[8/10] binfmt/elf: Load FDPIC modules through the ELF loader

binfmt/elf.c

@@ -252,6 +252,8 @@ static int elf_loadbinary(FAR struct binary_s *binp,
 
   binp->mod.textalloc = (FAR void *)loadinfo.textalloc;
   binp->mod.dataalloc = (FAR void *)loadinfo.datastart;
+  binp->mod.fdpic     = loadinfo.fdpic;
+  binp->mod.gotbase   = loadinfo.gotbase;
 #  ifdef CONFIG_BINFMT_CONSTRUCTORS
   binp->mod.initarr = loadinfo.initarr;
   binp->mod.finiarr = loadinfo.finiarr;
@@ -286,6 +288,15 @@ static int elf_loadbinary(FAR struct binary_s *binp,
     }
 #endif
 
+#ifdef HAVE_LIBC_ELF_PIN
+  /* Past the last thing that can fail, so the module owns the pin: it is
+   * given back when the task that runs the module exits.
+   */
+
+  binp->mod.pinfile = loadinfo.pinfile;
+  loadinfo.pinfile  = NULL;
+#endif
+
   libelf_uninitialize(&loadinfo);
   return OK;
 

include/nuttx/lib/elf.h

@@ -190,6 +190,18 @@ struct module_s
   uint16_t nsect;                      /* Number of entries in sectalloc array */
 #endif
   int dynamic;                         /* Module is a dynamic shared object */
+  bool fdpic;                          /* Module is an FDPIC object: its two
+                                        * segments were placed separately and
+                                        * the text is media, not an allocation
+                                        */
+  uintptr_t gotbase;                   /* An FDPIC object's data base, to
+                                        * enter its destructors with
+                                        */
+#ifdef HAVE_LIBC_ELF_PIN
+  FAR struct file *pinfile;            /* Holds the XIP pin on the text until
+                                        * the module is unloaded
+                                        */
+#endif
 #if defined(CONFIG_FS_PROCFS) && !defined(CONFIG_FS_PROCFS_EXCLUDE_MODULE)
   size_t textsize;                     /* Size of the kernel .text memory allocation */
   size_t datasize;                     /* Size of the kernel .bss/.data memory allocation */

libs/libc/elf/elf_bind.c

@@ -714,6 +714,24 @@ static int libelf_relocatedyn(FAR struct module_s *modp,
           case DT_PLTRELSZ:
             reldata.relsz[I_PLT] = dyn[i].d_un.d_val;
             break;
+          case DT_NEEDED:
+
+            /* Nothing loads DT_NEEDED yet, so refuse the module rather
+             * than let it fault on its first call into the library.
+             */
+
+            if (loadinfo->fdpic)
+              {
+                berr("ERROR: FDPIC module has a DT_NEEDED entry.  Shared "
+                     "libraries are not supported; link it statically.\n");
+                lib_free(sym);
+                lib_free(rels);
+                lib_free(dyn);
+                return -ENOEXEC;
+              }
+
+            break;
+
           case DT_PLTGOT:
 
             /* The object's data base.  Every function descriptor built

libs/libc/elf/elf_insert.c

@@ -29,6 +29,7 @@
 #include <sys/param.h>
 
 #include <nuttx/lib/lib.h>
+#include <nuttx/fdpic.h>
 #include <nuttx/lib/elf.h>
 
 #include "elf.h"
@@ -404,6 +405,12 @@ FAR void *libelf_insert(FAR const char *filename, FAR const char *modname)
 
   modp->textalloc = (FAR void *)loadinfo.textalloc;
   modp->dataalloc = (FAR void *)loadinfo.datastart;
+  modp->fdpic     = loadinfo.fdpic;
+  modp->gotbase   = loadinfo.gotbase;
+#ifdef HAVE_LIBC_ELF_PIN
+  modp->pinfile     = loadinfo.pinfile;
+  loadinfo.pinfile  = NULL;
+#endif
 #ifdef CONFIG_ARCH_USE_SEPARATED_SECTION
   modp->sectalloc = (FAR void **)loadinfo.sectalloc;
   modp->nsect = loadinfo.ehdr.e_shnum;
@@ -421,11 +428,26 @@ FAR void *libelf_insert(FAR const char *filename, FAR const char *modname)
       case ET_REL :
       case ET_DYN :
 
