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Re: [PATCH] i386: Add _startup_sbrk and _startup_fatal [BZ #21913]
On Mon, Aug 7, 2017 at 10:39 AM, H.J. Lu <hjl.tools@gmail.com> wrote:> On Mon, Aug 7, 2017 at 10:37 AM, Andreas Schwab <schwab@linux-m68k.org> wrote:>> On Aug 07 2017, "H.J. Lu" <hjl.tools@gmail.com> wrote:>>>>> Given this, we need a working sbrk before TLS is initialized.>>>> How about making sbrk always use int $0x80?>>>> Andreas.>> We can do that in sbrk.o and will make change less complex.> I will give it a try.>Here is a patch to add <startup.h>. Tested on i686. OK for master?-- H.J.
From 99dd28489e425c6f654126871f89d514331aa69f Mon Sep 17 00:00:00 2001From: "H.J. Lu" <hjl.tools@gmail.com>Date: Wed, 19 Jul 2017 14:32:42 -0700Subject: [PATCH] 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 isfaster than #3 and doesn't require relocation of _dl_sysinfo. Fordynamic executables, ld.so initializes TLS. However, for staticexecutables, before TLS is initialized by __libc_setup_tls, #3 shouldbe used for syscalls.This patch adds <startup.h> which defines _startup_fatal and defaultsit to __libc_fatal. It replaces __libc_fatal with _startup_fatal instatic executables where it is called before __libc_setup_tls is called.This header file is included in all files containing functions which arecalled before __libc_setup_tls is called. On Linux/i386, when PIE isenabled by default, _startup_fatal is turned into ABORT_INSTRUCTION andI386_USE_SYSENTER is defined to 0 so that "int $0x80" is used for systemcalls before __libc_setup_tls is called.[BZ #21913]* config.h.in (BUILD_PIE_DEFAULT): New.* csu/libc-tls.c: Include <startup.h>.* elf/dl-tunables.c: Likewise.* sysdeps/unix/sysv/linux/i386/brk.c: Likewise.* csu/libc-tls.c: Include <startup.h>.(__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.hdiff --git a/config.h.in b/config.h.inindex 22418576a0..a00eb511f2 100644--- a/config.h.in+++ b/config.h.in@@ -47,6 +47,12 @@ #undefSTACK_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). */ #undefUSE_REGPARMSdiff --git a/csu/libc-tls.c b/csu/libc-tls.cindex 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 <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.cindex 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 <http://www.gnu.org/licenses/>. */ +#include <startup.h> #include <stdint.h> #include <stdbool.h> #include <unistd.h>diff --git a/sysdeps/generic/startup.h b/sysdeps/generic/startup.hnew file mode 100644index 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+ <http://www.gnu.org/licenses/>. */++/* 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.cindex 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 <http://www.gnu.org/licenses/>. */ +#include <startup.h> #include <errno.h> #include <unistd.h> #include <sysdep.h>diff --git a/sysdeps/unix/sysv/linux/i386/startup.h b/sysdeps/unix/sysv/linux/i386/startup.hnew file mode 100644index 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+ <http://www.gnu.org/licenses/>. */++#ifdef BUILD_PIE_DEFAULT+# include <abort-instr.h>++/* 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 <startup.h>+#endif-- 2.13.3
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