Remove dependency on __got_{start,end} symbols and look at PT_GNU_RELRO

instead.  Result in a few more pages that aren't writable on some platforms
(such as hppa).  Based on an initial diff from guenther@.

Thanks to deraadt@ for testing.

ok guenther@

13 files changed, 42 insertions, 55 deletions

diff --git a/libexec/ld.so/alpha/archdep.h b/libexec/ld.so/alpha/archdep.h
index 7cb62da591e..5b6073fa1be 100644
--- a/libexec/ld.so/alpha/archdep.h
+++ b/libexec/ld.so/alpha/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.17 2015/12/06 23:36:12 guenther Exp $ */
+/*	$OpenBSD: archdep.h,v 1.18 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -65,6 +65,4 @@ RELOC_DYN(Elf64_Rela *r, const Elf64_Sym *s, Elf64_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS PROT_READ
-
 #endif /* _ALPHA_ARCHDEP_H_ */
diff --git a/libexec/ld.so/amd64/archdep.h b/libexec/ld.so/amd64/archdep.h
index d5c4eba610c..247bebf31c7 100644
--- a/libexec/ld.so/amd64/archdep.h
+++ b/libexec/ld.so/amd64/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.8 2016/05/18 20:40:20 deraadt Exp $	*/
+/*	$OpenBSD: archdep.h,v 1.9 2017/01/09 22:51:04 kettenis Exp $	*/
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -68,6 +68,4 @@ RELOC_DYN(Elf64_Rela *r, const Elf64_Sym *s, Elf64_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS PROT_READ
-
 #endif /* _X86_64_ARCHDEP_H_ */
diff --git a/libexec/ld.so/arm/archdep.h b/libexec/ld.so/arm/archdep.h
index 38c9af0c05b..b0df994afb1 100644
--- a/libexec/ld.so/arm/archdep.h
+++ b/libexec/ld.so/arm/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.8 2016/09/08 18:56:58 kettenis Exp $ */
+/*	$OpenBSD: archdep.h,v 1.9 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -73,6 +73,4 @@ RELOC_DYN(Elf_Rel *r, const Elf_Sym *s, Elf_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS (PROT_READ|PROT_EXEC)
-
 #endif /* _ARM_ARCHDEP_H_ */
diff --git a/libexec/ld.so/boot.c b/libexec/ld.so/boot.c
index 52a460fa6ce..a4ed06ea062 100644
--- a/libexec/ld.so/boot.c
+++ b/libexec/ld.so/boot.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: boot.c,v 1.14 2016/08/13 20:57:04 guenther Exp $ */
+/*	$OpenBSD: boot.c,v 1.15 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -87,6 +87,8 @@ _dl_boot_bind(const long sp, long *dl_data, Elf_Dyn *dynp)
 	long		loff;
 	Elf_Addr	i;
 	RELOC_TYPE	*rp;
+	Elf_Ehdr	*ehdp;
+	Elf_Phdr	*phdp;
 
