src/system_wrappers/source/cpu_features_arm.c - platform/external/webrtc - Git at Google

 /*
  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 // This file is derived from Android's NDK package r7, located at
 // <ndk>/sources/android/cpufeatures/ (downloadable from
 // http://developer.android.com/sdk/ndk/index.html).

 #include "cpu_features_wrapper.h"

 #include <fcntl.h>
 #include <errno.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>

 // Define CPU family.
 typedef enum {
   CPU_FAMILY_UNKNOWN = 0,
   CPU_FAMILY_ARM,
   CPU_FAMILY_X86,
   CPU_FAMILY_MAX  // Do not remove.
 } CpuFamily;

 static pthread_once_t g_once;
 static CpuFamily g_cpuFamily;
 static uint64_t g_cpuFeatures;
 static int g_cpuCount;

 static const int cpufeatures_debug = 0;

 #ifdef __arm__
 #  define DEFAULT_CPU_FAMILY  CPU_FAMILY_ARM
 #elif defined __i386__
 #  define DEFAULT_CPU_FAMILY  CPU_FAMILY_X86
 #else
 #  define DEFAULT_CPU_FAMILY  CPU_FAMILY_UNKNOWN
 #endif

 #define  D(...) \
   do { \
     if (cpufeatures_debug) { \
       printf(__VA_ARGS__); fflush(stdout); \
     } \
   } while (0)

 /* Read the content of /proc/cpuinfo into a user-provided buffer.
  * Return the length of the data, or -1 on error. Does *not*
  * zero-terminate the content. Will not read more
  * than 'buffsize' bytes.
  */
 static int read_file(const char*  pathname, char*  buffer, size_t  buffsize) {
   int  fd, len;

   fd = open(pathname, O_RDONLY);
   if (fd < 0)
     return -1;

   do {
     len = read(fd, buffer, buffsize);
   } while (len < 0 && errno == EINTR);

   close(fd);

   return len;
 }

 /* Extract the content of a the first occurence of a given field in
  * the content of /proc/cpuinfo and return it as a heap-allocated
  * string that must be freed by the caller.
  *
  * Return NULL if not found
  */
 static char* extract_cpuinfo_field(char* buffer, int buflen, const char* field) {
   int  fieldlen = strlen(field);
   char* bufend = buffer + buflen;
   char* result = NULL;
   int len, ignore;
   const char* p, *q;

   /* Look for first field occurence, and ensures it starts the line.
    */
   p = buffer;
   bufend = buffer + buflen;
   for (;;) {
     p = memmem(p, bufend - p, field, fieldlen);
     if (p == NULL)
       goto EXIT;

     if (p == buffer || p[-1] == '\n')
       break;

     p += fieldlen;
   }

   /* Skip to the first column followed by a space */
   p += fieldlen;
   p  = memchr(p, ':', bufend - p);
   if (p == NULL || p[1] != ' ')
     goto EXIT;

   /* Find the end of the line */
   p += 2;
   q = memchr(p, '\n', bufend - p);
   if (q == NULL)
     q = bufend;

   /* Copy the line into a heap-allocated buffer */
   len = q - p;
   result = malloc(len + 1);
   if (result == NULL)
     goto EXIT;

   memcpy(result, p, len);
   result[len] = '\0';

 EXIT:
   return result;
 }

 /* Count the number of occurences of a given field prefix in /proc/cpuinfo.
  */
 static int count_cpuinfo_field(char* buffer, int buflen, const char* field) {
   int fieldlen = strlen(field);
   const char* p = buffer;
   const char* bufend = buffer + buflen;
   const char* q;
   int count = 0;

   for (;;) {
     const char* q;

     p = memmem(p, bufend - p, field, fieldlen);
     if (p == NULL)
       break;

     /* Ensure that the field is at the start of a line */
     if (p > buffer && p[-1] != '\n') {
       p += fieldlen;
       continue;
     }


     /* skip any whitespace */
     q = p + fieldlen;
     while (q < bufend && (*q == ' ' || *q == '\t'))
       q++;

     /* we must have a colon now */
     if (q < bufend && *q == ':') {
       count += 1;
       q ++;
     }
     p = q;
   }

   return count;
 }

 /* Like strlen(), but for constant string literals */
 #define STRLEN_CONST(x)  ((sizeof(x)-1)


 /* Checks that a space-separated list of items contains one given 'item'.
  * Returns 1 if found, 0 otherwise.
  */
 static int has_list_item(const char* list, const char* item) {
   const char*  p = list;
   int itemlen = strlen(item);

   if (list == NULL)
     return 0;

   while (*p) {
     const char*  q;

     /* skip spaces */
     while (*p == ' ' || *p == '\t')
       p++;

