hugetlb: introduce generic version of hugetlb_free_pgd_range
[linux/fpc-iii.git] / arch / x86 / entry / common.c
blob3b2490b81918128a61f6df1807788436d4f8ceb7
1 /*
2 * common.c - C code for kernel entry and exit
3 * Copyright (c) 2015 Andrew Lutomirski
4 * GPL v2
6 * Based on asm and ptrace code by many authors. The code here originated
7 * in ptrace.c and signal.c.
8 */
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>
29 #include <asm/desc.h>
30 #include <asm/traps.h>
31 #include <asm/vdso.h>
32 #include <linux/uaccess.h>
33 #include <asm/cpufeature.h>
35 #define CREATE_TRACE_POINTS
36 #include <trace/events/syscalls.h>
38 #ifdef CONFIG_CONTEXT_TRACKING
39 /* Called on entry from user mode with IRQs off. */
40 __visible inline void enter_from_user_mode(void)
42 CT_WARN_ON(ct_state() != CONTEXT_USER);
43 user_exit_irqoff();
45 #else
46 static inline void enter_from_user_mode(void) {}
47 #endif
49 static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
51 #ifdef CONFIG_X86_64
52 if (arch == AUDIT_ARCH_X86_64) {
53 audit_syscall_entry(regs->orig_ax, regs->di,
54 regs->si, regs->dx, regs->r10);
55 } else
56 #endif
58 audit_syscall_entry(regs->orig_ax, regs->bx,
59 regs->cx, regs->dx, regs->si);
64 * Returns the syscall nr to run (which should match regs->orig_ax) or -1
65 * to skip the syscall.
67 static long syscall_trace_enter(struct pt_regs *regs)
69 u32 arch = in_ia32_syscall() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
71 struct thread_info *ti = current_thread_info();
72 unsigned long ret = 0;
73 bool emulated = false;
74 u32 work;
76 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
77 BUG_ON(regs != task_pt_regs(current));
79 work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
81 if (unlikely(work & _TIF_SYSCALL_EMU))
82 emulated = true;
84 if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
85 tracehook_report_syscall_entry(regs))
86 return -1L;
88 if (emulated)
89 return -1L;
91 #ifdef CONFIG_SECCOMP
93 * Do seccomp after ptrace, to catch any tracer changes.
95 if (work & _TIF_SECCOMP) {
96 struct seccomp_data sd;
98 sd.arch = arch;
99 sd.nr = regs->orig_ax;
100 sd.instruction_pointer = regs->ip;
101 #ifdef CONFIG_X86_64
102 if (arch == AUDIT_ARCH_X86_64) {
103 sd.args[0] = regs->di;
104 sd.args[1] = regs->si;
105 sd.args[2] = regs->dx;
106 sd.args[3] = regs->r10;
107 sd.args[4] = regs->r8;
108 sd.args[5] = regs->r9;
109 } else
110 #endif
112 sd.args[0] = regs->bx;
113 sd.args[1] = regs->cx;
114 sd.args[2] = regs->dx;
115 sd.args[3] = regs->si;
116 sd.args[4] = regs->di;
117 sd.args[5] = regs->bp;
120 ret = __secure_computing(&sd);
121 if (ret == -1)
122 return ret;
124 #endif
126 if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
127 trace_sys_enter(regs, regs->orig_ax);
129 do_audit_syscall_entry(regs, arch);
131 return ret ?: regs->orig_ax;
134 #define EXIT_TO_USERMODE_LOOP_FLAGS \
135 (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
136 _TIF_NEED_RESCHED | _TIF_USER_RETURN_NOTIFY | _TIF_PATCH_PENDING)
138 static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
141 * In order to return to user mode, we need to have IRQs off with
142 * none of EXIT_TO_USERMODE_LOOP_FLAGS set. Several of these flags
143 * can be set at any time on preemptable kernels if we have IRQs on,
144 * so we need to loop. Disabling preemption wouldn't help: doing the
145 * work to clear some of the flags can sleep.
