patch from Bernd Schmidt to abstract away load address checks

ldso/include/dl-defs.h

@@ -75,4 +75,19 @@ typedef struct {
 	((LOADADDR) = (BASEADDR))
 #endif
 
+/* Test whether a given ADDR is more likely to be within the memory
+ * region mapped to TPNT (a struct elf_resolve *) than to TFROM.
+ * Everywhere that this is used, TFROM is initially NULL, and whenever
+ * a potential match is found, it's updated.  One might want to walk
+ * the chain of elf_resolve to locate the best match and return false
+ * whenever TFROM is non-NULL, or use an exact-matching algorithm
+ * using additional information encoded in DL_LOADADDR_TYPE to test
+ * for exact containment.
+ */
+#ifndef DL_ADDR_IN_LOADADDR
+# define DL_ADDR_IN_LOADADDR(ADDR, TPNT, TFROM) \
+	((void*)(TPNT)->loadaddr < (void*)(ADDR) \
+	 && (!(TFROM) || (TFROM)->loadaddr < (TPNT)->loadaddr))
+#endif
+
 #endif	/* _LD_DEFS_H */

ldso/libdl/libdl.c

@@ -175,8 +175,7 @@ void *dlopen(const char *libname, int flag)
 		tfrom = NULL;
 		for (dpnt = _dl_symbol_tables; dpnt; dpnt = dpnt->next) {
 			tpnt = dpnt->dyn;
-			if (tpnt->loadaddr < from
-					&& (tfrom == NULL || tfrom->loadaddr < tpnt->loadaddr))
+			if (DL_ADDR_IN_LOADADDR(from, tpnt, tfrom))
 				tfrom = tpnt;
 		}
 	}
@@ -436,8 +435,7 @@ void *dlsym(void *vhandle, const char *name)
 		tfrom = NULL;
 		for (rpnt = _dl_symbol_tables; rpnt; rpnt = rpnt->next) {
 			tpnt = rpnt->dyn;
-			if (tpnt->loadaddr < from
-					&& (tfrom == NULL || tfrom->loadaddr < tpnt->loadaddr)) {
+			if (DL_ADDR_IN_LOADADDR(from, tpnt, tfrom)) {
 				tfrom = tpnt;
 				handle = rpnt->next;
 			}
@@ -664,10 +662,8 @@ int dladdr(const void *__address, Dl_info * __info)
 		fprintf(stderr, "Module \"%s\" at %p\n",
 				tpnt->libname, tpnt->loadaddr);
 #endif
-		if (tpnt->loadaddr < (ElfW(Addr)) __address
-				&& (pelf == NULL || pelf->loadaddr < tpnt->loadaddr)) {
+		if (DL_ADDR_IN_LOADADDR((ElfW(Addr)) __address,  tpnt, pelf))
 			pelf = tpnt;
-		}
 	}
 
 	if (!pelf) {