xref: /freebsd/sys/arm64/linux/linux_sysvec.c (revision 0a4b664ae8582b7596858317b53d84eb4f8bbf9a)

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 1994-1996 Søren Schmidt
 * Copyright (c) 2018 Turing Robotic Industries Inc.
 *
 * 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/cdefs.h>
#include <sys/elf.h>
#include <sys/exec.h>
#include <sys/imgact.h>
#include <sys/imgact_elf.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/stddef.h>
#include <sys/signalvar.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_param.h>

#include <arm64/linux/linux.h>
#include <arm64/linux/linux_proto.h>
#include <compat/linux/linux_dtrace.h>
#include <compat/linux/linux_emul.h>
#include <compat/linux/linux_fork.h>
#include <compat/linux/linux_ioctl.h>
#include <compat/linux/linux_mib.h>
#include <compat/linux/linux_misc.h>
#include <compat/linux/linux_signal.h>
#include <compat/linux/linux_util.h>
#include <compat/linux/linux_vdso.h>

#include <machine/md_var.h>

#ifdef VFP
#include <machine/vfp.h>
#endif

MODULE_VERSION(linux64elf, 1);

#define	LINUX_VDSOPAGE_SIZE	PAGE_SIZE * 2
#define	LINUX_VDSOPAGE		(VM_MAXUSER_ADDRESS - \
				    LINUX_VDSOPAGE_SIZE)
#define	LINUX_SHAREDPAGE	(LINUX_VDSOPAGE - PAGE_SIZE)
				/*
				 * PAGE_SIZE - the size
				 * of the native SHAREDPAGE
				 */
#define	LINUX_USRSTACK		LINUX_SHAREDPAGE
#define	LINUX_PS_STRINGS	(LINUX_USRSTACK - \
				    sizeof(struct ps_strings))

static int linux_szsigcode;
static vm_object_t linux_vdso_obj;
static char *linux_vdso_mapping;
extern char _binary_linux_vdso_so_o_start;
extern char _binary_linux_vdso_so_o_end;
static vm_offset_t linux_vdso_base;

extern struct sysent linux_sysent[LINUX_SYS_MAXSYSCALL];

SET_DECLARE(linux_ioctl_handler_set, struct linux_ioctl_handler);

static int	linux_copyout_strings(struct image_params *imgp,
		    uintptr_t *stack_base);
static int	linux_elf_fixup(uintptr_t *stack_base,
		    struct image_params *iparams);
static bool	linux_trans_osrel(const Elf_Note *note, int32_t *osrel);
static void	linux_vdso_install(const void *param);
static void	linux_vdso_deinstall(const void *param);
static void	linux_vdso_reloc(char *mapping, Elf_Addr offset);
static void	linux_set_syscall_retval(struct thread *td, int error);
static int	linux_fetch_syscall_args(struct thread *td);
static void	linux_exec_setregs(struct thread *td, struct image_params *imgp,
		    uintptr_t stack);
static void	linux_exec_sysvec_init(void *param);
static int	linux_on_exec_vmspace(struct proc *p,
		    struct image_params *imgp);

/* DTrace init */
LIN_SDT_PROVIDER_DECLARE(LINUX_DTRACE);

/* DTrace probes */
LIN_SDT_PROBE_DEFINE2(sysvec, linux_translate_traps, todo, "int", "int");
LIN_SDT_PROBE_DEFINE0(sysvec, linux_exec_setregs, todo);
LIN_SDT_PROBE_DEFINE0(sysvec, linux_copyout_auxargs, todo);
LIN_SDT_PROBE_DEFINE0(sysvec, linux_elf_fixup, todo);
LIN_SDT_PROBE_DEFINE0(sysvec, linux_rt_sigreturn, todo);
LIN_SDT_PROBE_DEFINE0(sysvec, linux_rt_sendsig, todo);
LIN_SDT_PROBE_DEFINE0(sysvec, linux_vdso_install, todo);
LIN_SDT_PROBE_DEFINE0(sysvec, linux_vdso_deinstall, todo);

LINUX_VDSO_SYM_CHAR(linux_platform);
LINUX_VDSO_SYM_INTPTR(kern_timekeep_base);
LINUX_VDSO_SYM_INTPTR(__kernel_rt_sigreturn);

