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

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https://sourceware.org/bugzilla/show_bug.cgi?id=21913

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;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.

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

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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