1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 1995 Linus Torvalds
4 *
5 * Pentium III FXSR, SSE support
6 * Gareth Hughes <gareth@valinux.com>, May 2000
7 *
8 * X86-64 port
9 * Andi Kleen.
10 *
11 * CPU hotplug support - ashok.raj@intel.com
12 */
13
14 /*
15 * This file handles the architecture-dependent parts of process handling..
16 */
17
18 #include <linux/cpu.h>
19 #include <linux/errno.h>
20 #include <linux/sched.h>
21 #include <linux/sched/task.h>
22 #include <linux/sched/task_stack.h>
23 #include <linux/fs.h>
24 #include <linux/kernel.h>
25 #include <linux/mm.h>
26 #include <linux/elfcore.h>
27 #include <linux/smp.h>
28 #include <linux/slab.h>
29 #include <linux/user.h>
30 #include <linux/interrupt.h>
31 #include <linux/delay.h>
32 #include <linux/export.h>
33 #include <linux/ptrace.h>
34 #include <linux/notifier.h>
35 #include <linux/kprobes.h>
36 #include <linux/kdebug.h>
37 #include <linux/prctl.h>
38 #include <linux/uaccess.h>
39 #include <linux/io.h>
40 #include <linux/ftrace.h>
41 #include <linux/syscalls.h>
42
43 #include <asm/processor.h>
44 #include <asm/fpu/internal.h>
45 #include <asm/mmu_context.h>
46 #include <asm/prctl.h>
47 #include <asm/desc.h>
48 #include <asm/proto.h>
49 #include <asm/ia32.h>
50 #include <asm/debugreg.h>
51 #include <asm/switch_to.h>
52 #include <asm/xen/hypervisor.h>
53 #include <asm/vdso.h>
54 #include <asm/resctrl.h>
55 #include <asm/unistd.h>
56 #include <asm/fsgsbase.h>
57 #ifdef CONFIG_IA32_EMULATION
58 /* Not included via unistd.h */
59 #include <asm/unistd_32_ia32.h>
60 #endif
61
62 #include "process.h"
63
64 /* Prints also some state that isn't saved in the pt_regs */
__show_regs(struct pt_regs * regs,enum show_regs_mode mode,const char * log_lvl)65 void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
66 const char *log_lvl)
67 {
68 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L, fs, gs, shadowgs;
69 unsigned long d0, d1, d2, d3, d6, d7;
70 unsigned int fsindex, gsindex;
71 unsigned int ds, es;
72
73 show_iret_regs(regs, log_lvl);
74
75 if (regs->orig_ax != -1)
76 pr_cont(" ORIG_RAX: %016lx\n", regs->orig_ax);
77 else
78 pr_cont("\n");
79
80 printk("%sRAX: %016lx RBX: %016lx RCX: %016lx\n",
81 log_lvl, regs->ax, regs->bx, regs->cx);
82 printk("%sRDX: %016lx RSI: %016lx RDI: %016lx\n",
83 log_lvl, regs->dx, regs->si, regs->di);
84 printk("%sRBP: %016lx R08: %016lx R09: %016lx\n",
85 log_lvl, regs->bp, regs->r8, regs->r9);
86 printk("%sR10: %016lx R11: %016lx R12: %016lx\n",
87 log_lvl, regs->r10, regs->r11, regs->r12);
88 printk("%sR13: %016lx R14: %016lx R15: %016lx\n",
89 log_lvl, regs->r13, regs->r14, regs->r15);
90
91 if (mode == SHOW_REGS_SHORT)
92 return;
93
94 if (mode == SHOW_REGS_USER) {
95 rdmsrl(MSR_FS_BASE, fs);
96 rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
97 printk("%sFS: %016lx GS: %016lx\n",
98 log_lvl, fs, shadowgs);
99 return;
100 }
101
102 asm("movl %%ds,%0" : "=r" (ds));
103 asm("movl %%es,%0" : "=r" (es));
104 asm("movl %%fs,%0" : "=r" (fsindex));
105 asm("movl %%gs,%0" : "=r" (gsindex));
106
107 rdmsrl(MSR_FS_BASE, fs);
108 rdmsrl(MSR_GS_BASE, gs);
109 rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
110
111 cr0 = read_cr0();
112 cr2 = read_cr2();
113 cr3 = __read_cr3();
114 cr4 = __read_cr4();
115
