hurd: Fix static-PIE startup

hurd initialization stages use RUN_HOOK to run various initialization
functions.  That is however using absolute addresses which need to be
relocated, which is done later by csu.  We can however easily make the
linker compute relative addresses which thus don't need a relocation.
The new SET_RELHOOK and RUN_RELHOOK macros implement this.

hurd/dtable.c

@@ -36,7 +36,7 @@ DEFINE_HOOK (_hurd_fd_subinit, (void));
 
 /* Initialize the file descriptor table at startup.  */
 
-static void
+static void attribute_used_retain
 init_dtable (void)
 {
   int i;
@@ -91,12 +91,10 @@ init_dtable (void)
 
   /* Run things that want to run after the file descriptor table
      is initialized.  */
-  RUN_HOOK (_hurd_fd_subinit, ());
+  RUN_RELHOOK (_hurd_fd_subinit, ());
-
-  (void) &init_dtable;		/* Avoid "defined but not used" warning.  */
 }
 
-text_set_element (_hurd_subinit, init_dtable);
+SET_RELHOOK (_hurd_subinit, init_dtable);
 
 /* XXX when the linker supports it, the following functions should all be
    elsewhere and just have text_set_elements here.  */

hurd/hurdid.c

@@ -17,6 +17,7 @@
 
 #include <hurd.h>
 #include <hurd/id.h>
+#include "set-hooks.h"
 
 struct hurd_id_data _hurd_id;
 
@@ -74,7 +75,7 @@ _hurd_check_ids (void)
   return 0;
 }
 
-static void
+static void attribute_used_retain
 init_id (void)
 {
   __mutex_init (&_hurd_id.lock);
@@ -84,7 +85,5 @@ init_id (void)
   _hurd_id.gen.nuids = _hurd_id.aux.nuids = 0;
   _hurd_id.gen.gids = _hurd_id.aux.gids = NULL;
   _hurd_id.gen.ngids = _hurd_id.aux.ngids = 0;
-
-  (void) &init_id;		/* Avoid "defined but not used" warning.  */
 }
-text_set_element (_hurd_preinit_hook, init_id);
+SET_RELHOOK (_hurd_preinit_hook, init_id);

hurd/hurdinit.c

@@ -108,7 +108,7 @@ _hurd_init (int flags, char **argv,
   /* Call other things which want to do some initialization.  These are not
      on the __libc_subinit hook because things there like to be able to
      assume the availability of the POSIX.1 services we provide.  */
-  RUN_HOOK (_hurd_subinit, ());
+  RUN_RELHOOK (_hurd_subinit, ());
 }
 libc_hidden_def (_hurd_init)
 
@@ -190,7 +190,7 @@ _hurd_new_proc_init (char **argv,
   /* Call other things which want to do some initialization.  These are not
      on the _hurd_subinit hook because things there assume that things done
      here, like _hurd_pid, are already initialized.  */
-  RUN_HOOK (_hurd_proc_subinit, ());
+  RUN_RELHOOK (_hurd_proc_subinit, ());
 
   /* XXX This code should probably be removed entirely at some point.  This
      conditional should make it reasonably usable with old gdb's for a
@@ -242,7 +242,7 @@ _hurd_setproc (process_t procserver)
 
     /* Call these functions again so they can fetch the
        new information from the new proc server.  */
-    RUN_HOOK (_hurd_proc_subinit, ());
+    RUN_RELHOOK (_hurd_proc_subinit, ());
 
     if (_hurd_pgrp != oldpgrp)
       {

hurd/hurdmalloc.c

@@ -1,5 +1,6 @@
 #include <stdlib.h>
 #include <string.h>
+#include "set-hooks.h"
 
 #include "hurdmalloc.h"		/* XXX see that file */
 
@@ -148,7 +149,7 @@ static struct free_list malloc_free_list[NBUCKETS];
    It preserves the values of data variables like malloc_free_list, but
    does not save the vm_allocate'd space allocated by this malloc.  */
 
-static void
+static void attribute_used_retain
 malloc_init (void)
 {
   int i;
@@ -160,11 +161,6 @@ malloc_init (void)
       malloc_free_list[i].in_use = 0;
 #endif
     }
-
-  /* This not only suppresses a `defined but not used' warning,
-     but it is ABSOLUTELY NECESSARY to avoid the hyperclever
-     compiler from "optimizing out" the entire function!  */
-  (void) &malloc_init;
 }
 
 static void
@@ -445,4 +441,4 @@ _hurd_malloc_fork_child(void)
 }
 
 
-text_set_element (_hurd_preinit_hook, malloc_init);
+SET_RELHOOK (_hurd_preinit_hook, malloc_init);

hurd/hurdpid.c

@@ -17,11 +17,12 @@
 
 #include <hurd.h>
 #include <lowlevellock.h>
+#include "set-hooks.h"
 
 pid_t _hurd_pid, _hurd_ppid, _hurd_pgrp;
 int _hurd_orphaned;
 
