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Re: [PATCH] Add hidden __tls_get_addr/___tls_get_addr alias
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Chris Metcalf <cmetcalf at ezchip dot com>
- Cc: Andreas Schwab <schwab at linux-m68k dot org>, Carlos O'Donell <carlos at redhat dot com>, GLIBC Devel <libc-alpha at sourceware dot org>
- Date: Sun, 21 Dec 2014 09:31:11 -0800
- Subject: Re: [PATCH] Add hidden __tls_get_addr/___tls_get_addr alias
- Authentication-results: sourceware.org; auth=none
- References: <5494CB6E dot 6090706 at ezchip dot com> <5494F4A3 dot 9030609 at redhat dot com> <20141220203247 dot GA22423 at gmail dot com> <878ui2rqd7 dot fsf at igel dot home> <20141220211055 dot GA9637 at gmail dot com> <5496FDE2 dot 8070800 at ezchip dot com>
On Sun, Dec 21, 2014 at 12:05:38PM -0500, Chris Metcalf wrote:
> On 12/20/2014 4:10 PM, H.J. Lu wrote:
> >index d7d6734..1a40cf9 100644
> >--- a/sysdeps/generic/localplt.data
> >+++ b/sysdeps/generic/localplt.data
> >@@ -7,10 +7,9 @@ libc.so: malloc
> > libc.so: memalign
> > libc.so: realloc
> > libm.so: matherr
> >-# The dynamic loader needs __tls_get_addr for TLS, and uses __libc_memalign
> >-# internally to allocate aligned TLS storage. The other malloc family of
> >-# functions are expected to allow user symbol interposition.
> >-ld.so: __tls_get_addr
> >+# The dynamic loader uses __libc_memalign internally to allocate aligned
> >+# TLS storage. The other malloc family of functions are expected to allow
> >+# user symbol interposition.
> > ld.so: __libc_memalign
> > ld.so: malloc
> > ld.so: calloc
>
> Great, thanks. I will remove the tile-specific version when this is pushed.
>
This is what I checked in.
Thanks.
H.J.
--
>From 050f7298e1ecc39887c329037575ccd972071255 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sun, 21 Dec 2014 09:12:04 -0800
Subject: [PATCH] Add hidden __tls_get_addr/___tls_get_addr alias
__tls_get_addr/___tls_get_addr is always defined in ld.so. There is
no need to call them via PLT inside ld.so. This patch adds the hidden
__tls_get_addr/___tls_get_addr aliases and calls them directly from
_dl_tlsdesc_dynamic. There is no need to set up the EBX register in
i386 _dl_tlsdesc_dynamic when calling the hidden ___tls_get_addr.
* elf/dl-tls.c (__tls_get_addr): Provide the hidden definition
if not defined.
* sysdeps/i386/dl-tls.h (___tls_get_addr): Provide the hidden
definition.
* sysdeps/i386/dl-tlsdesc.S (_dl_tlsdesc_dynamic): Call the
hidden ___tls_get_addr.
* sysdeps/x86_64/dl-tlsdesc.S (_dl_tlsdesc_dynamic): Call the
hidden __tls_get_addr.
* sysdeps/generic/localplt.data (__tls_get_addr): Removed.
* sysdeps/unix/sysv/linux/i386/localplt.data (___tls_get_addr):
Likewise.
---
ChangeLog | 14 ++++++++++++++
elf/dl-tls.c | 10 ++++++++++
sysdeps/generic/localplt.data | 7 +++----
sysdeps/i386/dl-tls.h | 2 ++
sysdeps/i386/dl-tlsdesc.S | 5 +----
sysdeps/unix/sysv/linux/i386/localplt.data | 9 +++------
sysdeps/x86_64/dl-tlsdesc.S | 2 +-
7 files changed, 34 insertions(+), 15 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 078af75..28c293d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2014-12-21 H.J. Lu <hongjiu.lu@intel.com>
+
+ * elf/dl-tls.c (__tls_get_addr): Provide the hidden definition
+ if not defined.
+ * sysdeps/i386/dl-tls.h (___tls_get_addr): Provide the hidden
+ definition.
+ * sysdeps/i386/dl-tlsdesc.S (_dl_tlsdesc_dynamic): Call the
+ hidden ___tls_get_addr.
+ * sysdeps/x86_64/dl-tlsdesc.S (_dl_tlsdesc_dynamic): Call the
+ hidden __tls_get_addr.
+ * sysdeps/generic/localplt.data (__tls_get_addr): Removed.
+ * sysdeps/unix/sysv/linux/i386/localplt.data (___tls_get_addr):
+ Likewise.
