csu: Always use __executable_start in gmon-start.c

Current binutils defines __executable_start as the lowest text
address, so using the entry point address as a fallback is no
longer necessary.  As a result, overriding <entry.h> is only
necessary if the entry point is not called _start.

The previous approach to define __ASSEMBLY__ to suppress the
declaration breaks if headers included by <entry.h> are not
compatible with __ASSEMBLY__.  This happens with rseq integration
because it is necessary to include kernel headers in more places.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

csu/gmon-start.c

@@ -38,32 +38,12 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <elf-initfini.h>
-#define __ASSEMBLY__
-#include <entry.h>
-
-/* Beginning and end of our code segment. We cannot declare them
-   as the external functions since we want the addresses of those
-   labels. Taking the address of a function may have different
-   meanings on different platforms. */
-#ifdef ENTRY_POINT_DECL
-ENTRY_POINT_DECL(extern)
-#else
-extern char ENTRY_POINT[];
-#endif
-extern char etext[];
 
 /* Use __executable_start as the lowest address to keep profiling records
    if it provided by the linker.  */
-extern const char executable_start[] asm ("__executable_start")
+extern const char __executable_start[] __attribute__ ((visibility ("hidden")));
-  __attribute__ ((weak, visibility ("hidden")));
 
-#ifndef TEXT_START
+extern char etext[];
-# ifdef ENTRY_POINT_DECL
-#  define TEXT_START ENTRY_POINT
-# else
-#  define TEXT_START &ENTRY_POINT
-# endif
-#endif
 
 #if !ELF_INITFINI
 /* Instead of defining __gmon_start__ globally in gcrt1.o, we make it
@@ -97,10 +77,7 @@ __gmon_start__ (void)
   called = 1;
 
   /* Start keeping profiling records.  */
-  if (&executable_start != NULL)
+  __monstartup ((u_long) &__executable_start, (u_long) &etext);
-    __monstartup ((u_long) &executable_start, (u_long) &etext);
-  else
-    __monstartup ((u_long) TEXT_START, (u_long) &etext);
 
   /* Call _mcleanup before exiting; it will write out gmon.out from the
      collected data.  */

sysdeps/hppa/entry.h

@@ -1,13 +0,0 @@
-#ifndef __ASSEMBLY__
-extern void _start (void);
-#endif
-
-/* Lives in libgcc.so and canonicalizes function pointers for comparison.  */
-extern unsigned int __canonicalize_funcptr_for_compare (unsigned int fptr);
-
-/* The function's entry point is stored in the first word of the
-   function descriptor (plabel) of _start().  */
-#define ENTRY_POINT __canonicalize_funcptr_for_compare((unsigned int)_start)
-
-/* We have to provide a special declaration.  */
-#define ENTRY_POINT_DECL(class) class void _start (void);

sysdeps/ia64/entry.h

@@ -1,13 +0,0 @@
-#include <link.h>
-#include <dl-fptr.h>
-
-#ifndef __ASSEMBLY__
-extern void _start (void);
-#endif
-
-/* The function's entry point is stored in the first word of the
-   function descriptor (plabel) of _start().  */
-#define ENTRY_POINT ELF_PTR_TO_FDESC (_start)->ip
-
-/* We have to provide a special declaration.  */
-#define ENTRY_POINT_DECL(class) class void _start (void);

sysdeps/powerpc/powerpc64/entry.h

@@ -1,37 +0,0 @@
-/* Finding the entry point and start of text.  PowerPC64 version.
-   Copyright (C) 2002-2021 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-
-#ifndef __ASSEMBLY__
-extern void _start (void);
-#endif
-
-#define ENTRY_POINT _start
-
-#if _CALL_ELF != 2
-/* We have to provide a special declaration.  */
-#define ENTRY_POINT_DECL(class) class void _start (void);
-
-/* Use the address of ._start as the lowest address for which we need
-   to keep profiling records.  We can't copy the ia64 scheme as our
-   entry poiny address is really the address of the function
-   descriptor, not the actual function entry.  */
-#define TEXT_START \
-  ({ extern unsigned long int _start_as_data[] asm ("_start");  \
-     _start_as_data[0]; })
-#endif