From 99dd28489e425c6f654126871f89d514331aa69f Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Wed, 19 Jul 2017 14:32:42 -0700 Subject: i386: Add [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 syscalls. This patch adds 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. [BZ #21913] * config.h.in (BUILD_PIE_DEFAULT): New. * csu/libc-tls.c: Include . * elf/dl-tunables.c: Likewise. * sysdeps/unix/sysv/linux/i386/brk.c: Likewise. * csu/libc-tls.c: Include . (__libc_setup_tls): Call _startup_fatal instead of __libc_fatal. * sysdeps/generic/startup.h: New file. * sysdeps/unix/sysv/linux/i386/startup.h: Likewise. --- config.h.in | 6 ++++++ csu/libc-tls.c | 3 ++- elf/dl-tunables.c | 1 + sysdeps/generic/startup.h | 20 +++++++++++++++++++ sysdeps/unix/sysv/linux/i386/brk.c | 1 + sysdeps/unix/sysv/linux/i386/startup.h | 36 ++++++++++++++++++++++++++++++++++ 6 files changed, 66 insertions(+), 1 deletion(-) create mode 100644 sysdeps/generic/startup.h create mode 100644 sysdeps/unix/sysv/linux/i386/startup.h diff --git a/config.h.in b/config.h.in index 22418576a0..a00eb511f2 100644 --- a/config.h.in +++ b/config.h.in @@ -47,6 +47,12 @@ #undef STACK_PROTECTOR_LEVEL #endif +/* When PIC is defined and SHARED isn't defined, we are building PIE + by default. */ +#if defined PIC && !defined SHARED +# define BUILD_PIE_DEFAULT +#endif + /* Define if the regparm attribute shall be used for local functions (gcc on ix86 only). */ #undef USE_REGPARMS diff --git a/csu/libc-tls.c b/csu/libc-tls.c index 3c897bf28b..00138eb43a 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 . */ +#include #include #include #include @@ -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 231fb8ca93..b964a09413 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 . */ +#include #include #include #include diff --git a/sysdeps/generic/startup.h b/sysdeps/generic/startup.h new file mode 100644 index 0000000000..196f49edc3 --- /dev/null +++ b/sysdeps/generic/startup.h @@ -0,0 +1,20 @@ +/* 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 + 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 + . */ + +/* Use macro instead of inline function to avoid including . */ +#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 25ab1015d3..bb9cf7ac35 100644 --- a/sysdeps/unix/sysv/linux/i386/brk.c +++ b/sysdeps/unix/sysv/linux/i386/brk.c @@ -16,6 +16,7 @@ License along with the GNU C Library; if not, see . */ +#include #include #include #include diff --git a/sysdeps/unix/sysv/linux/i386/startup.h b/sysdeps/unix/sysv/linux/i386/startup.h new file mode 100644 index 0000000000..a8fd3134b7 --- /dev/null +++ b/sysdeps/unix/sysv/linux/i386/startup.h @@ -0,0 +1,36 @@ +/* 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 + 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 + . */ + +#ifdef BUILD_PIE_DEFAULT +# include + +/* Can't use "call *%gs:SYSINFO_OFFSET" during statup in static PIE. */ +# define I386_USE_SYSENTER 0 + +__attribute__ ((__noreturn__)) +static inline void +_startup_fatal (const char *message __attribute__ ((unused))) +{ + /* This is only called very early during startup in static PIE. + FIXME: How can it be improved? */ + ABORT_INSTRUCTION; + __builtin_unreachable (); +} +#else +# include_next +#endif -- cgit 1.4.1