+
2014-12-21 Andreas Schwab <schwab@linux-m68k.org>
* sysdeps/m68k/dl-machine.h (RTLD_START): Remove @PLTPC from
diff --git a/elf/dl-tls.c b/elf/dl-tls.c
index 76b8b36..0abb024 100644
--- a/elf/dl-tls.c
+++ b/elf/dl-tls.c
@@ -809,6 +809,16 @@ update_get_addr (GET_ADDR_ARGS)
return (void *) p + GET_ADDR_OFFSET;
}
+/* For all machines that have a non-macro version of __tls_get_addr, we
+ want to use rtld_hidden_proto/rtld_hidden_def in order to call the
+ internal alias for __tls_get_addr from ld.so. This avoids a PLT entry
+ in ld.so for __tls_get_addr. */
+
+#ifndef __tls_get_addr
+extern void * __tls_get_addr (GET_ADDR_ARGS);
+rtld_hidden_proto (__tls_get_addr)
+rtld_hidden_def (__tls_get_addr)
+#endif
/* The generic dynamic and local dynamic model cannot be used in
statically linked applications. */
diff --git a/sysdeps/generic/localplt.data b/sysdeps/generic/localplt.data
index d7d6734..1a40cf9 100644
--- a/sysdeps/generic/localplt.data
+++ b/sysdeps/generic/localplt.data
@@ -7,10 +7,9 @@ libc.so: malloc
libc.so: memalign
libc.so: realloc
libm.so: matherr
-# The dynamic loader needs __tls_get_addr for TLS, and uses __libc_memalign
-# internally to allocate aligned TLS storage. The other malloc family of
-# functions are expected to allow user symbol interposition.
-ld.so: __tls_get_addr
+# The dynamic loader uses __libc_memalign internally to allocate aligned
+# TLS storage. The other malloc family of functions are expected to allow
+# user symbol interposition.
ld.so: __libc_memalign
ld.so: malloc
ld.so: calloc
diff --git a/sysdeps/i386/dl-tls.h b/sysdeps/i386/dl-tls.h
index 48809a5..99b86f9 100644
--- a/sysdeps/i386/dl-tls.h
+++ b/sysdeps/i386/dl-tls.h
@@ -50,6 +50,8 @@ __tls_get_addr (tls_index *ti)
version of this file. */
# define __tls_get_addr __attribute__ ((__regparm__ (1))) ___tls_get_addr
strong_alias (___tls_get_addr, ___tls_get_addr_internal)
+rtld_hidden_proto (___tls_get_addr)
+rtld_hidden_def (___tls_get_addr)
#else
/* Users should get the better interface. */
diff --git a/sysdeps/i386/dl-tlsdesc.S b/sysdeps/i386/dl-tlsdesc.S
index e6753e9..570b180 100644
--- a/sysdeps/i386/dl-tlsdesc.S
+++ b/sysdeps/i386/dl-tlsdesc.S
@@ -126,10 +126,7 @@ _dl_tlsdesc_dynamic:
.p2align 4,,7
.Lslow:
cfi_adjust_cfa_offset (28)
- movl %ebx, 16(%esp)
- LOAD_PIC_REG (bx)
- call ___tls_get_addr@PLT
- movl 16(%esp), %ebx
+ call HIDDEN_JUMPTARGET (___tls_get_addr)
jmp .Lret
cfi_endproc
.size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
diff --git a/sysdeps/unix/sysv/linux/i386/localplt.data b/sysdeps/unix/sysv/linux/i386/localplt.data
index 009797b..b25abf8 100644
--- a/sysdeps/unix/sysv/linux/i386/localplt.data
+++ b/sysdeps/unix/sysv/linux/i386/localplt.data
@@ -5,12 +5,9 @@ libc.so: malloc
libc.so: memalign
libc.so: realloc
libm.so: matherr
-# The dynamic loader needs ___tls_get_addr for TLS, and uses __libc_memalign
-# internally to allocate aligned TLS storage. The other malloc family of
-# functions are expected to allow user symbol interposition.
-# Note that it is triple underscore for ___tls_get_addr e.g. the alternate
-# ABI.
-ld.so: ___tls_get_addr
+# The dynamic loader uses __libc_memalign internally to allocate aligned
+# TLS storage. The other malloc family of functions are expected to allow
+# user symbol interposition.
ld.so: __libc_memalign
ld.so: malloc
ld.so: calloc
diff --git a/sysdeps/x86_64/dl-tlsdesc.S b/sysdeps/x86_64/dl-tlsdesc.S
index 92e18a5..03f5ca4 100644
--- a/sysdeps/x86_64/dl-tlsdesc.S
+++ b/sysdeps/x86_64/dl-tlsdesc.S
@@ -128,7 +128,7 @@ _dl_tlsdesc_dynamic:
movq %r10, 40(%rsp)
movq %r11, 48(%rsp)
/* %rdi already points to the tlsinfo data structure. */
- call __tls_get_addr@PLT
+ call HIDDEN_JUMPTARGET (__tls_get_addr)
movq 8(%rsp), %rdx
movq 16(%rsp), %rcx
movq 24(%rsp), %r8
--
1.9.3