[scudo] Touch memory to count as RSS

[Hahnfeld]

Summary

This should fix the test from https://reviews.llvm.org/D41128.

[cryptoad]

How about using calloc instead and benefiting of the "included" zero'd memory feature? That would avoid implementing the touch function.
I won't be able to test anything before Jan. 2nd.

[Hahnfeld]

In D41649#965470, @cryptoad wrote:

How about using calloc instead and benefiting of the "included" zero'd memory feature? That would avoid implementing the touch function.
I won't be able to test anything before Jan. 2nd.

calloc doesn't work because the kernel can use copy-on-write zero pages, see https://willnewton.name/uncategorized/calloc-versus-malloc-and-memset/ for a full explanation. I can use the mentioned memset though and get rid of the touch function :-)

[Hahnfeld]

Use memset instead of custom touch function.

compiler-rt/trunk/test/scudo/interface.cpp

 // RUN: %clangxx_scudo %s -lstdc++ -o %t
 // RUN:                                                   %run %t ownership          2>&1
 // RUN:                                                   %run %t ownership-and-size 2>&1
 // RUN:                                                   %run %t heap-size          2>&1
 // RUN: %env_scudo_opts="allocator_may_return_null=1"     %run %t soft-limit         2>&1
 // RUN: %env_scudo_opts="allocator_may_return_null=1" not %run %t hard-limit         2>&1
-// UNSUPPORTED: armhf-linux
 
 // Tests that the sanitizer interface functions behave appropriately.
 
 #include <stdlib.h>
 #include <assert.h>
 #include <string.h>
 #include <unistd.h>
 
if (!strcmp(argv[1], "heap-size")) {
     // Ensures that __sanitizer_get_heap_size can be called before any other
     // allocator function.
     assert(__sanitizer_get_heap_size() >= 0);
   }
   if (!strcmp(argv[1], "soft-limit")) {
     // Verifies that setting the soft RSS limit at runtime works as expected.
     std::vector<void *> pointers;
     size_t size = 1 << 19;  // 512Kb
-    for (int i = 0; i < 5; i++)
-      pointers.push_back(malloc(size));
+    for (int i = 0; i < 5; i++) {
+      void *p = malloc(size);
+      memset(p, 0, size);
+      pointers.push_back(p);
+    }
     // Set the soft RSS limit to 1Mb.
     __scudo_set_rss_limit(1, 0);
     usleep(20000);
     // The following allocation should return NULL.
     void *p = malloc(size);
     assert(!p);
     // Remove the soft RSS limit.
     __scudo_set_rss_limit(0, 0);
     // The following allocation should succeed.
     p = malloc(size);
     assert(p);
     free(p);
     while (!pointers.empty()) {
       free(pointers.back());
       pointers.pop_back();
     }
   }
   if (!strcmp(argv[1], "hard-limit")) {
     // Verifies that setting the hard RSS limit at runtime works as expected.
     std::vector<void *> pointers;
     size_t size = 1 << 19;  // 512Kb
-    for (int i = 0; i < 5; i++)
-      pointers.push_back(malloc(size));
+    for (int i = 0; i < 5; i++) {
+      void *p = malloc(size);
+      memset(p, 0, size);
+      pointers.push_back(p);
+    }
     // Set the hard RSS limit to 1Mb
     __scudo_set_rss_limit(1, 1);
     usleep(20000);
     // The following should trigger our death.
     void *p = malloc(size);
   }
 
   return 0;
 }