sys/kern/kern_sharedpage.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   3  *
   4  * Copyright (c) 2010, 2012 Konstantin Belousov <kib@FreeBSD.org>
   5  * Copyright (c) 2015 The FreeBSD Foundation
   6  * All rights reserved.
   7  *
   8  * Portions of this software were developed by Konstantin Belousov
   9  * under sponsorship from the FreeBSD Foundation.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <sys/cdefs.h>
  34 #include "opt_vm.h"
  35
  36 #include <sys/param.h>
  37 #include <sys/systm.h>
  38 #include <sys/kernel.h>
  39 #include <sys/lock.h>
  40 #include <sys/malloc.h>
  41 #include <sys/rwlock.h>
  42 #include <sys/stddef.h>
  43 #include <sys/sysent.h>
  44 #include <sys/sysctl.h>
  45 #include <sys/vdso.h>
  46
  47 #include <vm/vm.h>
  48 #include <vm/vm_param.h>
  49 #include <vm/pmap.h>
  50 #include <vm/vm_extern.h>
  51 #include <vm/vm_kern.h>
  52 #include <vm/vm_map.h>
  53 #include <vm/vm_object.h>
  54 #include <vm/vm_page.h>
  55 #include <vm/vm_pager.h>
  56
  57 static struct sx shared_page_alloc_sx;
  58 static vm_object_t shared_page_obj;
  59 static int shared_page_free;
  60 char *shared_page_mapping;
  61
  62 #ifdef RANDOM_FENESTRASX
  63 static struct vdso_fxrng_generation *fxrng_shpage_mapping;
  64
  65 static bool fxrng_enabled = true;
  66 SYSCTL_BOOL(_debug, OID_AUTO, fxrng_vdso_enable, CTLFLAG_RWTUN, &fxrng_enabled,
  67     0, "Enable FXRNG VDSO");
  68 #endif
  69
  70 void
  71 shared_page_write(int base, int size, const void *data)
  72 {
  73
  74         bcopy(data, shared_page_mapping + base, size);
  75 }
  76
  77 static int
  78 shared_page_alloc_locked(int size, int align)
  79 {
  80         int res;
  81
  82         res = roundup(shared_page_free, align);
  83         if (res + size >= IDX_TO_OFF(shared_page_obj->size))
  84                 res = -1;
  85         else
  86                 shared_page_free = res + size;
  87         return (res);
  88 }
  89
  90 int
  91 shared_page_alloc(int size, int align)
  92 {
  93         int res;
  94
  95         sx_xlock(&shared_page_alloc_sx);
  96         res = shared_page_alloc_locked(size, align);
  97         sx_xunlock(&shared_page_alloc_sx);
  98         return (res);
  99 }
 100
 101 int
 102 shared_page_fill(int size, int align, const void *data)
 103 {
 104         int res;
 105
 106         sx_xlock(&shared_page_alloc_sx);
 107         res = shared_page_alloc_locked(size, align);
 108         if (res != -1)
 109                 shared_page_write(res, size, data);
 110         sx_xunlock(&shared_page_alloc_sx);
 111         return (res);
 112 }
 113
 114 static void
 115 shared_page_init(void *dummy __unused)
 116 {
 117         vm_page_t m;
 118         vm_offset_t addr;
 119
 120         sx_init(&shared_page_alloc_sx, "shpsx");
 121         shared_page_obj = vm_pager_allocate(OBJT_PHYS, 0, PAGE_SIZE,
 122             VM_PROT_DEFAULT, 0, NULL);
 123         VM_OBJECT_WLOCK(shared_page_obj);
 124         m = vm_page_grab(shared_page_obj, 0, VM_ALLOC_ZERO);
 125         VM_OBJECT_WUNLOCK(shared_page_obj);
 126         vm_page_valid(m);
 127         vm_page_xunbusy(m);
 128         addr = kva_alloc(PAGE_SIZE);
 129         pmap_qenter(addr, &m, 1);
 130         shared_page_mapping = (char *)addr;
 131 }
 132
 133 SYSINIT(shp, SI_SUB_EXEC, SI_ORDER_FIRST, (sysinit_cfunc_t)shared_page_init,
 134     NULL);
 135
 136 /*
 137  * Push the timehands update to the shared page.
