x86/syscalls: Split the x32 syscalls into their own table
[sfrench/cifs-2.6.git] / arch / x86 / entry / common.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * common.c - C code for kernel entry and exit
4  * Copyright (c) 2015 Andrew Lutomirski
5  *
6  * Based on asm and ptrace code by many authors.  The code here originated
7  * in ptrace.c and signal.c.
8  */
9
10 #include <linux/kernel.h>
11 #include <linux/sched.h>
12 #include <linux/sched/task_stack.h>
13 #include <linux/mm.h>
14 #include <linux/smp.h>
15 #include <linux/errno.h>
16 #include <linux/ptrace.h>
17 #include <linux/tracehook.h>
18 #include <linux/audit.h>
19 #include <linux/seccomp.h>
20 #include <linux/signal.h>
21 #include <linux/export.h>
22 #include <linux/context_tracking.h>
23 #include <linux/user-return-notifier.h>
24 #include <linux/nospec.h>
25 #include <linux/uprobes.h>
26 #include <linux/livepatch.h>
27 #include <linux/syscalls.h>
28 #include <linux/uaccess.h>
29
30 #include <asm/desc.h>
31 #include <asm/traps.h>
32 #include <asm/vdso.h>
33 #include <asm/cpufeature.h>
34 #include <asm/fpu/api.h>
35 #include <asm/nospec-branch.h>
36
37 #define CREATE_TRACE_POINTS
38 #include <trace/events/syscalls.h>
39
40 #ifdef CONFIG_CONTEXT_TRACKING
41 /* Called on entry from user mode with IRQs off. */
42 __visible inline void enter_from_user_mode(void)
43 {
44         CT_WARN_ON(ct_state() != CONTEXT_USER);
45         user_exit_irqoff();
46 }
47 #else
48 static inline void enter_from_user_mode(void) {}
49 #endif
50
51 static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
52 {
53 #ifdef CONFIG_X86_64
54         if (arch == AUDIT_ARCH_X86_64) {
55                 audit_syscall_entry(regs->orig_ax, regs->di,
56                                     regs->si, regs->dx, regs->r10);
57         } else
58 #endif
59         {
60                 audit_syscall_entry(regs->orig_ax, regs->bx,
61                                     regs->cx, regs->dx, regs->si);
62         }
63 }
64
65 /*
66  * Returns the syscall nr to run (which should match regs->orig_ax) or -1
67  * to skip the syscall.
68  */
69 static long syscall_trace_enter(struct pt_regs *regs)
70 {
71         u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
72
73         struct thread_info *ti = current_thread_info();
74         unsigned long ret = 0;
75         u32 work;
76
77         if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
78                 BUG_ON(regs != task_pt_regs(current));
79
80         work = READ_ONCE(ti->flags);
81
82         if (work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
83                 ret = tracehook_report_syscall_entry(regs);
84                 if (ret || (work & _TIF_SYSCALL_EMU))
85                         return -1L;
86         }
87
88 #ifdef CONFIG_SECCOMP
89         /*
90          * Do seccomp after ptrace, to catch any tracer changes.
91          */
92         if (work & _TIF_SECCOMP) {
93                 struct seccomp_data sd;
94
95                 sd.arch = arch;
96                 sd.nr = regs->orig_ax;
97                 sd.instruction_pointer = regs->ip;
98 #ifdef CONFIG_X86_64
99                 if (arch == AUDIT_ARCH_X86_64) {
100                         sd.args[0] = regs->di;
101                         sd.args[1] = regs->si;
102                         sd.args[2] = regs->dx;
103                         sd.args[3] = regs->r10;
104                         sd.args[4] = regs->r8;
105                         sd.args[5] = regs->r9;
106                 } else
107 #endif
108                 {
109                         sd.args[0] = regs->bx;
110                         sd.args[1] = regs->cx;
111                         sd.args[2] = regs->dx;
112                         sd.args[3] = regs->si;
113                         sd.args[4] = regs->di;
114                         sd.args[5] = regs->bp;
115                 }
116
117                 ret = __secure_computing(&sd);
118                 if (ret == -1)
119                         return ret;
120         }
121 #endif
122
123         if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
124                 trace_sys_enter(regs, regs->orig_ax);
125
126         do_audit_syscall_entry(regs, arch);
127
128         return ret ?: regs->orig_ax;
129 }
130
131 #define EXIT_TO_USERMODE_LOOP_FLAGS                             \
132         (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |   \
133          _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY | _TIF_PATCH_PENDING)
134
135 static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
136 {
137         /*
138          * In order to return to user mode, we need to have IRQs off with
139          * none of EXIT_TO_USERMODE_LOOP_FLAGS set.  Several of these flags
140          * can be set at any time on preemptible kernels if we have IRQs on,
141          * so we need to loop.  Disabling preemption wouldn't help: doing the
142          * work to clear some of the flags can sleep.
