1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // The following is the C version of code from base/process_utils_linux.cc. 6 // We shouldn't link against C++ code in a setuid binary. 7 8 #define _GNU_SOURCE // needed for O_DIRECTORY 9 10 #include "process_util.h" 11 12 #include <fcntl.h> 13 #include <inttypes.h> 14 #include <limits.h> 15 #include <stdio.h> 16 #include <stdlib.h> 17 #include <string.h> 18 #include <sys/stat.h> 19 #include <sys/types.h> 20 #include <unistd.h> 21 22 // Ranges for the current (oom_score_adj) and previous (oom_adj) 23 // flavors of OOM score. 24 static const int kMaxOomScore = 1000; 25 static const int kMaxOldOomScore = 15; 26 27 // NOTE: This is not the only version of this function in the source: 28 // the base library (in process_util_linux.cc) also has its own C++ version. 29 bool AdjustOOMScore(pid_t process, int score) { 30 if (score < 0 || score > kMaxOomScore) 31 return false; 32 33 char oom_adj[27]; // "/proc/" + log_10(2**64) + "\0" 34 // 6 + 20 + 1 = 27 35 snprintf(oom_adj, sizeof(oom_adj), "/proc/%" PRIdMAX, (intmax_t)process); 36 37 const int dirfd = open(oom_adj, O_RDONLY | O_DIRECTORY); 38 if (dirfd < 0) 39 return false; 40 41 struct stat statbuf; 42 if (fstat(dirfd, &statbuf) < 0) { 43 close(dirfd); 44 return false; 45 } 46 if (getuid() != statbuf.st_uid) { 47 close(dirfd); 48 return false; 49 } 50 51 int fd = openat(dirfd, "oom_score_adj", O_WRONLY); 52 if (fd < 0) { 53 // We failed to open oom_score_adj, so let's try for the older 54 // oom_adj file instead. 55 fd = openat(dirfd, "oom_adj", O_WRONLY); 56 if (fd < 0) { 57 // Nope, that doesn't work either. 58 return false; 59 } else { 60 // If we're using the old oom_adj file, the allowed range is now 61 // [0, kMaxOldOomScore], so we scale the score. This may result in some 62 // aliasing of values, of course. 63 score = score * kMaxOldOomScore / kMaxOomScore; 64 } 65 } 66 close(dirfd); 67 68 char buf[11]; // 0 <= |score| <= kMaxOomScore; using log_10(2**32) + 1 size 69 snprintf(buf, sizeof(buf), "%d", score); 70 size_t len = strlen(buf); 71 72 ssize_t bytes_written = write(fd, buf, len); 73 close(fd); 74 return (bytes_written == len); 75 } 76
