dynamic linker support for PIE binaries (position-independent main program)

even with this change, PIE will not work yet due to deficiencies in
the crt1.o startup code.

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index e1c2ad7d883a4eaa3abc1d1baee7a85095ec18ec..df54230c8cf2517ce9941f14b711f51297b3fcae 100644 (file)
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -511,10 +511,13 @@ void *__dynlink(int argc, char **argv)
                ehdr->e_phnum, ehdr->e_phentsize));
        decode_dyn(lib);
 
-       /* Assume base address of 0 for the main program. This is not
-        * valid for PIE code; we will have to search the PHDR to get
-        * the correct load address in the PIE case (not yet supported). */
+       /* Find load address of the main program, via AT_PHDR vs PT_PHDR. */
        app->base = 0;
+       phdr = (void *)aux[AT_PHDR];
+       for (i=aux[AT_PHNUM]; i; i--, phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
+               if (phdr->p_type == PT_PHDR)
+                       app->base = (void *)(aux[AT_PHDR] - phdr->p_vaddr);
+       }
        app->name = argv[0];
        app->global = 1;
        app->dynv = (void *)(app->base + find_dyn(