389 lines
10 KiB
C
389 lines
10 KiB
C
/*
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* Copyright (c) 2022 Alexey Dobriyan <adobriyan@gmail.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* Create a process without mappings by unmapping everything at once and
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* holding it with ptrace(2). See what happens to
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*
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* /proc/${pid}/maps
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* /proc/${pid}/numa_maps
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* /proc/${pid}/smaps
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* /proc/${pid}/smaps_rollup
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*/
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#undef NDEBUG
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#include <assert.h>
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#include <errno.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <sys/ptrace.h>
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#include <sys/resource.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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/*
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* 0: vsyscall VMA doesn't exist vsyscall=none
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* 1: vsyscall VMA is --xp vsyscall=xonly
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* 2: vsyscall VMA is r-xp vsyscall=emulate
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*/
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static volatile int g_vsyscall;
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static const char *g_proc_pid_maps_vsyscall;
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static const char *g_proc_pid_smaps_vsyscall;
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static const char proc_pid_maps_vsyscall_0[] = "";
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static const char proc_pid_maps_vsyscall_1[] =
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"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n";
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static const char proc_pid_maps_vsyscall_2[] =
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"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n";
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static const char proc_pid_smaps_vsyscall_0[] = "";
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static const char proc_pid_smaps_vsyscall_1[] =
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"ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]\n"
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"Size: 4 kB\n"
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"KernelPageSize: 4 kB\n"
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"MMUPageSize: 4 kB\n"
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"Rss: 0 kB\n"
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"Pss: 0 kB\n"
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"Pss_Dirty: 0 kB\n"
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"Shared_Clean: 0 kB\n"
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"Shared_Dirty: 0 kB\n"
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"Private_Clean: 0 kB\n"
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"Private_Dirty: 0 kB\n"
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"Referenced: 0 kB\n"
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"Anonymous: 0 kB\n"
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"LazyFree: 0 kB\n"
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"AnonHugePages: 0 kB\n"
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"ShmemPmdMapped: 0 kB\n"
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"FilePmdMapped: 0 kB\n"
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"Shared_Hugetlb: 0 kB\n"
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"Private_Hugetlb: 0 kB\n"
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"Swap: 0 kB\n"
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"SwapPss: 0 kB\n"
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"Locked: 0 kB\n"
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"THPeligible: 0\n"
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/*
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* "ProtectionKey:" field is conditional. It is possible to check it as well,
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* but I don't have such machine.
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*/
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;
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static const char proc_pid_smaps_vsyscall_2[] =
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"ffffffffff600000-ffffffffff601000 --xp 00000000 00:00 0 [vsyscall]\n"
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"Size: 4 kB\n"
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"KernelPageSize: 4 kB\n"
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"MMUPageSize: 4 kB\n"
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"Rss: 0 kB\n"
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"Pss: 0 kB\n"
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"Pss_Dirty: 0 kB\n"
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"Shared_Clean: 0 kB\n"
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"Shared_Dirty: 0 kB\n"
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"Private_Clean: 0 kB\n"
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"Private_Dirty: 0 kB\n"
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"Referenced: 0 kB\n"
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"Anonymous: 0 kB\n"
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"LazyFree: 0 kB\n"
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"AnonHugePages: 0 kB\n"
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"ShmemPmdMapped: 0 kB\n"
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"FilePmdMapped: 0 kB\n"
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"Shared_Hugetlb: 0 kB\n"
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"Private_Hugetlb: 0 kB\n"
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"Swap: 0 kB\n"
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"SwapPss: 0 kB\n"
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"Locked: 0 kB\n"
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"THPeligible: 0\n"
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/*
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* "ProtectionKey:" field is conditional. It is possible to check it as well,
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* but I'm too tired.
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*/
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;
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static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)
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{
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_exit(EXIT_FAILURE);
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}
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static void sigaction_SIGSEGV_vsyscall(int _, siginfo_t *__, void *___)
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{
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_exit(g_vsyscall);
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}
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/*
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* vsyscall page can't be unmapped, probe it directly.