 138  *
 139  * The lockless update scheme is similar to the one used to update the
 140  * in-kernel timehands, see sys/kern/kern_tc.c:tc_windup() (which
 141  * calls us after the timehands are updated).
 142  */
 143 static void
 144 timehands_update(struct vdso_sv_tk *svtk)
 145 {
 146         struct vdso_timehands th;
 147         struct vdso_timekeep *tk;
 148         uint32_t enabled, idx;
 149
 150         enabled = tc_fill_vdso_timehands(&th);
 151         th.th_gen = 0;
 152         idx = svtk->sv_timekeep_curr;
 153         if (++idx >= VDSO_TH_NUM)
 154                 idx = 0;
 155         svtk->sv_timekeep_curr = idx;
 156         if (++svtk->sv_timekeep_gen == 0)
 157                 svtk->sv_timekeep_gen = 1;
 158
 159         tk = (struct vdso_timekeep *)(shared_page_mapping +
 160             svtk->sv_timekeep_off);
 161         tk->tk_th[idx].th_gen = 0;
 162         atomic_thread_fence_rel();
 163         if (enabled)
 164                 tk->tk_th[idx] = th;
 165         atomic_store_rel_32(&tk->tk_th[idx].th_gen, svtk->sv_timekeep_gen);
 166         atomic_store_rel_32(&tk->tk_current, idx);
 167
 168         /*
 169          * The ordering of the assignment to tk_enabled relative to
 170          * the update of the vdso_timehands is not important.
 171          */
 172         tk->tk_enabled = enabled;
 173 }
 174
 175 #ifdef COMPAT_FREEBSD32
 176 static void
 177 timehands_update32(struct vdso_sv_tk *svtk)
 178 {
 179         struct vdso_timehands32 th;
 180         struct vdso_timekeep32 *tk;
 181         uint32_t enabled, idx;
 182
 183         enabled = tc_fill_vdso_timehands32(&th);
 184         th.th_gen = 0;
 185         idx = svtk->sv_timekeep_curr;
 186         if (++idx >= VDSO_TH_NUM)
 187                 idx = 0;
 188         svtk->sv_timekeep_curr = idx;
 189         if (++svtk->sv_timekeep_gen == 0)
 190                 svtk->sv_timekeep_gen = 1;
 191
 192         tk = (struct vdso_timekeep32 *)(shared_page_mapping +
 193             svtk->sv_timekeep_off);
 194         tk->tk_th[idx].th_gen = 0;
 195         atomic_thread_fence_rel();
 196         if (enabled)
 197                 tk->tk_th[idx] = th;
 198         atomic_store_rel_32(&tk->tk_th[idx].th_gen, svtk->sv_timekeep_gen);
 199         atomic_store_rel_32(&tk->tk_current, idx);
 200         tk->tk_enabled = enabled;
 201 }
 202 #endif
 203
 204 /*
 205  * This is hackish, but easiest way to avoid creating list structures
 206  * that needs to be iterated over from the hardclock interrupt
 207  * context.
