1 files changed, 146 insertions, 102 deletions

diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index 9d7d69a523b..897e9ad0c10 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -1,161 +1,205 @@
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
 #include <stdio.h>
-#include <stdlib.h>
 #include <stddef.h>
-#include <stdarg.h>
+#include <stdlib.h>
 #include <unistd.h>
 #include <errno.h>
-#include <string.h>
 #include <fcntl.h>
-#include <sys/types.h>
+#include <string.h>
+#include <sys/stat.h>
 #include <sys/mman.h>
-#include "kern_util.h"
-#include "user.h"
-#include "user_util.h"
-#include "mem_user.h"
-#include "init.h"
-#include "os.h"
-#include "tempfile.h"
-#include "kern_constants.h"
-
-#include <sys/param.h>
+#include <sys/vfs.h>
+#include <linux/magic.h>
+#include <init.h>
+#include <os.h>
 
+/* Set by make_tempfile() during early boot. */
 static char *tempdir = NULL;
 
-static void __init find_tempdir(void)
+/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
+static int __init check_tmpfs(const char *dir)
 {
-	char *dirs[] = { "TMP", "TEMP", "TMPDIR", NULL };
-	int i;
-	char *dir = NULL;
+	struct statfs st;
+
+	printf("Checking if %s is on tmpfs...", dir);
+	if (statfs(dir, &st) < 0) {
+		printf("%s\n", strerror(errno));
+	} else if (st.f_type != TMPFS_MAGIC) {
+		printf("no\n");
+	} else {
+		printf("OK\n");
+		return 0;
+	}
+	return -1;
+}
 
-	if(tempdir != NULL) return;	/* We've already been called */
-	for(i = 0; dirs[i]; i++){
-		dir = getenv(dirs[i]);
-		if((dir != NULL) && (*dir != '\0'))
-			break;
+/*
+ * Choose the tempdir to use. We want something on tmpfs so that our memory is
+ * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
+ * environment, we use that even if it's not on tmpfs, but we warn the user.
+ * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
+ * then we fall back to /tmp.
+ */
+static char * __init choose_tempdir(void)
+{
+	static const char * const vars[] = {
+		"TMPDIR",
+		"TMP",
+		"TEMP",
+		NULL
+	};
+	static const char fallback_dir[] = "/tmp";
+	static const char * const tmpfs_dirs[] = {
+		"/dev/shm",
+		fallback_dir,
+		NULL
+	};
+	int i;
+	const char *dir;
+
+	printf("Checking environment variables for a tempdir...");
+	for (i = 0; vars[i]; i++) {
+		dir = getenv(vars[i]);
+		if ((dir != NULL) && (*dir != '\0')) {
+			printf("%s\n", dir);
+			if (check_tmpfs(dir) >= 0)
+				goto done;
+			else
+				goto warn;
+		}
 	}
-	if((dir == NULL) || (*dir == '\0'))
-		dir = "/tmp";
-
-	tempdir = malloc(strlen(dir) + 2);
-	if(tempdir == NULL){
-		fprintf(stderr, "Failed to malloc tempdir, "
-			"errno = %d\n", errno);
-		return;
+	printf("none found\n");
+
+	for (i = 0; tmpfs_dirs[i]; i++) {
+		dir = tmpfs_dirs[i];
+		if (check_tmpfs(dir) >= 0)
+			goto done;
 	}
-	strcpy(tempdir, dir);
-	strcat(tempdir, "/");
+
+	dir = fallback_dir;
+warn:
+	printf("Warning: tempdir %s is not on tmpfs\n", dir);
+done:
+	/* Make a copy since getenv results may not remain valid forever. */
+	return strdup(dir);
 }
 
 /*
- * This proc still used in tt-mode
- * (file: kernel/tt/ptproxy/proxy.c, proc: start_debugger).
- * So it isn't 'static' yet.
+ * Create an unlinked tempfile in a suitable tempdir. template must be the
+ * basename part of the template with a leading '/'.
  */
-int make_tempfile(const char *template, char **out_tempname, int do_unlink)
+static int __init make_tempfile(const char *template)
 {
-	char tempname[MAXPATHLEN];
+	char *tempname;
 	int fd;
 