116 printk("%sFS: %016lx(%04x) GS:%016lx(%04x) knlGS:%016lx\n",
117 log_lvl, fs, fsindex, gs, gsindex, shadowgs);
118 printk("%sCS: %04lx DS: %04x ES: %04x CR0: %016lx\n",
119 log_lvl, regs->cs, ds, es, cr0);
120 printk("%sCR2: %016lx CR3: %016lx CR4: %016lx\n",
121 log_lvl, cr2, cr3, cr4);
122
123 get_debugreg(d0, 0);
124 get_debugreg(d1, 1);
125 get_debugreg(d2, 2);
126 get_debugreg(d3, 3);
127 get_debugreg(d6, 6);
128 get_debugreg(d7, 7);
129
130 /* Only print out debug registers if they are in their non-default state. */
131 if (!((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
132 (d6 == DR6_RESERVED) && (d7 == 0x400))) {
133 printk("%sDR0: %016lx DR1: %016lx DR2: %016lx\n",
134 log_lvl, d0, d1, d2);
135 printk("%sDR3: %016lx DR6: %016lx DR7: %016lx\n",
136 log_lvl, d3, d6, d7);
137 }
138
139 if (boot_cpu_has(X86_FEATURE_OSPKE))
140 printk("%sPKRU: %08x\n", log_lvl, read_pkru());
141 }
142
release_thread(struct task_struct * dead_task)143 void release_thread(struct task_struct *dead_task)
144 {
145 WARN_ON(dead_task->mm);
146 }
147
148 enum which_selector {
149 FS,
150 GS
151 };
152
153 /*
154 * Out of line to be protected from kprobes and tracing. If this would be
155 * traced or probed than any access to a per CPU variable happens with
156 * the wrong GS.
157 *
158 * It is not used on Xen paravirt. When paravirt support is needed, it
159 * needs to be renamed with native_ prefix.
160 */
__rdgsbase_inactive(void)161 static noinstr unsigned long __rdgsbase_inactive(void)
162 {
163 unsigned long gsbase;
164
165 lockdep_assert_irqs_disabled();
166
167 if (!static_cpu_has(X86_FEATURE_XENPV)) {
168 native_swapgs();
169 gsbase = rdgsbase();
170 native_swapgs();
171 } else {
172 instrumentation_begin();
173 rdmsrl(MSR_KERNEL_GS_BASE, gsbase);
174 instrumentation_end();
175 }
176
177 return gsbase;
178 }
179
180 /*
181 * Out of line to be protected from kprobes and tracing. If this would be
182 * traced or probed than any access to a per CPU variable happens with
183 * the wrong GS.
184 *
185 * It is not used on Xen paravirt. When paravirt support is needed, it
186 * needs to be renamed with native_ prefix.
187 */
__wrgsbase_inactive(unsigned long gsbase)188 static noinstr void __wrgsbase_inactive(unsigned long gsbase)
189 {
190 lockdep_assert_irqs_disabled();
191
192 if (!static_cpu_has(X86_FEATURE_XENPV)) {
193 native_swapgs();
194 wrgsbase(gsbase);
195 native_swapgs();
196 } else {
197 instrumentation_begin();
198 wrmsrl(MSR_KERNEL_GS_BASE, gsbase);
199 instrumentation_end();
200 }
201 }
202
203 /*
204 * Saves the FS or GS base for an outgoing thread if FSGSBASE extensions are
205 * not available. The goal is to be reasonably fast on non-FSGSBASE systems.
206 * It's forcibly inlined because it'll generate better code and this function
207 * is hot.
208 */
save_base_legacy(struct task_struct * prev_p,unsigned short selector,enum which_selector which)209 static __always_inline void save_base_legacy(struct task_struct *prev_p,
210 unsigned short selector,
211 enum which_selector which)
212 {
213 if (likely(selector == 0)) {
214 /*
215 * On Intel (without X86_BUG_NULL_SEG), the segment base could
216 * be the pre-existing saved base or it could be zero. On AMD
217 * (with X86_BUG_NULL_SEG), the segment base could be almost
218 * anything.
