Introduce ltrace(1). This tool works with ld.so to inject utrace record for

each plt call, allowing to trace a binary linked against shared library at the
public function call level.

To do so, ltrace(1) sets up some environment variables to enable plt tracing
in ld.so, and invokes ktrace(2) for utrace events. ld.so will force lazy
binding and will send an utrace record in the plt resolver, without updating
the plt.

Minimal filtering capabilities are provided, inspired by Solaris' truss -u,
to limit tracing to libraries and/or symbol names. Non-traced libraries and
symbols will have the regular resolver processing, with the expected plt
update.

"Get it in" deraadt

3 files changed, 17 insertions, 6 deletions

diff --git a/libexec/ld.so/alpha/ldasm.S b/libexec/ld.so/alpha/ldasm.S
index 6264cd5f7f1..5fb82ed6d0c 100644
--- a/libexec/ld.so/alpha/ldasm.S
+++ b/libexec/ld.so/alpha/ldasm.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ldasm.S,v 1.19 2013/04/05 12:58:03 kurt Exp $ */
+/*	$OpenBSD: ldasm.S,v 1.20 2013/06/01 09:57:57 miod Exp $ */
 
 /*
  * Copyright (c) 2001 Niklas Hallqvist
@@ -325,3 +325,8 @@ LEAF_NOPROFILE(_dl_getcwd, 2)
 	RET
 END(_dl_getcwd)
 
+LEAF_NOPROFILE(_dl_utrace, 2)
+	ldiq	v0, SYS_utrace
+	call_pal PAL_OSF1_callsys
+	RET
+END(_dl_utrace)
diff --git a/libexec/ld.so/alpha/rtld_machine.c b/libexec/ld.so/alpha/rtld_machine.c
index 37480b01f54..5fa6273707d 100644
--- a/libexec/ld.so/alpha/rtld_machine.c
+++ b/libexec/ld.so/alpha/rtld_machine.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rtld_machine.c,v 1.48 2013/05/08 20:55:14 guenther Exp $ */
+/*	$OpenBSD: rtld_machine.c,v 1.49 2013/06/01 09:57:57 miod Exp $ */
 
 /*
  * Copyright (c) 1999 Dale Rahn
@@ -208,6 +208,7 @@ _dl_bind(elf_object_t *object, int reloff)
 	Elf_Addr *addr, ooff;
 	const Elf_Sym *sym, *this;
 	const char *symn;
+	const elf_object_t *sobj;
 	sigset_t savedmask;
 
 	rela = (Elf_RelA *)(object->Dyn.info[DT_JMPREL] + reloff);
@@ -229,13 +230,15 @@ _dl_bind(elf_object_t *object, int reloff)
 
 	this = NULL;
 	ooff = _dl_find_symbol(symn, &this,
-	    SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym,
-	    object, NULL);
+	    SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym, object, &sobj);
 	if (this == NULL) {
 		_dl_printf("lazy binding failed!\n");
 		*((int *)0) = 0;	/* XXX */
 	}
 
+	if (sobj->traced && _dl_trace_plt(sobj, symn))
+		return ooff + this->st_value + rela->r_addend;
+
 	/* if PLT is protected, allow the write */
 	if (object->plt_size != 0) {
 		_dl_thread_bind_lock(0, &savedmask);
@@ -268,7 +271,6 @@ _dl_md_reloc_got(elf_object_t *object, int lazy)
 	Elf_Addr plt_addr;
 	const Elf_Sym *this;
 
-
 	pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT];
 
 	object->got_addr = 0;
@@ -314,6 +316,9 @@ _dl_md_reloc_got(elf_object_t *object, int lazy)
 		object->plt_size = ELF_ROUND(object->plt_size, _dl_pagesz);
 	}
 
+	if (object->traced)
+		lazy = 1;
+
 	if (object->obj_type == OBJTYPE_LDR || !lazy || pltgot == NULL) {
 		fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ);
 	} else {
diff --git a/libexec/ld.so/alpha/syscall.h b/libexec/ld.so/alpha/syscall.h
index c5d48531659..d4c58fd98f0 100644
--- a/libexec/ld.so/alpha/syscall.h
+++ b/libexec/ld.so/alpha/syscall.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: syscall.h,v 1.19 2013/04/05 12:58:03 kurt Exp $ */
+/*	$OpenBSD: syscall.h,v 1.20 2013/06/01 09:57:57 miod Exp $ */
 
 /*
  * Copyright (c) 2001 Niklas Hallqvist
@@ -56,6 +56,7 @@ int	_dl_gettimeofday(struct timeval *tp, struct timezone *tzp);
 int	_dl_readlink(const char *path, char *buf, size_t bufsiz);
 int	_dl_lstat(const char *path, struct stat *sb);
 int	_dl_getcwd(char *buf, size_t size);
+int	_dl_utrace(const char *label, const void *addr, size_t len);
 
 static inline off_t
 _dl_lseek(int fildes, off_t offset, int whence)