glibc/sysdeps/generic
Maciej W. Rozycki e7feec374c elf: Correct absolute (SHN_ABS) symbol run-time calculation [BZ #19818]
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.
2018-04-04 23:09:37 +01:00
..
net Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
netinet generic if_ether.h: Fix build 2018-01-19 01:51:10 +01:00
nfs Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
sys Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
_G_config.h Post-cleanup 2: minimize _G_config.h. 2018-02-07 10:10:32 -05:00
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allocalim.h
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c++-types.data
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dl-procinfo.c
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entry.h
errqueue.h
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float128-abi.h Move some float128 symbol version definitions. 2017-10-16 22:04:42 +00:00
fork.h
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ifunc-init.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
ifunc-sel.h Do not stack-protect ifunc resolvers [BZ #7065] 2016-12-26 10:08:41 +01:00
internal-signals.h Make sysdeps/generic/internal-signals.h less stubby. 2018-04-04 12:37:23 -04:00
intr-msg.h
inttypes.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
ld.abilist
ldbl-classify-compat.h Move LDBL_CLASSIFY_COMPAT to its own header. 2018-02-01 21:01:00 +00:00
ldconfig.h Add support for the RISC-V-specific ELF flags 2018-01-25 10:06:19 -08:00
ldsodefs.h elf: Correct absolute (SHN_ABS) symbol run-time calculation [BZ #19818] 2018-04-04 23:09:37 +01:00
libanl.abilist
libBrokenLocale.abilist
libc-lock.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
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libc-start.h hurd: Initialize TLS and libpthread before signal thread start 2018-03-25 00:52:39 +01:00
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libc.abilist
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libdl.abilist
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libm-test-ulps
libm-test-ulps-name Do not hardcode platform names in manual/libm-err-tab.pl (bug 14139). 2016-11-04 16:49:06 +00:00
libm.abilist
libnsl.abilist
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libnss_db.abilist
libnss_dns.abilist
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libpthread.abilist
libresolv.abilist
librt.abilist
libutil.abilist
link_map.h ld.so: Add architecture specific fields 2017-11-13 08:02:52 -08:00
linkmap.h
local-setxid.h
localplt.data ld.so: Introduce struct dl_exception 2017-08-10 16:54:57 +02:00
machine-gmon.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
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Makefile Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
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math_ldbl_opt.h
math_ldbl.h Allow direct use of math_ldbl.h in testsuite. 2017-02-25 10:40:48 -05:00
math_private_calls.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
math_private.h Remove slow paths from exp 2018-02-12 11:33:33 +00:00
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not-cancel.h hurd: fix warnings 2018-01-27 16:45:10 +01:00
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rtld-lowlevel.h
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siglist.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
sigset-cvt-mask.h hurd: fix warning 2018-01-27 16:45:55 +01:00
sigsetops.h hurd: fix warnings 2018-01-27 16:47:36 +01:00
stackguard-macros.h
stackinfo.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
startup.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
stdint.h Define char16_t, char32_t consistently with uint_least16_t, uint_least32_t (bug 17979). 2018-02-07 20:33:55 +00:00
stdio-lock.h Mechanically remove _IO_ name aliases for types and constants. 2018-02-21 14:11:05 -05:00
string_private.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
symbol-hacks.h PLT avoidance for __stack_chk_fail [BZ #7065] 2016-12-26 10:11:05 +01:00
sysdep-cancel.h
sysdep.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
thread_state.h hurd: add TLS support 2018-03-17 03:17:36 +01:00
tininess.h Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
tls-macros.h
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tst-audit.h
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unsecvars.h Ignore and remove LD_HWCAP_MASK for AT_SECURE programs (bug #21209) 2017-03-07 20:52:04 +05:30
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