 208  */
 209 static struct vdso_sv_tk *host_svtk;
 210 #ifdef COMPAT_FREEBSD32
 211 static struct vdso_sv_tk *compat32_svtk;
 212 #endif
 213
 214 void
 215 timekeep_push_vdso(void)
 216 {
 217
 218         if (host_svtk != NULL)
 219                 timehands_update(host_svtk);
 220 #ifdef COMPAT_FREEBSD32
 221         if (compat32_svtk != NULL)
 222                 timehands_update32(compat32_svtk);
 223 #endif
 224 }
 225
 226 struct vdso_sv_tk *
 227 alloc_sv_tk(void)
 228 {
 229         struct vdso_sv_tk *svtk;
 230         int tk_base;
 231         uint32_t tk_ver;
 232
 233         tk_ver = VDSO_TK_VER_CURR;
 234         svtk = malloc(sizeof(struct vdso_sv_tk), M_TEMP, M_WAITOK | M_ZERO);
 235         tk_base = shared_page_alloc(sizeof(struct vdso_timekeep) +
 236             sizeof(struct vdso_timehands) * VDSO_TH_NUM, 16);
 237         KASSERT(tk_base != -1, ("tk_base -1 for native"));
 238         shared_page_write(tk_base + offsetof(struct vdso_timekeep, tk_ver),
 239             sizeof(uint32_t), &tk_ver);
 240         svtk->sv_timekeep_off = tk_base;
 241         timekeep_push_vdso();
 242         return (svtk);
 243 }
 244
 245 #ifdef COMPAT_FREEBSD32
 246 struct vdso_sv_tk *
 247 alloc_sv_tk_compat32(void)
 248 {
 249         struct vdso_sv_tk *svtk;
 250         int tk_base;
 251         uint32_t tk_ver;
 252
 253         svtk = malloc(sizeof(struct vdso_sv_tk), M_TEMP, M_WAITOK | M_ZERO);
 254         tk_ver = VDSO_TK_VER_CURR;
 255         tk_base = shared_page_alloc(sizeof(struct vdso_timekeep32) +
 256             sizeof(struct vdso_timehands32) * VDSO_TH_NUM, 16);
 257         KASSERT(tk_base != -1, ("tk_base -1 for 32bit"));
 258         shared_page_write(tk_base + offsetof(struct vdso_timekeep32,
 259             tk_ver), sizeof(uint32_t), &tk_ver);
 260         svtk->sv_timekeep_off = tk_base;
 261         timekeep_push_vdso();
 262         return (svtk);
 263 }
 264 #endif
 265
 266 #ifdef RANDOM_FENESTRASX
 267 void
 268 fxrng_push_seed_generation(uint64_t gen)
 269 {
 270         if (fxrng_shpage_mapping == NULL || !fxrng_enabled)
 271                 return;
 272         KASSERT(gen < INT32_MAX,
 273             ("fxrng seed version shouldn't roll over a 32-bit counter "
 274              "for approximately 456,000 years"));
 275         atomic_store_rel_32(&fxrng_shpage_mapping->fx_generation32,
 276             (uint32_t)gen);
 277 }
 278
 279 static void
 280 alloc_sv_fxrng_generation(void)
 281 {
 282         int base;
 283
 284         /*
 285          * Allocate a full cache line for the fxrng root generation (64-bit
 286          * counter, or truncated 32-bit counter on ILP32 userspace).  It is
 287          * important that the line is not shared with frequently dirtied data,
 288          * and the shared page allocator lacks a __read_mostly mechanism.
 289          * However, PAGE_SIZE is typically large relative to the amount of
 290          * stuff we've got in it so far, so maybe the possible waste isn't an
 291          * issue.
