aboutsummaryrefslogtreecommitdiff
path: root/elf/Makefile
diff options
context:
space:
mode:
authorMaciej W. Rozycki <macro@mips.com>2018-04-04 23:09:37 +0100
committerMaciej W. Rozycki <macro@mips.com>2018-04-04 23:09:37 +0100
commite7feec374c635b6a29d65c39ae5e1855528fed39 (patch)
tree66022e087f86c5dde38a9e6b565565d4e909f60c /elf/Makefile
parent10a446ddcc1100d6d76c6aa0c6d4775209388152 (diff)
downloadglibc-e7feec374c635b6a29d65c39ae5e1855528fed39.tar
glibc-e7feec374c635b6a29d65c39ae5e1855528fed39.tar.gz
glibc-e7feec374c635b6a29d65c39ae5e1855528fed39.tar.bz2
glibc-e7feec374c635b6a29d65c39ae5e1855528fed39.zip
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.
Diffstat (limited to 'elf/Makefile')
-rw-r--r--elf/Makefile8
1 files changed, 6 insertions, 2 deletions
diff --git a/elf/Makefile b/elf/Makefile
index 59bcca5046..e658928305 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -186,7 +186,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
tst-tlsalign tst-tlsalign-extern tst-nodelete-opened \
tst-nodelete2 tst-audit11 tst-audit12 tst-dlsym-error tst-noload \
tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose \
- tst-debug1 tst-main1
+ tst-debug1 tst-main1 tst-absolute-sym
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
@@ -272,7 +272,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
tst-audit12mod1 tst-audit12mod2 tst-audit12mod3 tst-auditmod12 \
tst-latepthreadmod $(tst-tls-many-dynamic-modules) \
tst-nodelete-dlclose-dso tst-nodelete-dlclose-plugin \
- tst-main1mod tst-libc_dlvsym-dso
+ tst-main1mod tst-libc_dlvsym-dso tst-absolute-sym-lib
ifeq (yes,$(have-mtls-dialect-gnu2))
tests += tst-gnu2-tls1
modules-names += tst-gnu2-tls1mod
@@ -1437,6 +1437,10 @@ tst-main1-no-pie = yes
LDLIBS-tst-main1 = $(libsupport)
tst-main1mod.so-no-z-defs = yes
+LDLIBS-tst-absolute-sym-lib.so = tst-absolute-sym-lib.lds
+$(objpfx)tst-absolute-sym-lib.so: $(LDLIBS-tst-absolute-sym-lib.so)
+$(objpfx)tst-absolute-sym: $(objpfx)tst-absolute-sym-lib.so
+
# Both the main program and the DSO for tst-libc_dlvsym need to link
# against libdl.
$(objpfx)tst-libc_dlvsym: $(libdl)