219 *
220 * This branch is very hot (it's hit twice on almost every
221 * context switch between 64-bit programs), and avoiding
222 * the RDMSR helps a lot, so we just assume that whatever
223 * value is already saved is correct. This matches historical
224 * Linux behavior, so it won't break existing applications.
225 *
226 * To avoid leaking state, on non-X86_BUG_NULL_SEG CPUs, if we
227 * report that the base is zero, it needs to actually be zero:
228 * see the corresponding logic in load_seg_legacy.
229 */
230 } else {
231 /*
232 * If the selector is 1, 2, or 3, then the base is zero on
233 * !X86_BUG_NULL_SEG CPUs and could be anything on
234 * X86_BUG_NULL_SEG CPUs. In the latter case, Linux
235 * has never attempted to preserve the base across context
236 * switches.
237 *
238 * If selector > 3, then it refers to a real segment, and
239 * saving the base isn't necessary.
240 */
241 if (which == FS)
242 prev_p->thread.fsbase = 0;
243 else
244 prev_p->thread.gsbase = 0;
245 }
246 }
247
save_fsgs(struct task_struct * task)248 static __always_inline void save_fsgs(struct task_struct *task)
249 {
250 savesegment(fs, task->thread.fsindex);
251 savesegment(gs, task->thread.gsindex);
252 if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
253 /*
254 * If FSGSBASE is enabled, we can't make any useful guesses
255 * about the base, and user code expects us to save the current
256 * value. Fortunately, reading the base directly is efficient.
257 */
258 task->thread.fsbase = rdfsbase();
259 task->thread.gsbase = __rdgsbase_inactive();
260 } else {
261 save_base_legacy(task, task->thread.fsindex, FS);
262 save_base_legacy(task, task->thread.gsindex, GS);
263 }
264 }
265
266 /*
267 * While a process is running,current->thread.fsbase and current->thread.gsbase
268 * may not match the corresponding CPU registers (see save_base_legacy()).
269 */
current_save_fsgs(void)270 void current_save_fsgs(void)
271 {
272 unsigned long flags;
273
274 /* Interrupts need to be off for FSGSBASE */
275 local_irq_save(flags);
276 save_fsgs(current);
277 local_irq_restore(flags);
278 }
279 #if IS_ENABLED(CONFIG_KVM)
280 EXPORT_SYMBOL_GPL(current_save_fsgs);
281 #endif
282
loadseg(enum which_selector which,unsigned short sel)283 static __always_inline void loadseg(enum which_selector which,
284 unsigned short sel)
285 {
286 if (which == FS)
287 loadsegment(fs, sel);
288 else
289 load_gs_index(sel);
290 }
291
load_seg_legacy(unsigned short prev_index,unsigned long prev_base,unsigned short next_index,unsigned long next_base,enum which_selector which)292 static __always_inline void load_seg_legacy(unsigned short prev_index,
293 unsigned long prev_base,
294 unsigned short next_index,
295 unsigned long next_base,
296 enum which_selector which)
297 {
298 if (likely(next_index <= 3)) {
299 /*
300 * The next task is using 64-bit TLS, is not using this
301 * segment at all, or is having fun with arcane CPU features.
302 */
303 if (next_base == 0) {
304 /*
305 * Nasty case: on AMD CPUs, we need to forcibly zero
306 * the base.
307 */
308 if (static_cpu_has_bug(X86_BUG_NULL_SEG)) {
309 loadseg(which, __USER_DS);
310 loadseg(which, next_index);
311 } else {
312 /*
313 * We could try to exhaustively detect cases
314 * under which we can skip the segment load,
315 * but there's really only one case that matters
316 * for performance: if both the previous and
317 * next states are fully zeroed, we can skip
318 * the load.
319 *
320 * (This assumes that prev_base == 0 has no
321 * false positives. This is the case on
322 * Intel-style CPUs.)
323 */
324 if (likely(prev_index | next_index | prev_base))
325 loadseg(which, next_index);
326 }
327 } else {
328 if (prev_index != next_index)
329 loadseg(which, next_index);
330 wrmsrl(which == FS ? MSR_FS_BASE : MSR_KERNEL_GS_BASE,
331 next_base);
332 }
333 } else {
334 /*
335 * The next task is using a real segment. Loading the selector
336 * is sufficient.
