[scudo] Make release to OS test more specific.

[cferris1000]

The original version of ResidentMemorySize could be a little flaky. Replace the test with a version that verifies exactly how much of the map is resident.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Christopher Ferris (cferris1000)

Changes

The original version of ResidentMemorySize could be a little flaky. Replace the test with a version that verifies exactly how much of the map is resident.

---

Full diff: https://github.com/llvm/llvm-project/pull/147852.diff

1 Files Affected:

• (modified) compiler-rt/lib/scudo/standalone/tests/common_test.cpp (+117-25)

diff --git a/compiler-rt/lib/scudo/standalone/tests/common_test.cpp b/compiler-rt/lib/scudo/standalone/tests/common_test.cpp
index e6ddbb00b843c..df692aca99621 100644
--- a/compiler-rt/lib/scudo/standalone/tests/common_test.cpp
+++ b/compiler-rt/lib/scudo/standalone/tests/common_test.cpp
@@ -11,44 +11,136 @@
 
 #include "common.h"
 #include "mem_map.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
 #include <algorithm>
-#include <fstream>
+#include <string>
 
 namespace scudo {
 
-static uptr getResidentMemorySize() {
+static void GetRssKbFromString(uptr MapAddress, std::string &Buffer,
+                               size_t &ParsedBytes, size_t &RssKb,
+                               bool &Found) {
+  size_t LineStart = 0;
+  bool FindRss = false;
+  while (true) {
+    size_t LineEnd = Buffer.find('\n', LineStart);
+    if (LineEnd == std::string::npos) {
+      ParsedBytes = LineStart;
+      ASSERT_NE(0U, ParsedBytes)
+          << "The current buffer size (" << Buffer.size()
+          << ") is not large enough to contain a single line.";
+      break;
+    }
+    Buffer[LineEnd] = '\0';
+    // The format of the address line is:
+    //   55ecba642000-55ecba644000 r--p 00000000 fd:01 66856632
+    uptr StartAddr;
+    uptr EndAddr;
+    char Perms[5];
+    if (sscanf(&Buffer[LineStart], "%" SCNxPTR "-%" SCNxPTR " %4s", &StartAddr,
+               &EndAddr, Perms) == 3) {
+      if (StartAddr == MapAddress) {
+        FindRss = true;
+      }
+    } else if (FindRss && strncmp(&Buffer[LineStart], "Rss:", 4) == 0) {
+      // The format of the RSS line is:
+      //   Rss:                   8 kB
+      ASSERT_EQ(1, sscanf(&Buffer[LineStart], "Rss: %zd kB", &RssKb))
+          << "Bad Rss Line: " << &Buffer[LineStart];
+      Found = true;
+      ParsedBytes = LineStart;
+      break;
+    }
+    LineStart = LineEnd + 1;
+  }
+}
+
+static void GetRssKb(void *BaseAddress, size_t &RssKb) {
   if (!SCUDO_LINUX)
     UNREACHABLE("Not implemented!");
-  uptr Size;
-  uptr Resident;
-  std::ifstream IFS("/proc/self/statm");
-  IFS >> Size;
-  IFS >> Resident;
-  return Resident * getPageSizeCached();
+
+  size_t MapAddress = reinterpret_cast<size_t>(BaseAddress);
+
+  int Fd = open("/proc/self/smaps", O_RDONLY);
+  ASSERT_NE(-1, Fd) << "Failed to open /proc/self/smaps: " << strerror(errno);
+
+  std::string Buffer(10 * 1024, '\0');
+  size_t LeftoverBytes = 0;
+  RssKb = 0;
+  bool FoundMap = false;
+  while (LeftoverBytes != Buffer.size()) {
+    ssize_t ReadBytes =
+        read(Fd, &Buffer[LeftoverBytes], Buffer.size() - LeftoverBytes);
+    if (ReadBytes < 0) {
+      EXPECT_GT(0, ReadBytes) << "read failed: " << strerror(errno);
+      break;
+    }
+    if (ReadBytes == 0) {
+      // Nothing left to read.
+      break;
+    }
+    size_t End = static_cast<size_t>(ReadBytes) + LeftoverBytes;
+    Buffer[End] = '\0';
+    size_t ParsedBytes = 0;
+    GetRssKbFromString(MapAddress, Buffer, ParsedBytes, RssKb, FoundMap);
+    if (TEST_HAS_FAILURE || FoundMap)
+      break;
+    // Need to copy the leftover bytes back to the front of the buffer.
+    LeftoverBytes = End - ParsedBytes;
+    if (LeftoverBytes != 0) {
+      memmove(Buffer.data(), &Buffer[ParsedBytes], LeftoverBytes);
+    }
+  }
+  close(Fd);
+
+  EXPECT_TRUE(FoundMap) << "Could not find map at address " << BaseAddress;
 }
 
