1d7822b1eSMathieu Desnoyers // SPDX-License-Identifier: GPL-2.0+
2d7822b1eSMathieu Desnoyers /*
3d7822b1eSMathieu Desnoyers * Restartable sequences system call
4d7822b1eSMathieu Desnoyers *
5d7822b1eSMathieu Desnoyers * Copyright (C) 2015, Google, Inc.,
6d7822b1eSMathieu Desnoyers * Paul Turner <pjt@google.com> and Andrew Hunter <ahh@google.com>
7d7822b1eSMathieu Desnoyers * Copyright (C) 2015-2018, EfficiOS Inc.,
8d7822b1eSMathieu Desnoyers * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
9d7822b1eSMathieu Desnoyers */
10d7822b1eSMathieu Desnoyers
11d7822b1eSMathieu Desnoyers #include <linux/sched.h>
12d7822b1eSMathieu Desnoyers #include <linux/uaccess.h>
13d7822b1eSMathieu Desnoyers #include <linux/syscalls.h>
14d7822b1eSMathieu Desnoyers #include <linux/rseq.h>
15d7822b1eSMathieu Desnoyers #include <linux/types.h>
16d7822b1eSMathieu Desnoyers #include <asm/ptrace.h>
17d7822b1eSMathieu Desnoyers
18d7822b1eSMathieu Desnoyers #define CREATE_TRACE_POINTS
19d7822b1eSMathieu Desnoyers #include <trace/events/rseq.h>
20d7822b1eSMathieu Desnoyers
21ee3e3ac0SMathieu Desnoyers /* The original rseq structure size (including padding) is 32 bytes. */
22ee3e3ac0SMathieu Desnoyers #define ORIG_RSEQ_SIZE 32
23ee3e3ac0SMathieu Desnoyers
240190e419SMathieu Desnoyers #define RSEQ_CS_NO_RESTART_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT | \
250190e419SMathieu Desnoyers RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL | \
260190e419SMathieu Desnoyers RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE)
27d7822b1eSMathieu Desnoyers
28d7822b1eSMathieu Desnoyers /*
29d7822b1eSMathieu Desnoyers *
30d7822b1eSMathieu Desnoyers * Restartable sequences are a lightweight interface that allows
31d7822b1eSMathieu Desnoyers * user-level code to be executed atomically relative to scheduler
32d7822b1eSMathieu Desnoyers * preemption and signal delivery. Typically used for implementing
33d7822b1eSMathieu Desnoyers * per-cpu operations.
34d7822b1eSMathieu Desnoyers *
35d7822b1eSMathieu Desnoyers * It allows user-space to perform update operations on per-cpu data
36d7822b1eSMathieu Desnoyers * without requiring heavy-weight atomic operations.
37d7822b1eSMathieu Desnoyers *
38d7822b1eSMathieu Desnoyers * Detailed algorithm of rseq user-space assembly sequences:
39d7822b1eSMathieu Desnoyers *
40d7822b1eSMathieu Desnoyers * init(rseq_cs)
41d7822b1eSMathieu Desnoyers * cpu = TLS->rseq::cpu_id_start
42d7822b1eSMathieu Desnoyers * [1] TLS->rseq::rseq_cs = rseq_cs
43d7822b1eSMathieu Desnoyers * [start_ip] ----------------------------
44d7822b1eSMathieu Desnoyers * [2] if (cpu != TLS->rseq::cpu_id)
45d7822b1eSMathieu Desnoyers * goto abort_ip;
46d7822b1eSMathieu Desnoyers * [3] <last_instruction_in_cs>
47d7822b1eSMathieu Desnoyers * [post_commit_ip] ----------------------------
48d7822b1eSMathieu Desnoyers *
49d7822b1eSMathieu Desnoyers * The address of jump target abort_ip must be outside the critical
50d7822b1eSMathieu Desnoyers * region, i.e.:
51d7822b1eSMathieu Desnoyers *
52d7822b1eSMathieu Desnoyers * [abort_ip] < [start_ip] || [abort_ip] >= [post_commit_ip]
53d7822b1eSMathieu Desnoyers *
54d7822b1eSMathieu Desnoyers * Steps [2]-[3] (inclusive) need to be a sequence of instructions in
55d7822b1eSMathieu Desnoyers * userspace that can handle being interrupted between any of those
56d7822b1eSMathieu Desnoyers * instructions, and then resumed to the abort_ip.
