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Re: [PATCH COMMITTED] Do not require memset elimination in explicit_bzero test
- From: Stefan Liebler <stli at linux dot vnet dot ibm dot com>
- To: libc-alpha at sourceware dot org
- Cc: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- Date: Tue, 10 Jan 2017 09:22:54 +0100
- Subject: Re: [PATCH COMMITTED] Do not require memset elimination in explicit_bzero test
- Authentication-results: sourceware.org; auth=none
- References: <20161220100941.B4FA5401BD5F6@oldenburg.str.redhat.com> <e32dc56f-0e8b-dc05-127e-b83a932a3e4a@redhat.com> <5c0d3ac6-b4d9-21b9-19b6-ae9173102a9c@redhat.com>
On 12/30/2016 01:16 PM, Florian Weimer wrote:
On 12/21/2016 07:04 PM, Florian Weimer wrote:
On 12/20/2016 11:09 AM, Florian Weimer wrote:
Some targets fail to apply dead store elimination to the
memset call in setup_ordinary_clear. Before this commit,
this causes the test case to fail. Instead, the test case
now logs lack of memset elimination as an informational
message.
2016-12-20 Florian Weimer <fweimer@redhat.com>
Do not require memset elimination in explicit_bzero test.
* string/tst-xbzero-opt.c (prepare_test_buffer): Force inlining.
(enum test_expectation): Add NO_EXPECTATIONS.
(subtests): NO_EXPECTATIONS for ordinary clear.
(check_test_buffer): Handle NO_EXPECTATIONS.
* string/Makefile (CFLAGS-tst-xbzero-opt.c): Compile with -O3.
Stefan, this test still fails for me on s390x:
PASS: no clear/prepare: expected 32 got 32
PASS: no clear/test: expected some got 32
PASS: ordinary clear/prepare: expected 32 got 32
INFO: ordinary clear/test: found 0 patterns (memset not eliminated)
PASS: explicit clear/prepare: expected 32 got 32
FAIL: explicit clear/test: expected 0 got 1
Do you have an idea what's going on there?
I filed bug 21006 and will add it as a release blocker.
Thanks,
Florian
Hi Florian,
the test is also failing on my system and I've had a look into it.
In setup_explicit_clear, the buffer is filled with the test_pattern.
On s390x the memcpy in prepare_test_buffer is done by loading
r4 / r5 with the test_pattern and using store multiple instruction
to store r4 / r5 to buf.
If explicit_bzero is resolved in setup_explicit_clear, r4 / r5 is
stored to stack by _dl_runtime_resolve and the call to memmem in
count_test_patterns finds a hit of the test_pattern on the stack.
The attached patch resolves all symbols at program startup by linking
with -z now. This omits the call of _dl_runtime_resolve within
setup_explicit_clear and the test passes.
If this is okay, I'll commit this patch and clear this bug in the
release blockers list in the release-wiki.
Bye
Stefan
ChangeLog:
[BZ #21006]
* string/Makefile (LDFLAGS-tst-xbzero-opt): New variable.
commit a07f447fd235d1898a56af7317a4ff6a11a603b9
Author: Stefan Liebler <stli@linux.vnet.ibm.com>
Date: Tue Jan 10 08:47:13 2017 +0100
S390: Fix FAIL in test string/tst-xbzero-opt [BZ #21006]
On s390x this test failed with:
FAIL: explicit clear/test: expected 0 got 1
In setup_explicit_clear, the buffer is filled with the test_pattern.
On s390x the memcpy in prepare_test_buffer is done by loading
r4 / r5 with the test_pattern and using store multiple instruction
to store r4 / r5 to buf.
If explicit_bzero is resolved in setup_explicit_clear, r4 / r5 is
stored to stack by _dl_runtime_resolve and the call to memmem in
count_test_patterns finds a hit of the test_pattern on the stack.
This patch resolves all symbols at program startup by linking with
-z now. This omits the call of _dl_runtime_resolve within
setup_explicit_clear and the test passes.
ChangeLog:
[BZ #21006]
* string/Makefile (LDFLAGS-tst-xbzero-opt): New variable.
diff --git a/string/Makefile b/string/Makefile
index 04e9da9..87e0d1d 100644
--- a/string/Makefile
+++ b/string/Makefile
@@ -73,6 +73,14 @@ CFLAGS-stratcliff.c = -fno-builtin
CFLAGS-test-ffs.c = -fno-builtin
CFLAGS-tst-inlcall.c = -fno-builtin
CFLAGS-tst-xbzero-opt.c = -O3
+# BZ 21006: Resolve all functions but at least explicit_bzero at startup.
+# Otherwise the test fails on s390x as the memcpy in prepare_test_buffer is
+# done by loading r4 / r5 with the test_pattern and using store multiple
+# instruction to store r4 / r5 to buf. If explicit_bzero would be resolved in
+# setup_explicit_clear, r4 / r5 would be stored to stack by _dl_runtime_resolve
+# and the call to memmem in count_test_patterns will find a hit of the
+# test_pattern on the stack.
+LDFLAGS-tst-xbzero-opt = -z now
# Called during TLS initialization.
CFLAGS-memcpy.c = $(no-stack-protector)