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*/
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static void vsyscall(void)
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{
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pid_t pid;
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int wstatus;
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pid = fork();
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if (pid < 0) {
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fprintf(stderr, "fork, errno %d\n", errno);
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exit(1);
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}
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if (pid == 0) {
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setrlimit(RLIMIT_CORE, &(struct rlimit){});
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/* Hide "segfault at ffffffffff600000" messages. */
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struct sigaction act = {};
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act.sa_flags = SA_SIGINFO;
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act.sa_sigaction = sigaction_SIGSEGV_vsyscall;
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sigaction(SIGSEGV, &act, NULL);
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g_vsyscall = 0;
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/* gettimeofday(NULL, NULL); */
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uint64_t rax = 0xffffffffff600000;
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asm volatile (
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"call *%[rax]"
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: [rax] "+a" (rax)
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: "D" (NULL), "S" (NULL)
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: "rcx", "r11"
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);
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g_vsyscall = 1;
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*(volatile int *)0xffffffffff600000UL;
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g_vsyscall = 2;
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exit(g_vsyscall);
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}
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waitpid(pid, &wstatus, 0);
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if (WIFEXITED(wstatus)) {
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g_vsyscall = WEXITSTATUS(wstatus);
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} else {
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fprintf(stderr, "error: vsyscall wstatus %08x\n", wstatus);
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exit(1);
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}
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}
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static int test_proc_pid_maps(pid_t pid)
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{
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char buf[4096];
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snprintf(buf, sizeof(buf), "/proc/%u/maps", pid);
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int fd = open(buf, O_RDONLY);
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if (fd == -1) {
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perror("open /proc/${pid}/maps");
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return EXIT_FAILURE;
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} else {
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ssize_t rv = read(fd, buf, sizeof(buf));
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close(fd);
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if (g_vsyscall == 0) {
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assert(rv == 0);
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} else {
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size_t len = strlen(g_proc_pid_maps_vsyscall);
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assert(rv == len);
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assert(memcmp(buf, g_proc_pid_maps_vsyscall, len) == 0);
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}
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return EXIT_SUCCESS;
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}
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}
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static int test_proc_pid_numa_maps(pid_t pid)
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{
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char buf[4096];
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snprintf(buf, sizeof(buf), "/proc/%u/numa_maps", pid);
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int fd = open(buf, O_RDONLY);
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if (fd == -1) {
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if (errno == ENOENT) {
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/*
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* /proc/${pid}/numa_maps is under CONFIG_NUMA,
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* it doesn't necessarily exist.
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*/
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return EXIT_SUCCESS;
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}
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perror("open /proc/${pid}/numa_maps");
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return EXIT_FAILURE;
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} else {
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ssize_t rv = read(fd, buf, sizeof(buf));
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close(fd);
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assert(rv == 0);
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return EXIT_SUCCESS;
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}
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}
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static int test_proc_pid_smaps(pid_t pid)
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{
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char buf[4096];
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snprintf(buf, sizeof(buf), "/proc/%u/smaps", pid);
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int fd = open(buf, O_RDONLY);
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if (fd == -1) {
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if (errno == ENOENT) {
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/*
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* /proc/${pid}/smaps is under CONFIG_PROC_PAGE_MONITOR,
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* it doesn't necessarily exist.
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*/
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return EXIT_SUCCESS;
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}
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perror("open /proc/${pid}/smaps");
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return EXIT_FAILURE;
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} else {
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ssize_t rv = read(fd, buf, sizeof(buf));
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close(fd);
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if (g_vsyscall == 0) {
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assert(rv == 0);
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} else {
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size_t len = strlen(g_proc_pid_maps_vsyscall);
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/* TODO "ProtectionKey:" */
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assert(rv > len);
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assert(memcmp(buf, g_proc_pid_maps_vsyscall, len) == 0);
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}
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return EXIT_SUCCESS;
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}
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}
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static const char g_smaps_rollup[] =
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"00000000-00000000 ---p 00000000 00:00 0 [rollup]\n"
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"Rss: 0 kB\n"
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"Pss: 0 kB\n"
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"Pss_Dirty: 0 kB\n"
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"Pss_Anon: 0 kB\n"
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"Pss_File: 0 kB\n"
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"Pss_Shmem: 0 kB\n"
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"Shared_Clean: 0 kB\n"
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"Shared_Dirty: 0 kB\n"
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"Private_Clean: 0 kB\n"
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"Private_Dirty: 0 kB\n"
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"Referenced: 0 kB\n"
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"Anonymous: 0 kB\n"
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"LazyFree: 0 kB\n"
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"AnonHugePages: 0 kB\n"
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"ShmemPmdMapped: 0 kB\n"
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"FilePmdMapped: 0 kB\n"
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"Shared_Hugetlb: 0 kB\n"
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"Private_Hugetlb: 0 kB\n"
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"Swap: 0 kB\n"
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"SwapPss: 0 kB\n"
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"Locked: 0 kB\n"
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;
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static int test_proc_pid_smaps_rollup(pid_t pid)
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{
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char buf[4096];
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snprintf(buf, sizeof(buf), "/proc/%u/smaps_rollup", pid);
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int fd = open(buf, O_RDONLY);
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if (fd == -1) {
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if (errno == ENOENT) {
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/*
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* /proc/${pid}/smaps_rollup is under CONFIG_PROC_PAGE_MONITOR,
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* it doesn't necessarily exist.
