kern_sharedpage.c

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/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2010, 2012 Konstantin Belousov <kib@FreeBSD.org>
 * Copyright (c) 2015 The FreeBSD Foundation
 * All rights reserved.
 *
 * Portions of this software were developed by Konstantin Belousov
 * under sponsorship from the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include "opt_vm.h"
 
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/rwlock.h>
#include <sys/stddef.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/vdso.h>
 
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
 
static struct sx shared_page_alloc_sx;
static vm_object_t shared_page_obj;
static int shared_page_free;
char *shared_page_mapping;
 
#ifdef RANDOM_FENESTRASX
static struct vdso_fxrng_generation *fxrng_shpage_mapping;
 
static bool fxrng_enabled = true;
SYSCTL_BOOL(_debug, OID_AUTO, fxrng_vdso_enable, CTLFLAG_RWTUN, &fxrng_enabled,
    0, "Enable FXRNG VDSO");
#endif
 
void
shared_page_write(int base, int size, const void *data)
{
 
        bcopy(data, shared_page_mapping + base, size);
}
 
static int
shared_page_alloc_locked(int size, int align)
{
        int res;
 
        res = roundup(shared_page_free, align);
        if (res + size >= IDX_TO_OFF(shared_page_obj->size))
                res = -1;
        else
                shared_page_free = res + size;
        return (res);
}
 
int
shared_page_alloc(int size, int align)
{
        int res;
 
        sx_xlock(&shared_page_alloc_sx);
        res = shared_page_alloc_locked(size, align);
        sx_xunlock(&shared_page_alloc_sx);
        return (res);
}
 
int
shared_page_fill(int size, int align, const void *data)
{
        int res;
 
        sx_xlock(&shared_page_alloc_sx);
        res = shared_page_alloc_locked(size, align);
        if (res != -1)
                shared_page_write(res, size, data);
        sx_xunlock(&shared_page_alloc_sx);
        return (res);
}
 
static void
shared_page_init(void *dummy __unused)
{
        vm_page_t m;
        vm_offset_t addr;
 
        sx_init(&shared_page_alloc_sx, "shpsx");
        shared_page_obj = vm_pager_allocate(OBJT_PHYS, 0, PAGE_SIZE,
            VM_PROT_DEFAULT, 0, NULL);
        VM_OBJECT_WLOCK(shared_page_obj);
        m = vm_page_grab(shared_page_obj, 0, VM_ALLOC_ZERO);
        VM_OBJECT_WUNLOCK(shared_page_obj);
        vm_page_valid(m);
        vm_page_xunbusy(m);
        addr = kva_alloc(PAGE_SIZE);
        pmap_qenter(addr, &m, 1);
        shared_page_mapping = (char *)addr;
}
 
SYSINIT(shp, SI_SUB_EXEC, SI_ORDER_FIRST, (sysinit_cfunc_t)shared_page_init,
    NULL);
 
/*
 * Push the timehands update to the shared page.
 *
 * The lockless update scheme is similar to the one used to update the
 * in-kernel timehands, see sys/kern/kern_tc.c:tc_windup() (which
 * calls us after the timehands are updated).
 */
static void
timehands_update(struct vdso_sv_tk *svtk)
{
        struct vdso_timehands th;
        struct vdso_timekeep *tk;
        uint32_t enabled, idx;
 
        enabled = tc_fill_vdso_timehands(&th);
        th.th_gen = 0;
        idx = svtk->sv_timekeep_curr;
        if (++idx >= VDSO_TH_NUM)
                idx = 0;
        svtk->sv_timekeep_curr = idx;
        if (++svtk->sv_timekeep_gen == 0)
                svtk->sv_timekeep_gen = 1;
 
        tk = (struct vdso_timekeep *)(shared_page_mapping +
            svtk->sv_timekeep_off);
        tk->tk_th[idx].th_gen = 0;
        atomic_thread_fence_rel();
        if (enabled)
                tk->tk_th[idx] = th;
        atomic_store_rel_32(&tk->tk_th[idx].th_gen, svtk->sv_timekeep_gen);
        atomic_store_rel_32(&tk->tk_current, idx);
 
        /*
         * The ordering of the assignment to tk_enabled relative to
         * the update of the vdso_timehands is not important.
         */
        tk->tk_enabled = enabled;
}
 
