Refactors CPU feature detection.

runtime/vm/cpuinfo_linux.cc

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "vm/globals.h"
+#if defined(TARGET_OS_LINUX)
+
+#include "vm/cpuinfo.h"
+
+#include <ctype.h>  // NOLINT
+#include <string.h>  // NOLINT
+
+#include "platform/assert.h"
+
+namespace dart {
+
+char* CpuInfo::data_ = NULL;
+intptr_t CpuInfo::datalen_ = 0;
+
+void CpuInfo::InitOnce() {
+  InitializeFields();
+
+  // Get the size of the cpuinfo file by reading it until the end. This is
+  // required because files under /proc do not always return a valid size
+  // when using fseek(0, SEEK_END) + ftell(). Nor can they be mmap()-ed.
+  static const char PATHNAME[] = "/proc/cpuinfo";
+  FILE* fp = fopen(PATHNAME, "r");
+  if (fp != NULL) {
+    for (;;) {
+      char buffer[256];
+      size_t n = fread(buffer, 1, sizeof(buffer), fp);
+      if (n == 0) {
+        break;
+      }
+      datalen_ += n;
+    }
+    fclose(fp);
+  }
+
+  // Read the contents of the cpuinfo file.
+  data_ = new char[datalen_ + 1];
+  fp = fopen(PATHNAME, "r");

[siva, 2014/02/11 01:13:22]

We need to rethink this CL.

The renderer process in chrome is not going to allow reading of files like this.


The current assertion that we are hitting in Dartium with debug builds is
because the fields are not initialized and HasField returns false resulting in
the assertion
HasField(FieldName(kCpuInfoModel)) being triggered.

[zra, 2014/02/11 02:57:48]

We can revert ia32 and x64 to assemble and run the cpuinfo instruction, but the
analogous instruction is privileged on ARM and MIPS, so reading /proc/cpuinfo is
the only way on Linux and Android to find out what CPU we're running on. Is
there some other way to read files in Dartium?

On 2014/02/11 01:13:22, siva wrote:

+  if (fp != NULL) {
+    for (intptr_t offset = 0; offset < datalen_; ) {
+      size_t n = fread(data_ + offset, 1, datalen_ - offset, fp);
+      if (n == 0) {
+        break;
+      }
+      offset += n;
+    }
+    fclose(fp);
+  }
+
+  // Zero-terminate the data.
+  data_[datalen_] = '\0';
+}
+
+
+static char* FieldStart(char* data, const char* field) {
+  // Look for first field occurrence, and ensure it starts the line.
+  size_t fieldlen = strlen(field);
+  char* p = data;
+  for (;;) {
+    p = strstr(p, field);
+    if (p == NULL) {
+      return NULL;
+    }
+    if (p == data || p[-1] == '\n') {
+      break;
+    }
+    p += fieldlen;
+  }
+
+  // Skip to the first colon followed by a space.
+  p = strchr(p + fieldlen, ':');
+  if (p == NULL || !isspace(p[1])) {
+    return NULL;
+  }
+  p += 2;
+
+  return p;
+}
+
+
+bool CpuInfo::FieldContains(const char* field, const char* search_string) {
+  ASSERT(data_ != NULL);
+  ASSERT(search_string != NULL);
+
+  char *p = FieldStart(data_, field);
+  if (p == NULL) {
+    return false;
+  }
+
+  // Find the end of the line.
+  char* q = strchr(p, '\n');
+  if (q == NULL) {
+    q = data_ + datalen_;
+  }
+
+  char saved_end = *q;
+  *q = '\0';
+  bool ret = (strcasestr(p, search_string) != NULL);
+  *q = saved_end;
+
+  return ret;
+}
+
+
+// Extract the content of a the first occurrence of a given field in
+// the content of the cpuinfo file and return it as a heap-allocated
+// string that must be freed by the caller using delete[].
+// Return NULL if not found.
+char* CpuInfo::ExtractField(const char* field) {
+  ASSERT(field != NULL);
+  ASSERT(data_ != NULL);
+
+  char* p = FieldStart(data_, field);
+  if (p == NULL) {
+    return NULL;
+  }
+
+  // Find the end of the line.
+  char* q = strchr(p, '\n');
+  if (q == NULL) {
+    q = data_ + datalen_;
+  }
+
+  intptr_t len = q - p;
+  char *result = new char[len + 1];  // plus one for null-terminator.
+  // Copy the line into result, leaving enough room for a null-terminator.
+  char saved_end = *q;
+  *q = '\0';
+  strncpy(result, p, len);
+  result[len] = '\0';
+  *q = saved_end;
+
+  return result;
+}
+
+
+bool CpuInfo::HasField(const char* field) {
+  ASSERT(field != NULL);
+  ASSERT(data_ != NULL);
+  return (FieldStart(data_, field) != NULL);
+}
+
+
+const char* CpuInfo::fields_[kCpuInfoMax] = {0};
+void CpuInfo::InitializeFields() {
+#if defined(HOST_ARCH_IA32) || defined(HOST_ARCH_X64)
+  fields_[kCpuInfoProcessor] = "vendor_id";
+  fields_[kCpuInfoModel] = "model name";
+  fields_[kCpuInfoFeatures] = "flags";
+#elif defined(HOST_ARCH_ARM)
+  fields_[kCpuInfoProcessor] = "Processor";
+  fields_[kCpuInfoModel] = "Hardware";
+  fields_[kCpuInfoFeatures] = "Features";
+#elif defined(HOST_ARCH_MIPS)
+  fields_[kCpuInfoProcessor] = "system type";
+  fields_[kCpuInfoModel] = "cpu model";
+  fields_[kCpuInfoFeatures] = "ASEs implemented";
+#else
+#error Unrecognized target architecture
+#endif
+}
+
+}  // namespace dart
+
+#endif  // defined(TARGET_OS_LINUX)