147 while (true) {
148 /* We have work to do. */
149 local_irq_enable();
151 if (cached_flags & _TIF_NEED_RESCHED)
152 schedule();
154 if (cached_flags & _TIF_UPROBE)
155 uprobe_notify_resume(regs);
157 if (cached_flags & _TIF_PATCH_PENDING)
158 klp_update_patch_state(current);
160 /* deal with pending signal delivery */
161 if (cached_flags & _TIF_SIGPENDING)
162 do_signal(regs);
164 if (cached_flags & _TIF_NOTIFY_RESUME) {
165 clear_thread_flag(TIF_NOTIFY_RESUME);
166 tracehook_notify_resume(regs);
167 rseq_handle_notify_resume(NULL, regs);
170 if (cached_flags & _TIF_USER_RETURN_NOTIFY)
171 fire_user_return_notifiers();
173 /* Disable IRQs and retry */
174 local_irq_disable();
176 cached_flags = READ_ONCE(current_thread_info()->flags);
178 if (!(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
179 break;
183 /* Called with IRQs disabled. */
184 __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
186 struct thread_info *ti = current_thread_info();
187 u32 cached_flags;
189 addr_limit_user_check();
191 lockdep_assert_irqs_disabled();
192 lockdep_sys_exit();
194 cached_flags = READ_ONCE(ti->flags);
196 if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
197 exit_to_usermode_loop(regs, cached_flags);
199 #ifdef CONFIG_COMPAT
201 * Compat syscalls set TS_COMPAT. Make sure we clear it before
202 * returning to user mode. We need to clear it *after* signal
203 * handling, because syscall restart has a fixup for compat
204 * syscalls. The fixup is exercised by the ptrace_syscall_32
205 * selftest.
207 * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
208 * special case only applies after poking regs and before the
209 * very next return to user mode.
211 ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
212 #endif
214 user_enter_irqoff();
217 #define SYSCALL_EXIT_WORK_FLAGS \
218 (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
219 _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)
221 static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
223 bool step;
225 audit_syscall_exit(regs);
227 if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
228 trace_sys_exit(regs, regs->ax);
231 * If TIF_SYSCALL_EMU is set, we only get here because of
232 * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
233 * We already reported this syscall instruction in
234 * syscall_trace_enter().
236 step = unlikely(
237 (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
238 == _TIF_SINGLESTEP);
239 if (step || cached_flags & _TIF_SYSCALL_TRACE)
240 tracehook_report_syscall_exit(regs, step);
244 * Called with IRQs on and fully valid regs. Returns with IRQs off in a
245 * state such that we can immediately switch to user mode.
247 __visible inline void syscall_return_slowpath(struct pt_regs *regs)
249 struct thread_info *ti = current_thread_info();
250 u32 cached_flags = READ_ONCE(ti->flags);
252 CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
254 if (IS_ENABLED(CONFIG_PROVE_LOCKING) &&
255 WARN(irqs_disabled(), "syscall %ld left IRQs disabled", regs->orig_ax))
256 local_irq_enable();
258 rseq_syscall(regs);
261 * First do one-time work. If these work items are enabled, we
262 * want to run them exactly once per syscall exit with IRQs on.
264 if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
265 syscall_slow_exit_work(regs, cached_flags);
267 local_irq_disable();
268 prepare_exit_to_usermode(regs);
271 #ifdef CONFIG_X86_64
272 __visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
274 struct thread_info *ti;
276 enter_from_user_mode();
277 local_irq_enable();
278 ti = current_thread_info();
279 if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
280 nr = syscall_trace_enter(regs);
283 * NB: Native and x32 syscalls are dispatched from the same
284 * table. The only functional difference is the x32 bit in
285 * regs->orig_ax, which changes the behavior of some syscalls.
287 nr &= __SYSCALL_MASK;
288 if (likely(nr < NR_syscalls)) {
289 nr = array_index_nospec(nr, NR_syscalls);
290 regs->ax = sys_call_table[nr](regs);
293 syscall_return_slowpath(regs);
295 #endif
297 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
299 * Does a 32-bit syscall. Called with IRQs on in CONTEXT_KERNEL. Does
300 * all entry and exit work and returns with IRQs off. This function is
301 * extremely hot in workloads that use it, and it's usually called from
302 * do_fast_syscall_32, so forcibly inline it to improve performance.
