[asan] Add test case for alignment of FakeStack frames for 4KB objects with smaller thread stack sizes #152892
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This test case demonstrates that ASan does not currently align FakeStack frames correctly for 4KB objects. It deliberately uses a smaller thread stack size (64KB), which forces the FakeStack frames to no longer be 4KB aligned. This differs from llvm#152889, which is a test case for objects >4KB, which relies on the fact that the default 4KB alignment for fake stack sizes >64KB is insufficient. llvm#152819 will fix both issues.
llvmbot
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compiler-rt
compiler-rt:asan
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@llvm/pr-subscribers-compiler-rt-sanitizer Author: Thurston Dang (thurstond) ChangesThis test case demonstrates that ASan does not currently align FakeStack frames correctly for 4KB objects when using a smaller thread stack size (64KB), which forces the FakeStack frames to no longer be 4KB aligned. This differs from #152889, which is a test case for objects >4KB, which relies on the fact that the default 4KB alignment for fake stack sizes >64KB is insufficient. #152819 will fix both issues. Full diff: https://github.com/llvm/llvm-project/pull/152892.diff 1 Files Affected:
diff --git a/compiler-rt/test/asan/TestCases/fakestack_alignment2.cpp b/compiler-rt/test/asan/TestCases/fakestack_alignment2.cpp
new file mode 100644
index 0000000000000..3f0b77a5eb889
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/fakestack_alignment2.cpp
@@ -0,0 +1,37 @@
+// RUN: %clangxx_asan -fsanitize-address-use-after-return=always -O0 %s -o %t && %run %t 2>&1
+// XFAIL: *
+
+#include <assert.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct alignas(4096) page {
+ int x;
+};
+
+void *Thread(void *unused) {
+ page p1;
+ uint alignment = (unsigned long)&p1 % alignof(page);
+ printf ("Thread: address modulo alignment is %u\n", alignment);
+ assert(alignment == 0);
+
+ return NULL;
+}
+
+int main(int argc, char **argv) {
+ pthread_attr_t attr;
+ pthread_attr_init(&attr);
+
+ // When the stack size is 1<<16, FakeStack's GetFrame() is out of alignment,
+ // because SizeRequiredForFlags(16) == 2K.
+ pthread_attr_setstacksize(&attr, 1<<16);
+
+ pthread_t t;
+ pthread_create(&t, &attr, Thread, 0);
+ pthread_attr_destroy(&attr);
+ pthread_join(t, 0);
+
+ return 0;
+}
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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see the > 4K test. I think we should merge the two and use defines |
I shall consolidate the tests to provide durable savings. |
3 participants
This test case demonstrates that ASan does not currently align FakeStack frames correctly for 4KB objects when using a smaller thread stack size (64KB), which forces the FakeStack frames to no longer be 4KB aligned.
This differs from #152889, which is a test case for objects >4KB, which relies on the fact that the default 4KB alignment for fake stack sizes >64KB is insufficient.
#152819 will fix both issues.