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elf/tst-big-note: Improve accuracy of test [BZ #20419]

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It is possible that the link editor injects an allocated ABI tag note
before the artificial, allocated large note in the test.  Note parsing
in open_verify stops when the first ABI tag note is encountered, so if
the ABI tag note comes first, the problematic code is not actually
exercised.

Also tweak the artificial note so that it is a syntactically valid
4-byte aligned note, in case the link editor tries to parse notes and
process them.

Improves the testing part of commit 0065aaaaae.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Florian Weimer 2019-03-01 18:53:03 +01:00
parent 928b305d3f
commit c259196b50
3 changed files with 23 additions and 4 deletions
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8
ChangeLog
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@ -1,3 +1,11 @@
2019-03-01 Florian Weimer <fweimer@redhat.com>
[BZ #20419]
* elf/tst-big-note-lib.S: Create a syntactically valid note.
* elf/Makefile (tst-big-note-lib.so): Do not link with startup
code, to avoid creating an ABI tag note.
(modules-names-nobuild): Add tst-big-note-lib.
2019-03-01 Stefan Liebler <stli@linux.ibm.com>
* sysdeps/s390/wcscpy-vx.S: Add strong aliases to

9
elf/Makefile
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@ -316,8 +316,8 @@ endif
modules-execstack-yes = tst-execstack-mod
extra-test-objs += $(addsuffix .os,$(strip $(modules-names)))
# filtmod1.so has a special rule
modules-names-nobuild := filtmod1
# filtmod1.so, tst-big-note-lib.so have special rules.
modules-names-nobuild := filtmod1 tst-big-note-lib
tests += $(tests-static)
@ -1515,6 +1515,11 @@ tst-libc_dlvsym-static-ENV = \
$(objpfx)tst-libc_dlvsym-static.out: $(objpfx)tst-libc_dlvsym-dso.so
$(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so
# Avoid creating an ABI tag note, which may come before the
# artificial, large note in tst-big-note-lib.o and invalidate the
# test.
$(objpfx)tst-big-note-lib.so: $(objpfx)tst-big-note-lib.o
$(LINK.o) -shared -o $@ $(LDFLAGS.so) $<
$(objpfx)tst-unwind-ctor: $(objpfx)tst-unwind-ctor-lib.so

10
elf/tst-big-note-lib.S
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@ -20,7 +20,13 @@
On a typical Linux system with 8MiB "ulimit -s", that was enough
to trigger stack overflow in open_verify. */
#define NOTE_SIZE 8*1024*1024
.pushsection .note.big,"a"
.balign 4
.fill 8*1024*1024, 1, 0
.balign 4
.long 5 /* n_namesz. Length of "GLIBC". */
.long NOTE_SIZE /* n_descsz. */
.long 0 /* n_type. */
.ascii "GLIBC\0\0\0" /* Name and alignment to four bytes. */
.fill NOTE_SIZE, 1, 0
.popsection