Add elf_aux_info(3)

Designed to let userland peek at AT_HWCAP and AT_HWCAP2 using an already
existing interface coming from FreeBSD. Headers bits were snatched from
there.  Input & ok kettenis@

libc bump and sets sync will follow soon

6 files changed, 186 insertions, 5 deletions

diff --git a/lib/libc/Symbols.list b/lib/libc/Symbols.list
index eb4d78cc947..48c4965a6d9 100644
--- a/lib/libc/Symbols.list
+++ b/lib/libc/Symbols.list
@@ -608,6 +608,7 @@ daemon
 devname
 dirfd
 dirname
+elf_aux_info
 endfsent
 endgrent
 endnetgrent
diff --git a/lib/libc/dlfcn/init.c b/lib/libc/dlfcn/init.c
index 9fc63c97f98..c7b8fd2bc37 100644
--- a/lib/libc/dlfcn/init.c
+++ b/lib/libc/dlfcn/init.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: init.c,v 1.22 2024/01/21 17:18:13 kettenis Exp $ */
+/*	$OpenBSD: init.c,v 1.23 2024/07/14 09:48:48 jca Exp $ */
 /*
  * Copyright (c) 2014,2015 Philip Guenther <guenther@openbsd.org>
  *
@@ -49,6 +49,8 @@ char	***_csu_finish(char **_argv, char **_envp, void (*_cleanup)(void));
 /* provide definitions for these */
 int	_pagesize = 0;
 struct timekeep	*_timekeep;
+unsigned long	_hwcap, _hwcap2;
+int	_hwcap_avail, _hwcap2_avail;
 
 /*
  * In dynamically linked binaries environ and __progname are overridden by
@@ -96,6 +98,14 @@ _libc_preinit(int argc, char **argv, char **envp, dl_cb_cb *cb)
 		;
 	for (aux = (void *)envp; aux->au_id != AUX_null; aux++) {
 		switch (aux->au_id) {
+		case AUX_hwcap:
+			_hwcap = aux->au_v;
+			_hwcap_avail = 1;
+			break;
+		case AUX_hwcap2:
+			_hwcap2 = aux->au_v;
+			_hwcap2_avail = 1;
+			break;
 		case AUX_pagesz:
 			_pagesize = aux->au_v;
 			break;
diff --git a/lib/libc/gen/Makefile.inc b/lib/libc/gen/Makefile.inc
index cf36ead40e9..f87cc7a89e5 100644
--- a/lib/libc/gen/Makefile.inc
+++ b/lib/libc/gen/Makefile.inc
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile.inc,v 1.82 2019/09/02 21:18:40 deraadt Exp $
+#	$OpenBSD: Makefile.inc,v 1.83 2024/07/14 09:48:48 jca Exp $
 
 # gen sources
 .PATH: ${LIBCSRCDIR}/arch/${MACHINE_CPU}/gen ${LIBCSRCDIR}/gen
@@ -6,8 +6,8 @@
 SRCS+=  alarm.c assert.c auth_subr.c authenticate.c \
         basename.c clock.c clock_getcpuclockid.c \
         closedir.c confstr.c ctermid.c ctype_.c \
-        daemon.c devname.c dirfd.c dirname.c disklabel.c err.c \
-        errc.c errx.c errlist.c errno.c exec.c \
+        daemon.c devname.c dirfd.c dirname.c disklabel.c elf_aux_info.c \
+        err.c errc.c errx.c errlist.c errno.c exec.c \
         fdatasync.c fnmatch.c fpclassify.c frexp.c \
         fstab.c ftok.c fts.c ftw.c getbsize.c getcap.c getcwd.c \
         getdomainname.c getgrent.c getgrouplist.c gethostname.c \
@@ -36,7 +36,7 @@ SRCS+=  alarm.c assert.c auth_subr.c authenticate.c \
 
