GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: large_pages/node_large_page.cc Lines: 86 115 74.8 %
Date: 2022-05-08 04:15:02 Branches: 28 64 43.8 %

Line Branch Exec Source
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// Copyright (C) 2018 Intel Corporation
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"),
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// to deal in the Software without restriction, including without limitation
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom
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// the Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included
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// in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
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// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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// OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
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// OR OTHER DEALINGS IN THE SOFTWARE.
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//
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// SPDX-License-Identifier: MIT
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23
// The functions in this file map the .text section of Node.js into 2MB pages.
24
// They perform the following steps:
25
//
26
// 1: Find the Node.js binary's `.text` section in memory. This is done below in
27
//    `FindNodeTextRegion`. It is accomplished in a platform-specific way. On
28
//    Linux and FreeBSD, `dl_iterate_phdr(3)` is used. When the region is found,
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//    it is "trimmed" as follows:
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//    * Modify the start to point to the very beginning of the Node.js `.text`
31
//      section (from symbol `__node_text_start` declared in node_text_start.S).
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//    * Possibly modify the end to account for the `lpstub` section which
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//      contains `MoveTextRegionToLargePages`, the function we do not wish to
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//      move (see below).
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//    * Align the address of the start to its nearest higher large page
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//      boundary.
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//    * Align the address of the end to its nearest lower large page boundary.
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//
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// 2: Move the text region to large pages. This is done below in
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//    `MoveTextRegionToLargePages`. We need to be very careful:
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//    a) `MoveTextRegionToLargePages` itself should not be moved.
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//       We use gcc attributes
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//       (__section__) to put it outside the `.text` section,
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//       (__aligned__) to align it at the 2M boundary, and
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//       (__noline__) to not inline this function.
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//    b) `MoveTextRegionToLargePages` should not call any function(s) that might
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//       be moved.
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//    To move the .text section, perform the following steps:
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//      * Map a new, temporary area and copy the original code there.
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//      * Use mmap using the start address with MAP_FIXED so we get exactly the
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//        same virtual address (except on OSX). On platforms other than Linux,
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//        use mmap flags to request hugepages.
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//      * On Linux use madvise with MADV_HUGEPAGE to use anonymous 2MB pages.
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//      * If successful copy the code to the newly mapped area and protect it to
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//        be readable and executable.
56
//      * Unmap the temporary area.
57
58
#include "node_large_page.h"
59
60
#include <cerrno>   // NOLINT(build/include)
61
62
// Besides returning ENOTSUP at runtime we do nothing if this define is missing.
63
#if defined(NODE_ENABLE_LARGE_CODE_PAGES) && NODE_ENABLE_LARGE_CODE_PAGES
64
#include "debug_utils-inl.h"
65
66
#if defined(__linux__) || defined(__FreeBSD__)
67
#if defined(__linux__)
68
#ifndef _GNU_SOURCE
69
#define _GNU_SOURCE
70
#endif  // ifndef _GNU_SOURCE
71
#include <sys/prctl.h>
72
#if !defined(PR_SET_VMA)
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#define PR_SET_VMA 0x53564d41
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#define PR_SET_VMA_ANON_NAME 0
75
#endif
76
#elif defined(__FreeBSD__)
77
#include "uv.h"  // uv_exepath
78
#endif  // defined(__linux__)
79
#include <link.h>
80
#endif  // defined(__linux__) || defined(__FreeBSD__)
81
82
#include <sys/types.h>
83
#include <sys/mman.h>
84
#if defined(__FreeBSD__)
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#include <sys/sysctl.h>
86
#elif defined(__APPLE__)
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#include <mach/vm_map.h>
88
#endif
89
90
#include <climits>  // PATH_MAX
91
#include <cstdlib>
92
#include <cstdint>
93
#include <cstring>
94
#include <string>
95
#include <fstream>
96
97
#if defined(__linux__) || defined(__FreeBSD__)
98
extern "C" {
99
// This symbol must be declared weak because this file becomes part of all
100
// Node.js targets (like node_mksnapshot, node_mkcodecache, and cctest) and
101
// those files do not supply the symbol.
102
extern char __attribute__((weak)) __node_text_start;
103
extern char __start_lpstub;
104
}  // extern "C"
105
#endif  // defined(__linux__) || defined(__FreeBSD__)
106
107
#endif  // defined(NODE_ENABLE_LARGE_CODE_PAGES) && NODE_ENABLE_LARGE_CODE_PAGES
108
namespace node {
109
#if defined(NODE_ENABLE_LARGE_CODE_PAGES) && NODE_ENABLE_LARGE_CODE_PAGES
110
111
namespace {
112
113
struct text_region {
114
  char* from = nullptr;
115
  char* to = nullptr;
116
  bool found_text_region = false;
117
};
118
119
static const size_t hps = 2L * 1024 * 1024;
120
121
template <typename... Args>
122
8
inline void Debug(std::string fmt, Args&&... args) {
123
16
  node::Debug(&per_process::enabled_debug_list,
124
              DebugCategory::HUGEPAGES,
125
              (std::string("Hugepages info: ") + fmt).c_str(),
126
              std::forward<Args>(args)...);
127
8
}
128
129
inline void PrintWarning(const char* warn) {
130
  fprintf(stderr, "Hugepages WARNING: %s\n", warn);
131
}
132
133
inline void PrintSystemError(int error) {
134
  PrintWarning(strerror(error));
135
}
136
137
1
inline uintptr_t hugepage_align_up(uintptr_t addr) {
138
1
  return (((addr) + (hps) - 1) & ~((hps) - 1));
139
}
140
141
1
inline uintptr_t hugepage_align_down(uintptr_t addr) {
142
1
  return ((addr) & ~((hps) - 1));
143
}
144
145
#if defined(__linux__) || defined(__FreeBSD__)
146
#if defined(__FreeBSD__)
147
#ifndef ElfW
148
#define ElfW(name) Elf_##name
149
#endif  // ifndef ElfW
150
#endif  // defined(__FreeBSD__)
151
152
struct dl_iterate_params {
153
  uintptr_t start = 0;
154
  uintptr_t end = 0;
155
  uintptr_t reference_sym = reinterpret_cast<uintptr_t>(&__node_text_start);
156
  std::string exename;
157
};
158
159
1
int FindMapping(struct dl_phdr_info* info, size_t, void* data) {
160
1
  auto dl_params = static_cast<dl_iterate_params*>(data);
161
1
  if (dl_params->exename == std::string(info->dlpi_name)) {
162
3
    for (int idx = 0; idx < info->dlpi_phnum; idx++) {
163
3
      const ElfW(Phdr)* phdr = &info->dlpi_phdr[idx];
164

