From 541e57af0b09cc226f89cc33027d9b9daf47812e Mon Sep 17 00:00:00 2001
From: trasz <trasz@FreeBSD.org>
Date: Tue, 3 Sep 2019 19:48:23 +0000
Subject: [PATCH] Unbreak Linux binaries linked against new glibc, such as the
 ones from recent Ubuntu versions.  Without it they segfault on startup.

Reviewed by:	emaste
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D20687
---
 sys/amd64/linux/linux_sysvec.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sys/amd64/linux/linux_sysvec.c b/sys/amd64/linux/linux_sysvec.c
index caef96cffa19..368b5196fba4 100644
--- a/sys/amd64/linux/linux_sysvec.c
+++ b/sys/amd64/linux/linux_sysvec.c
@@ -343,6 +343,12 @@ linux_copyout_strings(struct image_params *imgp)
 	 */
 	vectp -= imgp->args->argc + 1 + imgp->args->envc + 1;
 
+	/*
+	 * Starting with 2.24, glibc depends on a 16-byte stack alignment.
+	 * One "long argc" will be prepended later.
+	 */
+	vectp = (char **)((((uintptr_t)vectp + 8) & ~0xF) - 8);
+
 	/* vectp also becomes our initial stack base. */
 	stack_base = (register_t *)vectp;