/* LINUXTODO: do we have traps to translate? */
static int
linux_translate_traps(int signal, int trap_code)
{

	LIN_SDT_PROBE2(sysvec, linux_translate_traps, todo, signal, trap_code);
	return (signal);
}

static int
linux_fetch_syscall_args(struct thread *td)
{
	struct proc *p;
	struct syscall_args *sa;
	register_t *ap;

	p = td->td_proc;
	ap = td->td_frame->tf_x;
	sa = &td->td_sa;

	sa->code = td->td_frame->tf_x[8];
	sa->original_code = sa->code;
	/* LINUXTODO: generic syscall? */
	if (sa->code >= p->p_sysent->sv_size)
		sa->callp = &p->p_sysent->sv_table[0];
	else
		sa->callp = &p->p_sysent->sv_table[sa->code];

	if (sa->callp->sy_narg > MAXARGS)
		panic("ARM64TODO: Could we have more than %d args?", MAXARGS);
	memcpy(sa->args, ap, MAXARGS * sizeof(register_t));

	td->td_retval[0] = 0;
	return (0);
}

static void
linux_set_syscall_retval(struct thread *td, int error)
{

	td->td_retval[1] = td->td_frame->tf_x[1];
	cpu_set_syscall_retval(td, error);

	if (__predict_false(error != 0)) {
		if (error != ERESTART && error != EJUSTRETURN)
			td->td_frame->tf_x[0] = bsd_to_linux_errno(error);
	}
}

static int
linux_copyout_auxargs(struct image_params *imgp, uintptr_t base)
{
	Elf_Auxargs *args;
	Elf_Auxinfo *argarray, *pos;
	struct proc *p;
	int error, issetugid;

	LIN_SDT_PROBE0(sysvec, linux_copyout_auxargs, todo);
	p = imgp->proc;

	args = (Elf64_Auxargs *)imgp->auxargs;
	argarray = pos = malloc(LINUX_AT_COUNT * sizeof(*pos), M_TEMP,
	    M_WAITOK | M_ZERO);

	issetugid = p->p_flag & P_SUGID ? 1 : 0;
	AUXARGS_ENTRY(pos, LINUX_AT_SYSINFO_EHDR, linux_vdso_base);
	AUXARGS_ENTRY(pos, LINUX_AT_HWCAP, *imgp->sysent->sv_hwcap);
	AUXARGS_ENTRY(pos, AT_PAGESZ, args->pagesz);
	AUXARGS_ENTRY(pos, LINUX_AT_CLKTCK, stclohz);
	AUXARGS_ENTRY(pos, AT_PHDR, args->phdr);
	AUXARGS_ENTRY(pos, AT_PHENT, args->phent);
	AUXARGS_ENTRY(pos, AT_PHNUM, args->phnum);
	AUXARGS_ENTRY(pos, AT_BASE, args->base);
	AUXARGS_ENTRY(pos, AT_FLAGS, args->flags);
	AUXARGS_ENTRY(pos, AT_ENTRY, args->entry);
	AUXARGS_ENTRY(pos, AT_UID, imgp->proc->p_ucred->cr_ruid);
	AUXARGS_ENTRY(pos, AT_EUID, imgp->proc->p_ucred->cr_svuid);
	AUXARGS_ENTRY(pos, AT_GID, imgp->proc->p_ucred->cr_rgid);
	AUXARGS_ENTRY(pos, AT_EGID, imgp->proc->p_ucred->cr_svgid);
	AUXARGS_ENTRY(pos, LINUX_AT_SECURE, issetugid);
	AUXARGS_ENTRY_PTR(pos, LINUX_AT_RANDOM, imgp->canary);
	AUXARGS_ENTRY(pos, LINUX_AT_HWCAP2, *imgp->sysent->sv_hwcap2);
	if (imgp->execpathp != 0)
		AUXARGS_ENTRY_PTR(pos, LINUX_AT_EXECFN, imgp->execpathp);
	if (args->execfd != -1)
		AUXARGS_ENTRY(pos, AT_EXECFD, args->execfd);
	AUXARGS_ENTRY(pos, LINUX_AT_PLATFORM, PTROUT(linux_platform));
	AUXARGS_ENTRY(pos, AT_NULL, 0);