3
      if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X)) {
165
1
        uintptr_t start = info->dlpi_addr + phdr->p_vaddr;
166
1
        uintptr_t end = start + phdr->p_memsz;
167
168
1
        if (dl_params->reference_sym >= start &&
169
1
            dl_params->reference_sym <= end) {
170
1
          dl_params->start = start;
171
1
          dl_params->end = end;
172
1
          return 1;
173
        }
174
      }
175
    }
176
  }
177
  return 0;
178
}
179
#endif  // defined(__linux__) || defined(__FreeBSD__)
180
181
1
struct text_region FindNodeTextRegion() {
182
1
  struct text_region nregion;
183
#if defined(__linux__) || defined(__FreeBSD__)
184
2
  dl_iterate_params dl_params;
185
1
  uintptr_t lpstub_start = reinterpret_cast<uintptr_t>(&__start_lpstub);
186
187
#if defined(__FreeBSD__)
188
  // On FreeBSD we need the name of the binary, because `dl_iterate_phdr` does
189
  // not pass in an empty string as the `dlpi_name` of the binary but rather its
190
  // absolute path.
191
  {
192
    char selfexe[PATH_MAX];
193
    size_t count = sizeof(selfexe);
194
    if (uv_exepath(selfexe, &count))
195
      return nregion;
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    dl_params.exename = std::string(selfexe, count);
197
  }
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#endif  // defined(__FreeBSD__)
199
200
1
  if (dl_iterate_phdr(FindMapping, &dl_params) == 1) {
201
1
    Debug("start: %p - sym: %p - end: %p\n",
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2
          reinterpret_cast<void*>(dl_params.start),
203
2
          reinterpret_cast<void*>(dl_params.reference_sym),
204
1
          reinterpret_cast<void*>(dl_params.end));
205
206
1
    dl_params.start = dl_params.reference_sym;
207