57d7822b1eSMathieu Desnoyers *
58d7822b1eSMathieu Desnoyers * 1. Userspace stores the address of the struct rseq_cs assembly
59d7822b1eSMathieu Desnoyers * block descriptor into the rseq_cs field of the registered
60d7822b1eSMathieu Desnoyers * struct rseq TLS area. This update is performed through a single
61d7822b1eSMathieu Desnoyers * store within the inline assembly instruction sequence.
62d7822b1eSMathieu Desnoyers * [start_ip]
63d7822b1eSMathieu Desnoyers *
64d7822b1eSMathieu Desnoyers * 2. Userspace tests to check whether the current cpu_id field match
65d7822b1eSMathieu Desnoyers * the cpu number loaded before start_ip, branching to abort_ip
66d7822b1eSMathieu Desnoyers * in case of a mismatch.
67d7822b1eSMathieu Desnoyers *
68d7822b1eSMathieu Desnoyers * If the sequence is preempted or interrupted by a signal
69d7822b1eSMathieu Desnoyers * at or after start_ip and before post_commit_ip, then the kernel
70d7822b1eSMathieu Desnoyers * clears TLS->__rseq_abi::rseq_cs, and sets the user-space return
71d7822b1eSMathieu Desnoyers * ip to abort_ip before returning to user-space, so the preempted
72d7822b1eSMathieu Desnoyers * execution resumes at abort_ip.
73d7822b1eSMathieu Desnoyers *
74d7822b1eSMathieu Desnoyers * 3. Userspace critical section final instruction before
75d7822b1eSMathieu Desnoyers * post_commit_ip is the commit. The critical section is
76d7822b1eSMathieu Desnoyers * self-terminating.
77d7822b1eSMathieu Desnoyers * [post_commit_ip]
78d7822b1eSMathieu Desnoyers *
79d7822b1eSMathieu Desnoyers * 4. <success>
80d7822b1eSMathieu Desnoyers *
81d7822b1eSMathieu Desnoyers * On failure at [2], or if interrupted by preempt or signal delivery
82d7822b1eSMathieu Desnoyers * between [1] and [3]:
83d7822b1eSMathieu Desnoyers *
84d7822b1eSMathieu Desnoyers * [abort_ip]
85d7822b1eSMathieu Desnoyers * F1. <failure>
86d7822b1eSMathieu Desnoyers */
87d7822b1eSMathieu Desnoyers
rseq_update_cpu_node_id(struct task_struct * t)88cbae6bacSMathieu Desnoyers static int rseq_update_cpu_node_id(struct task_struct *t)
89d7822b1eSMathieu Desnoyers {
9060af388dSEric Dumazet struct rseq __user *rseq = t->rseq;
91cbae6bacSMathieu Desnoyers u32 cpu_id = raw_smp_processor_id();
92cbae6bacSMathieu Desnoyers u32 node_id = cpu_to_node(cpu_id);
93*f7b01bb0SMathieu Desnoyers u32 mm_cid = task_mm_cid(t);
94d7822b1eSMathieu Desnoyers
95*f7b01bb0SMathieu Desnoyers WARN_ON_ONCE((int) mm_cid < 0);
96ee3e3ac0SMathieu Desnoyers if (!user_write_access_begin(rseq, t->rseq_len))
9760af388dSEric Dumazet goto efault;
9860af388dSEric Dumazet unsafe_put_user(cpu_id, &rseq->cpu_id_start, efault_end);
9960af388dSEric Dumazet unsafe_put_user(cpu_id, &rseq->cpu_id, efault_end);
100cbae6bacSMathieu Desnoyers unsafe_put_user(node_id, &rseq->node_id, efault_end);
101*f7b01bb0SMathieu Desnoyers unsafe_put_user(mm_cid, &rseq->mm_cid, efault_end);
102ee3e3ac0SMathieu Desnoyers /*
103ee3e3ac0SMathieu Desnoyers * Additional feature fields added after ORIG_RSEQ_SIZE
104ee3e3ac0SMathieu Desnoyers * need to be conditionally updated only if
105ee3e3ac0SMathieu Desnoyers * t->rseq_len != ORIG_RSEQ_SIZE.