	free(imgp->auxargs, M_TEMP);
	imgp->auxargs = NULL;
	KASSERT(pos - argarray <= LINUX_AT_COUNT, ("Too many auxargs"));

	error = copyout(argarray, (void *)base,
	    sizeof(*argarray) * LINUX_AT_COUNT);
	free(argarray, M_TEMP);
	return (error);
}

static int
linux_elf_fixup(uintptr_t *stack_base, struct image_params *imgp)
{

	LIN_SDT_PROBE0(sysvec, linux_elf_fixup, todo);

	return (0);
}

/*
 * Copy strings out to the new process address space, constructing new arg
 * and env vector tables. Return a pointer to the base so that it can be used
 * as the initial stack pointer.
 * LINUXTODO: deduplicate against other linuxulator archs
 */
static int
linux_copyout_strings(struct image_params *imgp, uintptr_t *stack_base)
{
	char **vectp;
	char *stringp;
	uintptr_t destp, ustringp;
	struct ps_strings *arginfo;
	char canary[LINUX_AT_RANDOM_LEN];
	size_t execpath_len;
	struct proc *p;
	int argc, envc, error;

	/* Calculate string base and vector table pointers. */
	if (imgp->execpath != NULL && imgp->auxargs != NULL)
		execpath_len = strlen(imgp->execpath) + 1;
	else
		execpath_len = 0;

	p = imgp->proc;
	arginfo = (struct ps_strings *)p->p_sysent->sv_psstrings;
	destp = (uintptr_t)arginfo;

	if (execpath_len != 0) {
		destp -= execpath_len;
		destp = rounddown2(destp, sizeof(void *));
		imgp->execpathp = (void *)destp;
		error = copyout(imgp->execpath, imgp->execpathp, execpath_len);
		if (error != 0)
			return (error);
	}

	/* Prepare the canary for SSP. */
	arc4rand(canary, sizeof(canary), 0);
	destp -= roundup(sizeof(canary), sizeof(void *));
	imgp->canary = (void *)destp;
	error = copyout(canary, imgp->canary, sizeof(canary));
	if (error != 0)
		return (error);

	/* Allocate room for the argument and environment strings. */
	destp -= ARG_MAX - imgp->args->stringspace;
	destp = rounddown2(destp, sizeof(void *));
	ustringp = destp;

	if (imgp->auxargs) {
		/*
		 * Allocate room on the stack for the ELF auxargs
		 * array.  It has up to LINUX_AT_COUNT entries.
		 */
		destp -= LINUX_AT_COUNT * sizeof(Elf64_Auxinfo);
		destp = rounddown2(destp, sizeof(void *));
	}

	vectp = (char **)destp;

	/*
	 * Allocate room for argc and the argv[] and env vectors including the
	 * terminating NULL pointers.
	 */
	vectp -= 1 + imgp->args->argc + 1 + imgp->args->envc + 1;
	vectp = (char **)STACKALIGN(vectp);

	/* vectp also becomes our initial stack base. */
	*stack_base = (uintptr_t)vectp;

	stringp = imgp->args->begin_argv;
	argc = imgp->args->argc;
	envc = imgp->args->envc;

	/* Copy out strings - arguments and environment. */
	error = copyout(stringp, (void *)ustringp,
	    ARG_MAX - imgp->args->stringspace);
	if (error != 0)
		return (error);

	/* Fill in "ps_strings" struct for ps, w, etc. */
	if (suword(&arginfo->ps_argvstr, (long)(intptr_t)vectp) != 0 ||
	    suword(&arginfo->ps_nargvstr, argc) != 0)
		return (EFAULT);

	if (suword(vectp++, argc) != 0)
		return (EFAULT);

	/* Fill in argument portion of vector table. */
	for (; argc > 0; --argc) {
		if (suword(vectp++, ustringp) != 0)
			return (EFAULT);
		while (*stringp++ != 0)
			ustringp++;
		ustringp++;
	}

