xref: /freebsd/sys/compat/linux/linux_mmap.c (revision 2f513db72b034fd5ef7f080b11be5c711c15186a)
1 /*-
2  * Copyright (c) 2004 Tim J. Robbins
3  * Copyright (c) 2002 Doug Rabson
4  * Copyright (c) 2000 Marcel Moolenaar
5  * Copyright (c) 1994-1995 Søren Schmidt
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer
13  *    in this position and unchanged.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. The name of the author may not be used to endorse or promote products
18  *    derived from this software without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30  *
31  * $FreeBSD$
32  */
33 
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36 
37 #include <sys/capsicum.h>
38 #include <sys/file.h>
39 #include <sys/imgact.h>
40 #include <sys/ktr.h>
41 #include <sys/mman.h>
42 #include <sys/proc.h>
43 #include <sys/resourcevar.h>
44 #include <sys/syscallsubr.h>
45 #include <sys/sysent.h>
46 #include <sys/sysproto.h>
47 
48 #include <vm/pmap.h>
49 #include <vm/vm_extern.h>
50 #include <vm/vm_map.h>
51 
52 #include <compat/linux/linux_emul.h>
53 #include <compat/linux/linux_mmap.h>
54 #include <compat/linux/linux_persona.h>
55 #include <compat/linux/linux_util.h>
56 
57 
58 #define STACK_SIZE  (2 * 1024 * 1024)
59 #define GUARD_SIZE  (4 * PAGE_SIZE)
60 
61 #if defined(__amd64__)
62 static void linux_fixup_prot(struct thread *td, int *prot);
63 #endif
64 
65 static int
66 linux_mmap_check_fp(struct file *fp, int flags, int prot, int maxprot)
67 {
68 
69 	/* Linux mmap() just fails for O_WRONLY files */
70 	if ((fp->f_flag & FREAD) == 0)
71 		return (EACCES);
72 
73 	return (0);
74 }
75 
76 int
77 linux_mmap_common(struct thread *td, uintptr_t addr, size_t len, int prot,
78     int flags, int fd, off_t pos)
79 {
80 	struct proc *p = td->td_proc;
81 	struct vmspace *vms = td->td_proc->p_vmspace;
82 	int bsd_flags, error;
83 	struct file *fp;
84 
85 	LINUX_CTR6(mmap2, "0x%lx, %ld, %ld, 0x%08lx, %ld, 0x%lx",
86 	    addr, len, prot, flags, fd, pos);
87 
88 	error = 0;
89 	bsd_flags = 0;
90 	fp = NULL;
91 
92 	/*
93 	 * Linux mmap(2):
94 	 * You must specify exactly one of MAP_SHARED and MAP_PRIVATE
95 	 */
96 	if (!((flags & LINUX_MAP_SHARED) ^ (flags & LINUX_MAP_PRIVATE)))
97 		return (EINVAL);
98 
99 	if (flags & LINUX_MAP_SHARED)
100 		bsd_flags |= MAP_SHARED;
101 	if (flags & LINUX_MAP_PRIVATE)
102 		bsd_flags |= MAP_PRIVATE;
103 	if (flags & LINUX_MAP_FIXED)
104 		bsd_flags |= MAP_FIXED;
105 	if (flags & LINUX_MAP_ANON) {
106 		/* Enforce pos to be on page boundary, then ignore. */
107 		if ((pos & PAGE_MASK) != 0)
108 			return (EINVAL);
109 		pos = 0;
110 		bsd_flags |= MAP_ANON;
111 	} else
112 		bsd_flags |= MAP_NOSYNC;
113 	if (flags & LINUX_MAP_GROWSDOWN)
114 		bsd_flags |= MAP_STACK;
115 
116 #if defined(__amd64__)
117 	/*
118 	 * According to the Linux mmap(2) man page, "MAP_32BIT flag
119 	 * is ignored when MAP_FIXED is set."
120 	 */
121 	if ((flags & LINUX_MAP_32BIT) && (flags & LINUX_MAP_FIXED) == 0)
122 		bsd_flags |= MAP_32BIT;
123 
124 	/*
125 	 * PROT_READ, PROT_WRITE, or PROT_EXEC implies PROT_READ and PROT_EXEC
126 	 * on Linux/i386 if the binary requires executable stack.
127 	 * We do this only for IA32 emulation as on native i386 this is does not
128 	 * make sense without PAE.
129 	 *
130 	 * XXX. Linux checks that the file system is not mounted with noexec.
