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Re: [PATCH] x86-64: Align the stack in __tls_get_addr [BZ #21609]
On Tue, Jul 4, 2017 at 1:16 PM, Florian Weimer <fweimer@redhat.com> wrote:
> On 07/04/2017 06:25 PM, H.J. Lu wrote:
>> Something like this.
>
> Sorry, I lost track of the patches.
>
> Would you please post the two patches you propose to apply?
>
Here are 2 patches.
--
H.J.
From 4198d7a3ac434a80d27ca3303f56fbf0f4403b3a Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 3 Jul 2017 13:16:57 -0700
Subject: [PATCH 1/2] x86-64: Align the stack in __tls_get_addr [BZ #21609]
This change forces realignment of the stack pointer in __tls_get_addr, so
that binaries compiled by GCCs older than GCC 4.9:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066
continue to work even if vector instructions are used in glibc which
require the ABI stack realignment.
__tls_get_addr_slow is added to handle the slow paths in the default
implementation of__tls_get_addr in elf/dl-tls.c. The new __tls_get_addr
calls __tls_get_addr_slow after realigning the stack. Internal calls
within ld.so go directly to the default implementation of __tls_get_addr
because they do not need stack realignment.
2017-07-04 Florian Weimer <fweimer@redhat.com>
H.J. Lu <hongjiu.lu@intel.com>
[BZ #21609]
* sysdeps/x86_64/Makefile (sysdep-dl-routines): Add tls_get_addr.
(gen-as-const-headers): Add rtld-offsets.sym.
* sysdeps/x86_64/dl-tls.c: New file.
* sysdeps/x86_64/rtld-offsets.sym: Likwise.
* sysdeps/x86_64/tls_get_addr.S: Likewise.
* sysdeps/x86_64/dl-tls.h: Add multiple inclusion guards.
* sysdeps/x86_64/tlsdesc.sym (TI_MODULE_OFFSET): New.
(TI_OFFSET_OFFSET): Likwise.
---
sysdeps/x86_64/Makefile | 4 +--
sysdeps/x86_64/dl-tls.c | 53 +++++++++++++++++++++++++++++++++++
sysdeps/x86_64/dl-tls.h | 5 ++++
sysdeps/x86_64/rtld-offsets.sym | 6 ++++
sysdeps/x86_64/tls_get_addr.S | 61 +++++++++++++++++++++++++++++++++++++++++
sysdeps/x86_64/tlsdesc.sym | 3 ++
6 files changed, 130 insertions(+), 2 deletions(-)
create mode 100644 sysdeps/x86_64/dl-tls.c
create mode 100644 sysdeps/x86_64/rtld-offsets.sym
create mode 100644 sysdeps/x86_64/tls_get_addr.S
diff --git a/sysdeps/x86_64/Makefile b/sysdeps/x86_64/Makefile
index 5075c91..132470d 100644
--- a/sysdeps/x86_64/Makefile
+++ b/sysdeps/x86_64/Makefile
@@ -27,7 +27,7 @@ ifeq ($(subdir),elf)
CFLAGS-.os += $(if $(filter $(@F),$(patsubst %,%.os,$(all-rtld-routines))),\
-mno-mmx)
-sysdep-dl-routines += tlsdesc dl-tlsdesc
+sysdep-dl-routines += tlsdesc dl-tlsdesc tls_get_addr
tests += ifuncmain8
modules-names += ifuncmod8
@@ -120,5 +120,5 @@ endif
endif
ifeq ($(subdir),csu)
-gen-as-const-headers += tlsdesc.sym
+gen-as-const-headers += tlsdesc.sym rtld-offsets.sym
endif
diff --git a/sysdeps/x86_64/dl-tls.c b/sysdeps/x86_64/dl-tls.c
new file mode 100644
index 0000000..3584805
--- /dev/null
+++ b/sysdeps/x86_64/dl-tls.c
@@ -0,0 +1,53 @@
+/* Thread-local storage handling in the ELF dynamic linker. x86-64 version.