#ifdef COMPAT_FREEBSD32
static void
timehands_update32(struct vdso_sv_tk *svtk)
{
        struct vdso_timehands32 th;
        struct vdso_timekeep32 *tk;
        uint32_t enabled, idx;
 
        enabled = tc_fill_vdso_timehands32(&th);
        th.th_gen = 0;
        idx = svtk->sv_timekeep_curr;
        if (++idx >= VDSO_TH_NUM)
                idx = 0;
        svtk->sv_timekeep_curr = idx;
        if (++svtk->sv_timekeep_gen == 0)
                svtk->sv_timekeep_gen = 1;
 
        tk = (struct vdso_timekeep32 *)(shared_page_mapping +
            svtk->sv_timekeep_off);
        tk->tk_th[idx].th_gen = 0;
        atomic_thread_fence_rel();
        if (enabled)
                tk->tk_th[idx] = th;
        atomic_store_rel_32(&tk->tk_th[idx].th_gen, svtk->sv_timekeep_gen);
        atomic_store_rel_32(&tk->tk_current, idx);
        tk->tk_enabled = enabled;
}
#endif
 
/*
 * This is hackish, but easiest way to avoid creating list structures
 * that needs to be iterated over from the hardclock interrupt
 * context.
 */
static struct vdso_sv_tk *host_svtk;
#ifdef COMPAT_FREEBSD32
static struct vdso_sv_tk *compat32_svtk;
#endif
 
void
timekeep_push_vdso(void)
{
 
        if (host_svtk != NULL)
                timehands_update(host_svtk);
#ifdef COMPAT_FREEBSD32
        if (compat32_svtk != NULL)
                timehands_update32(compat32_svtk);
#endif
}
 
struct vdso_sv_tk *
alloc_sv_tk(void)
{
        struct vdso_sv_tk *svtk;
        int tk_base;
        uint32_t tk_ver;
 
        tk_ver = VDSO_TK_VER_CURR;
        svtk = malloc(sizeof(struct vdso_sv_tk), M_TEMP, M_WAITOK | M_ZERO);
        tk_base = shared_page_alloc(sizeof(struct vdso_timekeep) +
            sizeof(struct vdso_timehands) * VDSO_TH_NUM, 16);
        KASSERT(tk_base != -1, ("tk_base -1 for native"));
        shared_page_write(tk_base + offsetof(struct vdso_timekeep, tk_ver),
            sizeof(uint32_t), &tk_ver);
        svtk->sv_timekeep_off = tk_base;
        timekeep_push_vdso();
        return (svtk);
}
 
#ifdef COMPAT_FREEBSD32
struct vdso_sv_tk *
alloc_sv_tk_compat32(void)
{
        struct vdso_sv_tk *svtk;
        int tk_base;
        uint32_t tk_ver;
 
        svtk = malloc(sizeof(struct vdso_sv_tk), M_TEMP, M_WAITOK | M_ZERO);
        tk_ver = VDSO_TK_VER_CURR;
        tk_base = shared_page_alloc(sizeof(struct vdso_timekeep32) +
            sizeof(struct vdso_timehands32) * VDSO_TH_NUM, 16);
        KASSERT(tk_base != -1, ("tk_base -1 for 32bit"));
        shared_page_write(tk_base + offsetof(struct vdso_timekeep32,
            tk_ver), sizeof(uint32_t), &tk_ver);
        svtk->sv_timekeep_off = tk_base;
        timekeep_push_vdso();
        return (svtk);
}
#endif
 
#ifdef RANDOM_FENESTRASX
void
fxrng_push_seed_generation(uint64_t gen)
{
        if (fxrng_shpage_mapping == NULL || !fxrng_enabled)
                return;
        KASSERT(gen < INT32_MAX,
            ("fxrng seed version shouldn't roll over a 32-bit counter "
             "for approximately 456,000 years"));
        atomic_store_rel_32(&fxrng_shpage_mapping->fx_generation32,
            (uint32_t)gen);
}
 
static void
alloc_sv_fxrng_generation(void)
{
        int base;
 
        /*
         * Allocate a full cache line for the fxrng root generation (64-bit
         * counter, or truncated 32-bit counter on ILP32 userspace).  It is
         * important that the line is not shared with frequently dirtied data,
         * and the shared page allocator lacks a __read_mostly mechanism.
         * However, PAGE_SIZE is typically large relative to the amount of
         * stuff we've got in it so far, so maybe the possible waste isn't an
         * issue.
         */
        base = shared_page_alloc(CACHE_LINE_SIZE, CACHE_LINE_SIZE);
        KASSERT(base != -1, ("%s: base allocation failed", __func__));
        fxrng_shpage_mapping = (void *)(shared_page_mapping + base);
        *fxrng_shpage_mapping = (struct vdso_fxrng_generation) {
                .fx_vdso_version = VDSO_FXRNG_VER_CURR,
        };
}
#endif /* RANDOM_FENESTRASX */
 
void
exec_sysvec_init(void *param)
{
        struct sysentvec *sv;
        vm_offset_t sb;
#ifdef RANDOM_FENESTRASX
        ptrdiff_t base;
#endif
        u_int flags;
        int res;
 