106ee3e3ac0SMathieu Desnoyers */
10760af388dSEric Dumazet user_write_access_end();
108d7822b1eSMathieu Desnoyers trace_rseq_update(t);
109d7822b1eSMathieu Desnoyers return 0;
11060af388dSEric Dumazet
11160af388dSEric Dumazet efault_end:
11260af388dSEric Dumazet user_write_access_end();
11360af388dSEric Dumazet efault:
11460af388dSEric Dumazet return -EFAULT;
115d7822b1eSMathieu Desnoyers }
116d7822b1eSMathieu Desnoyers
rseq_reset_rseq_cpu_node_id(struct task_struct * t)117cbae6bacSMathieu Desnoyers static int rseq_reset_rseq_cpu_node_id(struct task_struct *t)
118d7822b1eSMathieu Desnoyers {
119*f7b01bb0SMathieu Desnoyers u32 cpu_id_start = 0, cpu_id = RSEQ_CPU_ID_UNINITIALIZED, node_id = 0,
120*f7b01bb0SMathieu Desnoyers mm_cid = 0;
121d7822b1eSMathieu Desnoyers
122d7822b1eSMathieu Desnoyers /*
123d7822b1eSMathieu Desnoyers * Reset cpu_id_start to its initial state (0).
124d7822b1eSMathieu Desnoyers */
1258f281770SMathieu Desnoyers if (put_user(cpu_id_start, &t->rseq->cpu_id_start))
126d7822b1eSMathieu Desnoyers return -EFAULT;
127d7822b1eSMathieu Desnoyers /*
128d7822b1eSMathieu Desnoyers * Reset cpu_id to RSEQ_CPU_ID_UNINITIALIZED, so any user coming
129d7822b1eSMathieu Desnoyers * in after unregistration can figure out that rseq needs to be
130d7822b1eSMathieu Desnoyers * registered again.
131d7822b1eSMathieu Desnoyers */
1328f281770SMathieu Desnoyers if (put_user(cpu_id, &t->rseq->cpu_id))
133d7822b1eSMathieu Desnoyers return -EFAULT;
134ee3e3ac0SMathieu Desnoyers /*
135cbae6bacSMathieu Desnoyers * Reset node_id to its initial state (0).
136cbae6bacSMathieu Desnoyers */
137cbae6bacSMathieu Desnoyers if (put_user(node_id, &t->rseq->node_id))
138cbae6bacSMathieu Desnoyers return -EFAULT;
139cbae6bacSMathieu Desnoyers /*
140*f7b01bb0SMathieu Desnoyers * Reset mm_cid to its initial state (0).
141*f7b01bb0SMathieu Desnoyers */
142*f7b01bb0SMathieu Desnoyers if (put_user(mm_cid, &t->rseq->mm_cid))
143*f7b01bb0SMathieu Desnoyers return -EFAULT;
144*f7b01bb0SMathieu Desnoyers /*
145ee3e3ac0SMathieu Desnoyers * Additional feature fields added after ORIG_RSEQ_SIZE
146ee3e3ac0SMathieu Desnoyers * need to be conditionally reset only if
147ee3e3ac0SMathieu Desnoyers * t->rseq_len != ORIG_RSEQ_SIZE.