     /* find end of current list item */
     q = p;
     while (*q && *q != ' ' && *q != '\t')
       q++;

     if (itemlen == q - p && !memcmp(p, item, itemlen))
       return 1;

     /* skip to next item */
     p = q;
   }
   return 0;
 }


 static void cpuInit(void) {
   char cpuinfo[4096];
   int  cpuinfo_len;

   g_cpuFamily   = DEFAULT_CPU_FAMILY;
   g_cpuFeatures = 0;
   g_cpuCount    = 1;

   cpuinfo_len = read_file("/proc/cpuinfo", cpuinfo, sizeof cpuinfo);
   D("cpuinfo_len is (%d):\n%.*s\n", cpuinfo_len,
     cpuinfo_len >= 0 ? cpuinfo_len : 0, cpuinfo);

   if (cpuinfo_len < 0) { /* should not happen */
     return;
   }

   /* Count the CPU cores, the value may be 0 for single-core CPUs */
   g_cpuCount = count_cpuinfo_field(cpuinfo, cpuinfo_len, "processor");
   if (g_cpuCount == 0) {
     g_cpuCount = count_cpuinfo_field(cpuinfo, cpuinfo_len, "Processor");
     if (g_cpuCount == 0) {
       g_cpuCount = 1;
     }
   }

   D("found cpuCount = %d\n", g_cpuCount);

 #ifdef __arm__
   {
     char*  features = NULL;
     char*  architecture = NULL;

     /* Extract architecture from the "CPU Architecture" field.
      * The list is well-known, unlike the the output of
      * the 'Processor' field which can vary greatly.
      *
      * See the definition of the 'proc_arch' array in
      * $KERNEL/arch/arm/kernel/setup.c and the 'c_show' function in
      * same file.
      */
     char* cpuArch = extract_cpuinfo_field(cpuinfo, cpuinfo_len,
                                           "CPU architecture");

     if (cpuArch != NULL) {
       char*  end;
       long   archNumber;
       int    hasARMv7 = 0;

       D("found cpuArch = '%s'\n", cpuArch);

       /* read the initial decimal number, ignore the rest */
       archNumber = strtol(cpuArch, &end, 10);

       /* Here we assume that ARMv8 will be upwards compatible with v7
           * in the future. Unfortunately, there is no 'Features' field to
           * indicate that Thumb-2 is supported.
           */
       if (end > cpuArch && archNumber >= 7) {
         hasARMv7 = 1;
       }

       /* Unfortunately, it seems that certain ARMv6-based CPUs
        * report an incorrect architecture number of 7!
        *
        * We try to correct this by looking at the 'elf_format'
        * field reported by the 'Processor' field, which is of the
        * form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
        * an ARMv6-one.
        */
       if (hasARMv7) {
         char* cpuProc = extract_cpuinfo_field(cpuinfo, cpuinfo_len,
                                               "Processor");
         if (cpuProc != NULL) {
           D("found cpuProc = '%s'\n", cpuProc);
           if (has_list_item(cpuProc, "(v6l)")) {
             D("CPU processor and architecture mismatch!!\n");
             hasARMv7 = 0;
           }
           free(cpuProc);
         }
       }

       if (hasARMv7) {
         g_cpuFeatures |= kCPUFeatureARMv7;
       }

       /* The LDREX / STREX instructions are available from ARMv6 */
       if (archNumber >= 6) {
         g_cpuFeatures |= kCPUFeatureLDREXSTREX;
       }

       free(cpuArch);
     }

     /* Extract the list of CPU features from 'Features' field */
     char* cpuFeatures = extract_cpuinfo_field(cpuinfo, cpuinfo_len,
                                               "Features");

     if (cpuFeatures != NULL) {

       D("found cpuFeatures = '%s'\n", cpuFeatures);

       if (has_list_item(cpuFeatures, "vfpv3"))
         g_cpuFeatures |= kCPUFeatureVFPv3;

       else if (has_list_item(cpuFeatures, "vfpv3d16"))
         g_cpuFeatures |= kCPUFeatureVFPv3;

       if (has_list_item(cpuFeatures, "neon")) {
         /* Note: Certain kernels only report neon but not vfpv3
             *       in their features list. However, ARM mandates
             *       that if Neon is implemented, so must be VFPv3
             *       so always set the flag.
             */
         g_cpuFeatures |= kCPUFeatureNEON |
                          kCPUFeatureVFPv3;
       }
       free(cpuFeatures);
     }
   }
 #endif  // __arm__

 #ifdef __i386__
   g_cpuFamily = CPU_FAMILY_X86;
 #endif
 }


 uint64_t WebRtc_GetCPUFeaturesARM(void) {
   pthread_once(&g_once, cpuInit);
   return g_cpuFeatures;
 }
	/*
	* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	// This file is derived from Android's NDK package r7, located at
	// <ndk>/sources/android/cpufeatures/ (downloadable from
	// http://developer.android.com/sdk/ndk/index.html).

