[scudo] Change tests that use setrlimit to cause mmap to fail. (llvm#87004)

It appears that qemu does not actually cause mmap to fail when calling
setrlimit to limit the address space size. In the two tests that use
setrlimit, detect if mmap still works and skip the tests in that case.

Since all Android targets should support setrlimit, compile out the mmap
check code for them.

Author: cferris1000

compiler-rt/lib/scudo/standalone/tests/strings_test.cpp

@@ -129,16 +129,27 @@ TEST(ScudoStringsTest, Padding) {
 }
 
 #if defined(__linux__)
+
 #include <sys/resource.h>
 
 TEST(ScudoStringsTest, CapacityIncreaseFails) {
   scudo::ScopedString Str;
 
   rlimit Limit = {};
   EXPECT_EQ(0, getrlimit(RLIMIT_AS, &Limit));
+
   rlimit EmptyLimit = {.rlim_cur = 0, .rlim_max = Limit.rlim_max};
   EXPECT_EQ(0, setrlimit(RLIMIT_AS, &EmptyLimit));
 
+  // qemu does not honor the setrlimit, so verify before proceeding.
+  scudo::MemMapT MemMap;
+  if (MemMap.map(/*Addr=*/0U, scudo::getPageSizeCached(), "scudo:test",
+                 MAP_ALLOWNOMEM)) {
+    MemMap.unmap(MemMap.getBase(), MemMap.getCapacity());
+    setrlimit(RLIMIT_AS, &Limit);
+    GTEST_SKIP() << "Limiting address space does not prevent mmap.";
+  }
+
   // Test requires that the default length is at least 6 characters.
   scudo::uptr MaxSize = Str.capacity();
   EXPECT_LE(6u, MaxSize);

compiler-rt/lib/scudo/standalone/tests/vector_test.cpp

@@ -58,6 +58,15 @@ TEST(ScudoVectorTest, ReallocateFails) {
   rlimit EmptyLimit = {.rlim_cur = 0, .rlim_max = Limit.rlim_max};
   EXPECT_EQ(0, setrlimit(RLIMIT_AS, &EmptyLimit));
 
+  // qemu does not honor the setrlimit, so verify before proceeding.
+  scudo::MemMapT MemMap;
+  if (MemMap.map(/*Addr=*/0U, scudo::getPageSizeCached(), "scudo:test",
+                 MAP_ALLOWNOMEM)) {
+    MemMap.unmap(MemMap.getBase(), MemMap.getCapacity());
+    setrlimit(RLIMIT_AS, &Limit);
+    GTEST_SKIP() << "Limiting address space does not prevent mmap.";
+  }
+
   V.resize(capacity);
   // Set the last element so we can check it later.
   V.back() = '\0';