85b7c566f1
Pointer authentication allows userspace to add instructions to insert a Pointer Authentication Code (PAC) into a register based on an address and modifier and check if the PAC is correct. If the check fails it will either return an invalid address or fault to the kernel. As many of these instructions are a NOP when disabled and in earlier revisions of the architecture this can be used, for example, to sign the return address before pushing it to the stack making Return-oriented programming (ROP) attack more difficult on hardware that supports them. The kernel manages five 128 bit signing keys: 2 instruction keys, 2 data keys, and a generic key. The instructions then use one of these when signing the registers. Instructions that use the first four store the PAC in the register being signed, however the instructions that use the generic key store the PAC in a separate register. Currently all userspace threads share all the keys within a process with a new set of userspace keys being generated when executing a new process. This means a forked child will share its keys with its parent until it calls an appropriate exec system call. In the kernel we allow the use of one of the instruction keys, the ia key. This will be used to sign return addresses in function calls. Unlike userspace each kernel thread has its own randomly generated. Thread0 has a static key as does the early code on secondary CPUs. This should be safe as there is minimal user interaction with these threads, however we could generate random keys when the Armv8.5 Random number generation instructions are present. Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D31261
88 lines
2.9 KiB
C
88 lines
2.9 KiB
C
/*-
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* Copyright (c) 1991 Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)proc.h 7.1 (Berkeley) 5/15/91
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* from: FreeBSD: src/sys/i386/include/proc.h,v 1.11 2001/06/29
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* $FreeBSD$
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*/
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#ifndef _MACHINE_PROC_H_
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#define _MACHINE_PROC_H_
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struct ptrauth_key {
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uint64_t pa_key_lo;
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uint64_t pa_key_hi;
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};
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struct mdthread {
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int md_spinlock_count; /* (k) */
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register_t md_saved_daif; /* (k) */
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uintptr_t md_canary;
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/*
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* The pointer authentication keys. These are shared within a process,
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* however this may change for some keys as the PAuth ABI Extension to
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* ELF for the Arm 64-bit Architecture [1] is currently (July 2021) at
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* an Alpha release quality so may change.
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*
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* [1] https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst
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*/
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struct {
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struct ptrauth_key apia;
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struct ptrauth_key apib;
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struct ptrauth_key apda;
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struct ptrauth_key apdb;
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struct ptrauth_key apga;
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} md_ptrauth_user;
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struct {
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struct ptrauth_key apia;
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} md_ptrauth_kern;
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};
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struct mdproc {
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long md_dummy;
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};
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#define KINFO_PROC_SIZE 1088
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#define KINFO_PROC32_SIZE 816
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#ifdef _KERNEL
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#include <machine/pcb.h>
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#define GET_STACK_USAGE(total, used) do { \
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struct thread *td = curthread; \
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(total) = td->td_kstack_pages * PAGE_SIZE - sizeof(struct pcb); \
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(used) = td->td_kstack + (total) - (vm_offset_t)&td; \
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} while (0)
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#endif
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#endif /* !_MACHINE_PROC_H_ */
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