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From 3288c6da64add3b4561b8c10fff522027caea01c Mon Sep 17 00:00:00 2001
From: Nicholas Miell <nmiell@gmail.com>
Date: Sat, 17 Jun 2017 18:21:07 -0700
Subject: [PATCH] Align the stack on entry to __tls_get_addr()
Old versions of gcc (4 & 5) didn't align the stack according to the
AMD64 psABI when calling __tls_get_addr(). Apparently new versions of
gcc (7) got much more aggressive about vectorizing and generating MOVAPS
instructions, which means old binaries built with the buggy versions of
gcc are much more likely to crash when using versions of glibc built
using gcc 7.
For example, a large number of Linux games built using the Unity game
engine and available for purchase on Steam.
---
elf/dl-tls.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index 5aba33b3fa..3f3cb917de 100644
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -827,6 +827,10 @@ rtld_hidden_proto (__tls_get_addr)
rtld_hidden_def (__tls_get_addr)
#endif
+#ifdef __x86_64__
+/* Old versions of gcc didn't align the stack. */
+__attribute__((force_align_arg_pointer))
+#endif
/* The generic dynamic and local dynamic model cannot be used in
statically linked applications. */
void *
--
2.13.0
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