	#include "cpu_features_wrapper.h"

	#include <fcntl.h>
	#include <errno.h>
	#include <pthread.h>
	#include <stdio.h>
	#include <stdlib.h>

	// Define CPU family.
	typedef enum {
	CPU_FAMILY_UNKNOWN = 0,
	CPU_FAMILY_ARM,
	CPU_FAMILY_X86,
	CPU_FAMILY_MAX // Do not remove.
	} CpuFamily;

	static pthread_once_t g_once;
	static CpuFamily g_cpuFamily;
	static uint64_t g_cpuFeatures;
	static int g_cpuCount;

	static const int cpufeatures_debug = 0;

	#ifdef __arm__
	# define DEFAULT_CPU_FAMILY CPU_FAMILY_ARM
	#elif defined __i386__
	# define DEFAULT_CPU_FAMILY CPU_FAMILY_X86
	#else
	# define DEFAULT_CPU_FAMILY CPU_FAMILY_UNKNOWN
	#endif

	#define D(...) \
	do { \
	if (cpufeatures_debug) { \
	printf(__VA_ARGS__); fflush(stdout); \
	} \
	} while (0)

	/* Read the content of /proc/cpuinfo into a user-provided buffer.
	* Return the length of the data, or -1 on error. Does not
	* zero-terminate the content. Will not read more
	* than 'buffsize' bytes.
	*/
	static int read_file(const char* pathname, char* buffer, size_t buffsize) {
	int fd, len;

	fd = open(pathname, O_RDONLY);
	if (fd < 0)
	return -1;

	do {
	len = read(fd, buffer, buffsize);
	} while (len < 0 && errno == EINTR);

	close(fd);

	return len;
	}

	/* Extract the content of a the first occurence of a given field in
	* the content of /proc/cpuinfo and return it as a heap-allocated
	* string that must be freed by the caller.
	*
	* Return NULL if not found
	*/
	static char* extract_cpuinfo_field(char* buffer, int buflen, const char* field) {
	int fieldlen = strlen(field);
	char* bufend = buffer + buflen;
	char* result = NULL;
	int len, ignore;
	const char* p, *q;

	/* Look for first field occurence, and ensures it starts the line.
	*/
	p = buffer;
	bufend = buffer + buflen;
	for (;;) {
	p = memmem(p, bufend - p, field, fieldlen);
	if (p == NULL)
	goto EXIT;

	if (p == buffer \|\| p[-1] == '\n')
	break;

	p += fieldlen;
	}

	/* Skip to the first column followed by a space */
	p += fieldlen;
	p = memchr(p, ':', bufend - p);
	if (p == NULL \|\| p[1] != ' ')
	goto EXIT;

	/* Find the end of the line */
	p += 2;
	q = memchr(p, '\n', bufend - p);
	if (q == NULL)
	q = bufend;

	/* Copy the line into a heap-allocated buffer */
	len = q - p;
	result = malloc(len + 1);
	if (result == NULL)
	goto EXIT;

	memcpy(result, p, len);
	result[len] = '\0';

	EXIT:
	return result;
	}

	/* Count the number of occurences of a given field prefix in /proc/cpuinfo.
	*/
	static int count_cpuinfo_field(char* buffer, int buflen, const char* field) {
	int fieldlen = strlen(field);
	const char* p = buffer;
	const char* bufend = buffer + buflen;
	const char* q;
	int count = 0;

	for (;;) {
	const char* q;

	p = memmem(p, bufend - p, field, fieldlen);
	if (p == NULL)
	break;

	/* Ensure that the field is at the start of a line */
	if (p > buffer && p[-1] != '\n') {
	p += fieldlen;
	continue;
	}


	/* skip any whitespace */
	q = p + fieldlen;
	while (q < bufend && (q == ' ' \|\| q == '\t'))
	q++;

	/* we must have a colon now */
	if (q < bufend && *q == ':') {
	count += 1;
	q ++;
	}
	p = q;
	}

	return count;
	}

	/* Like strlen(), but for constant string literals */
	#define STRLEN_CONST(x) ((sizeof(x)-1)


	/* Checks that a space-separated list of items contains one given 'item'.
	* Returns 1 if found, 0 otherwise.
	*/
	static int has_list_item(const char* list, const char* item) {
	const char* p = list;
	int itemlen = strlen(item);

	if (list == NULL)
	return 0;

	while (*p) {
	const char* q;

	/* skip spaces */
	while (p == ' ' \|\| p == '\t')
	p++;

