Basic OpenBSD backend support.

Cannot enforce alignment so we just check its correctness.

src/override/malloc.cc

@@ -89,7 +89,7 @@ extern "C"
     return p;
   }
 
-#ifndef __FreeBSD__
+#if !defined(__FreeBSD__) && !defined(__OpenBSD__)
   SNMALLOC_EXPORT void*
     SNMALLOC_NAME_MANGLE(reallocarray)(void* ptr, size_t nmemb, size_t size)
   {
@@ -165,7 +165,7 @@ extern "C"
     return 0;
   }
 
-#ifndef __FreeBSD__
+#if !defined(__FreeBSD__) && !defined(__OpenBSD__)
   SNMALLOC_EXPORT void* SNMALLOC_NAME_MANGLE(valloc)(size_t size)
   {
     return SNMALLOC_NAME_MANGLE(memalign)(OS_PAGE_SIZE, size);

src/pal/pal.h

@@ -13,6 +13,7 @@ namespace snmalloc
 #  include "pal_free_bsd_kernel.h"
 #  include "pal_freebsd.h"
 #  include "pal_linux.h"
+#  include "pal_openbsd.h"
 #  include "pal_windows.h"
 #endif
 #include "pal_open_enclave.h"
@@ -32,6 +33,8 @@ namespace snmalloc
     PALFreeBSDKernel;
 #  elif defined(__FreeBSD__)
     PALFBSD;
+#  elif defined(__OpenBSD__)
+    PALOBSD;
 #  else
 #    error Unsupported platform
 #  endif

src/pal/pal_openbsd.h

@@ -0,0 +1,95 @@
+#pragma once
+
+#if defined(__OpenBSD__) && !defined(_KERNEL)
+#  include "../ds/bits.h"
+#  include "../mem/allocconfig.h"
+
+#  include <stdio.h>
+#  include <string.h>
+#  include <sys/mman.h>
+
+namespace snmalloc
+{
+  class PALOBSD
+  {
+  public:
+    /**
+     * Bitmap of PalFeatures flags indicating the optional features that this
+     * PAL supports.
+     */
+    static constexpr uint64_t pal_features = AlignedAllocation | LazyCommit;
+    static void error(const char* const str)
+    {
+      puts(str);
+      abort();
+    }
+
+    /// Notify platform that we will not be using these pages
+    void notify_not_using(void* p, size_t size) noexcept
+    {
+      assert(bits::is_aligned_block<OS_PAGE_SIZE>(p, size));
+      madvise(p, size, MADV_FREE);
+    }
+
+    /// Notify platform that we will be using these pages
+    template<ZeroMem zero_mem>
+    void notify_using(void* p, size_t size) noexcept
+    {
+      assert(
+        bits::is_aligned_block<OS_PAGE_SIZE>(p, size) || (zero_mem == NoZero));
+      if constexpr (zero_mem == YesZero)
+      {
+        zero(p, size);
+      }
+      else
+      {
+        UNUSED(size);
+        UNUSED(p);
+      }
+    }
+
+    /// OS specific function for zeroing memory
+    template<bool page_aligned = false>
+    void zero(void* p, size_t size) noexcept
+    {
+      if (page_aligned || bits::is_aligned_block<OS_PAGE_SIZE>(p, size))
+      {
+        assert(bits::is_aligned_block<OS_PAGE_SIZE>(p, size));
+        void* r = mmap(
+          p,
+          size,
+          PROT_READ | PROT_WRITE,
+          MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
+          -1,
+          0);
+
+        if (r != MAP_FAILED)
+          return;
+      }
+
+      ::memset(p, 0, size);
+    }
+
+    template<bool committed>
+    void* reserve(const size_t* size, size_t align) noexcept
+    {
+      size_t request = *size;
+      // Alignment must be a power of 2.
+      assert(align == bits::next_pow2(align));
+
+      void* p = mmap(
+        nullptr,
+        request,
+        PROT_READ | PROT_WRITE,
+        MAP_PRIVATE | MAP_ANONYMOUS,
+        -1,
+        0);
+
+      if (p == MAP_FAILED)
+        error("Out of memory");
+
+      return p;
+    }
+  };
+} // namespace snmalloc
+#endif