-static void
+static void attribute_used_retain
 init_pids (void)
 {
   __USEPORT (PROC,
@@ -29,11 +30,9 @@ init_pids (void)
 	       __proc_getpids (port, &_hurd_pid, &_hurd_ppid, &_hurd_orphaned);
 	       __proc_getpgrp (port, _hurd_pid, &_hurd_pgrp);
 	     }));
-
-  (void) &init_pids;		/* Avoid "defined but not used" warning.  */
 }
 
-text_set_element (_hurd_proc_subinit, init_pids);
+SET_RELHOOK (_hurd_proc_subinit, init_pids);
 
 #include <hurd/msg_server.h>
 #include "set-hooks.h"

hurd/hurdrlimit.c

@@ -19,6 +19,7 @@
 #include <hurd.h>
 #include <lock-intern.h>
 #include <hurd/resource.h>
+#include "set-hooks.h"
 
 /* This must be given an initializer, or the a.out linking rules will
    not include the entire file when this symbol is referenced. */
@@ -29,7 +30,7 @@ struct rlimit _hurd_rlimits[RLIM_NLIMITS] = { { 0, }, };
    mutex_init is still required below just in case of unexec.  */
 struct mutex _hurd_rlimit_lock = { SPIN_LOCK_INITIALIZER, };
 
-static void
+static void attribute_used_retain
 init_rlimit (void)
 {
   int i;
@@ -52,7 +53,5 @@ init_rlimit (void)
 	  }
 #undef	I
     }
-
-  (void) &init_rlimit;
 }
-text_set_element (_hurd_preinit_hook, init_rlimit);
+SET_RELHOOK (_hurd_preinit_hook, init_rlimit);

hurd/hurdsock.c

@@ -25,6 +25,7 @@
 #include <_itoa.h>
 #include <lock-intern.h>	/* For `struct mutex'.  */
 #include "hurdmalloc.h"		/* XXX */
+#include "set-hooks.h"
 
 static struct mutex lock;
 
@@ -109,7 +110,7 @@ retry:
   return server;
 }
 
-static void
+static void attribute_used_retain
 init (void)
 {
   int i;
@@ -118,7 +119,5 @@ init (void)
 
   for (i = 0; i < max_domain; ++i)
     servers[i] = MACH_PORT_NULL;
-
-  (void) &init;			/* Avoid "defined but not used" warning.  */
 }
-text_set_element (_hurd_preinit_hook, init);
+SET_RELHOOK (_hurd_preinit_hook, init);

include/set-hooks.h

@@ -24,6 +24,8 @@
 #include <sys/cdefs.h>
 #include <libc-symbols.h>
 
+#include "set-hooks-arch.h"
+
 #ifdef symbol_set_define
 /* Define a hook variable called NAME.  Functions put on this hook take
    arguments described by PROTO.  Use `text_set_element (NAME, FUNCTION)'
@@ -55,6 +57,25 @@ do {									      \
 DEFINE_HOOK (name, proto); \
 extern void runner proto; void runner proto { RUN_HOOK (name, args); }
 
+# ifdef SET_RELHOOK
+/* This is similar to RUN_RELHOOK, but the hooks were registered with
+ * SET_RELHOOK so that a relative offset was computed by the linker
+ * rather than an absolute address by the dynamic linker. */
+#  define RUN_RELHOOK(NAME, ARGS)				      \
+do {								      \
+  void *const *ptr;						      \
+  for (ptr = (void *const *) symbol_set_first_element (NAME);	      \
+       ! symbol_set_end_p (NAME, ptr); ++ptr) {			      \
+    __##NAME##_hook_function_t *f =				      \
+	(void*) ((uintptr_t) ptr + (ptrdiff_t) *ptr);		      \
+    (*f) ARGS;							      \
+  } \
+} while (0)
+# else
+#  define SET_RELHOOK(NAME, HOOK) text_set_element (NAME, HOOK)
+#  define RUN_RELHOOK(NAME, ARGS) RUN_HOOK(NAME, ARGS)
+# endif
+
 #else
 