+ Copyright (C) 2017 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
+ <http://www.gnu.org/licenses/>. */
+
+#ifdef SHARED
+/* Work around GCC PR58066, due to which __tls_get_addr may be called
+ with an unaligned stack. The compat implementation is in
+ tls_get_addr-compat.S. */
+
+# include <dl-tls.h>
+
+/* Define __tls_get_addr within elf/dl-tls.c under a different
+ name. */
+extern __typeof__ (__tls_get_addr) ___tls_get_addr;
+
+# define __tls_get_addr ___tls_get_addr
+# include <elf/dl-tls.c>
+# undef __tls_get_addr
+
+hidden_ver (___tls_get_addr, __tls_get_addr)
+
+/* Only handle slow paths for __tls_get_addr. */
+attribute_hidden
+void *
+__tls_get_addr_slow (GET_ADDR_ARGS)
+{
+ dtv_t *dtv = THREAD_DTV ();
+
+ if (__glibc_unlikely (dtv[0].counter != GL(dl_tls_generation)))
+ return update_get_addr (GET_ADDR_PARAM);
+
+ return tls_get_addr_tail (GET_ADDR_PARAM, dtv, NULL);
+}
+#else
+
+/* No compatibility symbol needed. */
+# include <elf/dl-tls.c>
+
+#endif
diff --git a/sysdeps/x86_64/dl-tls.h b/sysdeps/x86_64/dl-tls.h
index 4a59d2a..c2fb56c 100644
--- a/sysdeps/x86_64/dl-tls.h
+++ b/sysdeps/x86_64/dl-tls.h
@@ -16,6 +16,9 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#ifndef _X86_64_DL_TLS_H
+#define _X86_64_DL_TLS_H
+
#include <stdint.h>
/* Type used for the representation of TLS information in the GOT. */
@@ -27,3 +30,5 @@ typedef struct dl_tls_index
extern void *__tls_get_addr (tls_index *ti);
+
+#endif /* _X86_64_DL_TLS_H */
diff --git a/sysdeps/x86_64/rtld-offsets.sym b/sysdeps/x86_64/rtld-offsets.sym
new file mode 100644
index 0000000..fd41b51
--- /dev/null
+++ b/sysdeps/x86_64/rtld-offsets.sym
@@ -0,0 +1,6 @@
+#define SHARED
+#include <ldsodefs.h>
+
+--
+
+GL_TLS_GENERATION_OFFSET offsetof (struct rtld_global, _dl_tls_generation)
diff --git a/sysdeps/x86_64/tls_get_addr.S b/sysdeps/x86_64/tls_get_addr.S
new file mode 100644
index 0000000..9d38fb3
--- /dev/null
+++ b/sysdeps/x86_64/tls_get_addr.S
@@ -0,0 +1,61 @@
+/* Stack-aligning implementation of __tls_get_addr. x86-64 version.
+ Copyright (C) 2017 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
+ <http://www.gnu.org/licenses/>. */
+
+#ifdef SHARED
+
+# include <sysdep.h>
+# include "tlsdesc.h"
+# include "rtld-offsets.h"
+
+/* See __tls_get_addr and __tls_get_addr_slow in dl-tls.c. This function
+ call __tls_get_addr_slow on both slow paths. It realigns the stack
+ before the call to work around GCC PR58066. */
+
+ENTRY (__tls_get_addr)
+ mov %fs:DTV_OFFSET, %RDX_LP
+ mov GL_TLS_GENERATION_OFFSET+_rtld_local(%rip), %RAX_LP
+ /* GL(dl_tls_generation) == dtv[0].counter */
+ cmp %RAX_LP, (%rdx)
+ jne 1f
+ mov TI_MODULE_OFFSET(%rdi), %RAX_LP
+ /* dtv[ti->ti_module] */
+# ifdef __LP64__
+ salq $4, %rax
+ movq (%rdx,%rax), %rax
+# else
+ movl (%rdx,%rax, 8), %eax
+# endif
+ cmp $-1, %RAX_LP
+ je 1f
+ add TI_OFFSET_OFFSET(%rdi), %RAX_LP
+ ret
+1:
+ /* On the slow path, align the stack. */
+ pushq %rbp
+ cfi_def_cfa_offset (16)
+ cfi_offset (%rbp, -16)
+ mov %RSP_LP, %RBP_LP
+ cfi_def_cfa_register (%rbp)