337 */
338 loadseg(which, next_index);
339 }
340 }
341
x86_fsgsbase_load(struct thread_struct * prev,struct thread_struct * next)342 static __always_inline void x86_fsgsbase_load(struct thread_struct *prev,
343 struct thread_struct *next)
344 {
345 if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
346 /* Update the FS and GS selectors if they could have changed. */
347 if (unlikely(prev->fsindex || next->fsindex))
348 loadseg(FS, next->fsindex);
349 if (unlikely(prev->gsindex || next->gsindex))
350 loadseg(GS, next->gsindex);
351
352 /* Update the bases. */
353 wrfsbase(next->fsbase);
354 __wrgsbase_inactive(next->gsbase);
355 } else {
356 load_seg_legacy(prev->fsindex, prev->fsbase,
357 next->fsindex, next->fsbase, FS);
358 load_seg_legacy(prev->gsindex, prev->gsbase,
359 next->gsindex, next->gsbase, GS);
360 }
361 }
362
x86_fsgsbase_read_task(struct task_struct * task,unsigned short selector)363 unsigned long x86_fsgsbase_read_task(struct task_struct *task,
364 unsigned short selector)
365 {
366 unsigned short idx = selector >> 3;
367 unsigned long base;
368
369 if (likely((selector & SEGMENT_TI_MASK) == 0)) {
370 if (unlikely(idx >= GDT_ENTRIES))
371 return 0;
372
373 /*
374 * There are no user segments in the GDT with nonzero bases
375 * other than the TLS segments.
376 */
377 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
378 return 0;
379
380 idx -= GDT_ENTRY_TLS_MIN;
381 base = get_desc_base(&task->thread.tls_array[idx]);
382 } else {
383 #ifdef CONFIG_MODIFY_LDT_SYSCALL
384 struct ldt_struct *ldt;
385
386 /*
387 * If performance here mattered, we could protect the LDT
388 * with RCU. This is a slow path, though, so we can just
389 * take the mutex.
390 */
391 mutex_lock(&task->mm->context.lock);
392 ldt = task->mm->context.ldt;
393 if (unlikely(!ldt || idx >= ldt->nr_entries))
394 base = 0;
395 else
396 base = get_desc_base(ldt->entries + idx);
397 mutex_unlock(&task->mm->context.lock);
398 #else
399 base = 0;
400 #endif
401 }
402
403 return base;
404 }
405
x86_gsbase_read_cpu_inactive(void)406 unsigned long x86_gsbase_read_cpu_inactive(void)
407 {
408 unsigned long gsbase;
409
410 if (boot_cpu_has(X86_FEATURE_FSGSBASE)) {
411 unsigned long flags;
412
413 local_irq_save(flags);
414 gsbase = __rdgsbase_inactive();
415 local_irq_restore(flags);
416 } else {
417 rdmsrl(MSR_KERNEL_GS_BASE, gsbase);
418 }
419
420 return gsbase;
421 }
422
x86_gsbase_write_cpu_inactive(unsigned long gsbase)423 void x86_gsbase_write_cpu_inactive(unsigned long gsbase)
424 {
425 if (boot_cpu_has(X86_FEATURE_FSGSBASE)) {
426 unsigned long flags;
427
428 local_irq_save(flags);
429 __wrgsbase_inactive(gsbase);
430 local_irq_restore(flags);
431 } else {
432 wrmsrl(MSR_KERNEL_GS_BASE, gsbase);
433 }
434 }
435
x86_fsbase_read_task(struct task_struct * task)436 unsigned long x86_fsbase_read_task(struct task_struct *task)
437 {
438 unsigned long fsbase;
439
440 if (task == current)
441 fsbase = x86_fsbase_read_cpu();
442 else if (boot_cpu_has(X86_FEATURE_FSGSBASE) ||
443 (task->thread.fsindex == 0))
444 fsbase = task->thread.fsbase;
445 else
446 fsbase = x86_fsgsbase_read_task(task, task->thread.fsindex);
447
448 return fsbase;
449 }
450
x86_gsbase_read_task(struct task_struct * task)451 unsigned long x86_gsbase_read_task(struct task_struct *task)
452 {
453 unsigned long gsbase;
454
455 if (task == current)
456 gsbase = x86_gsbase_read_cpu_inactive();
457 else if (boot_cpu_has(X86_FEATURE_FSGSBASE) ||