304 static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
306 struct thread_info *ti = current_thread_info();
307 unsigned int nr = (unsigned int)regs->orig_ax;
309 #ifdef CONFIG_IA32_EMULATION
310 ti->status |= TS_COMPAT;
311 #endif
313 if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {
315 * Subtlety here: if ptrace pokes something larger than
316 * 2^32-1 into orig_ax, this truncates it. This may or
317 * may not be necessary, but it matches the old asm
318 * behavior.
320 nr = syscall_trace_enter(regs);
323 if (likely(nr < IA32_NR_syscalls)) {
324 nr = array_index_nospec(nr, IA32_NR_syscalls);
325 #ifdef CONFIG_IA32_EMULATION
326 regs->ax = ia32_sys_call_table[nr](regs);
327 #else
329 * It's possible that a 32-bit syscall implementation
330 * takes a 64-bit parameter but nonetheless assumes that
331 * the high bits are zero. Make sure we zero-extend all
332 * of the args.
334 regs->ax = ia32_sys_call_table[nr](
335 (unsigned int)regs->bx, (unsigned int)regs->cx,
336 (unsigned int)regs->dx, (unsigned int)regs->si,
337 (unsigned int)regs->di, (unsigned int)regs->bp);
338 #endif /* CONFIG_IA32_EMULATION */
341 syscall_return_slowpath(regs);
344 /* Handles int $0x80 */
345 __visible void do_int80_syscall_32(struct pt_regs *regs)
347 enter_from_user_mode();
348 local_irq_enable();
349 do_syscall_32_irqs_on(regs);
352 /* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
353 __visible long do_fast_syscall_32(struct pt_regs *regs)
356 * Called using the internal vDSO SYSENTER/SYSCALL32 calling
357 * convention. Adjust regs so it looks like we entered using int80.
360 unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
361 vdso_image_32.sym_int80_landing_pad;
364 * SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
365 * so that 'regs->ip -= 2' lands back on an int $0x80 instruction.
366 * Fix it up.
368 regs->ip = landing_pad;
370 enter_from_user_mode();
372 local_irq_enable();
374 /* Fetch EBP from where the vDSO stashed it. */
375 if (
376 #ifdef CONFIG_X86_64
378 * Micro-optimization: the pointer we're following is explicitly
379 * 32 bits, so it can't be out of range.
381 __get_user(*(u32 *)&regs->bp,
382 (u32 __user __force *)(unsigned long)(u32)regs->sp)
383 #else
384 get_user(*(u32 *)&regs->bp,
385 (u32 __user __force *)(unsigned long)(u32)regs->sp)
386 #endif
389 /* User code screwed up. */
390 local_irq_disable();
391 regs->ax = -EFAULT;
392 prepare_exit_to_usermode(regs);
393 return 0; /* Keep it simple: use IRET. */
396 /* Now this is just like a normal syscall. */
397 do_syscall_32_irqs_on(regs);
399 #ifdef CONFIG_X86_64
401 * Opportunistic SYSRETL: if possible, try to return using SYSRETL.
402 * SYSRETL is available on all 64-bit CPUs, so we don't need to
403 * bother with SYSEXIT.
405 * Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
406 * because the ECX fixup above will ensure that this is essentially
407 * never the case.
409 return regs->cs == __USER32_CS && regs->ss == __USER_DS &&
410 regs->ip == landing_pad &&
411 (regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF)) == 0;
412 #else
414 * Opportunistic SYSEXIT: if possible, try to return using SYSEXIT.
416 * Unlike 64-bit opportunistic SYSRET, we can't check that CX == IP,
417 * because the ECX fixup above will ensure that this is essentially
418 * never the case.
420 * We don't allow syscalls at all from VM86 mode, but we still
421 * need to check VM, because we might be returning from sys_vm86.
423 return static_cpu_has(X86_FEATURE_SEP) &&
424 regs->cs == __USER_CS && regs->ss == __USER_DS &&
425 regs->ip == landing_pad &&
426 (regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;
427 #endif
429 #endif