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[Bug libc/21913] static binaries SIGSEGV in __brk when host's gcc is pie-by-default (i386)
- From: "cvs-commit at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Mon, 07 Aug 2017 20:23:54 +0000
- Subject: [Bug libc/21913] static binaries SIGSEGV in __brk when host's gcc is pie-by-default (i386)
- Auto-submitted: auto-generated
- References: <bug-21913-131@http.sourceware.org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=21913
--- Comment #9 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
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The branch, hjl/pr21913/master has been created
at 99dd28489e425c6f654126871f89d514331aa69f (commit)
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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=99dd28489e425c6f654126871f89d514331aa69f
commit 99dd28489e425c6f654126871f89d514331aa69f
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Wed Jul 19 14:32:42 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 syscalls.
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.
[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.
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