Fixed profiling of main() for amd64 and i386. This started rotting

in 1993 in rev.1.5 of the i386 a.out version (csu/i386/crt0.c).
Profiling uses a magic label "eprol" to delimit the start of the part
of the text section covered by profiling.  This label must be placed
before the call to main() to get main() properly profiled.  It was
placed there in rev.1.1 of crt0.c.  Rev.1.5 imported the initial
implementation of shared libraries in FreeBSD and misplaced the label.
Fortunately, the misplaced label was misspelled and the old label
wasn't removed, so the new label had no effect.  Unfortunately, when
profiling was implemented for the ELF in 1998 in rev.1.2 of
csu/i386-elf/crt1.c, only the incorrectly placed label was copied
(after fixing its name).  The bug was then copied to all other arches.
The label seems to be still misplaced in NetBSD for most arches.  It
is in common.c for most arches so it is even further from being inside
the function that calls main().

I think "eprol" is short for "end of prologue", but it must be placed
before the end of the prologue so that it covers main().  crt0.c has
it before the calls atexit(_mcleanup) and monstartup(...), but it
cannot affect these calls so I moved it after the call to monstartup().
It now also covers the call to _init() but not the newer call to
_init_tls().  Profiling of _init() seems to be harmless, and the call
to _init_tls() seems to be misplaced.

Reviewed by:	jdp (long ago, for a slightly different i386 version)

2 files changed, 2 insertions, 12 deletions

diff --git a/lib/csu/amd64/crt1.c b/lib/csu/amd64/crt1.c
index f1f0f7b..943b07b 100644
--- a/lib/csu/amd64/crt1.c
+++ b/lib/csu/amd64/crt1.c
@@ -86,15 +86,10 @@ _start(char **ap, void (*cleanup)(void))
 	atexit(_fini);
 #ifdef GCRT
 	monstartup(&eprol, &etext);
+__asm__("eprol:");
 #endif
 	_init();
 	exit( main(argc, argv, env) );
 }
 
-#ifdef GCRT
-__asm__(".text");
-__asm__("eprol:");
-__asm__(".previous");
-#endif
-
 __asm__(".ident\t\"$FreeBSD$\"");
diff --git a/lib/csu/i386-elf/crt1.c b/lib/csu/i386-elf/crt1.c
index c6774b0..0934333 100644
--- a/lib/csu/i386-elf/crt1.c
+++ b/lib/csu/i386-elf/crt1.c
@@ -104,15 +104,10 @@ _start(char *ap, ...)
 	atexit(_fini);
 #ifdef GCRT
 	monstartup(&eprol, &etext);
+__asm__("eprol:");
 #endif
 	_init();
 	exit( main(argc, argv, env) );
 }
 
-#ifdef GCRT
-__asm__(".text");
-__asm__("eprol:");
-__asm__(".previous");
-#endif
-
 __asm__(".ident\t\"$FreeBSD$\"");