143          */
144         while (true) {
145                 /* We have work to do. */
146                 local_irq_enable();
147
148                 if (cached_flags & _TIF_NEED_RESCHED)
149                         schedule();
150
151                 if (cached_flags & _TIF_UPROBE)
152                         uprobe_notify_resume(regs);
153
154                 if (cached_flags & _TIF_PATCH_PENDING)
155                         klp_update_patch_state(current);
156
157                 /* deal with pending signal delivery */
158                 if (cached_flags & _TIF_SIGPENDING)
159                         do_signal(regs);
160
161                 if (cached_flags & _TIF_NOTIFY_RESUME) {
162                         clear_thread_flag(TIF_NOTIFY_RESUME);
163                         tracehook_notify_resume(regs);
164                         rseq_handle_notify_resume(NULL, regs);
165                 }
166
167                 if (cached_flags & _TIF_USER_RETURN_NOTIFY)
168                         fire_user_return_notifiers();
169
170                 /* Disable IRQs and retry */
171                 local_irq_disable();
172
173                 cached_flags = READ_ONCE(current_thread_info()->flags);
174
175                 if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
176                         break;
177         }
178 }
179
180 /* Called with IRQs disabled. */
181 __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
182 {
183         struct thread_info *ti = current_thread_info();
184         u32 cached_flags;
185
186         addr_limit_user_check();
187
188         lockdep_assert_irqs_disabled();
189         lockdep_sys_exit();
190
191         cached_flags = READ_ONCE(ti->flags);
192
193         if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
194                 exit_to_usermode_loop(regs, cached_flags);
195
196         /* Reload ti->flags; we may have rescheduled above. */
197         cached_flags = READ_ONCE(ti->flags);
198
199         fpregs_assert_state_consistent();
200         if (unlikely(cached_flags & _TIF_NEED_FPU_LOAD))
201                 switch_fpu_return();
202
203 #ifdef CONFIG_COMPAT
204         /*
205          * Compat syscalls set TS_COMPAT.  Make sure we clear it before
206          * returning to user mode.  We need to clear it *after* signal
207          * handling, because syscall restart has a fixup for compat
208          * syscalls.  The fixup is exercised by the ptrace_syscall_32
209          * selftest.
210          *
211          * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
212          * special case only applies after poking regs and before the
213          * very next return to user mode.
214          */
215         ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
216 #endif
217
218         user_enter_irqoff();
219
220         mds_user_clear_cpu_buffers();
221 }
222
223 #define SYSCALL_EXIT_WORK_FLAGS                         \
224         (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |      \
225          _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)
226
227 static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
228 {
229         bool step;
230
231         audit_syscall_exit(regs);
232
233         if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
234                 trace_sys_exit(regs, regs->ax);
235
236         /*
237          * If TIF_SYSCALL_EMU is set, we only get here because of
238          * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
239          * We already reported this syscall instruction in
240          * syscall_trace_enter().
241          */
242         step = unlikely(
243                 (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
244                 == _TIF_SINGLESTEP);
245         if (step || cached_flags & _TIF_SYSCALL_TRACE)
246                 tracehook_report_syscall_exit(regs, step);
247 }
248
249 /*
250  * Called with IRQs on and fully valid regs.  Returns with IRQs off in a
251  * state such that we can immediately switch to user mode.
252  */
253 __visible inline void syscall_return_slowpath(struct pt_regs *regs)
254 {
255         struct thread_info *ti = current_thread_info();
256         u32 cached_flags = READ_ONCE(ti->flags);
257
258         CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
259
260         if (IS_ENABLED(CONFIG_PROVE_LOCKING) &&
261             WARN(irqs_disabled(), "syscall %ld left IRQs disabled", regs->orig_ax))
262                 local_irq_enable();
263
264         rseq_syscall(regs);
265
266         /*
267          * First do one-time work.  If these work items are enabled, we
268          * want to run them exactly once per syscall exit with IRQs on.
269          */
270         if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
271                 syscall_slow_exit_work(regs, cached_flags);
272
273         local_irq_disable();
274         prepare_exit_to_usermode(regs);
275 }
276
277 #ifdef CONFIG_X86_64
278 __visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
279 {
280         struct thread_info *ti;
281
282         enter_from_user_mode();
283         local_irq_enable();
284         ti = current_thread_info();
285         if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
286                 nr = syscall_trace_enter(regs);
287
288         if (likely(nr < NR_syscalls)) {
289                 nr = array_index_nospec(nr, NR_syscalls);
290                 regs->ax = sys_call_table[nr](regs);
291 #ifdef CONFIG_X86_X32_ABI
292         } else if (likely((nr & __X32_SYSCALL_BIT) &&
293                           (nr & ~__X32_SYSCALL_BIT) < X32_NR_syscalls)) {
294                 nr = array_index_nospec(nr & ~__X32_SYSCALL_BIT,
295                                         X32_NR_syscalls);
296                 regs->ax = x32_sys_call_table[nr](regs);
297 #endif
298         }
299
300         syscall_return_slowpath(regs);
301 }
302 #endif
303
304 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
305 /*
306  * Does a 32-bit syscall.  Called with IRQs on in CONTEXT_KERNEL.  Does
307  * all entry and exit work and returns with IRQs off.  This function is
308  * extremely hot in workloads that use it, and it's usually called from
309  * do_fast_syscall_32, so forcibly inline it to improve performance.