-	find_tempdir();
-	if (*template != '/')
-		strcpy(tempname, tempdir);
-	else
-		*tempname = 0;
+	if (tempdir == NULL) {
+		tempdir = choose_tempdir();
+		if (tempdir == NULL) {
+			fprintf(stderr, "Failed to choose tempdir: %s\n",
+				strerror(errno));
+			return -1;
+		}
+	}
+
+	tempname = malloc(strlen(tempdir) + strlen(template) + 1);
+	if (tempname == NULL)
+		return -1;
+
+	strcpy(tempname, tempdir);
 	strcat(tempname, template);
 	fd = mkstemp(tempname);
-	if(fd < 0){
+	if (fd < 0) {
 		fprintf(stderr, "open - cannot create %s: %s\n", tempname,
 			strerror(errno));
-		return -1;
+		goto out;
 	}
-	if(do_unlink && (unlink(tempname) < 0)){
+	if (unlink(tempname) < 0) {
 		perror("unlink");
-		return -1;
+		goto close;
 	}
-	if(out_tempname){
-		*out_tempname = strdup(tempname);
-		if(*out_tempname == NULL){
-			perror("strdup");
-			return -1;
-		}
-	}
-	return(fd);
+	free(tempname);
+	return fd;
+close:
+	close(fd);
+out:
+	free(tempname);
+	return -1;
 }
 
-#define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
+#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
 
-/*
- * This proc is used in start_up.c
- * So it isn't 'static'.
- */
-int create_tmp_file(unsigned long long len)
+static int __init create_tmp_file(unsigned long long len)
 {
 	int fd, err;
 	char zero;
 
-	fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
-	if(fd < 0) {
+	fd = make_tempfile(TEMPNAME_TEMPLATE);
+	if (fd < 0)
 		exit(1);
-	}
 
 	err = fchmod(fd, 0777);
-	if(err < 0){
-		perror("os_mode_fd");
+	if (err < 0) {
+		perror("fchmod");
 		exit(1);
 	}
 
-        if (lseek64(fd, len, SEEK_SET) < 0) {
- 		perror("os_seek_file");
+	/*
+	 * Seek to len - 1 because writing a character there will
+	 * increase the file size by one byte, to the desired length.
+	 */
+	if (lseek64(fd, len - 1, SEEK_SET) < 0) {
+		perror("lseek64");
 		exit(1);
 	}
 
 	zero = 0;
 
-	err = os_write_file(fd, &zero, 1);
-	if(err != 1){
-		errno = -err;
-		perror("os_write_file");
+	err = write(fd, &zero, 1);
+	if (err != 1) {
+		perror("write");
 		exit(1);
 	}
 
-	return(fd);
+	return fd;
 }
 
-static int create_anon_file(unsigned long long len)
+int __init create_mem_file(unsigned long long len)
 {
-	void *addr;
-	int fd;
+	int err, fd;
 
-	fd = open("/dev/anon", O_RDWR);
-	if(fd < 0) {
-		perror("opening /dev/anon");
-		exit(1);
-	}
+	fd = create_tmp_file(len);
 
-	addr = mmap(NULL, len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-	if(addr == MAP_FAILED){
-		perror("mapping physmem file");
-		exit(1);
+	err = os_set_exec_close(fd);
+	if (err < 0) {
+		errno = -err;
+		perror("exec_close");
 	}
-	munmap(addr, len);
-
-	return(fd);
+	return fd;
 }
 
-extern int have_devanon;
-
-int create_mem_file(unsigned long long len)
+void __init check_tmpexec(void)
 {
-	int err, fd;
-
-	if(have_devanon)
-		fd = create_anon_file(len);
-	else fd = create_tmp_file(len);
-
-	err = os_set_exec_close(fd, 1);
-	if(err < 0){
-		errno = -err;
-		perror("exec_close");
+	void *addr;
+	int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
+
+	addr = mmap(NULL, UM_KERN_PAGE_SIZE,
+		    PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
+	printf("Checking PROT_EXEC mmap in %s...", tempdir);
+	if (addr == MAP_FAILED) {
+		err = errno;
+		printf("%s\n", strerror(err));
+		close(fd);
+		if (err == EPERM)
+			printf("%s must be not mounted noexec\n", tempdir);
+		exit(1);
 	}
-	return(fd);
+	printf("OK\n");
+	munmap(addr, UM_KERN_PAGE_SIZE);
+
+	close(fd);
 }