
 
-  if (loadinfo.ehdr.e_type == ET_REL)
+  switch (loadinfo.ehdr.e_type)
     {
+      case ET_REL :
           ret = initializer(&modp->modinfo);
           if (ret < 0)
             {
               binfo("Failed to initialize the module: %d\n", ret);
               goto errout_with_load;
             }
+          break;
+      case ET_DYN :
+
+          /* Process any preinit_array entries */
+
+          array = (void (**)(void)) loadinfo.preiarr;
+          for (i = 0; i < loadinfo.nprei; i++)
+            {
+              array[i]();
+            }
+
+          /* Process any init_array entries */
+
+          array = (void (**)(void)) loadinfo.initarr;
+          for (i = 0; i < loadinfo.ninit; i++)
+            {
+              array[i]();
+            }
+
+          modp->finiarr = loadinfo.finiarr;
+          modp->nfini = loadinfo.nfini;
+          break;
     }
 
   /* Add the new module entry to the registry */

libs/libc/modlib/modlib_bind.c

@@ -658,10 +658,19 @@ static int modlib_relocatedyn(FAR struct module_s *modp,
 
           if (!(i % CONFIG_MODLIB_RELOCATION_BUFFERCOUNT))
             {
+              size_t relSize = (sizeof(Elf_Rel) *
+                               CONFIG_MODLIB_RELOCATION_BUFFERCOUNT);
+
+              if (relData.relSz[idx_rel] < relSize)
+                {
+                  relSize = relData.relSz[idx_rel];
+                }
+
               ret = modlib_read(loadinfo, (FAR uint8_t *) rels,
-                                sizeof(Elf_Rel) * CONFIG_MODLIB_RELOCATION_BUFFERCOUNT,
+                                relSize,
                                 relData.relOff[idx_rel] +
                                 i * sizeof(Elf_Rel));
+
               if (ret < 0)
                 {
                   berr("ERROR: Section %d reloc %d:"
@@ -695,7 +704,8 @@ static int modlib_relocatedyn(FAR struct module_s *modp,
 
                     ep = modlib_findglobal(modp, loadinfo, symhdr,
                                            &sym[idx_sym]);
-                    if (ep == NULL)
+                    if ((ep == NULL) && (ELF_ST_BIND(sym[idx_sym].st_info)
+                        != STB_WEAK))
                       {
                         berr("ERROR: Unable to resolve addr of ext ref %s\n",
                              loadinfo->iobuffer);
@@ -834,6 +844,27 @@ int modlib_bind(FAR struct module_s *modp,
               case SHT_DYNSYM :
                   loadinfo->dsymtabidx = i;
                   break;
+              case SHT_INIT_ARRAY :
+                  loadinfo->initarr = loadinfo->shdr[i].sh_addr -
+                                      loadinfo->datasec +
+                                      loadinfo->datastart;
+                  loadinfo->ninit = loadinfo->shdr[i].sh_size /
+                                    sizeof(uintptr_t);
+                  break;
+              case SHT_FINI_ARRAY :
+                  loadinfo->finiarr = loadinfo->shdr[i].sh_addr -
+                                      loadinfo->datasec +
+                                      loadinfo->datastart;
+                  loadinfo->nfini = loadinfo->shdr[i].sh_size /
+                                    sizeof(uintptr_t);
+                  break;
+              case SHT_PREINIT_ARRAY :
+                  loadinfo->preiarr = loadinfo->shdr[i].sh_addr -
+                                      loadinfo->datasec +
+                                      loadinfo->datastart;
+                  loadinfo->nprei = loadinfo->shdr[i].sh_size /
+                                    sizeof(uintptr_t);
+                  break;
             }
         }
       else