xref: /openbmc/linux/arch/arm64/kernel/pointer_auth.c (revision d2e0d8f9)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <linux/compat.h>
4 #include <linux/errno.h>
5 #include <linux/prctl.h>
6 #include <linux/random.h>
7 #include <linux/sched.h>
8 #include <asm/cpufeature.h>
9 #include <asm/pointer_auth.h>
10 
ptrauth_prctl_reset_keys(struct task_struct * tsk,unsigned long arg)11 int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
12 {
13 	struct ptrauth_keys_user *keys = &tsk->thread.keys_user;
14 	unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY |
15 				      PR_PAC_APDAKEY | PR_PAC_APDBKEY;
16 	unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY;
17 
18 	if (!system_supports_address_auth() && !system_supports_generic_auth())
19 		return -EINVAL;
20 
21 	if (is_compat_thread(task_thread_info(tsk)))
22 		return -EINVAL;
23 
24 	if (!arg) {
25 		ptrauth_keys_init_user(keys);
26 		return 0;
27 	}
28 
29 	if (arg & ~key_mask)
30 		return -EINVAL;
31 
32 	if (((arg & addr_key_mask) && !system_supports_address_auth()) ||
33 	    ((arg & PR_PAC_APGAKEY) && !system_supports_generic_auth()))
34 		return -EINVAL;
35 
36 	if (arg & PR_PAC_APIAKEY)
37 		get_random_bytes(&keys->apia, sizeof(keys->apia));
38 	if (arg & PR_PAC_APIBKEY)
39 		get_random_bytes(&keys->apib, sizeof(keys->apib));
40 	if (arg & PR_PAC_APDAKEY)
41 		get_random_bytes(&keys->apda, sizeof(keys->apda));
42 	if (arg & PR_PAC_APDBKEY)
43 		get_random_bytes(&keys->apdb, sizeof(keys->apdb));
44 	if (arg & PR_PAC_APGAKEY)
45 		get_random_bytes(&keys->apga, sizeof(keys->apga));
46 	ptrauth_keys_install_user(keys);
47 
48 	return 0;
49 }
50 
arg_to_enxx_mask(unsigned long arg)51 static u64 arg_to_enxx_mask(unsigned long arg)
52 {
53 	u64 sctlr_enxx_mask = 0;
54 
55 	WARN_ON(arg & ~PR_PAC_ENABLED_KEYS_MASK);
56 	if (arg & PR_PAC_APIAKEY)
57 		sctlr_enxx_mask |= SCTLR_ELx_ENIA;
58 	if (arg & PR_PAC_APIBKEY)
59 		sctlr_enxx_mask |= SCTLR_ELx_ENIB;
60 	if (arg & PR_PAC_APDAKEY)
61 		sctlr_enxx_mask |= SCTLR_ELx_ENDA;
62 	if (arg & PR_PAC_APDBKEY)
63 		sctlr_enxx_mask |= SCTLR_ELx_ENDB;
64 	return sctlr_enxx_mask;
65 }
66 
ptrauth_set_enabled_keys(struct task_struct * tsk,unsigned long keys,unsigned long enabled)67 int ptrauth_set_enabled_keys(struct task_struct *tsk, unsigned long keys,
68 			     unsigned long enabled)
69 {
70 	u64 sctlr;
71 
72 	if (!system_supports_address_auth())
73 		return -EINVAL;
74 
75 	if (is_compat_thread(task_thread_info(tsk)))
76 		return -EINVAL;
77 
78 	if ((keys & ~PR_PAC_ENABLED_KEYS_MASK) || (enabled & ~keys))
79 		return -EINVAL;
80 
81 	preempt_disable();
82 	sctlr = tsk->thread.sctlr_user;
83 	sctlr &= ~arg_to_enxx_mask(keys);
84 	sctlr |= arg_to_enxx_mask(enabled);
85 	tsk->thread.sctlr_user = sctlr;
86 	if (tsk == current)
87 		update_sctlr_el1(sctlr);
88 	preempt_enable();
89 
90 	return 0;
91 }
92 
ptrauth_get_enabled_keys(struct task_struct * tsk)93 int ptrauth_get_enabled_keys(struct task_struct *tsk)
94 {
95 	int retval = 0;
96 
97 	if (!system_supports_address_auth())
98 		return -EINVAL;
99 
100 	if (is_compat_thread(task_thread_info(tsk)))
101 		return -EINVAL;
102 
103 	if (tsk->thread.sctlr_user & SCTLR_ELx_ENIA)
104 		retval |= PR_PAC_APIAKEY;
105 	if (tsk->thread.sctlr_user & SCTLR_ELx_ENIB)
106 		retval |= PR_PAC_APIBKEY;
107 	if (tsk->thread.sctlr_user & SCTLR_ELx_ENDA)
108 		retval |= PR_PAC_APDAKEY;
109 	if (tsk->thread.sctlr_user & SCTLR_ELx_ENDB)
110 		retval |= PR_PAC_APDBKEY;
111 
112 	return retval;
113 }
114