-// Fuchsia needs getResidentMemorySize implementation.
+// Fuchsia needs getRssKb implementation.
 TEST(ScudoCommonTest, SKIP_ON_FUCHSIA(ResidentMemorySize)) {
-  uptr OnStart = getResidentMemorySize();
-  EXPECT_GT(OnStart, 0UL);
-
-  const uptr Size = 1ull << 30;
-  const uptr Threshold = Size >> 3;
+  // Make sure to have the size of the map on a page boundary.
+  const uptr PageSize = getPageSizeCached();
+  const uptr SizeBytes = 1000 * PageSize;
+  const uptr ActualSizeBytes = SizeBytes - 2 * PageSize;
 
   MemMapT MemMap;
-  ASSERT_TRUE(MemMap.map(/*Addr=*/0U, Size, "ResidentMemorySize"));
+  ASSERT_TRUE(MemMap.map(/*Addr=*/0U, SizeBytes, "ResidentMemorySize"));
   ASSERT_NE(MemMap.getBase(), 0U);
-  void *P = reinterpret_cast<void *>(MemMap.getBase());
-  EXPECT_LT(getResidentMemorySize(), OnStart + Threshold);
 
-  memset(P, 1, Size);
-  EXPECT_GT(getResidentMemorySize(), OnStart + Size - Threshold);
-
-  MemMap.releasePagesToOS(MemMap.getBase(), Size);
-  EXPECT_LT(getResidentMemorySize(), OnStart + Threshold);
-
-  memset(P, 1, Size);
-  EXPECT_GT(getResidentMemorySize(), OnStart + Size - Threshold);
+  // Mark the first page and the last page as unreadable to make sure that
+  // the map shows up as distinct from all other maps.
+  EXPECT_EQ(0, mprotect(reinterpret_cast<void *>(MemMap.getBase()), PageSize,
+                        PROT_NONE));
+  EXPECT_EQ(0, mprotect(reinterpret_cast<void *>(MemMap.getBase() + SizeBytes -
+                                                 PageSize),
+                        PageSize, PROT_NONE));
+
+  size_t RssKb = 0;
+  void *P = reinterpret_cast<void *>(MemMap.getBase() + PageSize);
+  GetRssKb(P, RssKb);
+  EXPECT_EQ(RssKb, 0U);
+
+  // Make the entire map resident.
+  memset(P, 1, ActualSizeBytes);
+  GetRssKb(P, RssKb);
+  EXPECT_EQ(RssKb, (ActualSizeBytes >> 10));
+
+  // Should release the memory to the kernel immediately.
+  MemMap.releasePagesToOS(MemMap.getBase(), SizeBytes);
+  GetRssKb(P, RssKb);
+  EXPECT_EQ(RssKb, 0U);
+
+  // Make the entire map resident again.
+  memset(P, 1, ActualSizeBytes);
+  GetRssKb(P, RssKb);
+  EXPECT_EQ(RssKb, ActualSizeBytes >> 10);
 
   MemMap.unmap();
 }