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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=086df229eef36041cae4a633c6fde6150f18d75e

commit 086df229eef36041cae4a633c6fde6150f18d75e
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Aug 8 08:41:08 2017 -0700

    i386: Add <startup.h> [BZ #21913]
    
    On Linux/i386, there are 3 ways to make a system call:
    
    1. call *%gs:SYSINFO_OFFSET.  This requires TLS initialization.
    2. call *_dl_sysinfo.  This requires relocation of _dl_sysinfo.
    3. int $0x80.  This is slower than #2 and #3, but works everywhere.
    
    When an object file is compiled with PIC, #1 is prefered since it is
    faster than #3 and doesn't require relocation of _dl_sysinfo.  For
    dynamic executables, ld.so initializes TLS.  However, for static
    executables, before TLS is initialized by __libc_setup_tls, #3 should
    be used for system calls.
    
    This patch adds <startup.h> which defines _startup_fatal and defaults
    it to __libc_fatal.  It replaces __libc_fatal with _startup_fatal in
    static executables where it is called before __libc_setup_tls is called.
    This header file is included in all files containing functions which are
    called before __libc_setup_tls is called.  On Linux/i386, when PIE is
    enabled by default, _startup_fatal is turned into ABORT_INSTRUCTION and
    I386_USE_SYSENTER is defined to 0 so that "int $0x80" is used for system
    calls before __libc_setup_tls is called.
    
    Tested on i686 and x86-64.  Without this patch, all statically-linked
    tests will fail on i686 when the compiler defaults to -fPIE.
    
    	[BZ #21913]
    	* csu/libc-tls.c: Include <startup.h> first.
    	(__libc_setup_tls): Call _startup_fatal instead of __libc_fatal.
    	* elf/dl-tunables.c: Include <startup.h> first.
    	* include/libc-symbols.h (BUILD_PIE_DEFAULT): New.
    	* sysdeps/generic/startup.h: New file.
    	* sysdeps/unix/sysv/linux/i386/startup.h: Likewise.
    	* sysdeps/unix/sysv/linux/i386/brk.c [BUILD_PIE_DEFAULT != 0]
    	(I386_USE_SYSENTER): New.  Defined to 0.

diff --git a/ChangeLog b/ChangeLog
index 5b30f0c..8308b53 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2017-08-08  H.J. Lu  <hongjiu.lu@intel.com>
+
+	[BZ #21913]
+	* csu/libc-tls.c: Include <startup.h> first.
+	(__libc_setup_tls): Call _startup_fatal instead of __libc_fatal.
+	* elf/dl-tunables.c: Include <startup.h> first.
+	* include/libc-symbols.h (BUILD_PIE_DEFAULT): New.
+	* sysdeps/generic/startup.h: New file.
+	* sysdeps/unix/sysv/linux/i386/startup.h: Likewise.
+	* sysdeps/unix/sysv/linux/i386/brk.c [BUILD_PIE_DEFAULT != 0]
+	(I386_USE_SYSENTER): New.  Defined to 0.
+
 2017-08-08  Andreas Schwab  <schwab@suse.de>
 
 	[BZ #21041]
diff --git a/csu/libc-tls.c b/csu/libc-tls.c
index 3c897bf..00138eb 100644
--- a/csu/libc-tls.c
+++ b/csu/libc-tls.c
@@ -16,6 +16,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <startup.h>
 #include <errno.h>
 #include <ldsodefs.h>
 #include <tls.h>
@@ -193,7 +194,7 @@ __libc_setup_tls (void)
 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 #endif
   if (__builtin_expect (lossage != NULL, 0))
-    __libc_fatal (lossage);
+    _startup_fatal (lossage);
 
   /* Update the executable's link map with enough information to make
      the TLS routines happy.  */
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 231fb8c..b964a09 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -18,6 +18,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <startup.h>
 #include <stdint.h>
 #include <stdbool.h>
 #include <unistd.h>
diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index 3310e3a..fe3ab81 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -84,6 +84,14 @@
 
 #include <config.h>
 
+/* When PIC is defined and SHARED isn't defined, we are building PIE
+   by default.  */
+#if defined PIC && !defined SHARED
+# define BUILD_PIE_DEFAULT 1
+#else
+# define BUILD_PIE_DEFAULT 0
+#endif
+
 /* Define this for the benefit of portable GNU code that wants to check it.
    Code that checks with #if will not #include <config.h> again, since we've
    already done it (and this file is implicitly included in every compile,
diff --git a/sysdeps/unix/sysv/linux/i386/brk.c b/sysdeps/generic/startup.h
similarity index 51%
copy from sysdeps/unix/sysv/linux/i386/brk.c
copy to sysdeps/generic/startup.h
index 25ab101..a961e27 100644
--- a/sysdeps/unix/sysv/linux/i386/brk.c
+++ b/sysdeps/generic/startup.h
@@ -1,5 +1,5 @@
-/* brk system call for Linux/i386.
-   Copyright (C) 1995-2017 Free Software Foundation, Inc.
+/* Generic definitions of functions used by static libc main startup.
+   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
@@ -16,26 +16,8 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
-#include <unistd.h>
-#include <sysdep.h>
+/* Targets should override this file if the default definitions below
+   will not work correctly very early before TLS is initialized.  */
 