 292          */
 293         base = shared_page_alloc(CACHE_LINE_SIZE, CACHE_LINE_SIZE);
 294         KASSERT(base != -1, ("%s: base allocation failed", __func__));
 295         fxrng_shpage_mapping = (void *)(shared_page_mapping + base);
 296         *fxrng_shpage_mapping = (struct vdso_fxrng_generation) {
 297                 .fx_vdso_version = VDSO_FXRNG_VER_CURR,
 298         };
 299 }
 300 #endif /* RANDOM_FENESTRASX */
 301
 302 void
 303 exec_sysvec_init(void *param)
 304 {
 305         struct sysentvec *sv;
 306         u_int flags;
 307         int res;
 308
 309         sv = param;
 310         flags = sv->sv_flags;
 311         if ((flags & SV_SHP) == 0)
 312                 return;
 313         MPASS(sv->sv_shared_page_obj == NULL);
 314         MPASS(sv->sv_shared_page_base != 0);
 315
 316         sv->sv_shared_page_obj = shared_page_obj;
 317         if ((flags & SV_ABI_MASK) == SV_ABI_FREEBSD) {
 318                 if ((flags & SV_DSO_SIG) != 0) {
 319                         res = shared_page_fill((uintptr_t)sv->sv_szsigcode,
 320                             16, sv->sv_sigcode);
 321                         if (res == -1)
 322                                 panic("copying vdso to shared page");
 323                         sv->sv_vdso_offset = res;
 324                         sv->sv_sigcode_offset = res + sv->sv_sigcodeoff;
 325                 } else {
 326                         res = shared_page_fill(*(sv->sv_szsigcode),
 327                             16, sv->sv_sigcode);
 328                         if (res == -1)
 329                                 panic("copying sigtramp to shared page");
 330                         sv->sv_sigcode_offset = res;
 331                 }
 332         }
 333         if ((flags & SV_TIMEKEEP) != 0) {
 334 #ifdef COMPAT_FREEBSD32
 335                 if ((flags & SV_ILP32) != 0) {
 336                         if ((flags & SV_ABI_MASK) == SV_ABI_FREEBSD) {
 337                                 KASSERT(compat32_svtk == NULL,
 338                                     ("Compat32 already registered"));
 339                                 compat32_svtk = alloc_sv_tk_compat32();
 340                         } else {
 341                                 KASSERT(compat32_svtk != NULL,
 342                                     ("Compat32 not registered"));
 343                         }
 344                         sv->sv_timekeep_offset = compat32_svtk->sv_timekeep_off;
 345                 } else {
 346 #endif
 347                         if ((flags & SV_ABI_MASK) == SV_ABI_FREEBSD) {
 348                                 KASSERT(host_svtk == NULL,
 349                                     ("Host already registered"));
 350                                 host_svtk = alloc_sv_tk();
 351                         } else {
 352                                 KASSERT(host_svtk != NULL,
 353                                     ("Host not registered"));
 354                         }
 355                         sv->sv_timekeep_offset = host_svtk->sv_timekeep_off;
 356 #ifdef COMPAT_FREEBSD32
 357                 }
 358 #endif
 359         }
 360 #ifdef RANDOM_FENESTRASX
 361         if ((flags & (SV_ABI_MASK | SV_RNG_SEED_VER)) ==
 362             (SV_ABI_FREEBSD | SV_RNG_SEED_VER)) {
 363                 /*
 364                  * Only allocate a single VDSO entry for multiple sysentvecs,
 365                  * i.e., native and COMPAT32.
 366                  */
 367                 if (fxrng_shpage_mapping == NULL)
 368                         alloc_sv_fxrng_generation();
 369                 sv->sv_fxrng_gen_offset =
 370                     (char *)fxrng_shpage_mapping - shared_page_mapping;
 371         }
 372 #endif
 373 }
 374
 375 void
 376 exec_sysvec_init_secondary(struct sysentvec *sv, struct sysentvec *sv2)
 377 {
 378         MPASS((sv2->sv_flags & SV_ABI_MASK) == (sv->sv_flags & SV_ABI_MASK));
 379         MPASS((sv2->sv_flags & SV_TIMEKEEP) == (sv->sv_flags & SV_TIMEKEEP));
 380         MPASS((sv2->sv_flags & SV_SHP) != 0 && (sv->sv_flags & SV_SHP) != 0);
 381         MPASS((sv2->sv_flags & SV_DSO_SIG) == (sv->sv_flags & SV_DSO_SIG));
 382         MPASS((sv2->sv_flags & SV_RNG_SEED_VER) ==
 383             (sv->sv_flags & SV_RNG_SEED_VER));
 384
 385         sv2->sv_shared_page_obj = sv->sv_shared_page_obj;
 386         sv2->sv_sigcode_offset = sv->sv_sigcode_offset;
 387         sv2->sv_vdso_offset = sv->sv_vdso_offset;
 388         if ((sv2->sv_flags & SV_ABI_MASK) != SV_ABI_FREEBSD)
 389                 return;
 390         sv2->sv_timekeep_offset = sv->sv_timekeep_offset;
 391         sv2->sv_fxrng_gen_offset = sv->sv_fxrng_gen_offset;
 392 }