148ee3e3ac0SMathieu Desnoyers */
149d7822b1eSMathieu Desnoyers return 0;
150d7822b1eSMathieu Desnoyers }
151d7822b1eSMathieu Desnoyers
rseq_get_rseq_cs(struct task_struct * t,struct rseq_cs * rseq_cs)152d7822b1eSMathieu Desnoyers static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
153d7822b1eSMathieu Desnoyers {
154d7822b1eSMathieu Desnoyers struct rseq_cs __user *urseq_cs;
155ec9c82e0SMathieu Desnoyers u64 ptr;
156d7822b1eSMathieu Desnoyers u32 __user *usig;
157d7822b1eSMathieu Desnoyers u32 sig;
158d7822b1eSMathieu Desnoyers int ret;
159d7822b1eSMathieu Desnoyers
1605e0ccd4aSEric Dumazet #ifdef CONFIG_64BIT
161bfdf4e62SMathieu Desnoyers if (get_user(ptr, &t->rseq->rseq_cs))
1625e0ccd4aSEric Dumazet return -EFAULT;
1635e0ccd4aSEric Dumazet #else
164bfdf4e62SMathieu Desnoyers if (copy_from_user(&ptr, &t->rseq->rseq_cs, sizeof(ptr)))
165ec9c82e0SMathieu Desnoyers return -EFAULT;
1665e0ccd4aSEric Dumazet #endif
167d7822b1eSMathieu Desnoyers if (!ptr) {
168d7822b1eSMathieu Desnoyers memset(rseq_cs, 0, sizeof(*rseq_cs));
169d7822b1eSMathieu Desnoyers return 0;
170d7822b1eSMathieu Desnoyers }
171ec9c82e0SMathieu Desnoyers if (ptr >= TASK_SIZE)
172ec9c82e0SMathieu Desnoyers return -EINVAL;
173ec9c82e0SMathieu Desnoyers urseq_cs = (struct rseq_cs __user *)(unsigned long)ptr;
174d7822b1eSMathieu Desnoyers if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs)))
175d7822b1eSMathieu Desnoyers return -EFAULT;
176d7822b1eSMathieu Desnoyers
177e96d7135SMathieu Desnoyers if (rseq_cs->start_ip >= TASK_SIZE ||
178e96d7135SMathieu Desnoyers rseq_cs->start_ip + rseq_cs->post_commit_offset >= TASK_SIZE ||
179e96d7135SMathieu Desnoyers rseq_cs->abort_ip >= TASK_SIZE ||
180e96d7135SMathieu Desnoyers rseq_cs->version > 0)
181e96d7135SMathieu Desnoyers return -EINVAL;
182e96d7135SMathieu Desnoyers /* Check for overflow. */
183e96d7135SMathieu Desnoyers if (rseq_cs->start_ip + rseq_cs->post_commit_offset < rseq_cs->start_ip)
184e96d7135SMathieu Desnoyers return -EINVAL;
185d7822b1eSMathieu Desnoyers /* Ensure that abort_ip is not in the critical section. */
186d7822b1eSMathieu Desnoyers if (rseq_cs->abort_ip - rseq_cs->start_ip < rseq_cs->post_commit_offset)
187d7822b1eSMathieu Desnoyers return -EINVAL;
188d7822b1eSMathieu Desnoyers
189e96d7135SMathieu Desnoyers usig = (u32 __user *)(unsigned long)(rseq_cs->abort_ip - sizeof(u32));
190d7822b1eSMathieu Desnoyers ret = get_user(sig, usig);
191d7822b1eSMathieu Desnoyers if (ret)
192d7822b1eSMathieu Desnoyers return ret;
193d7822b1eSMathieu Desnoyers
194d7822b1eSMathieu Desnoyers if (current->rseq_sig != sig) {
195d7822b1eSMathieu Desnoyers printk_ratelimited(KERN_WARNING
196d7822b1eSMathieu Desnoyers "Possible attack attempt. Unexpected rseq signature 0x%x, expecting 0x%x (pid=%d, addr=%p).\n",
197d7822b1eSMathieu Desnoyers sig, current->rseq_sig, current->pid, usig);
198e96d7135SMathieu Desnoyers return -EINVAL;
199d7822b1eSMathieu Desnoyers }
200d7822b1eSMathieu Desnoyers return 0;
201d7822b1eSMathieu Desnoyers }
202d7822b1eSMathieu Desnoyers
rseq_warn_flags(const char * str,u32 flags)203448dca8cSMathieu Desnoyers static bool rseq_warn_flags(const char *str, u32 flags)
204448dca8cSMathieu Desnoyers {
205448dca8cSMathieu Desnoyers u32 test_flags;
206448dca8cSMathieu Desnoyers
