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