fix dynamic linker not to depend on DYNAMIC ptr in 0th entry of GOT

this fixes an issue using gold instead of gnu ld for linking. it also
should eliminate the need of the startup code to even load/pass the
got address to the dynamic linker.

based on patch submitted by sh4rm4 with minor cosmetic changes.

further cleanup will follow.

src/ldso/dynlink.c

@@ -467,6 +467,7 @@ void *__dynlink(int argc, char **argv, size_t *got)
 	size_t i;
 	Phdr *phdr;
 	Ehdr *ehdr;
+	size_t *lib_dynv;
 	static struct dso builtin_dsos[3];
 	struct dso *const app = builtin_dsos+0;
 	struct dso *const lib = builtin_dsos+1;
@@ -498,8 +499,16 @@ void *__dynlink(int argc, char **argv, size_t *got)
 		}
 	}
 
-	/* Relocate ldso's DYNAMIC pointer and load vector */
-	decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
+	/* Find the dynamic linker's DYNAMIC section and decode it */
+	ehdr = (void *)aux[AT_BASE];
+	phdr = (void *)(aux[AT_BASE] + ehdr->e_phoff);
+	for (i=ehdr->e_phnum; i--; phdr=(void *)((char *)phdr + ehdr->e_phentsize)) {
+		if (phdr->p_type == PT_DYNAMIC) {
+			lib_dynv = (void *)(aux[AT_BASE] + phdr->p_vaddr);
+			decode_vec(lib_dynv, lib_dyn, DYN_CNT);
+			break;
+		}
+	}
 
 	/* Find the program image's DYNAMIC section and decode it */
 	phdr = (void *)aux[AT_PHDR];
@@ -526,7 +535,7 @@ void *__dynlink(int argc, char **argv, size_t *got)
 		.strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
 		.hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
 		.syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
-		.dynv = (void *)(got[0]),
+		.dynv = lib_dynv,
 		.name = "libc.so",
 		.global = 1,
 		.relocated = 1