1
    if (lpstub_start > dl_params.start && lpstub_start <= dl_params.end) {
208
1
      Debug("Trimming end for lpstub: %p\n",
209
1
            reinterpret_cast<void*>(lpstub_start));
210
1
      dl_params.end = lpstub_start;
211
    }
212
213
1
    if (dl_params.start < dl_params.end) {
214
1
      char* from = reinterpret_cast<char*>(hugepage_align_up(dl_params.start));
215
1
      char* to = reinterpret_cast<char*>(hugepage_align_down(dl_params.end));
216
1
      Debug("Aligned range is %p - %p\n", from, to);
217
1
      if (from < to) {
218
1
        size_t pagecount = (to - from) / hps;
219
1
        if (pagecount > 0) {
220
1
          nregion.found_text_region = true;
221
1
          nregion.from = from;
222
1
          nregion.to = to;
223
        }
224
      }
225
    }
226
  }
227
#elif defined(__APPLE__)
228
  struct vm_region_submap_info_64 map;
229
  mach_msg_type_number_t count = VM_REGION_SUBMAP_INFO_COUNT_64;
230
  vm_address_t addr = 0UL;
231
  vm_size_t size = 0;
232
  natural_t depth = 1;
233
234
  while (true) {
235
    if (vm_region_recurse_64(mach_task_self(), &addr, &size, &depth,
236
                             reinterpret_cast<vm_region_info_64_t>(&map),
237
                             &count) != KERN_SUCCESS) {
238
      break;
239
    }
240
241
    if (map.is_submap) {
242
      depth++;
243
    } else {
244
      char* start = reinterpret_cast<char*>(hugepage_align_up(addr));
245
      char* end = reinterpret_cast<char*>(hugepage_align_down(addr+size));
246
247
      if (end > start && (map.protection & VM_PROT_READ) != 0 &&
248
          (map.protection & VM_PROT_EXECUTE) != 0) {
249
        nregion.found_text_region = true;
250
        nregion.from = start;
251
        nregion.to = end;
252
        break;
253
      }
254
255
      addr += size;
256
      size = 0;
257
    }
258
  }
259
#endif
260
1
  Debug("Found %d huge pages\n", (nregion.to - nregion.from) / hps);
261
1
  return nregion;
262
}
263
264
#if defined(__linux__)
265
1
bool IsTransparentHugePagesEnabled() {
266
  // File format reference:
267
  // https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/huge_memory.c?id=13391c60da3308ed9980de0168f74cce6c62ac1d#n163
268
1
  const char* filename = "/sys/kernel/mm/transparent_hugepage/enabled";
269
2
  std::ifstream config_stream(filename, std::ios::in);
270
1
  if (!config_stream.good()) {
271
    PrintWarning("could not open /sys/kernel/mm/transparent_hugepage/enabled");
272
    return false;
273
  }
274
275
2
  std::string token;
276
1
  config_stream >> token;
277
1
  if ("[always]" == token) return true;
278
1
  config_stream >> token;
279
1
  if ("[madvise]" == token) return true;
280
  return false;
281
}
282
#elif defined(__FreeBSD__)
283
bool IsSuperPagesEnabled() {
284
  // It is enabled by default on amd64.
285
  unsigned int super_pages = 0;
286
  size_t super_pages_length = sizeof(super_pages);
287
  return sysctlbyname("vm.pmap.pg_ps_enabled",
288
                      &super_pages,
289
                      &super_pages_length,
290
                      nullptr,
291
                      0) != -1 &&
292
         super_pages >= 1;
293
}
294
#endif
295
296
// Functions in this class must always be inlined because they must end up in
297
// the `lpstub` section rather than the `.text` section.
298
class MemoryMapPointer {
299
 public:
300
1
  FORCE_INLINE explicit MemoryMapPointer() {}
301
  FORCE_INLINE bool operator==(void* rhs) const { return mem_ == rhs; }
302
2
  FORCE_INLINE void* mem() const { return mem_; }
303
  MemoryMapPointer(const MemoryMapPointer&) = delete;
304
  MemoryMapPointer(MemoryMapPointer&&) = delete;
305
  void operator= (const MemoryMapPointer&) = delete;
306
  void operator= (const MemoryMapPointer&&) = delete;
307
  FORCE_INLINE void Reset(void* start,
308
                          size_t size,
309
                          int prot,
310
                          int flags,
311
                          int fd = -1,
312
                          size_t offset = 0) {
313
4
    mem_ = mmap(start, size, prot, flags, fd, offset);
314
2
    size_ = size;
315
  }
316
  FORCE_INLINE void Reset() {
317
1
    mem_ = nullptr;
318
1
    size_ = 0;
319
  }
320
1
  static void SetName(void* mem, size_t size, const char* name) {
321
#if defined(__linux__)
322
    // Available since the 5.17 kernel release and if the
323
    // CONFIG_ANON_VMA_NAME option, we can set an identifier
324
    // to an anonymous mapped region. However if the kernel
325
    // option is not present or it s an older kernel, it is a no-op.
326

1
    if (mem != MAP_FAILED && mem != nullptr)
327
1
        prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME,
328
            reinterpret_cast<uintptr_t>(mem),
329
            size,
330
            reinterpret_cast<uintptr_t>(name));
331
#else
332
    (void)name;
333
#endif
334
1
  }
335
  FORCE_INLINE ~MemoryMapPointer() {
336