 	/*
 	 * Scan argument and environment vectors. Find dynamic
@@ -189,4 +191,30 @@ _dl_boot_bind(const long sp, long *dl_data, Elf_Dyn *dynp)
 	 * we have been fully relocated here, so most things no longer
 	 * need the loff adjustment
 	 */
+
+	/*
+	 * No further changes to the PLT and/or GOT are needed so make
+	 * them read-only.
+	 */
+
+	/* do any RWX -> RX fixups for executable PLTs and apply GNU_RELRO */
+	ehdp = (Elf_Ehdr *)loff;
+	phdp = (Elf_Phdr *)(loff + ehdp->e_phoff);
+	for (i = 0; i < ehdp->e_phnum; i++, phdp++) {
+		switch (phdp->p_type) {
+#if defined(__alpha__) || defined(__hppa__) || defined(__powerpc__) || \
+    defined(__sparc64__)
+		case PT_LOAD:
+			if ((phdp->p_flags & (PF_X | PF_W)) != (PF_X | PF_W))
+				break;
+			_dl_mprotect((void *)(phdp->p_vaddr + loff),
+			    phdp->p_memsz, PROT_READ);
+			break;
+#endif
+		case PT_GNU_RELRO:
+			_dl_mprotect((void *)(phdp->p_vaddr + loff),
+			    phdp->p_memsz, PROT_READ);
+			break;
+		}
+	}
 }
diff --git a/libexec/ld.so/hppa/archdep.h b/libexec/ld.so/hppa/archdep.h
index 9bcc6e02826..11af4bbb767 100644
--- a/libexec/ld.so/hppa/archdep.h
+++ b/libexec/ld.so/hppa/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.11 2016/05/18 20:40:20 deraadt Exp $	*/
+/*	$OpenBSD: archdep.h,v 1.12 2017/01/09 22:51:04 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2004 Michael Shalayeff
@@ -85,8 +85,6 @@ RELOC_DYN(Elf_RelA *r, const Elf_Sym *s, Elf_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS PROT_READ
-
 void _hppa_dl_dtors(void);
 Elf_Addr _dl_md_plabel(Elf_Addr, Elf_Addr *);
 
diff --git a/libexec/ld.so/hppa/rtld_machine.c b/libexec/ld.so/hppa/rtld_machine.c
index c3633370991..1f6a9c80a2e 100644
--- a/libexec/ld.so/hppa/rtld_machine.c
+++ b/libexec/ld.so/hppa/rtld_machine.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rtld_machine.c,v 1.34 2016/08/27 22:52:21 guenther Exp $	*/
+/*	$OpenBSD: rtld_machine.c,v 1.35 2017/01/09 22:51:04 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2004 Michael Shalayeff
@@ -430,7 +430,7 @@ _dl_md_reloc_got(elf_object_t *object, int lazy)
 
 	/* mprotect the GOT */
 	_dl_protect_segment(object, 0, "__got_start", "__got_end",
-	    GOT_PERMS|PROT_EXEC);
+	    PROT_READ|PROT_EXEC);
 
 	return (fails);
 }
diff --git a/libexec/ld.so/i386/archdep.h b/libexec/ld.so/i386/archdep.h
index e2cf5fb8de2..f3152a7ec9e 100644
--- a/libexec/ld.so/i386/archdep.h
+++ b/libexec/ld.so/i386/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.15 2016/05/18 20:40:20 deraadt Exp $ */
+/*	$OpenBSD: archdep.h,v 1.16 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -77,6 +77,4 @@ RELOC_DYN(Elf32_Rel *r, const Elf32_Sym *s, Elf32_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS PROT_READ
-
 #endif /* _I386_ARCHDEP_H_ */
diff --git a/libexec/ld.so/loader.c b/libexec/ld.so/loader.c
index 1c29c0dba52..0ce7f59595a 100644
--- a/libexec/ld.so/loader.c
+++ b/libexec/ld.so/loader.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: loader.c,v 1.167 2016/08/28 04:33:17 guenther Exp $ */
+/*	$OpenBSD: loader.c,v 1.168 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -413,25 +413,6 @@ _dl_boot(const char **argv, char **envp, const long dyn_loff, long *dl_data)
 #define ROUND_PG(x) (((x) + align) & ~(align))
 #define TRUNC_PG(x) ((x) & ~(align))
 
-	/*
-	 * now that GOT and PLT have been relocated, and we know
-	 * page size, protect them from modification
-	 */
-#ifndef  RTLD_NO_WXORX
-	{
-		extern char *__got_start;
-		extern char *__got_end;
-
-		if (&__got_start != &__got_end) {
-			_dl_mprotect((void *)ELF_TRUNC((long)&__got_start,
-			    _dl_pagesz),
-			    ELF_ROUND((long)&__got_end,_dl_pagesz) -
-			    ELF_TRUNC((long)&__got_start, _dl_pagesz),
-			    GOT_PERMS);
-		}
-	}
-#endif
-
 	_dl_setup_env(argv[0], envp);
 
