1// Copyright (c) 2013, Google Inc.
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29
30#ifndef CLIENT_LINUX_MINIDUMP_WRITER_CPU_SET_H_
31#define CLIENT_LINUX_MINIDUMP_WRITER_CPU_SET_H_
32
33#include <stdint.h>
34#include <assert.h>
35#include <string.h>
36
37#include "common/linux/linux_libc_support.h"
38#include "third_party/lss/linux_syscall_support.h"
39
40namespace google_breakpad {
41
42// Helper class used to model a set of CPUs, as read from sysfs
43// files like /sys/devices/system/cpu/present
44// See See http://www.kernel.org/doc/Documentation/cputopology.txt
45class CpuSet {
46public:
47  // The maximum number of supported CPUs.
48  static const size_t kMaxCpus = 1024;
49
50  CpuSet() {
51    my_memset(mask_, 0, sizeof(mask_));
52  }
53
54  // Parse a sysfs file to extract the corresponding CPU set.
55  bool ParseSysFile(int fd) {
56    char buffer[512];
57    int ret = sys_read(fd, buffer, sizeof(buffer)-1);
58    if (ret < 0)
59      return false;
60
61    buffer[ret] = '\0';
62
63    // Expected format: comma-separated list of items, where each
64    // item can be a decimal integer, or two decimal integers separated
65    // by a dash.
66    // E.g.:
67    //       0
68    //       0,1,2,3
69    //       0-3
70    //       1,10-23
71    const char* p = buffer;
72    const char* p_end = p + ret;
73    while (p < p_end) {
74      // Skip leading space, if any
75      while (p < p_end && my_isspace(*p))
76        p++;
77
78      // Find start and size of current item.
79      const char* item = p;
80      size_t item_len = static_cast<size_t>(p_end - p);
81      const char* item_next =
82          static_cast<const char*>(my_memchr(p, ',', item_len));
83      if (item_next != NULL) {
84        p = item_next + 1;
85        item_len = static_cast<size_t>(item_next - item);
86      } else {
87        p = p_end;
88        item_next = p_end;
89      }
90
91      // Ignore trailing spaces.
92      while (item_next > item && my_isspace(item_next[-1]))
93        item_next--;
94
95      // skip empty items.
96      if (item_next == item)
97        continue;
98
99      // read first decimal value.
100      uintptr_t start = 0;
101      const char* next = my_read_decimal_ptr(&start, item);
102      uintptr_t end = start;
103      if (*next == '-')
104        my_read_decimal_ptr(&end, next+1);
105
106      while (start <= end)
107        SetBit(start++);
108    }
109    return true;
110  }
111
112  // Intersect this CPU set with another one.
113  void IntersectWith(const CpuSet& other) {
114    for (size_t nn = 0; nn < kMaskWordCount; ++nn)
115      mask_[nn] &= other.mask_[nn];
116  }
117
118  // Return the number of CPUs in this set.
119  int GetCount() {
120    int result = 0;
121    for (size_t nn = 0; nn < kMaskWordCount; ++nn) {
122      result += __builtin_popcount(mask_[nn]);
123    }
124    return result;
125  }
126
127private:
128  void SetBit(uintptr_t index) {
129    size_t nn = static_cast<size_t>(index);
130    if (nn < kMaxCpus)
131      mask_[nn / kMaskWordBits] |= (1U << (nn % kMaskWordBits));
132  }
133
134  typedef uint32_t MaskWordType;
135  static const size_t kMaskWordBits = 8*sizeof(MaskWordType);
136  static const size_t kMaskWordCount =
137      (kMaxCpus + kMaskWordBits - 1) / kMaskWordBits;
138
139  MaskWordType mask_[kMaskWordCount];
140};
141
142}  // namespace google_breakpad
143
144#endif  // CLIENT_LINUX_MINIDUMP_WRITER_CPU_SET_H_
145