 MAN+=	__tfork_thread.3 alarm.3 auth_subr.3 authenticate.3 basename.3 clock.3 \
 	clock_getcpuclockid.3 confstr.3 \
-	ctermid.3 daemon.3 devname.3 opendir.3 dirname.3 err.3 \
+	ctermid.3 daemon.3 devname.3 opendir.3 dirname.3 elf_aux_info.3 err.3 \
 	execv.3 fabs.3 fnmatch.3 fpclassify.3 fpgetmask.3 frexp.3 ftok.3 fts_open.3 \
 	ftw.3 getbsize.3 cgetent.3 getcwd.3 getdomainname.3 getdiskbyname.3 \
 	getfsent.3 getgrent.3 getgrouplist.3 gethostname.3 getloadavg.3 \
diff --git a/lib/libc/gen/elf_aux_info.3 b/lib/libc/gen/elf_aux_info.3
new file mode 100644
index 00000000000..1bd1a0923e0
--- /dev/null
+++ b/lib/libc/gen/elf_aux_info.3
@@ -0,0 +1,74 @@
+.\"	$OpenBSD: elf_aux_info.3,v 1.1 2024/07/14 09:48:48 jca Exp $
+.\"
+.\" Origin: FreeBSD auxv.3
+.\"
+.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org>
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\"
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd $Mdocdate: July 14 2024 $
+.Dt ELF_AUX_INFO 3
+.Os
+.Sh NAME
+.Nm elf_aux_info
+.Nd extract data from the elf auxiliary vector of the current process
+.Sh SYNOPSIS
+.In sys/auxv.h
+.Ft int
+.Fn elf_aux_info "int aux" "void *buf" "int buflen"
+.Sh DESCRIPTION
+The
+.Fn elf_aux_info
+function retrieves the auxiliary info vector requested in
+.Va aux .
+The information is stored into the provided buffer if it will fit.
+The following values can be requested (corresponding buffer sizes are
+specified in parenthesis):
+.Bl -tag -width AT_HWCAP2
+.It AT_HWCAP
+CPU / hardware feature flags
+.Dv (sizeof(unsigned long)) .
+.It AT_HWCAP2
+CPU / hardware feature flags
+.Dv (sizeof(unsigned long)) .
+.It AT_PAGESZ
+Page size in bytes
+.Dv (sizeof(int)) .
+.El
+.Sh RETURN VALUES
+Returns zero on success, or an error number on failure.
+.Sh ERRORS
+.Bl -tag -width Er
+.It Bq Er EINVAL
+An unknown item was requested.
+.It Bq Er EINVAL
+The provided buffer was not the right size for the requested item.
+.It Bq Er ENOENT
+The requested item is not available.
+.El
+.Sh HISTORY
+The
+.Fn elf_aux_info
+function appeared in
+.Fx 12.0
+and was first available in
+.Ox 7.6 .
diff --git a/lib/libc/gen/elf_aux_info.c b/lib/libc/gen/elf_aux_info.c
new file mode 100644
index 00000000000..a4b7667ba6f
--- /dev/null
+++ b/lib/libc/gen/elf_aux_info.c
@@ -0,0 +1,70 @@
+/*	$OpenBSD: elf_aux_info.c,v 1.1 2024/07/14 09:48:48 jca Exp $	*/
+
+/*
+ * Copyright (c) 2024 Jeremie Courreges-Anglas <jca@wxcvbn.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <sys/auxv.h>
+
+#include <errno.h>
+
+extern int _pagesize;
+extern unsigned long _hwcap, _hwcap2;
+extern int _hwcap_avail, _hwcap2_avail;
+
+int
+elf_aux_info(int request, void *buf, int buflen)
+{
+	int ret = 0;
+
+	if (buflen < 0)
+		return EINVAL;
+
+	switch (request) {
+	case AT_HWCAP:
+		if (buflen != sizeof(unsigned long))
+			ret = EINVAL;
+		else if (!_hwcap_avail)
+			ret = ENOENT;
+		else
+			*(unsigned long *)buf = _hwcap;
+		break;
+	case AT_HWCAP2:
+		if (buflen != sizeof(unsigned long))
+			ret = EINVAL;
+		else if (!_hwcap2_avail)
+			ret = ENOENT;
+		else
+			*(unsigned long *)buf = _hwcap2;
+		break;
+	case AT_PAGESZ:
+		if (buflen != sizeof(int))
+			ret = EINVAL;
+		else if (!_pagesize)
+			ret = ENOENT;
+		else
+			*(int *)buf = _pagesize;
+		break;
+	default:
+		if (request < 0 || request >= AT_COUNT)
+			ret = EINVAL;
+		else
+			ret = ENOENT;
+		break;
+	}
+
+	return ret;
+}
diff --git a/lib/libc/hidden/sys/auxv.h b/lib/libc/hidden/sys/auxv.h
new file mode 100644
index 00000000000..cd566b7b2a2
--- /dev/null
+++ b/lib/libc/hidden/sys/auxv.h
@@ -0,0 +1,26 @@
+/*	$OpenBSD: auxv.h,v 1.1 2024/07/14 09:48:48 jca Exp $	*/
+
+/*
+ * Copyright (c) 2024 Jeremie Courreges-Anglas <jca@wxcvbn.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef _LIBC_SYS_AUXV_H_
+#define _LIBC_SYS_AUXV_H_
+
+#include_next <sys/auxv.h>
+
+PROTO_DEPRECATED(elf_aux_info);
+
+#endif /* !_LIBC_SYS_AUXV_H_ */