+ and $-16, %RSP_LP
+ call __tls_get_addr_slow
+ mov %RBP_LP, %RSP_LP
+ popq %rbp
+ cfi_def_cfa (%rsp, 8)
+ ret
+END (__tls_get_addr)
+#endif /* SHARED */
diff --git a/sysdeps/x86_64/tlsdesc.sym b/sysdeps/x86_64/tlsdesc.sym
index 3385497..fc897ab 100644
--- a/sysdeps/x86_64/tlsdesc.sym
+++ b/sysdeps/x86_64/tlsdesc.sym
@@ -15,3 +15,6 @@ TLSDESC_ARG offsetof(struct tlsdesc, arg)
TLSDESC_GEN_COUNT offsetof(struct tlsdesc_dynamic_arg, gen_count)
TLSDESC_MODID offsetof(struct tlsdesc_dynamic_arg, tlsinfo.ti_module)
TLSDESC_MODOFF offsetof(struct tlsdesc_dynamic_arg, tlsinfo.ti_offset)
+
+TI_MODULE_OFFSET offsetof(tls_index, ti_module)
+TI_OFFSET_OFFSET offsetof(tls_index, ti_offset)
--
2.9.4
From b59d4b240c18673a9018e338702e51536d6f25d2 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Tue, 4 Jul 2017 09:24:09 -0700
Subject: [PATCH 2/2] x86-64: Export ___tls_get_addr
On x86-64, __tls_get_addr is changed to realign stack to support GCC
older than GCC 4.9.4:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066
This patch exports ___tls_get_addr as the alternative x86-64 runtime
interface to TLS with aligned stack.
This requires linker support for TLS optimization with ___tls_get_addr.
The GCC 4.9.4 and newer can generate call to ___tls_get_addr, instead of
__tls_get_addr. We can use the weakref assembly directive to redirect
__tls_get_addr to ___tls_get_addr if linker supports ___tls_get_addr and
GCC doesn't.
* sysdeps/unix/sysv/linux/x86_64/64/ld.abilist: Add GLIBC_2.26
and ___tls_get_addr.
* sysdeps/unix/sysv/linux/x86_64/x32/ld.abilist: Likewise.
* sysdeps/x86_64/Versions: Export ___tls_get_addr in GLIBC_2.26.
---
sysdeps/unix/sysv/linux/x86_64/64/ld.abilist | 2 ++
sysdeps/unix/sysv/linux/x86_64/x32/ld.abilist | 2 ++
sysdeps/x86_64/Versions | 6 ++++++
3 files changed, 10 insertions(+)
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/ld.abilist b/sysdeps/unix/sysv/linux/x86_64/64/ld.abilist
index 07cab4b..884e52c 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/ld.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/ld.abilist
@@ -6,6 +6,8 @@ GLIBC_2.2.5 calloc F
GLIBC_2.2.5 free F
GLIBC_2.2.5 malloc F
GLIBC_2.2.5 realloc F
+GLIBC_2.26 GLIBC_2.26 A
+GLIBC_2.26 ___tls_get_addr F
GLIBC_2.3 GLIBC_2.3 A
GLIBC_2.3 __tls_get_addr F
GLIBC_2.4 GLIBC_2.4 A
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/ld.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/ld.abilist
index 236357b..d42a7a4 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/ld.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/ld.abilist
@@ -7,3 +7,5 @@ GLIBC_2.16 calloc F
GLIBC_2.16 free F
GLIBC_2.16 malloc F
GLIBC_2.16 realloc F
+GLIBC_2.26 GLIBC_2.26 A
+GLIBC_2.26 ___tls_get_addr F
diff --git a/sysdeps/x86_64/Versions b/sysdeps/x86_64/Versions
index a437f85..b8c25c9 100644
--- a/sysdeps/x86_64/Versions
+++ b/sysdeps/x86_64/Versions
@@ -10,3 +10,9 @@ libm {
exp2l;
}
}
+ld {
+ GLIBC_2.26 {
+ # The alternative x86-64 runtime interface to TLS with aligned stack.
+ ___tls_get_addr;
+ }
+}
--
2.9.4