207448dca8cSMathieu Desnoyers if (!flags)
208448dca8cSMathieu Desnoyers return false;
209448dca8cSMathieu Desnoyers test_flags = flags & RSEQ_CS_NO_RESTART_FLAGS;
210448dca8cSMathieu Desnoyers if (test_flags)
211448dca8cSMathieu Desnoyers pr_warn_once("Deprecated flags (%u) in %s ABI structure", test_flags, str);
212448dca8cSMathieu Desnoyers test_flags = flags & ~RSEQ_CS_NO_RESTART_FLAGS;
213448dca8cSMathieu Desnoyers if (test_flags)
214448dca8cSMathieu Desnoyers pr_warn_once("Unknown flags (%u) in %s ABI structure", test_flags, str);
215448dca8cSMathieu Desnoyers return true;
216448dca8cSMathieu Desnoyers }
217448dca8cSMathieu Desnoyers
rseq_need_restart(struct task_struct * t,u32 cs_flags)218d7822b1eSMathieu Desnoyers static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
219d7822b1eSMathieu Desnoyers {
220d7822b1eSMathieu Desnoyers u32 flags, event_mask;
221d7822b1eSMathieu Desnoyers int ret;
222d7822b1eSMathieu Desnoyers
223448dca8cSMathieu Desnoyers if (rseq_warn_flags("rseq_cs", cs_flags))
2240190e419SMathieu Desnoyers return -EINVAL;
2250190e419SMathieu Desnoyers
226d7822b1eSMathieu Desnoyers /* Get thread flags. */
2278f281770SMathieu Desnoyers ret = get_user(flags, &t->rseq->flags);
228d7822b1eSMathieu Desnoyers if (ret)
229d7822b1eSMathieu Desnoyers return ret;
230d7822b1eSMathieu Desnoyers
231448dca8cSMathieu Desnoyers if (rseq_warn_flags("rseq", flags))
232d7822b1eSMathieu Desnoyers return -EINVAL;
233d7822b1eSMathieu Desnoyers
234d7822b1eSMathieu Desnoyers /*
235d7822b1eSMathieu Desnoyers * Load and clear event mask atomically with respect to
236d7822b1eSMathieu Desnoyers * scheduler preemption.
237d7822b1eSMathieu Desnoyers */
238d7822b1eSMathieu Desnoyers preempt_disable();
239d7822b1eSMathieu Desnoyers event_mask = t->rseq_event_mask;
240d7822b1eSMathieu Desnoyers t->rseq_event_mask = 0;
241d7822b1eSMathieu Desnoyers preempt_enable();
242d7822b1eSMathieu Desnoyers
2430190e419SMathieu Desnoyers return !!event_mask;
244d7822b1eSMathieu Desnoyers }
245d7822b1eSMathieu Desnoyers
clear_rseq_cs(struct task_struct * t)246d7822b1eSMathieu Desnoyers static int clear_rseq_cs(struct task_struct *t)
247d7822b1eSMathieu Desnoyers {
248d7822b1eSMathieu Desnoyers /*
249d7822b1eSMathieu Desnoyers * The rseq_cs field is set to NULL on preemption or signal
250d7822b1eSMathieu Desnoyers * delivery on top of rseq assembly block, as well as on top
251d7822b1eSMathieu Desnoyers * of code outside of the rseq assembly block. This performs
252d7822b1eSMathieu Desnoyers * a lazy clear of the rseq_cs field.
253d7822b1eSMathieu Desnoyers *
2540fb9a1abSMathieu Desnoyers * Set rseq_cs to NULL.
255d7822b1eSMathieu Desnoyers */
2565e0ccd4aSEric Dumazet #ifdef CONFIG_64BIT
257bfdf4e62SMathieu Desnoyers return put_user(0UL, &t->rseq->rseq_cs);
2585e0ccd4aSEric Dumazet #else
259bfdf4e62SMathieu Desnoyers if (clear_user(&t->rseq->rseq_cs, sizeof(t->rseq->rseq_cs)))
260ec9c82e0SMathieu Desnoyers return -EFAULT;
261ec9c82e0SMathieu Desnoyers return 0;
2625e0ccd4aSEric Dumazet #endif
263d7822b1eSMathieu Desnoyers }
264d7822b1eSMathieu Desnoyers
265d7822b1eSMathieu Desnoyers /*
266d7822b1eSMathieu Desnoyers * Unsigned comparison will be true when ip >= start_ip, and when
267d7822b1eSMathieu Desnoyers * ip < start_ip + post_commit_offset.