	/* A null vector table pointer separates the argp's from the envp's. */
	if (suword(vectp++, 0) != 0)
		return (EFAULT);

	if (suword(&arginfo->ps_envstr, (long)(intptr_t)vectp) != 0 ||
	    suword(&arginfo->ps_nenvstr, envc) != 0)
		return (EFAULT);

	/* Fill in environment portion of vector table. */
	for (; envc > 0; --envc) {
		if (suword(vectp++, ustringp) != 0)
			return (EFAULT);
		while (*stringp++ != 0)
			ustringp++;
		ustringp++;
	}

	/* The end of the vector table is a null pointer. */
	if (suword(vectp, 0) != 0)
		return (EFAULT);

	if (imgp->auxargs) {
		vectp++;
		error = imgp->sysent->sv_copyout_auxargs(imgp,
		    (uintptr_t)vectp);
		if (error != 0)
			return (error);
	}

	return (0);
}

/*
 * Reset registers to default values on exec.
 */
static void
linux_exec_setregs(struct thread *td, struct image_params *imgp,
    uintptr_t stack)
{
	struct trapframe *regs = td->td_frame;
	struct pcb *pcb = td->td_pcb;

	/* LINUXTODO: validate */
	LIN_SDT_PROBE0(sysvec, linux_exec_setregs, todo);

	memset(regs, 0, sizeof(*regs));
	/* glibc start.S registers function pointer in x0 with atexit. */
        regs->tf_sp = stack;
#if 0	/* LINUXTODO: See if this is used. */
	regs->tf_lr = imgp->entry_addr;
#else
        regs->tf_lr = 0xffffffffffffffff;
#endif
        regs->tf_elr = imgp->entry_addr;

	pcb->pcb_tpidr_el0 = 0;
	pcb->pcb_tpidrro_el0 = 0;
	WRITE_SPECIALREG(tpidrro_el0, 0);
	WRITE_SPECIALREG(tpidr_el0, 0);

#ifdef VFP
	vfp_reset_state(td, pcb);
#endif

	/*
	 * Clear debug register state. It is not applicable to the new process.
	 */
	bzero(&pcb->pcb_dbg_regs, sizeof(pcb->pcb_dbg_regs));
}

int
linux_rt_sigreturn(struct thread *td, struct linux_rt_sigreturn_args *args)
{
	struct l_sigframe frame;
	struct trapframe *tf;
	int error;

	tf = td->td_frame;

	if (copyin((void *)tf->tf_sp, &frame, sizeof(frame)))
		return (EFAULT);

	error = set_mcontext(td, &frame.sf_uc.uc_mcontext);
	if (error != 0)
		return (error);

	/* Restore signal mask. */
	kern_sigprocmask(td, SIG_SETMASK, &frame.sf_uc.uc_sigmask, NULL, 0);

	return (EJUSTRETURN);
}

static void
linux_rt_sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
{
	struct thread *td;
	struct proc *p;
	struct trapframe *tf;
	struct l_sigframe *fp, frame;
	struct sigacts *psp;
	int onstack, sig;
	uint32_t spsr;

	td = curthread;
	p = td->td_proc;
	PROC_LOCK_ASSERT(p, MA_OWNED);

	sig = ksi->ksi_signo;
	psp = p->p_sigacts;
	mtx_assert(&psp->ps_mtx, MA_OWNED);

	tf = td->td_frame;
	onstack = sigonstack(tf->tf_sp);

	CTR4(KTR_SIG, "sendsig: td=%p (%s) catcher=%p sig=%d", td, p->p_comm,
	    catcher, sig);

	/* Allocate and validate space for the signal handler context. */
	if ((td->td_pflags & TDP_ALTSTACK) != 0 && !onstack &&
	    SIGISMEMBER(psp->ps_sigonstack, sig)) {
		fp = (struct l_sigframe *)((uintptr_t)td->td_sigstk.ss_sp +
		    td->td_sigstk.ss_size);
#if defined(COMPAT_43)
		td->td_sigstk.ss_flags |= SS_ONSTACK;
#endif
	} else {
		fp = (struct l_sigframe *)td->td_frame->tf_sp;
	}

