/*
* OS and machine specific utility functions
* (C) 2015,2016 Jack Lloyd
* (C) 2016 Daniel Neus
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/internal/os_utils.h>
#include <botan/cpuid.h>
#include <botan/exceptn.h>
#include <botan/mem_ops.h>
#include <chrono>

#if defined(BOTAN_TARGET_OS_TYPE_IS_UNIX)
  #include <sys/types.h>
  #include <sys/mman.h>
  #include <sys/resource.h>
  #include <unistd.h>
#endif

#if defined(BOTAN_TARGET_OS_TYPE_IS_WINDOWS)
  #include <windows.h>
#endif

namespace Botan {

namespace OS {

uint32_t get_process_id()
   {
#if defined(BOTAN_TARGET_OS_IS_UNIX)
   return ::getpid();
#elif defined(BOTAN_TARGET_OS_IS_WINDOWS)
   return ::GetCurrentProcessId();
#else
   return 0;
#endif
   }

uint64_t get_processor_timestamp()
   {
   uint64_t rtc = 0;

#if defined(BOTAN_TARGET_OS_HAS_QUERY_PERF_COUNTER)
   LARGE_INTEGER tv;
   ::QueryPerformanceCounter(&tv);
   rtc = tv.QuadPart;
#endif

#if defined(BOTAN_USE_GCC_INLINE_ASM)

#if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
   if(CPUID::has_rdtsc()) // not available on all x86 CPUs
      {
      uint32_t rtc_low = 0, rtc_high = 0;
      asm volatile("rdtsc" : "=d" (rtc_high), "=a" (rtc_low));
      rtc = (static_cast<u64bit>(rtc_high) << 32) | rtc_low;
      }

#elif defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
   uint32_t rtc_low = 0, rtc_high = 0;
   asm volatile("mftbu %0; mftb %1" : "=r" (rtc_high), "=r" (rtc_low));
   rtc = (static_cast<u64bit>(rtc_high) << 32) | rtc_low;

#elif defined(BOTAN_TARGET_ARCH_IS_ALPHA)
   asm volatile("rpcc %0" : "=r" (rtc));

#elif defined(BOTAN_TARGET_ARCH_IS_SPARC64) && !defined(BOTAN_TARGET_OS_IS_OPENBSD)
   // OpenBSD does not trap access to the %tick register
   asm volatile("rd %%tick, %0" : "=r" (rtc));

#elif defined(BOTAN_TARGET_ARCH_IS_IA64)
   asm volatile("mov %0=ar.itc" : "=r" (rtc));

#elif defined(BOTAN_TARGET_ARCH_IS_S390X)
   asm volatile("stck 0(%0)" : : "a" (&rtc) : "memory", "cc");

#elif defined(BOTAN_TARGET_ARCH_IS_HPPA)
   asm volatile("mfctl 16,%0" : "=r" (rtc)); // 64-bit only?
#endif

#endif

   return rtc;
   }

uint64_t get_system_timestamp_ns()
   {
#if defined(BOTAN_TARGET_OS_HAS_CLOCK_GETTIME)
   struct timespec ts;
   if(::clock_gettime(CLOCK_REALTIME, &ts) == 0)
      {
      return (static_cast<uint64_t>(ts.tv_sec) * 1000000000) + static_cast<uint64_t>(ts.tv_nsec);
      }
#endif

   auto now = std::chrono::system_clock::now().time_since_epoch();
   return std::chrono::duration_cast<std::chrono::nanoseconds>(now).count();
   }

size_t get_memory_locking_limit()
   {
#if defined(BOTAN_TARGET_OS_HAS_POSIX_MLOCK)
   /*
   * Linux defaults to only 64 KiB of mlockable memory per process
   * (too small) but BSDs offer a small fraction of total RAM (more
   * than we need). Bound the total mlock size to 512 KiB which is
   * enough to run the entire test suite without spilling to non-mlock
   * memory (and thus presumably also enough for many useful
   * programs), but small enough that we should not cause problems
   * even if many processes are mlocking on the same machine.
   */
   size_t mlock_requested = BOTAN_MLOCK_ALLOCATOR_MAX_LOCKED_KB;