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*/
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return EXIT_SUCCESS;
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}
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perror("open /proc/${pid}/smaps_rollup");
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return EXIT_FAILURE;
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} else {
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ssize_t rv = read(fd, buf, sizeof(buf));
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close(fd);
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assert(rv == sizeof(g_smaps_rollup) - 1);
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assert(memcmp(buf, g_smaps_rollup, sizeof(g_smaps_rollup) - 1) == 0);
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return EXIT_SUCCESS;
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}
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}
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int main(void)
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{
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int rv = EXIT_SUCCESS;
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vsyscall();
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switch (g_vsyscall) {
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case 0:
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g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_0;
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g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_0;
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break;
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case 1:
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g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_1;
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g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_1;
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break;
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case 2:
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g_proc_pid_maps_vsyscall = proc_pid_maps_vsyscall_2;
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g_proc_pid_smaps_vsyscall = proc_pid_smaps_vsyscall_2;
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break;
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default:
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abort();
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}
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pid_t pid = fork();
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if (pid == -1) {
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perror("fork");
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return EXIT_FAILURE;
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} else if (pid == 0) {
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rv = ptrace(PTRACE_TRACEME, 0, NULL, NULL);
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if (rv != 0) {
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if (errno == EPERM) {
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fprintf(stderr,
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"Did you know? ptrace(PTRACE_TRACEME) doesn't work under strace.\n"
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);
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kill(getppid(), SIGTERM);
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return EXIT_FAILURE;
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}
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perror("ptrace PTRACE_TRACEME");
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return EXIT_FAILURE;
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}
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/*
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* Hide "segfault at ..." messages. Signal handler won't run.
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*/
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struct sigaction act = {};
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act.sa_flags = SA_SIGINFO;
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act.sa_sigaction = sigaction_SIGSEGV;
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sigaction(SIGSEGV, &act, NULL);
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#ifdef __amd64__
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munmap(NULL, ((size_t)1 << 47) - 4096);
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#else
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#error "implement 'unmap everything'"
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#endif
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return EXIT_FAILURE;
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} else {
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/*
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* TODO find reliable way to signal parent that munmap(2) completed.
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* Child can't do it directly because it effectively doesn't exist
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* anymore. Looking at child's VM files isn't 100% reliable either:
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* due to a bug they may not become empty or empty-like.
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*/
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sleep(1);
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if (rv == EXIT_SUCCESS) {
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rv = test_proc_pid_maps(pid);
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}
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if (rv == EXIT_SUCCESS) {
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rv = test_proc_pid_numa_maps(pid);
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}
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if (rv == EXIT_SUCCESS) {
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rv = test_proc_pid_smaps(pid);
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}
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if (rv == EXIT_SUCCESS) {
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rv = test_proc_pid_smaps_rollup(pid);
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}
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/*
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* TODO test /proc/${pid}/statm, task_statm()
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* ->start_code, ->end_code aren't updated by munmap().
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* Output can be "0 0 0 2 0 0 0\n" where "2" can be anything.
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*/
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/* Cut the rope. */
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int wstatus;
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waitpid(pid, &wstatus, 0);
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assert(WIFSTOPPED(wstatus));
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assert(WSTOPSIG(wstatus) == SIGSEGV);
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}
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return rv;
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}
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