mmap: accept non-PROT_WRITE MAP_SHARED mappings

Currently we don't accept writable file mmap()s, as there is no
system in place to guarantee dirty buffers would make it back to
disk. But we can actually accept MAP_SHARED for PROT_READ mappings,
meaning the ranges aren't writable at all (and no private copy is
made as with MAP_PRIVATE), as it turns out a fairly large class of
usage.

	. fail writable MAP_SHARED mappings at runtime
	. reduces some minix-specific patches
	. lets binutils gold build on minix without further patching

Change-Id: If2896c0a555328ac5b324afa706063fc6d86519e

common/lib/libprop/prop_object.c

@@ -942,13 +942,9 @@ _prop_object_internalize_map_file(const char *fname)
 	if ((sb.st_size & pgmask) == 0)
 		need_guard = true;
 
-#ifndef __minix
 	mf->poimf_xml = mmap(NULL, need_guard ? mf->poimf_mapsize + pgsize
 			    		      : mf->poimf_mapsize,
 			    PROT_READ, MAP_FILE|MAP_SHARED, fd, (off_t)0);
-#else
-	mf->poimf_xml = MAP_FAILED;
-#endif
 	(void) close(fd);
 	if (mf->poimf_xml == MAP_FAILED) {
 		_PROP_FREE(mf, M_TEMP);

lib/libc/cdb/cdbr.c

@@ -57,10 +57,6 @@ __RCSID("$NetBSD: cdbr.c,v 1.4 2012/09/27 00:37:43 joerg Exp $");
 #include <string.h>
 #include <unistd.h>
 
-#if defined(__minix) && !defined(MAP_SHARED)
-#define MAP_SHARED MAP_PRIVATE /* LSC: We lose some memory, but it's OK as this is RO. */
-#endif /* defined(__minix) && !defined(MAP_SHARED) */
-
 #ifdef __weak_alias
 __weak_alias(cdbr_close,_cdbr_close)
 __weak_alias(cdbr_find,_cdbr_find)

lib/libc/nls/catopen.c

@@ -61,10 +61,6 @@ __RCSID("$NetBSD: catopen.c,v 1.32 2013/08/19 08:03:34 joerg Exp $");
 #define NLS_DEFAULT_PATH "/usr/share/nls/%L/%N.cat:/usr/share/nls/%N/%L"
 #define NLS_DEFAULT_LANG "C"
 
-#if defined(__minix) && !defined(MAP_SHARED)
-#define MAP_SHARED MAP_PRIVATE /* LSC: We lose some memory, but it's OK as this is RO. */
-#endif /* defined(__minix) && !defined(MAP_SHARED) */
-
 __weak_alias(catopen, _catopen)
 __weak_alias(catopen_l, _catopen_l)
 

libexec/ftpd/ftpd.c

@@ -2232,7 +2232,6 @@ send_data_with_mmap(int filefd, int netfd, const struct stat *st, int isdata)
 		(void)gettimeofday(&then, NULL);
 	} else
 		bufrem = winsize;
-#if !defined(__minix)
 	while (1) {
 		mapsize = MIN(filesize - off, winsize);
 		if (mapsize == 0)
@@ -2244,10 +2243,14 @@ send_data_with_mmap(int filefd, int netfd, const struct stat *st, int isdata)
 				goto try_read;
 			return (SS_FILE_ERROR);
 		}
+#ifndef __minix
 		(void) madvise(win, mapsize, MADV_SEQUENTIAL);
+#endif
 		error = write_data(netfd, win, mapsize, &bufrem, &then,
 		    isdata);
+#ifndef __minix
 		(void) madvise(win, mapsize, MADV_DONTNEED);
+#endif
 		munmap(win, mapsize);
 		if (urgflag && handleoobcmd())
 			return (SS_ABORTED);
@@ -2257,7 +2260,6 @@ send_data_with_mmap(int filefd, int netfd, const struct stat *st, int isdata)
 	}
 	return (SS_SUCCESS);
 
-#endif /* !defined(__minix) */
  try_read:
 	return (send_data_with_read(filefd, netfd, st, isdata));
 }

libexec/ld.elf_so/map_object.c

@@ -52,10 +52,6 @@ __RCSID("$NetBSD: map_object.c,v 1.52 2013/08/03 13:17:05 skrll Exp $");
 #if defined(__minix)
 #define MINIXVERBOSE 0
 
-#ifndef MAP_SHARED
-#define MAP_SHARED MAP_PRIVATE /* minix: MAP_SHARED should be MAP_PRIVATE */
-#endif
-
 #if MINIXVERBOSE
 #include <stdio.h>
 #endif

libexec/ld.elf_so/paths.c

@@ -61,15 +61,13 @@ __RCSID("$NetBSD: paths.c,v 1.41 2013/05/06 08:02:20 skrll Exp $");
 static Search_Path *_rtld_find_path(Search_Path *, const char *, size_t);
 static Search_Path **_rtld_append_path(Search_Path **, Search_Path **,
     const char *, const char *, const char *);
-#if !defined(__minix)
 static void _rtld_process_mapping(Library_Xform **, const char *,
     const char *);
-#endif /* !defined(__minix) */
 static char *exstrdup(const char *, const char *);
-#if !defined(__minix)
 static const char *getstr(const char **, const char *, const char *);
 static const char *getcstr(const char **, const char *, const char *);
 static const char *getword(const char **, const char *, const char *);
+#if !defined(__minix)
 static int matchstr(const char *, const char *, const char *);
 #endif /* !defined(__minix) */
 
