mirror of
git://sourceware.org/git/glibc.git
synced 2025-02-17 13:00:43 +08:00
e7feec374c
Do not relocate absolute symbols by the base address. Such symbols have
SHN_ABS as the section index and their value is not supposed to be
affected by relocation as per the ELF gABI[1]:
"SHN_ABS
The symbol has an absolute value that will not change because of
relocation."
The reason for our non-conformance here seems to be an old SysV linker
bug causing symbols like _DYNAMIC to be incorrectly emitted as absolute
symbols[2]. However in a previous discussion it was pointed that this
is seriously flawed by preventing the lone purpose of the existence of
absolute symbols from being used[3]:
"On the contrary, the only interpretation that makes sense to me is that
it will not change because of relocation at link time or at load time.
Absolute symbols, from the days of the earliest linking loaders, have
been used to represent addresses that are outside the address space of
the module (e.g., memory-mapped addresses or kernel gateway pages).
They've even been used to represent true symbolic constants (e.g.,
system entry point numbers, sizes, version numbers). There's no other
way to represent a true absolute symbol, while the meaning you seek is
easily represented by giving the symbol a non-negative st_shndx value."
and we ought to stop supporting our current broken interpretation.
Update processing for dladdr(3) and dladdr1(3) so that SHN_ABS symbols
are ignored, because under the corrected interpretation they do not
represent addresses within a mapped file and therefore are not supposed
to be considered.
References:
[1] "System V Application Binary Interface - DRAFT - 19 October 2010",
The SCO Group, Section "Symbol Table",
<http://www.sco.com/developers/gabi/2012-12-31/ch4.symtab.html>
[2] Alan Modra, "Absolute symbols"
<https://sourceware.org/ml/binutils/2012-05/msg00019.html>
[3] Cary Coutant, "Re: Absolute symbols"
<https://sourceware.org/ml/binutils/2012-05/msg00020.html>
[BZ #19818]
* sysdeps/generic/ldsodefs.h (SYMBOL_ADDRESS): Handle SHN_ABS
symbols.
* elf/dl-addr.c (determine_info): Ignore SHN_ABS symbols.
* elf/tst-absolute-sym.c: New file.
* elf/tst-absolute-sym-lib.c: New file.
* elf/tst-absolute-sym-lib.lds: New file.
* elf/Makefile (tests): Add `tst-absolute-sym'.
(modules-names): Add `tst-absolute-sym-lib'.
(LDLIBS-tst-absolute-sym-lib.so): New variable.
($(objpfx)tst-absolute-sym-lib.so): New dependency.
($(objpfx)tst-absolute-sym): New dependency.
|
||
|---|---|---|
| argp | ||
| assert | ||
| benchtests | ||
| bits | ||
| catgets | ||
| ChangeLog.old | ||
| conform | ||
| crypt | ||
| csu | ||
| ctype | ||
| debug | ||
| dirent | ||
| dlfcn | ||
| elf | ||
| gmon | ||
| gnulib | ||
| grp | ||
| gshadow | ||
| hesiod | ||
| htl | ||
| hurd | ||
| iconv | ||
| iconvdata | ||
| include | ||
| inet | ||
| intl | ||
| io | ||
| libidn | ||
| libio | ||
| locale | ||
| localedata | ||
| login | ||
| mach | ||
| malloc | ||
| manual | ||
| math | ||
| mathvec | ||
| misc | ||
| nis | ||
| nptl | ||
| nptl_db | ||
| nscd | ||
| nss | ||
| po | ||
| posix | ||
| pwd | ||
| resolv | ||
| resource | ||
| rt | ||
| scripts | ||
| setjmp | ||
| shadow | ||
| signal | ||
| socket | ||
| soft-fp | ||
| stdio-common | ||
| stdlib | ||
| streams | ||
| string | ||
| sunrpc | ||
| support | ||
| sysdeps | ||
| sysvipc | ||
| termios | ||
| time | ||
| timezone | ||
| wcsmbs | ||
| wctype | ||
| .gitattributes | ||
| .gitignore | ||
| abi-tags | ||
| aclocal.m4 | ||
| ChangeLog | ||
| config.h.in | ||
| config.make.in | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING.LIB | ||
| extra-lib.mk | ||
| gen-locales.mk | ||
| INSTALL | ||
| libc-abis | ||
| libof-iterator.mk | ||
| LICENSES | ||
| MAINTAINERS | ||
| Makeconfig | ||
| Makefile | ||
| Makefile.in | ||
| Makerules | ||
| NEWS | ||
| o-iterator.mk | ||
| README | ||
| Rules | ||
| shlib-versions | ||
| test-skeleton.c | ||
| version.h | ||
This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arm-*-linux-gnueabi hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu tilegx-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see http://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at http://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see http://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.