	/* Make room, keeping the stack aligned */
	fp--;
	fp = (struct l_sigframe *)STACKALIGN(fp);

	/* Fill in the frame to copy out */
	bzero(&frame, sizeof(frame));
	get_mcontext(td, &frame.sf_uc.uc_mcontext, 0);
	spsr = frame.sf_uc.uc_mcontext.mc_gpregs.gp_spsr;

	/* Translate the signal. */
	sig = bsd_to_linux_signal(sig);

	siginfo_to_lsiginfo(&ksi->ksi_info, &frame.sf_si, sig);
	frame.sf_uc.uc_sigmask = *mask;
	frame.sf_uc.uc_stack = td->td_sigstk;
	frame.sf_uc.uc_stack.ss_flags = (td->td_pflags & TDP_ALTSTACK) != 0 ?
	    (onstack ? SS_ONSTACK : 0) : SS_DISABLE;
	mtx_unlock(&psp->ps_mtx);
	PROC_UNLOCK(td->td_proc);

	/* Copy the sigframe out to the user's stack. */
	if (copyout(&frame, fp, sizeof(*fp)) != 0) {
		/* Process has trashed its stack. Kill it. */
		CTR2(KTR_SIG, "sendsig: sigexit td=%p fp=%p", td, fp);
		PROC_LOCK(p);
		sigexit(td, SIGILL);
	}

	tf->tf_x[0]= sig;
	tf->tf_x[1] = (register_t)&fp->sf_si;
	tf->tf_x[2] = (register_t)&fp->sf_uc;

	tf->tf_elr = (register_t)catcher;
	tf->tf_sp = (register_t)fp;
	tf->tf_lr = (register_t)__kernel_rt_sigreturn;

	CTR3(KTR_SIG, "sendsig: return td=%p pc=%#x sp=%#x", td, tf->tf_elr,
	    tf->tf_sp);

	PROC_LOCK(p);
	mtx_lock(&psp->ps_mtx);
}

struct sysentvec elf_linux_sysvec = {
	.sv_size	= LINUX_SYS_MAXSYSCALL,
	.sv_table	= linux_sysent,
	.sv_transtrap	= linux_translate_traps,
	.sv_fixup	= linux_elf_fixup,
	.sv_sendsig	= linux_rt_sendsig,
	.sv_sigcode	= &_binary_linux_vdso_so_o_start,
	.sv_szsigcode	= &linux_szsigcode,
	.sv_name	= "Linux ELF64",
	.sv_coredump	= elf64_coredump,
	.sv_elf_core_osabi = ELFOSABI_NONE,
	.sv_elf_core_abi_vendor = LINUX_ABI_VENDOR,
	.sv_elf_core_prepare_notes = linux64_prepare_notes,
	.sv_imgact_try	= linux_exec_imgact_try,
	.sv_minsigstksz	= LINUX_MINSIGSTKSZ,
	.sv_minuser	= VM_MIN_ADDRESS,
	.sv_maxuser	= VM_MAXUSER_ADDRESS,
	.sv_usrstack	= LINUX_USRSTACK,
	.sv_psstrings	= LINUX_PS_STRINGS,
	.sv_stackprot	= VM_PROT_READ | VM_PROT_WRITE,
	.sv_copyout_auxargs = linux_copyout_auxargs,
	.sv_copyout_strings = linux_copyout_strings,
	.sv_setregs	= linux_exec_setregs,
	.sv_fixlimit	= NULL,
	.sv_maxssiz	= NULL,
	.sv_flags	= SV_ABI_LINUX | SV_LP64 | SV_SHP | SV_SIG_DISCIGN |
	    SV_SIG_WAITNDQ | SV_TIMEKEEP,
	.sv_set_syscall_retval = linux_set_syscall_retval,
	.sv_fetch_syscall_args = linux_fetch_syscall_args,
	.sv_syscallnames = NULL,
	.sv_shared_page_base = LINUX_SHAREDPAGE,
	.sv_shared_page_len = PAGE_SIZE,
	.sv_schedtail	= linux_schedtail,
	.sv_thread_detach = linux_thread_detach,
	.sv_trap	= NULL,
	.sv_hwcap	= &elf_hwcap,
	.sv_hwcap2	= &elf_hwcap2,
	.sv_onexec	= linux_on_exec_vmspace,
	.sv_onexit	= linux_on_exit,
	.sv_ontdexit	= linux_thread_dtor,
	.sv_setid_allowed = &linux_setid_allowed_query,
};