2
    if (mem_ == nullptr) return;
337

1
    if (mem_ == MAP_FAILED) return;
338

1
    if (munmap(mem_, size_) == 0) return;
339
    PrintSystemError(errno);
340
  }
341
342
 private:
343
  size_t size_ = 0;
344
  void* mem_ = nullptr;
345
};
346
347
}  // End of anonymous namespace
348
349
int
350
#if !defined(__APPLE__)
351
__attribute__((__section__("lpstub")))
352
#else
353
__attribute__((__section__("__TEXT,__lpstub")))
354
#endif
355
__attribute__((__aligned__(hps)))
356
__attribute__((__noinline__))
357
1
MoveTextRegionToLargePages(const text_region& r) {
358
  MemoryMapPointer nmem;
359
  MemoryMapPointer tmem;
360
1
  void* start = r.from;
361
1
  size_t size = r.to - r.from;
362
363
  // Allocate a temporary region and back up the code we will re-map.
364
  nmem.Reset(nullptr, size,
365
             PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS);
366
1
  if (nmem.mem() == MAP_FAILED) goto fail;
367
1
  memcpy(nmem.mem(), r.from, size);
368
369
#if defined(__linux__)
370
// We already know the original page is r-xp
371
// (PROT_READ, PROT_EXEC, MAP_PRIVATE)
372
// We want PROT_WRITE because we are writing into it.
373
// We want it at the fixed address and we use MAP_FIXED.
374
  tmem.Reset(start, size,
375
             PROT_READ | PROT_WRITE | PROT_EXEC,
376
             MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED);
377
1
  if (tmem.mem() == MAP_FAILED) goto fail;
378
1
  if (madvise(tmem.mem(), size, 14 /* MADV_HUGEPAGE */) == -1) goto fail;
379
1
  memcpy(start, nmem.mem(), size);
380
#elif defined(__FreeBSD__)
381
  tmem.Reset(start, size,
382
             PROT_READ | PROT_WRITE | PROT_EXEC,
383
             MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED |
384
             MAP_ALIGNED_SUPER);
385
  if (tmem.mem() == MAP_FAILED) goto fail;
386
  memcpy(start, nmem.mem(), size);
387
#elif defined(__APPLE__)
388
  // There is not enough room to reserve the mapping close
389
  // to the region address so we content to give a hint
390
  // without forcing the new address being closed to.
391
  // We explicitally gives all permission since we plan
392
  // to write into it.
393
  tmem.Reset(start, size,
394
             PROT_READ | PROT_WRITE | PROT_EXEC,
395
             MAP_PRIVATE | MAP_ANONYMOUS,
396
             VM_FLAGS_SUPERPAGE_SIZE_2MB);
397
  if (tmem.mem() == MAP_FAILED) goto fail;
398
  memcpy(tmem.mem(), nmem.mem(), size);
399
  if (mprotect(start, size, PROT_READ | PROT_WRITE | PROT_EXEC) == -1)
400
    goto fail;
401
  memcpy(start, tmem.mem(), size);
402
#endif
403
404
1
  if (mprotect(start, size, PROT_READ | PROT_EXEC) == -1) goto fail;
405
1
  MemoryMapPointer::SetName(start, size, "nodejs Large Page");
406
407
  // We need not `munmap(tmem, size)` on success.
408
  tmem.Reset();
409
1
  return 0;
410
fail:
411
  PrintSystemError(errno);
412
  return -1;
413
}
414
#endif  // defined(NODE_ENABLE_LARGE_CODE_PAGES) && NODE_ENABLE_LARGE_CODE_PAGES
415
416
// This is the primary API called from main.
417
1
int MapStaticCodeToLargePages() {
418
#if defined(NODE_ENABLE_LARGE_CODE_PAGES) && NODE_ENABLE_LARGE_CODE_PAGES
419
1
  bool have_thp = false;
420
#if defined(__linux__)
421
1
  have_thp = IsTransparentHugePagesEnabled();
422
#elif defined(__FreeBSD__)
423
  have_thp = IsSuperPagesEnabled();
424
#elif defined(__APPLE__)
425
  // pse-36 flag is present in recent mac x64 products.
426
  have_thp = true;
427
#endif
428
1
  if (!have_thp)
429
    return EACCES;
430
431
1
  struct text_region r = FindNodeTextRegion();
432
1
  if (r.found_text_region == false)
433
    return ENOENT;
434
435
1
  return MoveTextRegionToLargePages(r);
436
#else
437
  return ENOTSUP;
438
#endif
439
}
440
441
const char* LargePagesError(int status) {
442
  switch (status) {
443
    case ENOTSUP:
444
      return "Mapping to large pages is not supported.";
445
446
    case EACCES:
447
      return "Large pages are not enabled.";
448
449
    case ENOENT:
450
      return "failed to find text region";
451
452
    case -1:
453
      return "Mapping code to large pages failed. Reverting to default page "
454
          "size.";
455
456
    case 0:
457
      return "OK";
458
459
    default:
460
      return "Unknown error";
461
  }
462
}
463
464
}  // namespace node