 	DL_DEB(("rtld loading: '%s'\n", __progname));
diff --git a/libexec/ld.so/m88k/archdep.h b/libexec/ld.so/m88k/archdep.h
index f55aa46bee9..40ae479b97b 100644
--- a/libexec/ld.so/m88k/archdep.h
+++ b/libexec/ld.so/m88k/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.2 2015/12/06 23:36:12 guenther Exp $	*/
+/*	$OpenBSD: archdep.h,v 1.3 2017/01/09 22:51:04 kettenis Exp $	*/
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -62,6 +62,4 @@ RELOC_DYN(Elf32_Rela *r, const Elf32_Sym *s, Elf32_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)	do { } while (0)
 
-#define GOT_PERMS		PROT_READ
-
 #endif /* _M88K_ARCHDEP_H_ */
diff --git a/libexec/ld.so/mips64/archdep.h b/libexec/ld.so/mips64/archdep.h
index 0709c7699ce..4ed01d1b96a 100644
--- a/libexec/ld.so/mips64/archdep.h
+++ b/libexec/ld.so/mips64/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.10 2015/12/06 23:36:12 guenther Exp $ */
+/*	$OpenBSD: archdep.h,v 1.11 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998-2002 Opsycon AB, Sweden.
@@ -90,6 +90,4 @@ do {									\
 	}								\
 } while (0)
 
-#define GOT_PERMS PROT_READ
-
 #endif /* _MIPS_ARCHDEP_H_ */
diff --git a/libexec/ld.so/powerpc/archdep.h b/libexec/ld.so/powerpc/archdep.h
index 9d4177c9448..15f3699502a 100644
--- a/libexec/ld.so/powerpc/archdep.h
+++ b/libexec/ld.so/powerpc/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.18 2015/12/06 23:36:12 guenther Exp $ */
+/*	$OpenBSD: archdep.h,v 1.19 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -87,6 +87,4 @@ RELOC_DYN(Elf32_Rela *r, const Elf32_Sym *s, Elf32_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS PROT_READ
-
 #endif /* _POWERPC_ARCHDEP_H_ */
diff --git a/libexec/ld.so/sh/archdep.h b/libexec/ld.so/sh/archdep.h
index b1d61b1c75f..46797555391 100644
--- a/libexec/ld.so/sh/archdep.h
+++ b/libexec/ld.so/sh/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.6 2016/05/18 20:40:20 deraadt Exp $ */
+/*	$OpenBSD: archdep.h,v 1.7 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -43,8 +43,6 @@
 #include "syscall.h"
 #include "util.h"
 
-#define  RTLD_NO_WXORX
-
 /*
  *	The following functions are declared inline so they can
  *	be used before bootstrap linking has been finished.
@@ -73,6 +71,4 @@ RELOC_DYN(Elf32_Rela *r, const Elf32_Sym *s, Elf32_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS (PROT_READ|PROT_EXEC)
-
 #endif /* _SH_ARCHDEP_H_ */
diff --git a/libexec/ld.so/sparc64/archdep.h b/libexec/ld.so/sparc64/archdep.h
index a27bd147a3c..c3afd159f11 100644
--- a/libexec/ld.so/sparc64/archdep.h
+++ b/libexec/ld.so/sparc64/archdep.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: archdep.h,v 1.21 2016/05/18 20:40:20 deraadt Exp $ */
+/*	$OpenBSD: archdep.h,v 1.22 2017/01/09 22:51:04 kettenis Exp $ */
 
 /*
  * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
@@ -66,6 +66,4 @@ RELOC_DYN(Elf_RelA *r, const Elf_Sym *s, Elf_Addr *p, unsigned long v)
 
 #define RELOC_GOT(obj, offs)
 
-#define GOT_PERMS PROT_READ
-
 #endif /* _SPARC64_ARCHDEP_H_ */