268d7822b1eSMathieu Desnoyers */
in_rseq_cs(unsigned long ip,struct rseq_cs * rseq_cs)269d7822b1eSMathieu Desnoyers static bool in_rseq_cs(unsigned long ip, struct rseq_cs *rseq_cs)
270d7822b1eSMathieu Desnoyers {
271d7822b1eSMathieu Desnoyers return ip - rseq_cs->start_ip < rseq_cs->post_commit_offset;
272d7822b1eSMathieu Desnoyers }
273d7822b1eSMathieu Desnoyers
rseq_ip_fixup(struct pt_regs * regs)274d7822b1eSMathieu Desnoyers static int rseq_ip_fixup(struct pt_regs *regs)
275d7822b1eSMathieu Desnoyers {
276d7822b1eSMathieu Desnoyers unsigned long ip = instruction_pointer(regs);
277d7822b1eSMathieu Desnoyers struct task_struct *t = current;
278d7822b1eSMathieu Desnoyers struct rseq_cs rseq_cs;
279d7822b1eSMathieu Desnoyers int ret;
280d7822b1eSMathieu Desnoyers
281d7822b1eSMathieu Desnoyers ret = rseq_get_rseq_cs(t, &rseq_cs);
282d7822b1eSMathieu Desnoyers if (ret)
283d7822b1eSMathieu Desnoyers return ret;
284d7822b1eSMathieu Desnoyers
285d7822b1eSMathieu Desnoyers /*
286d7822b1eSMathieu Desnoyers * Handle potentially not being within a critical section.
287d7822b1eSMathieu Desnoyers * If not nested over a rseq critical section, restart is useless.
288d7822b1eSMathieu Desnoyers * Clear the rseq_cs pointer and return.
289d7822b1eSMathieu Desnoyers */
290d7822b1eSMathieu Desnoyers if (!in_rseq_cs(ip, &rseq_cs))
291d7822b1eSMathieu Desnoyers return clear_rseq_cs(t);
292d7822b1eSMathieu Desnoyers ret = rseq_need_restart(t, rseq_cs.flags);
293d7822b1eSMathieu Desnoyers if (ret <= 0)
294d7822b1eSMathieu Desnoyers return ret;
295d7822b1eSMathieu Desnoyers ret = clear_rseq_cs(t);
296d7822b1eSMathieu Desnoyers if (ret)
297d7822b1eSMathieu Desnoyers return ret;
298d7822b1eSMathieu Desnoyers trace_rseq_ip_fixup(ip, rseq_cs.start_ip, rseq_cs.post_commit_offset,
299d7822b1eSMathieu Desnoyers rseq_cs.abort_ip);
300d7822b1eSMathieu Desnoyers instruction_pointer_set(regs, (unsigned long)rseq_cs.abort_ip);
301d7822b1eSMathieu Desnoyers return 0;
302d7822b1eSMathieu Desnoyers }
303d7822b1eSMathieu Desnoyers
304d7822b1eSMathieu Desnoyers /*
305d7822b1eSMathieu Desnoyers * This resume handler must always be executed between any of:
306d7822b1eSMathieu Desnoyers * - preemption,
307d7822b1eSMathieu Desnoyers * - signal delivery,
308d7822b1eSMathieu Desnoyers * and return to user-space.
309d7822b1eSMathieu Desnoyers *
310bff9504bSMathieu Desnoyers * This is how we can ensure that the entire rseq critical section
311d7822b1eSMathieu Desnoyers * will issue the commit instruction only if executed atomically with
312d7822b1eSMathieu Desnoyers * respect to other threads scheduled on the same CPU, and with respect
313d7822b1eSMathieu Desnoyers * to signal handlers.
314d7822b1eSMathieu Desnoyers */
__rseq_handle_notify_resume(struct ksignal * ksig,struct pt_regs * regs)315784e0300SWill Deacon void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *regs)
316d7822b1eSMathieu Desnoyers {
317d7822b1eSMathieu Desnoyers struct task_struct *t = current;
318784e0300SWill Deacon int ret, sig;
319d7822b1eSMathieu Desnoyers
320d7822b1eSMathieu Desnoyers if (unlikely(t->flags & PF_EXITING))
321d7822b1eSMathieu Desnoyers return;
3228646e536SSean Christopherson
3238646e536SSean Christopherson /*
3248646e536SSean Christopherson * regs is NULL if and only if the caller is in a syscall path. Skip
3258646e536SSean Christopherson * fixup and leave rseq_cs as is so that rseq_sycall() will detect and
3268646e536SSean Christopherson * kill a misbehaving userspace on debug kernels.
