[profile] Skip mmap() if there are no counters

If there are no counters, an mmap() of the counters section would fail due to the size argument being too small (EINVAL). rdar://78175925 Differential Revision: https://reviews.llvm.org/D102735

Author: vedantk

compiler-rt/lib/profile/InstrProfilingFile.c

@@ -638,34 +638,38 @@ static void initializeProfileForContinuousMode(void) {
  }
  }
 
- int Fileno = fileno(File);
-
- /* Determine how much padding is needed before/after the counters and after
- * the names. */
- uint64_t PaddingBytesBeforeCounters, PaddingBytesAfterCounters,
- PaddingBytesAfterNames;
- __llvm_profile_get_padding_sizes_for_counters(
- DataSize, CountersSize, NamesSize, &PaddingBytesBeforeCounters,
- &PaddingBytesAfterCounters, &PaddingBytesAfterNames);
-
- uint64_t PageAlignedCountersLength =
- (CountersSize * sizeof(uint64_t)) + PaddingBytesAfterCounters;
- uint64_t FileOffsetToCounters =
- CurrentFileOffset + sizeof(__llvm_profile_header) +
- (DataSize * sizeof(__llvm_profile_data)) + PaddingBytesBeforeCounters;
-
- uint64_t *CounterMmap = (uint64_t *)mmap(
- (void *)CountersBegin, PageAlignedCountersLength, PROT_READ | PROT_WRITE,
- MAP_FIXED | MAP_SHARED, Fileno, FileOffsetToCounters);
- if (CounterMmap != CountersBegin) {
- PROF_ERR(
- "Continuous counter sync mode is enabled, but mmap() failed (%s).\n"
- " - CountersBegin: %p\n"
- " - PageAlignedCountersLength: %" PRIu64 "\n"
- " - Fileno: %d\n"
- " - FileOffsetToCounters: %" PRIu64 "\n",
- strerror(errno), CountersBegin, PageAlignedCountersLength, Fileno,
- FileOffsetToCounters);
+ /* mmap() the profile counters so long as there is at least one counter.
+ * If there aren't any counters, mmap() would fail with EINVAL. */
+ if (CountersSize > 0) {
+ int Fileno = fileno(File);
+
+ /* Determine how much padding is needed before/after the counters and after
+ * the names. */
+ uint64_t PaddingBytesBeforeCounters, PaddingBytesAfterCounters,
+ PaddingBytesAfterNames;
+ __llvm_profile_get_padding_sizes_for_counters(
+ DataSize, CountersSize, NamesSize, &PaddingBytesBeforeCounters,
+ &PaddingBytesAfterCounters, &PaddingBytesAfterNames);
+
+ uint64_t PageAlignedCountersLength =
+ (CountersSize * sizeof(uint64_t)) + PaddingBytesAfterCounters;
+ uint64_t FileOffsetToCounters =
+ CurrentFileOffset + sizeof(__llvm_profile_header) +
+ (DataSize * sizeof(__llvm_profile_data)) + PaddingBytesBeforeCounters;
+
+ uint64_t *CounterMmap = (uint64_t *)mmap(
+ (void *)CountersBegin, PageAlignedCountersLength, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_SHARED, Fileno, FileOffsetToCounters);
+ if (CounterMmap != CountersBegin) {
+ PROF_ERR(
+ "Continuous counter sync mode is enabled, but mmap() failed (%s).\n"
+ " - CountersBegin: %p\n"
+ " - PageAlignedCountersLength: %" PRIu64 "\n"
+ " - Fileno: %d\n"
+ " - FileOffsetToCounters: %" PRIu64 "\n",
+ strerror(errno), CountersBegin, PageAlignedCountersLength, Fileno,
+ FileOffsetToCounters);
+ }
  }
 
  if (ProfileRequiresUnlock)

compiler-rt/test/profile/ContinuousSyncMode/image-with-no-counters.c

@@ -0,0 +1,11 @@
+// REQUIRES: darwin
+
+// RUN: echo "static void dead_code(void) {}" > %t.dso.c
+// RUN: %clang_profgen -fcoverage-mapping -O3 -dynamiclib -o %t.dso.dylib %t.dso.c
+// RUN: %clang_profgen -fcoverage-mapping -O3 -o %t.exe %s %t.dso.dylib
+// RUN: env LLVM_PROFILE_FILE="%c%t.profraw" %run %t.exe 2>&1 | count 0
+// RUN: llvm-profdata show --counts --all-functions %t.profraw | FileCheck %s
+
+// CHECK: Total functions: 1
+
+int main() {}