Calculate relocation base for the main object, and apply the relocation

adjustment for all virtual addresses encoded into the ELF structures of
it. PIE binary could and should be loaded at non-zero mapbase.

For sym_zero pseudosymbol used as a return value from find_symdef()
for undefined weak symbols, st_value also should be adjusted, since
_rtld_bind corrects symbol values by relocbase.

Discussed with:	bz
Reviewed by:	kan
Tested by:	bz (i386, amd64), bsam (linux)
MFC after:	some time

1 files changed, 15 insertions, 14 deletions

diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index 721fe89..2eebf22 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -474,6 +474,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
     /* Initialize a fake symbol for resolving undefined weak references. */
     sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
     sym_zero.st_shndx = SHN_UNDEF;
+    sym_zero.st_value = -(uintptr_t)obj_main->relocbase;
 
     if (!libmap_disable)
         libmap_disable = (bool)lm_init(libmap_override);
@@ -991,26 +992,26 @@ digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
 
     obj = obj_new();
     for (ph = phdr;  ph < phlimit;  ph++) {
-	switch (ph->p_type) {
+	if (ph->p_type != PT_PHDR)
+	    continue;
 
-	case PT_PHDR:
-	    if ((const Elf_Phdr *)ph->p_vaddr != phdr) {
-		_rtld_error("%s: invalid PT_PHDR", path);
-		return NULL;
-	    }
-	    obj->phdr = (const Elf_Phdr *) ph->p_vaddr;
-	    obj->phsize = ph->p_memsz;
-	    break;
+	obj->phdr = phdr;
+	obj->phsize = ph->p_memsz;
+	obj->relocbase = (caddr_t)phdr - ph->p_vaddr;
+	break;
+    }
+
+    for (ph = phdr;  ph < phlimit;  ph++) {
+	switch (ph->p_type) {
 
 	case PT_INTERP:
-	    obj->interp = (const char *) ph->p_vaddr;
+	    obj->interp = (const char *)(ph->p_vaddr + obj->relocbase);
 	    break;
 
 	case PT_LOAD:
 	    if (nsegs == 0) {	/* First load segment */
 		obj->vaddrbase = trunc_page(ph->p_vaddr);
-		obj->mapbase = (caddr_t) obj->vaddrbase;
-		obj->relocbase = obj->mapbase - obj->vaddrbase;
+		obj->mapbase = obj->vaddrbase + obj->relocbase;
 		obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
 		  obj->vaddrbase;
 	    } else {		/* Last load segment */
@@ -1021,7 +1022,7 @@ digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
 	    break;
 
 	case PT_DYNAMIC:
-	    obj->dynamic = (const Elf_Dyn *) ph->p_vaddr;
+	    obj->dynamic = (const Elf_Dyn *)(ph->p_vaddr + obj->relocbase);
 	    break;
 
 	case PT_TLS:
@@ -1029,7 +1030,7 @@ digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
 	    obj->tlssize = ph->p_memsz;
 	    obj->tlsalign = ph->p_align;
 	    obj->tlsinitsize = ph->p_filesz;
-	    obj->tlsinit = (void*) ph->p_vaddr;
+	    obj->tlsinit = (void*)(ph->p_vaddr + obj->relocbase);
 	    break;
 	}
     }