Add OS::run_cpu_instruction_probe

Needed for ARM detection, also probably useful on PowerPC for AltiVec

Works fine for me on Linux x86-64 testing with ud2 instruction.

2 files changed, 107 insertions, 13 deletions

diff --git a/src/lib/utils/os_utils.cpp b/src/lib/utils/os_utils.cpp
index 46ce2a056..233a3991c 100644
--- a/src/lib/utils/os_utils.cpp
+++ b/src/lib/utils/os_utils.cpp
@@ -17,6 +17,8 @@
   #include <sys/mman.h>
   #include <sys/resource.h>
   #include <unistd.h>
+  #include <signal.h>
+  #include <setjmp.h>
 #endif
 
 #if defined(BOTAN_TARGET_OS_IS_WINDOWS) || defined(BOTAN_TARGET_OS_IS_MINGW)
@@ -298,6 +300,74 @@ void free_locked_pages(void* ptr, size_t length)
 #endif
    }
 
+#if defined(BOTAN_TARGET_OS_TYPE_IS_UNIX)
+namespace {
+
+static ::sigjmp_buf g_sigill_jmp_buf;
+
+void botan_sigill_handler(int)
+   {
+   ::siglongjmp(g_sigill_jmp_buf, /*non-zero return value*/1);
+   }
+
+}
+#endif
+
+int run_cpu_instruction_probe(std::function<int ()> probe_fn)
+   {
+#if defined(BOTAN_TARGET_OS_TYPE_IS_UNIX)
+   struct sigaction old_sigaction;
+   struct sigaction sigaction;
+
+   sigaction.sa_handler = botan_sigill_handler;
+   ::sigemptyset(&sigaction.sa_mask);
+   sigaction.sa_flags = 0;
+
+   int rc = ::sigaction(SIGILL, &sigaction, &old_sigaction);
+
+   if(rc != 0)
+      throw Exception("run_cpu_instruction_probe sigaction failed");
+
+   /*
+   There doesn't seem to be any way for probe_result to not be initialized
+   by some code path below, but this initializer is left as error just in case.
+   */
+   int probe_result = -3;
+
+   try
+      {
+      rc = ::sigsetjmp(g_sigill_jmp_buf, /*save sigs*/1);
+
+      if(rc == 0)
+         {
+         // first call to sigsetjmp
+         probe_result = probe_fn();
+         }
+      else if(rc == 1)
+         {
+         // non-local return from siglongjmp in signal handler: return error
+         probe_result = -1;
+         }
+      else
+         throw Exception("run_cpu_instruction_probe unexpected sigsetjmp return value");
+      }
+   catch(...)
+      {
+      probe_result = -2;
+      }
+
+   rc = ::sigaction(SIGILL, &old_sigaction, nullptr);
+   if(rc != 0)
+      throw Exception("run_cpu_instruction_probe sigaction restore failed");
+
+   return probe_result;
+#else
+   // TODO: Windows support
+   return -9; // not supported
+#endif
+   }
+
+
 }
 
 }
diff --git a/src/lib/utils/os_utils.h b/src/lib/utils/os_utils.h
index 213c5982b..b06a72265 100644
--- a/src/lib/utils/os_utils.h
+++ b/src/lib/utils/os_utils.h
@@ -1,6 +1,6 @@
 /*
 * OS specific utility functions
-* (C) 2015,2016 Jack Lloyd
+* (C) 2015,2016,2017 Jack Lloyd
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 */
@@ -15,18 +15,21 @@ namespace Botan {
 namespace OS {
 
 /**
-* Returns the OS assigned process ID, if available. Otherwise throws.
+* @return process ID assigned by the operating system.
+* On Unix and Windows systems, this always returns a result
+* On IncludeOS it returns 0 since there is no process ID to speak of
+* in a unikernel.
 */
 uint32_t get_process_id();
 
 /**
-* Return the highest resolution clock available on the system.
+* @return highest resolution clock available on the system.
 *
 * The epoch and update rate of this clock is arbitrary and depending
 * on the hardware it may not tick at a constant rate.
 *
-* Returns the value of the hardware cycle counter, if available.
-* On Windows calls QueryPerformanceCounter.
+* Uses hardware cycle counter, if available.
+* On Windows, always calls QueryPerformanceCounter.
 * Under GCC or Clang on supported platforms the hardware cycle counter is queried:
 *  x86, PPC, Alpha, SPARC, IA-64, S/390x, and HP-PA
 * On other platforms clock_gettime is used with some monotonic timer, if available.
@@ -35,30 +38,51 @@ uint32_t get_process_id();
 uint64_t get_processor_timestamp();
 
 /**
-* Returns the value of the system clock with best resolution available,
-* normalized to nanoseconds resolution.
+* @return system clock with best resolution available, normalized to
+* nanoseconds resolution.
 */
 uint64_t get_system_timestamp_ns();
 
-/*
-* Returns the maximum amount of memory (in bytes) we could/should
-* hyptothetically allocate. Reads "BOTAN_MLOCK_POOL_SIZE" from
-* environment which can be set to zero.
+/**
+* @return maximum amount of memory (in bytes) Botan could/should
+* hyptothetically allocate for the memory poool. Reads environment
+* variable "BOTAN_MLOCK_POOL_SIZE", set to "0" to disable pool.
 */
 size_t get_memory_locking_limit();
 
-/*
+/**
 * Request so many bytes of page-aligned RAM locked into memory using
 * mlock, VirtualLock, or similar. Returns null on failure. The memory
 * returned is zeroed. Free it with free_locked_pages.
+* @param length requested allocation in bytes
 */
 void* allocate_locked_pages(size_t length);
 
-/*
+/**
 * Free memory allocated by allocate_locked_pages
+* @param ptr a pointer returned by allocate_locked_pages
+* @param length length passed to allocate_locked_pages
 */
 void free_locked_pages(void* ptr, size_t length);
 
+/**
+* Run a probe instruction to test for support for a CPU instruction.
+* Runs in system-specific env that catches illegal instructions; this
+* function always fails if the OS doesn't provide this.
+* Returns value of probe_fn, if it could run.
+* If error occurs, returns negative number.
+* This allows probe_fn to indicate errors of its own, if it wants.
+* For example the instruction might not only be only available on some
+* CPUs, but also buggy on some subset of these - the probe function
+* can test to make sure the instruction works properly before
+* indicating that the instruction is available.
+*
+* Return codes:
+* -1 illegal instruction detected
+* -2 exception thrown
+*/
+int run_cpu_instruction_probe(std::function<int ()> probe_fn);
+
 }
 
 }