@@ -90,7 +88,6 @@ exstrdup(const char *bp, const char *ep)
 	return (cp);
 }
 
-#if !defined(__minix)
 /*
  * Like strsep(), but takes end of string and doesn't put any NUL.  To
  * detect empty string, compare `*p' and return value.
@@ -149,6 +146,7 @@ getword(const char **p, const char *ep, const char *delim)
 	return (getstr(p, ep, delim));
 }
 
+#if !defined(__minix)
 /*
  * Match `bp' against NUL terminated string pointed by `p'.
  */
@@ -234,7 +232,6 @@ _rtld_add_paths(const char *execname, Search_Path **path_p, const char *pathstr)
 	}
 }
 
-#if !defined(__minix)
 /*
  * Process library mappings of the form:
  *	<library_name>	<machdep_variable> <value,...:library_name,...> ...
@@ -340,17 +337,11 @@ cleanup:
 		xfree(hwptr->name);
 	xfree(hwptr);
 }
-#endif /* !defined(__minix) */
 
 void
 _rtld_process_hints(const char *execname, Search_Path **path_p,
     Library_Xform **lib_p, const char *fname)
 {
-
-#if defined(__minix)
-	/* Minix doesn't support MAP_SHARED. */
-	return;
-#else
 	int fd;
 	char *buf, small[128];
 	const char *b, *ep, *ptr;
@@ -421,7 +412,6 @@ _rtld_process_hints(const char *execname, Search_Path **path_p,
 
 	if (buf != small)
 		(void)munmap(buf, sz);
-#endif /* defined(__minix) */
 }
 
 #if !defined(__minix)

servers/vm/mmap.c

@@ -256,9 +256,10 @@ int do_mmap(message *m)
 		/* File mapping might be disabled */
 		if(!enable_filemap) return ENXIO;
 
-		/* files get private copies of pages on writes. */
-		if(!(m->VMM_FLAGS & MAP_PRIVATE)) {
-			printf("VM: mmap file must MAP_PRIVATE\n");
+		/* For files, we only can't accept writable MAP_SHARED
+		 * mappings.
+		 */
+		if((m->VMM_FLAGS & MAP_SHARED) && (m->VMM_PROT & PROT_WRITE)) {
 			return ENXIO;
 		}
 

sys/sys/mman.h

@@ -68,9 +68,7 @@ typedef	__off_t		off_t;		/* file offset */
  * Flags contain sharing type and options.
  * Sharing types; choose one.
  */
-#if !defined(__minix)
 #define	MAP_SHARED	0x0001	/* share changes */
-#endif /* !defined(__minix) */
 #define	MAP_PRIVATE	0x0002	/* changes are private */
 
 #ifdef _KERNEL

test/test74.c

@@ -403,6 +403,16 @@ void basic_regression(void)
 	fd2 = open("../testsh2", O_RDONLY);
 	if(fd1 < 0 || fd2 < 0) { e(2); }
 
+	/* just check that we can't mmap() a file writable */
+	if(mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FILE, fd1, 0) != MAP_FAILED) {
+		e(1);
+	}
+
+	/* check that we can mmap() a file MAP_SHARED readonly */
+	if(mmap(NULL, PAGE_SIZE, PROT_READ, MAP_SHARED | MAP_FILE, fd1, 0) == MAP_FAILED) {
+		e(1);
+	}
+
 	/* clear cache of files before mmap so pages won't be present already */
 	if(fcntl(fd1, F_FLUSH_FS_CACHE) < 0) { e(1); }
 	if(fcntl(fd2, F_FLUSH_FS_CACHE) < 0) { e(1); }

usr.bin/msgc/msg_sys.def

@@ -104,11 +104,7 @@ msg_file(const char *file)
 	if (fd == -1)
 		return -1;
 	msgmapsz = lseek(fd, 0, SEEK_END);
-#ifdef __minix
-	msgmap = mmap(0, msgmapsz, PROT_READ, MAP_PRIVATE, fd, 0);
-#else /* ! __minix */
 	msgmap = mmap(0, msgmapsz, PROT_READ, MAP_SHARED, fd, 0);
-#endif /* ! __minix */
 	close(fd);
 	if (msgmap == MAP_FAILED)
 		return -1;

usr.bin/xinstall/xinstall.c

@@ -819,9 +819,7 @@ copy(int from_fd, char *from_name, int to_fd, char *to_name, off_t size)
 {
 	ssize_t	nr, nw;
 	int	serrno;
-#if !defined(__minix)
 	u_char	*p;
-#endif /* !defined(__minix) */
 	u_char	buf[MAXBSIZE];
 	MD5_CTX		ctxMD5;
 	RMD160_CTX	ctxRMD160;
@@ -868,15 +866,12 @@ copy(int from_fd, char *from_name, int to_fd, char *to_name, off_t size)
 		 */
 
 		if (size <= 8 * 1048576) {
-#if defined(__minix)
-			goto mmap_failed;
-#else
 			if ((p = mmap(NULL, (size_t)size, PROT_READ,
 			    MAP_FILE|MAP_SHARED, from_fd, (off_t)0))
 			    == MAP_FAILED) {
 				goto mmap_failed;
 			}
-#if defined(MADV_SEQUENTIAL) && !defined(__APPLE__)
+#if defined(MADV_SEQUENTIAL) && !defined(__APPLE__) && !defined(__minix)
 			if (madvise(p, (size_t)size, MADV_SEQUENTIAL) == -1
 			    && errno != EOPNOTSUPP)
 				warnx("madvise: %s", strerror(errno));
@@ -911,7 +906,6 @@ copy(int from_fd, char *from_name, int to_fd, char *to_name, off_t size)
 				break;
 			}
 			(void)munmap(p, size);
-#endif /* defined(__minix) */
 		} else {
  mmap_failed:
 			while ((nr = read(from_fd, buf, sizeof(buf))) > 0) {