3278646e536SSean Christopherson */
3288646e536SSean Christopherson if (regs) {
329d7822b1eSMathieu Desnoyers ret = rseq_ip_fixup(regs);
330d7822b1eSMathieu Desnoyers if (unlikely(ret < 0))
331d7822b1eSMathieu Desnoyers goto error;
3328646e536SSean Christopherson }
333cbae6bacSMathieu Desnoyers if (unlikely(rseq_update_cpu_node_id(t)))
334d7822b1eSMathieu Desnoyers goto error;
335d7822b1eSMathieu Desnoyers return;
336d7822b1eSMathieu Desnoyers
337d7822b1eSMathieu Desnoyers error:
338784e0300SWill Deacon sig = ksig ? ksig->sig : 0;
339cb44c9a0SEric W. Biederman force_sigsegv(sig);
340d7822b1eSMathieu Desnoyers }
341d7822b1eSMathieu Desnoyers
342d7822b1eSMathieu Desnoyers #ifdef CONFIG_DEBUG_RSEQ
343d7822b1eSMathieu Desnoyers
344d7822b1eSMathieu Desnoyers /*
345d7822b1eSMathieu Desnoyers * Terminate the process if a syscall is issued within a restartable
346d7822b1eSMathieu Desnoyers * sequence.
347d7822b1eSMathieu Desnoyers */
rseq_syscall(struct pt_regs * regs)348d7822b1eSMathieu Desnoyers void rseq_syscall(struct pt_regs *regs)
349d7822b1eSMathieu Desnoyers {
350d7822b1eSMathieu Desnoyers unsigned long ip = instruction_pointer(regs);
351d7822b1eSMathieu Desnoyers struct task_struct *t = current;
352d7822b1eSMathieu Desnoyers struct rseq_cs rseq_cs;
353d7822b1eSMathieu Desnoyers
354d7822b1eSMathieu Desnoyers if (!t->rseq)
355d7822b1eSMathieu Desnoyers return;
3560ed96051SEric Dumazet if (rseq_get_rseq_cs(t, &rseq_cs) || in_rseq_cs(ip, &rseq_cs))
3573cf5d076SEric W. Biederman force_sig(SIGSEGV);
358d7822b1eSMathieu Desnoyers }
359d7822b1eSMathieu Desnoyers
360d7822b1eSMathieu Desnoyers #endif
361d7822b1eSMathieu Desnoyers
362d7822b1eSMathieu Desnoyers /*
363d7822b1eSMathieu Desnoyers * sys_rseq - setup restartable sequences for caller thread.
364d7822b1eSMathieu Desnoyers */
SYSCALL_DEFINE4(rseq,struct rseq __user *,rseq,u32,rseq_len,int,flags,u32,sig)365d7822b1eSMathieu Desnoyers SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
366d7822b1eSMathieu Desnoyers int, flags, u32, sig)
367d7822b1eSMathieu Desnoyers {
368d7822b1eSMathieu Desnoyers int ret;
369d7822b1eSMathieu Desnoyers
370d7822b1eSMathieu Desnoyers if (flags & RSEQ_FLAG_UNREGISTER) {
37166528a45SMathieu Desnoyers if (flags & ~RSEQ_FLAG_UNREGISTER)
37266528a45SMathieu Desnoyers return -EINVAL;
373d7822b1eSMathieu Desnoyers /* Unregister rseq for current thread. */
374d7822b1eSMathieu Desnoyers if (current->rseq != rseq || !current->rseq)
375d7822b1eSMathieu Desnoyers return -EINVAL;
376ee3e3ac0SMathieu Desnoyers if (rseq_len != current->rseq_len)
377d7822b1eSMathieu Desnoyers return -EINVAL;
378d7822b1eSMathieu Desnoyers if (current->rseq_sig != sig)
379d7822b1eSMathieu Desnoyers return -EPERM;
380cbae6bacSMathieu Desnoyers ret = rseq_reset_rseq_cpu_node_id(current);
381d7822b1eSMathieu Desnoyers if (ret)
382d7822b1eSMathieu Desnoyers return ret;
383d7822b1eSMathieu Desnoyers current->rseq = NULL;
384d7822b1eSMathieu Desnoyers current->rseq_sig = 0;
385ee3e3ac0SMathieu Desnoyers current->rseq_len = 0;
386d7822b1eSMathieu Desnoyers return 0;
387d7822b1eSMathieu Desnoyers }
388d7822b1eSMathieu Desnoyers
389d7822b1eSMathieu Desnoyers if (unlikely(flags))
390d7822b1eSMathieu Desnoyers return -EINVAL;
391d7822b1eSMathieu Desnoyers
392d7822b1eSMathieu Desnoyers if (current->rseq) {
393d7822b1eSMathieu Desnoyers /*
394d7822b1eSMathieu Desnoyers * If rseq is already registered, check whether
395d7822b1eSMathieu Desnoyers * the provided address differs from the prior
396d7822b1eSMathieu Desnoyers * one.
