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freebsd-dev/sys/compat/ia32/ia32_sysvec.c
Konstantin Belousov fc83c5a7d0 Make randomized stack gap between strings and pointers to argv/envs. 
This effectively makes the stack base on the csu _start entry
randomized.

The gap is enabled if ASLR is for the ABI is enabled, and then
kern.elf{64,32}.aslr.stack_gap specify the max percentage of the
initial stack size that can be wasted for gap.  Setting it to zero
disables the gap, and max is capped at 50%.

Only amd64 for now.

Reviewed by:	cem, markj
Discussed with:	emaste
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D21081
2019-07-31 20:23:10 +00:00

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/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2002 Doug Rabson
* Copyright (c) 2003 Peter Wemm
* All rights reserved.
*
* 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("$FreeBSD$");
#define __ELF_WORD_SIZE 32
#include <sys/param.h>
#include <sys/exec.h>
#include <sys/fcntl.h>
#include <sys/imgact.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/mman.h>
#include <sys/namei.h>
#include <sys/pioctl.h>
#include <sys/proc.h>
#include <sys/procfs.h>
#include <sys/resourcevar.h>
#include <sys/systm.h>
#include <sys/signalvar.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/syscall.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/vnode.h>
#include <sys/imgact_elf.h>
#include <vm/vm.h>
#include <vm/vm_kern.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <compat/freebsd32/freebsd32_signal.h>
#include <compat/freebsd32/freebsd32_util.h>
#include <compat/freebsd32/freebsd32_proto.h>
#include <compat/freebsd32/freebsd32_syscall.h>
#include <compat/ia32/ia32_signal.h>
#include <machine/frame.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/cpufunc.h>
CTASSERT(sizeof(struct ia32_mcontext) == 640);
CTASSERT(sizeof(struct ia32_ucontext) == 704);
CTASSERT(sizeof(struct ia32_sigframe) == 800);
CTASSERT(sizeof(struct siginfo32) == 64);
#ifdef COMPAT_FREEBSD4
CTASSERT(sizeof(struct ia32_mcontext4) == 260);
CTASSERT(sizeof(struct ia32_ucontext4) == 324);
CTASSERT(sizeof(struct ia32_sigframe4) == 408);
#endif
extern const char *freebsd32_syscallnames[];
static SYSCTL_NODE(_compat, OID_AUTO, ia32, CTLFLAG_RW, 0, "ia32 mode");
static u_long ia32_maxdsiz = IA32_MAXDSIZ;
SYSCTL_ULONG(_compat_ia32, OID_AUTO, maxdsiz, CTLFLAG_RWTUN, &ia32_maxdsiz, 0, "");
u_long ia32_maxssiz = IA32_MAXSSIZ;
SYSCTL_ULONG(_compat_ia32, OID_AUTO, maxssiz, CTLFLAG_RWTUN, &ia32_maxssiz, 0, "");
static u_long ia32_maxvmem = IA32_MAXVMEM;
SYSCTL_ULONG(_compat_ia32, OID_AUTO, maxvmem, CTLFLAG_RWTUN, &ia32_maxvmem, 0, "");
struct sysentvec ia32_freebsd_sysvec = {
.sv_size = FREEBSD32_SYS_MAXSYSCALL,
.sv_table = freebsd32_sysent,
.sv_errsize = 0,
.sv_errtbl = NULL,
.sv_transtrap = NULL,
.sv_fixup = elf32_freebsd_fixup,
.sv_sendsig = ia32_sendsig,
.sv_sigcode = ia32_sigcode,
.sv_szsigcode = &sz_ia32_sigcode,
.sv_name = "FreeBSD ELF32",
.sv_coredump = elf32_coredump,
.sv_imgact_try = NULL,
.sv_minsigstksz = MINSIGSTKSZ,
.sv_minuser = FREEBSD32_MINUSER,
