1 files changed, 151 insertions, 0 deletions
diff --git a/compiler-rt/test/profile/ContinuousSyncMode/darwin-proof-of-concept.c b/compiler-rt/test/profile/ContinuousSyncMode/darwin-proof-of-concept.c
new file mode 100644
index 00000000000..85caca9a56b
--- /dev/null
+++ b/compiler-rt/test/profile/ContinuousSyncMode/darwin-proof-of-concept.c
@@ -0,0 +1,151 @@
+// Test whether mmap'ing profile counters onto an open file is feasible. As
+// this involves some platform-specific logic, this test is designed to be a
+// minimum viable proof-of-concept: it may be useful when porting the mmap()
+// mode to a new platform, but is not in and of itself a test of the profiling
+// runtime.
+
+// REQUIRES: darwin
+
+// Align counters and data to the maximum expected page size (16K).
+// RUN: %clang -g -o %t %s \
+// RUN:   -Wl,-sectalign,__DATA,__pcnts,0x4000 \
+// RUN:   -Wl,-sectalign,__DATA,__pdata,0x4000
+
+// Create a 'profile' using mmap() and validate it.
+// RUN: %run %t create %t.tmpfile
+// RUN: %run %t validate %t.tmpfile
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+__attribute__((section("__DATA,__pcnts"))) int counters[] = {0xbad};
+extern int cnts_start __asm("section$start$__DATA$__pcnts");
+const size_t cnts_len = 0x4000;
+
+__attribute__((section("__DATA,__pdata"))) int data[] = {1, 2, 3};
+extern int data_start __asm("section$start$__DATA$__pdata");
+const size_t data_len = sizeof(int) * 3;
+
+int create_tmpfile(char *path) {
+  // Create a temp file.
+  int fd = open(path, O_RDWR | O_TRUNC | O_CREAT, 0666);
+  if (fd == -1) {
+    perror("open");
+    return EXIT_FAILURE;
+  }
+
+  // Grow the file to hold data and counters.
+  if (0 != ftruncate(fd, cnts_len + data_len)) {
+    perror("ftruncate");
+    return EXIT_FAILURE;
+  }
+
+  // Write the data first (at offset 0x4000, after the counters).
+  if (data_len != pwrite(fd, &data, data_len, 0x4000)) {
+    perror("write");
+    return EXIT_FAILURE;
+  }
+
+  // Map the counters into the file, before the data.
+  //
+  // Requirements (on Darwin):
+  // - &cnts_start must be page-aligned.
+  // - The length and offset-into-fd must be page-aligned.
+  int *counter_map = (int *)mmap(&cnts_start, 0x4000, PROT_READ | PROT_WRITE,
+      MAP_FIXED | MAP_SHARED, fd, 0);
+  if (counter_map != &cnts_start) {
+    perror("mmap");
+    return EXIT_FAILURE;
+  }
+
+  // Update counters 1..9. These updates should be visible in the file.
+  // Expect counter 0 (0xbad), which is not updated, to be zero in the file.
+  for (int i = 1; i < 10; ++i)
+    counter_map[i] = i;
+
+  // Intentionally do not msync(), munmap(), or close().
+  return EXIT_SUCCESS;
+}
+
+int validate_tmpfile(char *path) {
+  int fd = open(path, O_RDONLY);
+  if (fd == -1) {
+    perror("open");
+    return EXIT_FAILURE;
+  }
+
+  // Verify that the file length is: sizeof(counters) + sizeof(data).
+  const size_t num_bytes = cnts_len + data_len;
+  int buf[num_bytes];
+  if (num_bytes != read(fd, &buf, num_bytes)) {
+    perror("read");
+    return EXIT_FAILURE;
+  }
+
+  // Verify the values of counters 1..9 (i.e. that the mmap() worked).
+  for (int i = 0; i < 10; ++i) {
+    if (buf[i] != i) {
+      fprintf(stderr,
+          "validate_tmpfile: Expected '%d' at pos=%d, but got '%d' instead.\n",
+          i, i, buf[i]);
+      return EXIT_FAILURE;
+    }
+  }
+
+  // Verify that the rest of the counters (after counter 9) are 0.
+  const int num_cnts = 0x4000 / sizeof(int);
+  for (int i = 10; i < num_cnts; ++i) {
+    if (buf[i] != 0) {
+      fprintf(stderr,
+          "validate_tmpfile: Expected '%d' at pos=%d, but got '%d' instead.\n",
+          0, i, buf[i]);
+      return EXIT_FAILURE;
+    }
+  }
+
+  // Verify that the data written after the counters is equal to the "data[]"
+  // array (i.e. {1, 2, 3}).
+  for (int i = num_cnts; i < num_cnts + 3; ++i) {
+    if (buf[i] != (i - num_cnts + 1)) {
+      fprintf(stderr,
+          "validate_tmpfile: Expected '%d' at pos=%d, but got '%d' instead.\n",
+          i - num_cnts + 1, i, buf[i]);
+      return EXIT_FAILURE;
+    }
+  }
+
+  // Intentionally do not close().
+  return EXIT_SUCCESS;
+}
+
+int main(int argc, char **argv) {
+  intptr_t cnts_start_int = (intptr_t)&cnts_start;
+  intptr_t data_start_int = (intptr_t)&data_start;
+  int pagesz = getpagesize();
+
+  if (cnts_start_int % pagesz != 0) {
+    fprintf(stderr, "__pcnts is not page-aligned: 0x%lx.\n", cnts_start_int);
+    return EXIT_FAILURE;
+  }
+  if (data_start_int % pagesz != 0) {
+    fprintf(stderr, "__pdata is not page-aligned: 0x%lx.\n", data_start_int);
+    return EXIT_FAILURE;
+  }
+  if (cnts_start_int + 0x4000 != data_start_int) {
+    fprintf(stderr, "__pdata not ordered after __pcnts.\n");
+    return EXIT_FAILURE;
+  }
+
+  char *action = argv[1];
+  char *path = argv[2];
+  if (0 == strcmp(action, "create"))
+    return create_tmpfile(path);
+  else if (0 == strcmp(action, "validate"))
+    return validate_tmpfile(path);
+  else
+    return EXIT_FAILURE;
+}