310  */
311 static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
312 {
313         struct thread_info *ti = current_thread_info();
314         unsigned int nr = (unsigned int)regs->orig_ax;
315
316 #ifdef CONFIG_IA32_EMULATION
317         ti->status |= TS_COMPAT;
318 #endif
319
320         if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
321                 /*
322                  * Subtlety here: if ptrace pokes something larger than
323                  * 2^32-1 into orig_ax, this truncates it.  This may or
324                  * may not be necessary, but it matches the old asm
325                  * behavior.
326                  */
327                 nr = syscall_trace_enter(regs);
328         }
329
330         if (likely(nr < IA32_NR_syscalls)) {
331                 nr = array_index_nospec(nr, IA32_NR_syscalls);
332 #ifdef CONFIG_IA32_EMULATION
333                 regs->ax = ia32_sys_call_table[nr](regs);
334 #else
335                 /*
336                  * It's possible that a 32-bit syscall implementation
337                  * takes a 64-bit parameter but nonetheless assumes that
338                  * the high bits are zero.  Make sure we zero-extend all
339                  * of the args.
340                  */
341                 regs->ax = ia32_sys_call_table[nr](
342                         (unsigned int)regs->bx, (unsigned int)regs->cx,
343                         (unsigned int)regs->dx, (unsigned int)regs->si,
344                         (unsigned int)regs->di, (unsigned int)regs->bp);
345 #endif /* CONFIG_IA32_EMULATION */
346         }
347
348         syscall_return_slowpath(regs);
349 }
350
351 /* Handles int $0x80 */
352 __visible void do_int80_syscall_32(struct pt_regs *regs)
353 {
354         enter_from_user_mode();
355         local_irq_enable();
356         do_syscall_32_irqs_on(regs);
357 }
358
359 /* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
360 __visible long do_fast_syscall_32(struct pt_regs *regs)
361 {
362         /*
363          * Called using the internal vDSO SYSENTER/SYSCALL32 calling
364          * convention.  Adjust regs so it looks like we entered using int80.
365          */
366
367         unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
368                 vdso_image_32.sym_int80_landing_pad;
369
370         /*
371          * SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
372          * so that 'regs->ip -= 2' lands back on an int $0x80 instruction.
373          * Fix it up.
374          */
375         regs->ip = landing_pad;
376
377         enter_from_user_mode();
378
379         local_irq_enable();
380
381         /* Fetch EBP from where the vDSO stashed it. */
382         if (
383 #ifdef CONFIG_X86_64
384                 /*
385                  * Micro-optimization: the pointer we're following is explicitly
386                  * 32 bits, so it can't be out of range.
387                  */
388                 __get_user(*(u32 *)&regs->bp,
389                             (u32 __user __force *)(unsigned long)(u32)regs->sp)
390 #else
391                 get_user(*(u32 *)&regs->bp,
392                          (u32 __user __force *)(unsigned long)(u32)regs->sp)
393 #endif
394                 ) {
395
396                 /* User code screwed up. */
397                 local_irq_disable();
398                 regs->ax = -EFAULT;
399                 prepare_exit_to_usermode(regs);
400                 return 0;       /* Keep it simple: use IRET. */
401         }
402
403         /* Now this is just like a normal syscall. */
404         do_syscall_32_irqs_on(regs);
405
406 #ifdef CONFIG_X86_64
407         /*
408          * Opportunistic SYSRETL: if possible, try to return using SYSRETL.
409          * SYSRETL is available on all 64-bit CPUs, so we don't need to
410          * bother with SYSEXIT.
411          *
412          * Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
413          * because the ECX fixup above will ensure that this is essentially
414          * never the case.
415          */
416         return regs->cs == __USER32_CS && regs->ss == __USER_DS &&
417                 regs->ip == landing_pad &&
418                 (regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)) == 0;
419 #else
420         /*
421          * Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
422          *
423          * Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
424          * because the ECX fixup above will ensure that this is essentially
425          * never the case.
426          *
427          * We don't allow syscalls at all from VM86 mode, but we still
428          * need to check VM, because we might be returning from sys_vm86.
429          */
430         return static_cpu_has(X86_FEATURE_SEP) &&
431                 regs->cs == __USER_CS && regs->ss == __USER_DS &&
432                 regs->ip == landing_pad &&
433                 (regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;
434 #endif
435 }
436 #endif