Attachment 11770 Details for Bug 24488 – Factor out loading of ebl backend library and try multiple times with bin/lib origin paths

[patch] Factor out loading of ebl backend library and try multiple times with bin/lib origin paths

try_dlopen.patch (text/plain), 4.65 KB, created by Mark Wielaard on 2019-05-11 15:49:52 UTC

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Creator: Mark Wielaard

Created: 2019-05-11 15:49:52 UTC

Size: 4.65 KB

patch

obsolete

>commit 96e8fd942e2165aa138ccbce8fb0003ed8c649f1
>Author: Mark Wielaard <mark@klomp.org>
>Date:   Sat May 11 16:55:01 2019 +0200
>
>    WIP try_dlopen, try BINORIGIN, LIBORIGIN...
>
>diff --git a/libebl/eblopenbackend.c b/libebl/eblopenbackend.c
>index d54b720..36a2492 100644
>--- a/libebl/eblopenbackend.c
>+++ b/libebl/eblopenbackend.c
>@@ -251,6 +251,50 @@ fill_defaults (Ebl *result)
>   result->sysvhash_entrysize = sizeof (Elf32_Word);
> }
> 
>+static Ebl *
>+try_dlopen (const char *dsoname, Elf *elf, GElf_Half machine, size_t cnt,
>+	    Ebl *result)
>+{
>+  void *h = dlopen (dsoname, RTLD_LAZY);
>+
>+  if (h != NULL)
>+    {
>+      /* We managed to load the object.  Now see whether the
>+	 initialization function likes our file.  */
>+      static const char version[] = MODVERSION;
>+      const char *modversion;
>+      ebl_bhinit_t initp;
>+
>+      // We use a static number to help the compiler see we don't
>+      // overflow the stack with an arbitrary number.
>+      assert (machines[cnt].prefix_len <= MAX_PREFIX_LEN);
>+      char symname[MAX_PREFIX_LEN + sizeof "_init"];
>+
>+      strcpy (mempcpy (symname, machines[cnt].prefix,
>+		       machines[cnt].prefix_len), "_init");
>+
>+      initp = (ebl_bhinit_t) dlsym (h, symname);
>+      if (initp != NULL
>+	  && (modversion = initp (elf, machine, result, sizeof (Ebl)))
>+	  && strcmp (version, modversion) == 0)
>+	{
>+	  /* We found a module to handle our file.  */
>+	  result->dlhandle = h;
>+	  result->elf = elf;
>+
>+	  /* A few entries are mandatory.  */
>+	  assert (result->name != NULL);
>+	  assert (result->destr != NULL);
>+
>+	  return result;
>+	}
>+
>+      /* Not the module we need.  */
>+      (void) dlclose (h);
>+    }
>+
>+  return NULL;
>+}
> 
> /* Find an appropriate backend for the file associated with ELF.  */
> static Ebl *
>@@ -316,60 +360,39 @@ openbackend (Elf *elf, const char *emulation, GElf_Half machine)
> #ifndef LIBEBL_SUBDIR
> # define LIBEBL_SUBDIR PACKAGE
> #endif
>-#define ORIGINDIR "$ORIGIN/../$LIB/" LIBEBL_SUBDIR "/"
>+
>+/* This works if libebl has been staticly linked into a binary.
>+   It might also work for shared libraries when installed in
>+   ${prefix}/lib/ or ${prefix}/lib64/, but not for multiarch
>+   library installs like ${prefix}/lib/i386-linux-gnu/  */
>+#define BINORIGINDIR "$ORIGIN/../$LIB/" LIBEBL_SUBDIR "/"
>+
>+/* This works if libebl has been linked into a shared library,
>+   just look in the subdir.  */
>+#define LIBORIGINDIR "$ORIGIN/" LIBEBL_SUBDIR "/"
> 
> 	/* Give it a try.  At least the machine type matches.  First
>-           try to load the module.  */
>+           try to load the module from the (bin) origin path.  */
> 	char dsoname[100];
>-	strcpy (stpcpy (stpcpy (dsoname, ORIGINDIR "libebl_"),
>+	strcpy (stpcpy (stpcpy (dsoname, BINORIGINDIR "libebl_"),
> 			machines[cnt].dsoname),
> 		".so");
>+	if (try_dlopen (dsoname, elf, machine, cnt, result) != NULL)
>+	  return result;
> 
>-	void *h = dlopen (dsoname, RTLD_LAZY);
>-	if (h == NULL)
>-	  {
>-	    strcpy (stpcpy (stpcpy (dsoname, "libebl_"),
>-			    machines[cnt].dsoname),
>-		    ".so");
>-	    h = dlopen (dsoname, RTLD_LAZY);
>-	  }
>+	/* Retry with the (lib) origin path.  */
>+	strcpy (stpcpy (stpcpy (dsoname, LIBORIGINDIR "libebl_"),
>+			machines[cnt].dsoname),
>+		".so");
>+	if (try_dlopen (dsoname, elf, machine, cnt, result) != NULL)
>+	  return result;
> 
>-	  /* Try without an explicit path.  */
>-	if (h != NULL)
>-	  {
>-	    /* We managed to load the object.  Now see whether the
>-	       initialization function likes our file.  */
>-	    static const char version[] = MODVERSION;
>-	    const char *modversion;
>-	    ebl_bhinit_t initp;
>-
>-	    // We use a static number to help the compiler see we don't
>-	    // overflow the stack with an arbitrary number.
>-	    assert (machines[cnt].prefix_len <= MAX_PREFIX_LEN);
>-	    char symname[MAX_PREFIX_LEN + sizeof "_init"];
>-
>-	    strcpy (mempcpy (symname, machines[cnt].prefix,
>-			     machines[cnt].prefix_len), "_init");
>-
>-	    initp = (ebl_bhinit_t) dlsym (h, symname);
>-	    if (initp != NULL
>-		&& (modversion = initp (elf, machine, result, sizeof (Ebl)))
>-		&& strcmp (version, modversion) == 0)
>-	      {
>-		/* We found a module to handle our file.  */
>-		result->dlhandle = h;
>-		result->elf = elf;
>-
>-		/* A few entries are mandatory.  */
>-		assert (result->name != NULL);
>-		assert (result->destr != NULL);
>-
>-		return result;
>-	      }
>-
>-	    /* Not the module we need.  */
>-	    (void) dlclose (h);
>-	  }
>+	/* Try without an explicit path (LD_LIBRARY_PATH or RPATH).  */
>+	strcpy (stpcpy (stpcpy (dsoname, "libebl_"),
>+			machines[cnt].dsoname),
>+		".so");
>+	if (try_dlopen (dsoname, elf, machine, cnt, result) != NULL)
>+	  return result;
> 
> 	/* We cannot find a DSO but the emulation/machine ID matches.
> 	   Return that information.  */

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Attachments on bug 24488: 11770