 /* The system does not provide necessary support for this.  */
@@ -66,6 +87,10 @@ extern void runner proto; void runner proto { RUN_HOOK (name, args); }
 
 # define DEFINE_HOOK_RUNNER(name, runner, proto, args)
 
+# define SET_RELHOOK(NAME, HOOK)
+
+# define RUN_RELHOOK(NAME, ARGS)
+
 #endif
 
 #endif /* set-hooks.h */

sysdeps/generic/set-hooks-arch.h

@@ -0,0 +1,31 @@
+/* Machine-dependent macros for using symbol sets for running lists of
+   functions. Generic/stub version.
+   Copyright (C) 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 _SET_HOOKS_ARCH_H
+#define _SET_HOOKS_ARCH_H
+
+/* Define SET_RELHOOK to a variant of text_set_element that records a relative
+   offset rather than an absolute address. See sysdeps/i386/set-hooks-arch.h
+   for an example.
+
+#define SET_RELHOOK(NAME, HOOK) ...
+
+ */
+
+#endif /* set_hooks_arch.h */

sysdeps/i386/set-hooks-arch.h

@@ -0,0 +1,28 @@
+/* Machine-dependent macros for using symbol sets for running lists of
+   functions. i386 version.
+   Copyright (C) 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 _SET_HOOKS_ARCH_H
+#define _SET_HOOKS_ARCH_H
+
+#define SET_RELHOOK(NAME, HOOK) \
+	asm(".section " #NAME",\"aR\"\n" \
+	    ".long "#HOOK" - .\n" \
+	    ".section .text");
+
+#endif /* set_hooks_arch.h */

sysdeps/mach/hurd/brk.c

@@ -21,6 +21,8 @@
 #include <lock-intern.h>	/* For `struct mutex'.  */
 #include <vm_param.h>
 
+#include "set-hooks.h"
+
 
 /* Initial maximum size of the data segment (this is arbitrary).  */
 #define	DATA_SIZE	(128 * 1024 * 1024)
@@ -130,7 +132,7 @@ _hurd_set_brk (vm_address_t addr)
   return 0;
 }
 
-static void
+static void attribute_used_retain
 init_brk (void)
 {
   vm_address_t pagend;
@@ -160,7 +162,5 @@ init_brk (void)
 	/* Couldn't allocate the memory.  The break will be very short.  */
 	_hurd_data_end = pagend;
     }
-
-  (void) &init_brk;		/* Avoid ``defined but not used'' warning.  */
 }
-text_set_element (_hurd_preinit_hook, init_brk);
+SET_RELHOOK (_hurd_preinit_hook, init_brk);

sysdeps/mach/hurd/check_fds.c

@@ -79,7 +79,7 @@ check_standard_fds (void)
   check_one_fd (STDERR_FILENO, O_RDWR);
 }
 
-static void
+static void attribute_used_retain
 init_standard_fds (void)
 {
   /* Now that we have FDs, make sure that, if this is a SUID program,
@@ -87,10 +87,8 @@ init_standard_fds (void)
      ourselves.  If that's not possible we stop the program.  */
   if (__builtin_expect (__libc_enable_secure, 0))
     check_standard_fds ();
-
-  (void) &init_standard_fds;	/* Avoid "defined but not used" warning.  */
 }
-text_set_element (_hurd_fd_subinit, init_standard_fds);
+SET_RELHOOK (_hurd_fd_subinit, init_standard_fds);
 
 
 #ifndef SHARED

sysdeps/mach/hurd/i386/init-first.c

@@ -242,7 +242,7 @@ first_init (void)
   /* Initialize data structures so we can do RPCs.  */
   __mach_init ();
 
-  RUN_HOOK (_hurd_preinit_hook, ());
+  RUN_RELHOOK (_hurd_preinit_hook, ());
 }
 
 #ifdef SHARED

sysdeps/x86_64/set-hooks-arch.h

@@ -0,0 +1,28 @@
+/* Machine-dependent macros for using symbol sets for running lists of
+   functions. x86-64 version.
+   Copyright (C) 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 _SET_HOOKS_ARCH_H
+#define _SET_HOOKS_ARCH_H
+
+#define SET_RELHOOK(NAME, HOOK) \
+	asm(".section " #NAME",\"aR\"\n" \
+	    ".quad "#HOOK" - .\n" \
+	    ".section .text");
+
+#endif /* set_hooks_arch.h */