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[Bug libc/21913] static binaries SIGSEGV in __brk when host's gcc is pie-by-default (i386)

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commit 99dd28489e425c6f654126871f89d514331aa69f
Author: H.J. Lu <>
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, 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]
        * (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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