.sv_maxuser = FREEBSD32_MAXUSER,
.sv_usrstack = FREEBSD32_USRSTACK,
.sv_psstrings = FREEBSD32_PS_STRINGS,
.sv_stackprot = VM_PROT_ALL,
.sv_copyout_strings = freebsd32_copyout_strings,
.sv_setregs = ia32_setregs,
.sv_fixlimit = ia32_fixlimit,
.sv_maxssiz = &ia32_maxssiz,
.sv_flags = SV_ABI_FREEBSD | SV_ASLR | SV_IA32 | SV_ILP32 |
SV_SHP | SV_TIMEKEEP,
.sv_set_syscall_retval = ia32_set_syscall_retval,
.sv_fetch_syscall_args = ia32_fetch_syscall_args,
.sv_syscallnames = freebsd32_syscallnames,
.sv_shared_page_base = FREEBSD32_SHAREDPAGE,
.sv_shared_page_len = PAGE_SIZE,
.sv_schedtail = NULL,
.sv_thread_detach = NULL,
.sv_trap = NULL,
.sv_stackgap = elf32_stackgap,
};
INIT_SYSENTVEC(elf_ia32_sysvec, &ia32_freebsd_sysvec);
static Elf32_Brandinfo ia32_brand_info = {
.brand = ELFOSABI_FREEBSD,
.machine = EM_386,
.compat_3_brand = "FreeBSD",
.emul_path = NULL,
.interp_path = "/libexec/ld-elf.so.1",
.sysvec = &ia32_freebsd_sysvec,
.interp_newpath = "/libexec/ld-elf32.so.1",
.brand_note = &elf32_freebsd_brandnote,
.flags = BI_CAN_EXEC_DYN | BI_BRAND_NOTE
};
SYSINIT(ia32, SI_SUB_EXEC, SI_ORDER_MIDDLE,
(sysinit_cfunc_t) elf32_insert_brand_entry,
&ia32_brand_info);
static Elf32_Brandinfo ia32_brand_oinfo = {
.brand = ELFOSABI_FREEBSD,
.machine = EM_386,
.compat_3_brand = "FreeBSD",
.emul_path = NULL,
.interp_path = "/usr/libexec/ld-elf.so.1",
.sysvec = &ia32_freebsd_sysvec,
.interp_newpath = "/libexec/ld-elf32.so.1",
.brand_note = &elf32_freebsd_brandnote,
.flags = BI_CAN_EXEC_DYN | BI_BRAND_NOTE
};
SYSINIT(oia32, SI_SUB_EXEC, SI_ORDER_ANY,
(sysinit_cfunc_t) elf32_insert_brand_entry,
&ia32_brand_oinfo);
static Elf32_Brandinfo kia32_brand_info = {
.brand = ELFOSABI_FREEBSD,
.machine = EM_386,
.compat_3_brand = "FreeBSD",
.emul_path = NULL,
.interp_path = "/lib/ld.so.1",
.sysvec = &ia32_freebsd_sysvec,
.brand_note = &elf32_kfreebsd_brandnote,
.flags = BI_CAN_EXEC_DYN | BI_BRAND_NOTE_MANDATORY
};
SYSINIT(kia32, SI_SUB_EXEC, SI_ORDER_ANY,
(sysinit_cfunc_t) elf32_insert_brand_entry,
&kia32_brand_info);
void
elf32_dump_thread(struct thread *td, void *dst, size_t *off)
{
void *buf;
size_t len;
len = 0;
if (use_xsave) {
if (dst != NULL) {
fpugetregs(td);
len += elf32_populate_note(NT_X86_XSTATE,
get_pcb_user_save_td(td), dst,
cpu_max_ext_state_size, &buf);
*(uint64_t *)((char *)buf + X86_XSTATE_XCR0_OFFSET) =
xsave_mask;
} else
len += elf32_populate_note(NT_X86_XSTATE, NULL, NULL,
cpu_max_ext_state_size, NULL);
}
*off = len;
}
void
ia32_fixlimit(struct rlimit *rl, int which)
{
switch (which) {
case RLIMIT_DATA:
if (ia32_maxdsiz != 0) {
if (rl->rlim_cur > ia32_maxdsiz)
rl->rlim_cur = ia32_maxdsiz;
if (rl->rlim_max > ia32_maxdsiz)
rl->rlim_max = ia32_maxdsiz;
}
break;
case RLIMIT_STACK:
if (ia32_maxssiz != 0) {
if (rl->rlim_cur > ia32_maxssiz)
rl->rlim_cur = ia32_maxssiz;
if (rl->rlim_max > ia32_maxssiz)
rl->rlim_max = ia32_maxssiz;
}
break;
case RLIMIT_VMEM:
if (ia32_maxvmem != 0) {
if (rl->rlim_cur > ia32_maxvmem)
rl->rlim_cur = ia32_maxvmem;
if (rl->rlim_max > ia32_maxvmem)
rl->rlim_max = ia32_maxvmem;
}
break;
}
}
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