static int
linux_on_exec_vmspace(struct proc *p, struct image_params *imgp)
{
	int error;

	error = linux_map_vdso(p, linux_vdso_obj, linux_vdso_base,
	    LINUX_VDSOPAGE_SIZE, imgp);
	if (error == 0)
		linux_on_exec(p, imgp);
	return (error);
}

/*
 * linux_vdso_install() and linux_exec_sysvec_init() must be called
 * after exec_sysvec_init() which is SI_SUB_EXEC (SI_ORDER_ANY).
 */
static void
linux_exec_sysvec_init(void *param)
{
	l_uintptr_t *ktimekeep_base;
	struct sysentvec *sv;
	ptrdiff_t tkoff;

	sv = param;
	/* Fill timekeep_base */
	exec_sysvec_init(sv);

	tkoff = kern_timekeep_base - linux_vdso_base;
	ktimekeep_base = (l_uintptr_t *)(linux_vdso_mapping + tkoff);
	*ktimekeep_base = sv->sv_timekeep_base;
}
SYSINIT(elf_linux_exec_sysvec_init, SI_SUB_EXEC + 1, SI_ORDER_ANY,
    linux_exec_sysvec_init, &elf_linux_sysvec);

static void
linux_vdso_install(const void *param)
{
	char *vdso_start = &_binary_linux_vdso_so_o_start;
	char *vdso_end = &_binary_linux_vdso_so_o_end;

	linux_szsigcode = vdso_end - vdso_start;
	MPASS(linux_szsigcode <= LINUX_VDSOPAGE_SIZE);

	linux_vdso_base = LINUX_VDSOPAGE;

	__elfN(linux_vdso_fixup)(vdso_start, linux_vdso_base);

	linux_vdso_obj = __elfN(linux_shared_page_init)
	    (&linux_vdso_mapping, LINUX_VDSOPAGE_SIZE);
	bcopy(vdso_start, linux_vdso_mapping, linux_szsigcode);

	linux_vdso_reloc(linux_vdso_mapping, linux_vdso_base);
}
SYSINIT(elf_linux_vdso_init, SI_SUB_EXEC + 1, SI_ORDER_FIRST,
    linux_vdso_install, NULL);

static void
linux_vdso_deinstall(const void *param)
{

	__elfN(linux_shared_page_fini)(linux_vdso_obj,
	    linux_vdso_mapping, LINUX_VDSOPAGE_SIZE);
}
SYSUNINIT(elf_linux_vdso_uninit, SI_SUB_EXEC, SI_ORDER_FIRST,
    linux_vdso_deinstall, NULL);

static void
linux_vdso_reloc(char *mapping, Elf_Addr offset)
{
	Elf_Size rtype, symidx;
	const Elf_Rela *rela;
	const Elf_Shdr *shdr;
	const Elf_Ehdr *ehdr;
	Elf_Addr *where;
	Elf_Addr addr, addend;
	int i, relacnt;

	MPASS(offset != 0);

	relacnt = 0;
	ehdr = (const Elf_Ehdr *)mapping;
	shdr = (const Elf_Shdr *)(mapping + ehdr->e_shoff);
	for (i = 0; i < ehdr->e_shnum; i++)
	{
		switch (shdr[i].sh_type) {
		case SHT_REL:
			printf("Linux Aarch64 vDSO: unexpected Rel section\n");
			break;
		case SHT_RELA:
			rela = (const Elf_Rela *)(mapping + shdr[i].sh_offset);
			relacnt = shdr[i].sh_size / sizeof(*rela);
		}
	}

	for (i = 0; i < relacnt; i++, rela++) {
		where = (Elf_Addr *)(mapping + rela->r_offset);
		addend = rela->r_addend;
		rtype = ELF_R_TYPE(rela->r_info);
		symidx = ELF_R_SYM(rela->r_info);

		switch (rtype) {
		case R_AARCH64_NONE:	/* none */
			break;

		case R_AARCH64_RELATIVE:	/* B + A */
			addr = (Elf_Addr)(mapping + addend);
			if (*where != addr)
				*where = addr;
			break;
		default:
			printf("Linux Aarch64 vDSO: unexpected relocation type %ld, "
			    "symbol index %ld\n", rtype, symidx);
		}
	}
}

static char GNU_ABI_VENDOR[] = "GNU";
static int GNU_ABI_LINUX = 0;