-        /* Process any preinit_array entries */
+        /* Process any preinit_array entries.  An FDPIC object's
+         * constructors need its own data base, not the loading thread's.
+         */
 
         array = (FAR void (**)(void))loadinfo.preiarr;
         for (i = 0; i < loadinfo.nprei; i++)
           {
+#ifdef CONFIG_FDPIC
+            if (loadinfo.fdpic)
+              {
+                struct fdpic_desc_s desc;
+
+                desc.entry = (uintptr_t)array[i];
+                desc.got   = loadinfo.gotbase;
+
+                fdpic_invoke(0, &desc);
+                continue;
+              }
+#endif
+
             array[i]();
           }
 
@@ -434,6 +456,19 @@ FAR void *libelf_insert(FAR const char *filename, FAR const char *modname)
         array = (FAR void (**)(void))loadinfo.initarr;
         for (i = 0; i < loadinfo.ninit; i++)
           {
+#ifdef CONFIG_FDPIC
+            if (loadinfo.fdpic)
+              {
+                struct fdpic_desc_s desc;
+
+                desc.entry = (uintptr_t)array[i];
+                desc.got   = loadinfo.gotbase;
+
+                fdpic_invoke(0, &desc);
+                continue;
+              }
+#endif
+
             array[i]();
           }
 

libs/libc/elf/elf_remove.c

@@ -29,8 +29,11 @@
 
 #include <nuttx/arch.h>
 #include <nuttx/lib/lib.h>
+#include <nuttx/fdpic.h>
 #include <nuttx/lib/elf.h>
 
+#include "elf/elf.h"
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -64,6 +67,24 @@ int libelf_uninit(FAR struct module_s *modp)
   array = (FAR void (**)(void))modp->finiarr;
   for (i = 0; i < modp->nfini; i++)
     {
+      /* Like the constructors, an FDPIC object's destructors reach its
+       * globals through its own data base, which the unloading thread does
+       * not carry.
+       */
+
+#ifdef CONFIG_FDPIC
+      if (modp->fdpic)
+        {
+          struct fdpic_desc_s desc;
+
+          desc.entry = (uintptr_t)array[i];
+          desc.got   = modp->gotbase;
+
+          fdpic_invoke(0, &desc);
+          continue;
+        }
+#endif
+
       array[i]();
     }
 
@@ -93,6 +114,14 @@ int libelf_uninit(FAR struct module_s *modp)
 #endif
     }
 
+#ifdef HAVE_LIBC_ELF_PIN
+  /* Give the pin back before the text goes out of use.  This does nothing if
+   * the loader took no pin.
+   */
+
+  libelf_pinrelease(&modp->pinfile);
+#endif
+
   /* Release resources held by the module */
 
   if (modp->textalloc != NULL || modp->dataalloc != NULL)
@@ -148,6 +177,24 @@ int libelf_uninit(FAR struct module_s *modp)
 #  endif
 #endif
         }
+      else if (modp->fdpic)
+        {
+          /* An FDPIC object placed its two segments separately.  Free each
+           * one.  If the text stayed on the media, it was never allocated,
+           * thus leave it.
+           */
+
+          if (modp->xipbase == 0)
+            {
+#if defined(CONFIG_ARCH_USE_TEXT_HEAP)
+              up_textheap_free((FAR void *)modp->textalloc);
+#else
+              lib_free((FAR void *)modp->textalloc);
+#endif
+            }
+
+          lib_free((FAR void *)modp->dataalloc);
+        }
       else
         {
           lib_free((FAR void *)modp->textalloc);