Sonny Rao discovered a bug which affects powerpc machines. If the stack
is allowed to grow into a segment that has been converted over to huge
pages, current kernels will try to instantiate normal pages into a huge
page-only segment. This test case reproduces this behavior for 32bit
and 64bit binaries.
Since there is no upstream fix for this bug yet, I don't think it's wise
to run it all the time and needlessly render machines unstable.
However, we don't want to forget that it's not being run by default
either. This patch also introduces a SKIP mode to run_tests.sh. It
will cause the named test to be skipped and a message printed that
indicates that a test was skipped.
Signed-off-by: Adam Litke <[EMAIL PROTECTED]>
diff --git a/tests/Makefile b/tests/Makefile
index 7cd823a..7ba7ba7 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -6,7 +6,7 @@ LIB_TESTS = gethugepagesize test_root fi
chunk-overcommit mprotect alloc-instantiate-race mlock \
truncate_reserve_wraparound truncate_sigbus_versus_oom \
map_high_truncate_2 truncate_above_4GB direct \
- misaligned_offset brk_near_huge task-size-overrun
+ misaligned_offset brk_near_huge task-size-overrun stack_grow_into_huge
LIB_TESTS_64 = straddle_4GB huge_at_4GB_normal_below \
huge_below_4GB_normal_above
NOLIB_TESTS = malloc malloc_manysmall dummy
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index 30ca82a..a914813 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -35,7 +35,10 @@ run_test_bits () {
BITS=$1
shift
- if [ -d obj$BITS ]; then
+ if [ "$1" == "SKIP" ]; then
+ shift
+ echo "$@ ($BITS): SKIPPED"
+ elif [ -d obj$BITS ]; then
echo -n "$@ ($BITS): "
PATH="obj$BITS:$PATH" LD_LIBRARY_PATH="$LD_LIBRARY_PATH:../obj$BITS"
$ENV "$@"
fi
@@ -154,6 +157,7 @@ # Specific kernel bug tests
run_test truncate_above_4GB
run_test brk_near_huge
run_test task-size-overrun
+ run_test SKIP stack_grow_into_huge
# Tests requiring an active mount and hugepage COW
run_test private
diff --git a/tests/stack_grow_into_huge.c b/tests/stack_grow_into_huge.c
new file mode 100644
index 0000000..ff1058e
--- /dev/null
+++ b/tests/stack_grow_into_huge.c
@@ -0,0 +1,89 @@
+/*
+ * libhugetlbfs - Easy use of Linux hugepages
+ * Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/wait.h>
+
+#include <hugetlbfs.h>
+#include "hugetests.h"
+
+/*
+ * Test rationale:
+ *
+ * On PowerPC, the address space is divided into segments. These segments can
+ * contain either huge pages or normal pages, but not both. All segments are
+ * initially set up to map normal pages. When a huge page mapping is created
+ * within a set of empty segments, they are "enabled" for huge pages at that
+ * time. Once enabled for huge pages, they can not be used again for normal
+ * pages for the remaining lifetime of the process.
+ *
+ * If the segment immediately preceeding the segment containing the stack is
+ * converted to huge pages and the stack is made to grow into the this
+ * preceeding segment, some kernels may attempt to map normal pages into the
+ * huge page-only segment -- resulting in bugs.
+ */
+
+int main(int argc, char *argv[])
+{
+ int fd, i, pid, s;
+ struct rlimit r;
+ char *b;
+ unsigned long hpage_size = gethugepagesize();
+
+ test_init(argc, argv);
+
+ i = getrlimit(RLIMIT_STACK, &r);
+ if (i)
+ CONFIG("getrlimit failed");
+
+ if (r.rlim_cur != RLIM_INFINITY)
+ CONFIG("Stack rlimit must be 'unlimited'");
+
+ fd = hugetlbfs_unlinked_fd();
+ if (fd < 0)
+ CONFIG("Couldn't get hugepage fd");
+
+ b = mmap(0, hpage_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+ if (b != MAP_FAILED) {
+ munmap(b, hpage_size);
+ } else
+ FAIL("mmap");
+
+ if ((pid = fork()) < 0)
+ FAIL("fork");
+
+ if (pid == 0) {
+ while (1) { alloca(16*1024*1024); }
+ exit (0);
+ } else {
+ waitpid(pid, &s, 0);
+ if (WIFSIGNALED(s)) {
+ if (WTERMSIG(s) == SIGTRAP) {
+ FAIL("SIGTRAP received");
+ } else {
+ PASS();
+ }
+ }
+ }
+ FAIL("Child not signalled");
+}
--
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center
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