/* LINUXTODO: deduplicate */
static bool
linux_trans_osrel(const Elf_Note *note, int32_t *osrel)
{
	const Elf32_Word *desc;
	uintptr_t p;

	p = (uintptr_t)(note + 1);
	p += roundup2(note->n_namesz, sizeof(Elf32_Addr));

	desc = (const Elf32_Word *)p;
	if (desc[0] != GNU_ABI_LINUX)
		return (false);

	*osrel = LINUX_KERNVER(desc[1], desc[2], desc[3]);
	return (true);
}

static Elf_Brandnote linux64_brandnote = {
	.hdr.n_namesz	= sizeof(GNU_ABI_VENDOR),
	.hdr.n_descsz	= 16,
	.hdr.n_type	= 1,
	.vendor		= GNU_ABI_VENDOR,
	.flags		= BN_TRANSLATE_OSREL,
	.trans_osrel	= linux_trans_osrel
};

static Elf64_Brandinfo linux_glibc2brand = {
	.brand		= ELFOSABI_LINUX,
	.machine	= EM_AARCH64,
	.compat_3_brand	= "Linux",
	.emul_path	= linux_emul_path,
	.interp_path	= "/lib64/ld-linux-x86-64.so.2",
	.sysvec		= &elf_linux_sysvec,
	.interp_newpath	= NULL,
	.brand_note	= &linux64_brandnote,
	.flags		= BI_CAN_EXEC_DYN | BI_BRAND_NOTE
};

Elf64_Brandinfo *linux_brandlist[] = {
	&linux_glibc2brand,
	NULL
};

static int
linux64_elf_modevent(module_t mod, int type, void *data)
{
	Elf64_Brandinfo **brandinfo;
	struct linux_ioctl_handler**lihp;
	int error;

	error = 0;
	switch(type) {
	case MOD_LOAD:
		for (brandinfo = &linux_brandlist[0]; *brandinfo != NULL;
		    ++brandinfo)
			if (elf64_insert_brand_entry(*brandinfo) < 0)
				error = EINVAL;
		if (error == 0) {
			SET_FOREACH(lihp, linux_ioctl_handler_set)
				linux_ioctl_register_handler(*lihp);
			stclohz = (stathz ? stathz : hz);
			if (bootverbose)
				printf("Linux arm64 ELF exec handler installed\n");
		}
		break;
	case MOD_UNLOAD:
		for (brandinfo = &linux_brandlist[0]; *brandinfo != NULL;
		    ++brandinfo)
			if (elf64_brand_inuse(*brandinfo))
				error = EBUSY;
		if (error == 0) {
			for (brandinfo = &linux_brandlist[0];
			    *brandinfo != NULL; ++brandinfo)
				if (elf64_remove_brand_entry(*brandinfo) < 0)
					error = EINVAL;
		}
		if (error == 0) {
			SET_FOREACH(lihp, linux_ioctl_handler_set)
				linux_ioctl_unregister_handler(*lihp);
			if (bootverbose)
				printf("Linux arm64 ELF exec handler removed\n");
		} else
			printf("Could not deinstall Linux arm64 ELF interpreter entry\n");
		break;
	default:
		return (EOPNOTSUPP);
	}
	return (error);
}

static moduledata_t linux64_elf_mod = {
	"linux64elf",
	linux64_elf_modevent,
	0
};

DECLARE_MODULE_TIED(linux64elf, linux64_elf_mod, SI_SUB_EXEC, SI_ORDER_ANY);
MODULE_DEPEND(linux64elf, linux_common, 1, 1, 1);
FEATURE(linux64, "AArch64 Linux 64bit support");