	/* find end of current list item */
	q = p;
	while (q && q != ' ' && *q != '\t')
	q++;

	if (itemlen == q - p && !memcmp(p, item, itemlen))
	return 1;

	/* skip to next item */
	p = q;
	}
	return 0;
	}


	static void cpuInit(void) {
	char cpuinfo[4096];
	int cpuinfo_len;

	g_cpuFamily = DEFAULT_CPU_FAMILY;
	g_cpuFeatures = 0;
	g_cpuCount = 1;

	cpuinfo_len = read_file("/proc/cpuinfo", cpuinfo, sizeof cpuinfo);
	D("cpuinfo_len is (%d):\n%.*s\n", cpuinfo_len,
	cpuinfo_len >= 0 ? cpuinfo_len : 0, cpuinfo);

	if (cpuinfo_len < 0) { /* should not happen */
	return;
	}

	/* Count the CPU cores, the value may be 0 for single-core CPUs */
	g_cpuCount = count_cpuinfo_field(cpuinfo, cpuinfo_len, "processor");
	if (g_cpuCount == 0) {
	g_cpuCount = count_cpuinfo_field(cpuinfo, cpuinfo_len, "Processor");
	if (g_cpuCount == 0) {
	g_cpuCount = 1;
	}
	}

	D("found cpuCount = %d\n", g_cpuCount);

	#ifdef __arm__
	{
	char* features = NULL;
	char* architecture = NULL;

	/* Extract architecture from the "CPU Architecture" field.
	* The list is well-known, unlike the the output of
	* the 'Processor' field which can vary greatly.
	*
	* See the definition of the 'proc_arch' array in
	* $KERNEL/arch/arm/kernel/setup.c and the 'c_show' function in
	* same file.
	*/
	char* cpuArch = extract_cpuinfo_field(cpuinfo, cpuinfo_len,
	"CPU architecture");

	if (cpuArch != NULL) {
	char* end;
	long archNumber;
	int hasARMv7 = 0;

	D("found cpuArch = '%s'\n", cpuArch);

	/* read the initial decimal number, ignore the rest */
	archNumber = strtol(cpuArch, &end, 10);

	/* Here we assume that ARMv8 will be upwards compatible with v7
	* in the future. Unfortunately, there is no 'Features' field to
	* indicate that Thumb-2 is supported.
	*/
	if (end > cpuArch && archNumber >= 7) {
	hasARMv7 = 1;
	}

	/* Unfortunately, it seems that certain ARMv6-based CPUs
	* report an incorrect architecture number of 7!
	*
	* We try to correct this by looking at the 'elf_format'
	* field reported by the 'Processor' field, which is of the
	* form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
	* an ARMv6-one.
	*/
	if (hasARMv7) {
	char* cpuProc = extract_cpuinfo_field(cpuinfo, cpuinfo_len,
	"Processor");
	if (cpuProc != NULL) {
	D("found cpuProc = '%s'\n", cpuProc);
	if (has_list_item(cpuProc, "(v6l)")) {
	D("CPU processor and architecture mismatch!!\n");
	hasARMv7 = 0;
	}
	free(cpuProc);
	}
	}

	if (hasARMv7) {
	g_cpuFeatures \|= kCPUFeatureARMv7;
	}

	/* The LDREX / STREX instructions are available from ARMv6 */
	if (archNumber >= 6) {
	g_cpuFeatures \|= kCPUFeatureLDREXSTREX;
	}

	free(cpuArch);
	}

	/* Extract the list of CPU features from 'Features' field */
	char* cpuFeatures = extract_cpuinfo_field(cpuinfo, cpuinfo_len,
	"Features");

	if (cpuFeatures != NULL) {

	D("found cpuFeatures = '%s'\n", cpuFeatures);

	if (has_list_item(cpuFeatures, "vfpv3"))
	g_cpuFeatures \|= kCPUFeatureVFPv3;

	else if (has_list_item(cpuFeatures, "vfpv3d16"))
	g_cpuFeatures \|= kCPUFeatureVFPv3;

	if (has_list_item(cpuFeatures, "neon")) {
	/* Note: Certain kernels only report neon but not vfpv3
	* in their features list. However, ARM mandates
	* that if Neon is implemented, so must be VFPv3
	* so always set the flag.
	*/
	g_cpuFeatures \|= kCPUFeatureNEON \|
	kCPUFeatureVFPv3;
	}
	free(cpuFeatures);
	}
	}
	#endif // __arm__

	#ifdef __i386__
	g_cpuFamily = CPU_FAMILY_X86;
	#endif
	}


	uint64_t WebRtc_GetCPUFeaturesARM(void) {
	pthread_once(&g_once, cpuInit);
	return g_cpuFeatures;
	}