397d7822b1eSMathieu Desnoyers */
398ee3e3ac0SMathieu Desnoyers if (current->rseq != rseq || rseq_len != current->rseq_len)
399d7822b1eSMathieu Desnoyers return -EINVAL;
400d7822b1eSMathieu Desnoyers if (current->rseq_sig != sig)
401d7822b1eSMathieu Desnoyers return -EPERM;
402d7822b1eSMathieu Desnoyers /* Already registered. */
403d7822b1eSMathieu Desnoyers return -EBUSY;
404d7822b1eSMathieu Desnoyers }
405d7822b1eSMathieu Desnoyers
406d7822b1eSMathieu Desnoyers /*
407ee3e3ac0SMathieu Desnoyers * If there was no rseq previously registered, ensure the provided rseq
408ee3e3ac0SMathieu Desnoyers * is properly aligned, as communcated to user-space through the ELF
409ee3e3ac0SMathieu Desnoyers * auxiliary vector AT_RSEQ_ALIGN. If rseq_len is the original rseq
410ee3e3ac0SMathieu Desnoyers * size, the required alignment is the original struct rseq alignment.
411ee3e3ac0SMathieu Desnoyers *
412ee3e3ac0SMathieu Desnoyers * In order to be valid, rseq_len is either the original rseq size, or
413ee3e3ac0SMathieu Desnoyers * large enough to contain all supported fields, as communicated to
414ee3e3ac0SMathieu Desnoyers * user-space through the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE.
415d7822b1eSMathieu Desnoyers */
416ee3e3ac0SMathieu Desnoyers if (rseq_len < ORIG_RSEQ_SIZE ||
417ee3e3ac0SMathieu Desnoyers (rseq_len == ORIG_RSEQ_SIZE && !IS_ALIGNED((unsigned long)rseq, ORIG_RSEQ_SIZE)) ||
418ee3e3ac0SMathieu Desnoyers (rseq_len != ORIG_RSEQ_SIZE && (!IS_ALIGNED((unsigned long)rseq, __alignof__(*rseq)) ||
419ee3e3ac0SMathieu Desnoyers rseq_len < offsetof(struct rseq, end))))
420d7822b1eSMathieu Desnoyers return -EINVAL;
42196d4f267SLinus Torvalds if (!access_ok(rseq, rseq_len))
422d7822b1eSMathieu Desnoyers return -EFAULT;
423d7822b1eSMathieu Desnoyers current->rseq = rseq;
424ee3e3ac0SMathieu Desnoyers current->rseq_len = rseq_len;
425d7822b1eSMathieu Desnoyers current->rseq_sig = sig;
426d7822b1eSMathieu Desnoyers /*
427d7822b1eSMathieu Desnoyers * If rseq was previously inactive, and has just been
428d7822b1eSMathieu Desnoyers * registered, ensure the cpu_id_start and cpu_id fields
429d7822b1eSMathieu Desnoyers * are updated before returning to user-space.
430d7822b1eSMathieu Desnoyers */
431d7822b1eSMathieu Desnoyers rseq_set_notify_resume(current);
432d7822b1eSMathieu Desnoyers
433d7822b1eSMathieu Desnoyers return 0;
434d7822b1eSMathieu Desnoyers }
435