131 	 */
132 	linux_fixup_prot(td, &prot);
133 #endif
134 
135 	/* Linux does not check file descriptor when MAP_ANONYMOUS is set. */
136 	fd = (bsd_flags & MAP_ANON) ? -1 : fd;
137 	if (flags & LINUX_MAP_GROWSDOWN) {
138 		/*
139 		 * The Linux MAP_GROWSDOWN option does not limit auto
140 		 * growth of the region.  Linux mmap with this option
141 		 * takes as addr the initial BOS, and as len, the initial
142 		 * region size.  It can then grow down from addr without
143 		 * limit.  However, Linux threads has an implicit internal
144 		 * limit to stack size of STACK_SIZE.  Its just not
145 		 * enforced explicitly in Linux.  But, here we impose
146 		 * a limit of (STACK_SIZE - GUARD_SIZE) on the stack
147 		 * region, since we can do this with our mmap.
148 		 *
149 		 * Our mmap with MAP_STACK takes addr as the maximum
150 		 * downsize limit on BOS, and as len the max size of
151 		 * the region.  It then maps the top SGROWSIZ bytes,
152 		 * and auto grows the region down, up to the limit
153 		 * in addr.
154 		 *
155 		 * If we don't use the MAP_STACK option, the effect
156 		 * of this code is to allocate a stack region of a
157 		 * fixed size of (STACK_SIZE - GUARD_SIZE).
158 		 */
159 
160 		if ((caddr_t)addr + len > vms->vm_maxsaddr) {
161 			/*
162 			 * Some Linux apps will attempt to mmap
163 			 * thread stacks near the top of their
164 			 * address space.  If their TOS is greater
165 			 * than vm_maxsaddr, vm_map_growstack()
166 			 * will confuse the thread stack with the
167 			 * process stack and deliver a SEGV if they
168 			 * attempt to grow the thread stack past their
169 			 * current stacksize rlimit.  To avoid this,
170 			 * adjust vm_maxsaddr upwards to reflect
171 			 * the current stacksize rlimit rather
172 			 * than the maximum possible stacksize.
173 			 * It would be better to adjust the
174 			 * mmap'ed region, but some apps do not check
175 			 * mmap's return value.
176 			 */
177 			PROC_LOCK(p);
178 			vms->vm_maxsaddr = (char *)p->p_sysent->sv_usrstack -
179 			    lim_cur_proc(p, RLIMIT_STACK);
180 			PROC_UNLOCK(p);
181 		}
182 
183 		/*
184 		 * This gives us our maximum stack size and a new BOS.
185 		 * If we're using VM_STACK, then mmap will just map
186 		 * the top SGROWSIZ bytes, and let the stack grow down
187 		 * to the limit at BOS.  If we're not using VM_STACK
188 		 * we map the full stack, since we don't have a way
189 		 * to autogrow it.
190 		 */
191 		if (len <= STACK_SIZE - GUARD_SIZE) {
192 			addr = addr - (STACK_SIZE - GUARD_SIZE - len);
193 			len = STACK_SIZE - GUARD_SIZE;
194 		}
195 	}
196 
197 	/*
198 	 * FreeBSD is free to ignore the address hint if MAP_FIXED wasn't
199 	 * passed.  However, some Linux applications, like the ART runtime,
200 	 * depend on the hint.  If the MAP_FIXED wasn't passed, but the
201 	 * address is not zero, try with MAP_FIXED and MAP_EXCL first,
202 	 * and fall back to the normal behaviour if that fails.
203 	 */
204 	if (addr != 0 && (bsd_flags & MAP_FIXED) == 0 &&
205 	    (bsd_flags & MAP_EXCL) == 0) {
206 		error = kern_mmap_fpcheck(td, addr, len, prot,
207 		    bsd_flags | MAP_FIXED | MAP_EXCL, fd, pos,
208 		    linux_mmap_check_fp);
209 		if (error == 0)
210 			goto out;
211 	}
212 
213 	error = kern_mmap_fpcheck(td, addr, len, prot, bsd_flags, fd, pos,
214 	    linux_mmap_check_fp);
215 out:
216 	LINUX_CTR2(mmap2, "return: %d (%p)", error, td->td_retval[0]);
217 
218 	return (error);
219 }
220 
221 int
222 linux_mprotect_common(struct thread *td, uintptr_t addr, size_t len, int prot)
223 {
224 
225 	/* XXX Ignore PROT_GROWSDOWN and PROT_GROWSUP for now. */
226 	prot &= ~(LINUX_PROT_GROWSDOWN | LINUX_PROT_GROWSUP);
227 	if ((prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC)) != 0)
228 		return (EINVAL);
229 
230 #if defined(__amd64__)
231 	linux_fixup_prot(td, &prot);
232 #endif
233 	return (kern_mprotect(td, addr, len, prot));
234 }
235 
236 #if defined(__amd64__)
237 static void
238 linux_fixup_prot(struct thread *td, int *prot)
239 {
240 	struct linux_pemuldata *pem;
241 
242 	if (SV_PROC_FLAG(td->td_proc, SV_ILP32) && *prot & PROT_READ) {
243 		pem = pem_find(td->td_proc);
244 		if (pem->persona & LINUX_READ_IMPLIES_EXEC)
245 			*prot |= PROT_EXEC;
246 	}
247 
248 }
249 #endif
250