Botan::High_Resolution_Timestamp Class Reference

#include <hres_timer.h>

Inheritance diagram for Botan::High_Resolution_Timestamp:

Public Member Functions
std::string	name () const
void	poll (Entropy_Accumulator &accum)

Detailed Description

Entropy source using high resolution timers

Note

Any results from timers are marked as not contributing entropy to the poll, as a local attacker could observe them directly.

Definition at line 21 of file hres_timer.h.

Member Function Documentation

name()

std::string Botan::High_Resolution_Timestamp::name ( ) const

inlinevirtual

Returns

name identifying this entropy source

Implements Botan::EntropySource.

Definition at line 24 of file hres_timer.h.

{ return "High Resolution Timestamp"; }

poll()

void Botan::High_Resolution_Timestamp::poll ( Entropy_Accumulator & accum )

virtual

Perform an entropy gathering poll

Parameters

accum

is an accumulator object that will be given entropy

Implements Botan::EntropySource.

Definition at line 21 of file hres_timer.cpp.

   {
   // If Windows, grab the Performance Counter (usually TSC or PIT)
#if defined(BOTAN_TARGET_OS_IS_WINDOWS)
   {
   LARGE_INTEGER tv;
   ::QueryPerformanceCounter(&tv);
   accum.add(tv.QuadPart, 0);
   }
#endif
 
#if defined(BOTAN_TARGET_OS_HAS_CLOCK_GETTIME)
 
#define CLOCK_POLL(src)                     \
   do {                                     \
     struct timespec ts;                    \
     clock_gettime(src, &ts);               \
     accum.add(&ts, sizeof(ts), 0);         \
   } while(0)
 
#if defined(CLOCK_REALTIME)
   CLOCK_POLL(CLOCK_REALTIME);
#endif
 
#if defined(CLOCK_MONOTONIC)
   CLOCK_POLL(CLOCK_MONOTONIC);
#endif
 
#if defined(CLOCK_MONOTONIC_RAW)
   CLOCK_POLL(CLOCK_MONOTONIC_RAW);
#endif
 
#if defined(CLOCK_PROCESS_CPUTIME_ID)
   CLOCK_POLL(CLOCK_PROCESS_CPUTIME_ID);
#endif
 
#if defined(CLOCK_THREAD_CPUTIME_ID)
   CLOCK_POLL(CLOCK_THREAD_CPUTIME_ID);
#endif
 
#undef CLOCK_POLL
 
#endif
 
#if BOTAN_USE_GCC_INLINE_ASM
 
   u64bit rtc = 0;
 
#if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
   if(CPUID::has_rdtsc()) // not availble on all x86 CPUs
      {
      u32bit 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)
   u32bit 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)
   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
 
   // Don't count the timestamp as contributing entropy
   accum.add(rtc, 0);
 
#endif
   }

References Botan::Entropy_Accumulator::add(), and Botan::CPUID::has_rdtsc().

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The documentation for this class was generated from the following files:

• src/entropy/hres_timer/hres_timer.h
• src/entropy/hres_timer/hres_timer.cpp