   /*
   * Allow override via env variable
   */
   if(const char* env = ::getenv("BOTAN_MLOCK_POOL_SIZE"))
      {
      try
         {
         const size_t user_req = std::stoul(env, nullptr);
         mlock_requested = std::min(user_req, mlock_requested);
         }
      catch(std::exception&) { /* ignore it */ }
      }

   if(mlock_requested > 0)
      {
      struct ::rlimit limits;

      ::getrlimit(RLIMIT_MEMLOCK, &limits);

      if(limits.rlim_cur < limits.rlim_max)
         {
         limits.rlim_cur = limits.rlim_max;
         ::setrlimit(RLIMIT_MEMLOCK, &limits);
         ::getrlimit(RLIMIT_MEMLOCK, &limits);
         }

      return std::min<size_t>(limits.rlim_cur, mlock_requested * 1024);
      }
#elif defined BOTAN_TARGET_OS_HAS_VIRTUAL_LOCK
   SIZE_T working_min = 0, working_max = 0;
   DWORD working_flags = 0;
   if(!::GetProcessWorkingSetSizeEx(::GetCurrentProcess(), &working_min, &working_max, &working_flags))
      {
      return 0;
      }

   SYSTEM_INFO sSysInfo;
   ::GetSystemInfo(&sSysInfo);

   // According to Microsoft MSDN:
   // The maximum number of pages that a process can lock is equal to the number of pages in its minimum working set minus a small overhead
   // In the book "Windows Internals Part 2": the maximum lockable pages are minimum working set size - 8 pages 
   // But the information in the book seems to be inaccurate/outdated
   // I've tested this on Windows 8.1 x64, Windows 10 x64 and Windows 7 x86
   // On all three OS the value is 11 instead of 8
   size_t overhead = sSysInfo.dwPageSize * 11ULL;
   if(working_min > overhead)
      {
      size_t lockable_bytes = working_min - overhead;
      if(lockable_bytes < (BOTAN_MLOCK_ALLOCATOR_MAX_LOCKED_KB * 1024ULL))
         {
         return lockable_bytes;
         }
      else
         {
         return BOTAN_MLOCK_ALLOCATOR_MAX_LOCKED_KB * 1024ULL;
         }
      }
#endif

   return 0;
   }

void* allocate_locked_pages(size_t length)
   {
#if defined(BOTAN_TARGET_OS_HAS_POSIX_MLOCK)

#if !defined(MAP_NOCORE)
   #define MAP_NOCORE 0
#endif

#if !defined(MAP_ANONYMOUS)
   #define MAP_ANONYMOUS MAP_ANON
#endif

   void* ptr = ::mmap(nullptr,
                      length,
                      PROT_READ | PROT_WRITE,
                      MAP_ANONYMOUS | MAP_SHARED | MAP_NOCORE,
                      /*fd*/-1,
                      /*offset*/0);

   if(ptr == MAP_FAILED)
      {
      return nullptr;
      }

#if defined(MADV_DONTDUMP)
   ::madvise(ptr, length, MADV_DONTDUMP);
#endif

   if(::mlock(ptr, length) != 0)
      {
      ::munmap(ptr, length);
      return nullptr; // failed to lock
      }

   ::memset(ptr, 0, length);

   return ptr;
#elif defined BOTAN_TARGET_OS_HAS_VIRTUAL_LOCK
   LPVOID ptr = ::VirtualAlloc(nullptr, length, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
   if(!ptr)
      {
      return nullptr;
      }

   if(::VirtualLock(ptr, length) == 0)
      {
      ::VirtualFree(ptr, 0, MEM_RELEASE);
      return nullptr; // failed to lock
      }

   return ptr;
#else
   return nullptr; /* not implemented */
#endif
   }

void free_locked_pages(void* ptr, size_t length)
   {
   if(ptr == nullptr || length == 0)
      return;

#if defined(BOTAN_TARGET_OS_HAS_POSIX_MLOCK)
   zero_mem(ptr, length);
   ::munlock(ptr, length);
   ::munmap(ptr, length);
#elif defined BOTAN_TARGET_OS_HAS_VIRTUAL_LOCK
   zero_mem(ptr, length);
   ::VirtualUnlock(ptr, length);
   ::VirtualFree(ptr, 0, MEM_RELEASE);
#else
   // Invalid argument because no way this pointer was allocated by us
   throw Invalid_Argument("Invalid ptr to free_locked_pages");
#endif
   }

}

}