        sv = param;
        flags = sv->sv_flags;
        if ((flags & SV_SHP) == 0)
                return;
        MPASS(sv->sv_shared_page_obj == NULL);
        MPASS(sv->sv_shared_page_base != 0);
 
        sv->sv_shared_page_obj = shared_page_obj;
        if ((flags & SV_ABI_MASK) == SV_ABI_FREEBSD) {
                if ((flags & SV_DSO_SIG) != 0) {
                        sb = sv->sv_shared_page_base;
                        res = shared_page_fill((uintptr_t)sv->sv_szsigcode,
                            16, sv->sv_sigcode);
                        if (res == -1)
                                panic("copying sigtramp to shared page");
                        sb += res;
                        sv->sv_vdso_base = sb;
                        sb += sv->sv_sigcodeoff;
                        sv->sv_sigcode_base = sb;
                } else {
                        sv->sv_sigcode_base = sv->sv_shared_page_base +
                            shared_page_fill(*(sv->sv_szsigcode), 16,
                            sv->sv_sigcode);
                }
        }
        if ((flags & SV_TIMEKEEP) != 0) {
#ifdef COMPAT_FREEBSD32
                if ((flags & SV_ILP32) != 0) {
                        if ((flags & SV_ABI_MASK) == SV_ABI_FREEBSD) {
                                KASSERT(compat32_svtk == NULL,
                                    ("Compat32 already registered"));
                                compat32_svtk = alloc_sv_tk_compat32();
                        } else {
                                KASSERT(compat32_svtk != NULL,
                                    ("Compat32 not registered"));
                        }
                        sv->sv_timekeep_base = sv->sv_shared_page_base +
                            compat32_svtk->sv_timekeep_off;
                } else {
#endif
                        if ((flags & SV_ABI_MASK) == SV_ABI_FREEBSD) {
                                KASSERT(host_svtk == NULL,
                                    ("Host already registered"));
                                host_svtk = alloc_sv_tk();
                        } else {
                                KASSERT(host_svtk != NULL,
                                    ("Host not registered"));
                        }
                        sv->sv_timekeep_base = sv->sv_shared_page_base +
                            host_svtk->sv_timekeep_off;
#ifdef COMPAT_FREEBSD32
                }
#endif
        }
#ifdef RANDOM_FENESTRASX
        if ((flags & (SV_ABI_MASK | SV_RNG_SEED_VER)) ==
            (SV_ABI_FREEBSD | SV_RNG_SEED_VER)) {
                /*
                 * Only allocate a single VDSO entry for multiple sysentvecs,
                 * i.e., native and COMPAT32.
                 */
                if (fxrng_shpage_mapping == NULL)
                        alloc_sv_fxrng_generation();
                base = (char *)fxrng_shpage_mapping - shared_page_mapping;
                sv->sv_fxrng_gen_base = sv->sv_shared_page_base + base;
        }
#endif
}
 
void
exec_sysvec_init_secondary(struct sysentvec *sv, struct sysentvec *sv2)
{
        MPASS((sv2->sv_flags & SV_ABI_MASK) == (sv->sv_flags & SV_ABI_MASK));
        MPASS((sv2->sv_flags & SV_TIMEKEEP) == (sv->sv_flags & SV_TIMEKEEP));
        MPASS((sv2->sv_flags & SV_SHP) != 0 && (sv->sv_flags & SV_SHP) != 0);
        MPASS((sv2->sv_flags & SV_DSO_SIG) == (sv->sv_flags & SV_DSO_SIG));
        MPASS((sv2->sv_flags & SV_RNG_SEED_VER) ==
            (sv->sv_flags & SV_RNG_SEED_VER));
 
        sv2->sv_shared_page_obj = sv->sv_shared_page_obj;
        sv2->sv_sigcode_base = sv2->sv_shared_page_base +
            (sv->sv_sigcode_base - sv->sv_shared_page_base);
        if ((sv2->sv_flags & SV_DSO_SIG) != 0) {
                sv2->sv_vdso_base = sv2->sv_shared_page_base +
                    (sv->sv_vdso_base - sv->sv_shared_page_base);
        }
        if ((sv2->sv_flags & SV_ABI_MASK) != SV_ABI_FREEBSD)
                return;
        if ((sv2->sv_flags & SV_TIMEKEEP) != 0) {
                sv2->sv_timekeep_base = sv2->sv_shared_page_base +
                    (sv->sv_timekeep_base - sv->sv_shared_page_base);
        }
        if ((sv2->sv_flags & SV_RNG_SEED_VER) != 0) {
                sv2->sv_fxrng_gen_base = sv2->sv_shared_page_base +
                    (sv->sv_fxrng_gen_base - sv->sv_shared_page_base);
        }
}