-/* This must be initialized data because commons can't have aliases.  */
-void *__curbrk = 0;
-
-/* Old braindamage in GCC's crtstuff.c requires this symbol in an attempt
-   to work around different old braindamage in the old Linux ELF dynamic
-   linker.  */
-weak_alias (__curbrk, ___brk_addr)
-
-int
-__brk (void *addr)
-{
-  INTERNAL_SYSCALL_DECL (err);
-  void *newbrk = (void *) INTERNAL_SYSCALL (brk, err, 1, addr);
-  __curbrk = newbrk;
-  if (newbrk < addr)
-    return INLINE_SYSCALL_ERROR_RETURN_VALUE (ENOMEM);
-  return 0;
-}
-weak_alias (__brk, brk)
+/* Use macro instead of inline function to avoid including <stdio.h>.  */
+#define _startup_fatal(message) __libc_fatal ((message))
diff --git a/sysdeps/unix/sysv/linux/i386/brk.c b/sysdeps/unix/sysv/linux/i386/brk.c
index 25ab101..d67b279 100644
--- a/sysdeps/unix/sysv/linux/i386/brk.c
+++ b/sysdeps/unix/sysv/linux/i386/brk.c
@@ -16,6 +16,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#if BUILD_PIE_DEFAULT
+/* Can't use "call *%gs:SYSINFO_OFFSET" during statup in static PIE.  */
+# define I386_USE_SYSENTER 0
+#endif
+
 #include <errno.h>
 #include <unistd.h>
 #include <sysdep.h>
diff --git a/sysdeps/unix/sysv/linux/i386/brk.c b/sysdeps/unix/sysv/linux/i386/startup.h
similarity index 51%
copy from sysdeps/unix/sysv/linux/i386/brk.c
copy to sysdeps/unix/sysv/linux/i386/startup.h
index 25ab101..b73565a 100644
--- a/sysdeps/unix/sysv/linux/i386/brk.c
+++ b/sysdeps/unix/sysv/linux/i386/startup.h
@@ -1,5 +1,5 @@
-/* brk system call for Linux/i386.
-   Copyright (C) 1995-2017 Free Software Foundation, Inc.
+/* Linux/i386 definitions of functions used by static libc main startup.
+   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
@@ -16,26 +16,21 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
-#include <unistd.h>
-#include <sysdep.h>
+#if BUILD_PIE_DEFAULT
+# include <abort-instr.h>
 
-/* This must be initialized data because commons can't have aliases.  */
-void *__curbrk = 0;
+/* Can't use "call *%gs:SYSINFO_OFFSET" during statup in static PIE.  */
+# define I386_USE_SYSENTER 0
 
-/* Old braindamage in GCC's crtstuff.c requires this symbol in an attempt
-   to work around different old braindamage in the old Linux ELF dynamic
-   linker.  */
-weak_alias (__curbrk, ___brk_addr)
-
-int
-__brk (void *addr)
+__attribute__ ((__noreturn__))
+static inline void
+_startup_fatal (const char *message __attribute__ ((unused)))
 {
-  INTERNAL_SYSCALL_DECL (err);
-  void *newbrk = (void *) INTERNAL_SYSCALL (brk, err, 1, addr);
-  __curbrk = newbrk;
-  if (newbrk < addr)
-    return INLINE_SYSCALL_ERROR_RETURN_VALUE (ENOMEM);
-  return 0;
+  /* This is only called very early during startup in static PIE.
+     FIXME: How can it be improved?  */
+  ABORT_INSTRUCTION;
+  __builtin_unreachable ();
 }
-weak_alias (__brk, brk)
+#else
+# include_next <startup.h>
+#endif

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                                          |   12 +++++++
 csu/libc-tls.c                                     |    3 +-
 elf/dl-tunables.c                                  |    1 +
 include/libc-symbols.h                             |    8 +++++
 .../huge_val_flt128.h => sysdeps/generic/startup.h |   10 +++---
 sysdeps/unix/sysv/linux/i386/brk.c                 |    5 +++
 .../linux/{open_by_handle_at.c => i386/startup.h}  |   31 +++++++++----------
 7 files changed, 48 insertions(+), 22 deletions(-)
 copy bits/huge_val_flt128.h => sysdeps/generic/startup.h (69%)
 copy sysdeps/unix/sysv/linux/{open_by_handle_at.c => i386/startup.h} (60%)


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