458 (task->thread.gsindex == 0))
459 gsbase = task->thread.gsbase;
460 else
461 gsbase = x86_fsgsbase_read_task(task, task->thread.gsindex);
462
463 return gsbase;
464 }
465
x86_fsbase_write_task(struct task_struct * task,unsigned long fsbase)466 void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase)
467 {
468 WARN_ON_ONCE(task == current);
469
470 task->thread.fsbase = fsbase;
471 }
472
x86_gsbase_write_task(struct task_struct * task,unsigned long gsbase)473 void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase)
474 {
475 WARN_ON_ONCE(task == current);
476
477 task->thread.gsbase = gsbase;
478 }
479
480 static void
start_thread_common(struct pt_regs * regs,unsigned long new_ip,unsigned long new_sp,unsigned int _cs,unsigned int _ss,unsigned int _ds)481 start_thread_common(struct pt_regs *regs, unsigned long new_ip,
482 unsigned long new_sp,
483 unsigned int _cs, unsigned int _ss, unsigned int _ds)
484 {
485 WARN_ON_ONCE(regs != current_pt_regs());
486
487 if (static_cpu_has(X86_BUG_NULL_SEG)) {
488 /* Loading zero below won't clear the base. */
489 loadsegment(fs, __USER_DS);
490 load_gs_index(__USER_DS);
491 }
492
493 loadsegment(fs, 0);
494 loadsegment(es, _ds);
495 loadsegment(ds, _ds);
496 load_gs_index(0);
497
498 regs->ip = new_ip;
499 regs->sp = new_sp;
500 regs->cs = _cs;
501 regs->ss = _ss;
502 regs->flags = X86_EFLAGS_IF;
503 }
504
505 void
start_thread(struct pt_regs * regs,unsigned long new_ip,unsigned long new_sp)506 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
507 {
508 start_thread_common(regs, new_ip, new_sp,
509 __USER_CS, __USER_DS, 0);
510 }
511 EXPORT_SYMBOL_GPL(start_thread);
512
513 #ifdef CONFIG_COMPAT
compat_start_thread(struct pt_regs * regs,u32 new_ip,u32 new_sp,bool x32)514 void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp, bool x32)
515 {
516 start_thread_common(regs, new_ip, new_sp,
517 x32 ? __USER_CS : __USER32_CS,
518 __USER_DS, __USER_DS);
519 }
520 #endif
521
522 /*
523 * switch_to(x,y) should switch tasks from x to y.
524 *
525 * This could still be optimized:
526 * - fold all the options into a flag word and test it with a single test.
527 * - could test fs/gs bitsliced
528 *
529 * Kprobes not supported here. Set the probe on schedule instead.
530 * Function graph tracer not supported too.
531 */
532 __visible __notrace_funcgraph struct task_struct *
__switch_to(struct task_struct * prev_p,struct task_struct * next_p)533 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
534 {
535 struct thread_struct *prev = &prev_p->thread;
536 struct thread_struct *next = &next_p->thread;
537 struct fpu *prev_fpu = &prev->fpu;
538 struct fpu *next_fpu = &next->fpu;
539 int cpu = smp_processor_id();
540
541 WARN_ON_ONCE(IS_ENABLED(CONFIG_DEBUG_ENTRY) &&
542 this_cpu_read(hardirq_stack_inuse));
543
544 if (!test_thread_flag(TIF_NEED_FPU_LOAD))
545 switch_fpu_prepare(prev_fpu, cpu);
546
547 /* We must save %fs and %gs before load_TLS() because
548 * %fs and %gs may be cleared by load_TLS().
549 *
550 * (e.g. xen_load_tls())
551 */
552 save_fsgs(prev_p);
553
554 /*
555 * Load TLS before restoring any segments so that segment loads
556 * reference the correct GDT entries.
557 */
558 load_TLS(next, cpu);
559
560 /*
561 * Leave lazy mode, flushing any hypercalls made here. This
562 * must be done after loading TLS entries in the GDT but before
563 * loading segments that might reference them.
564 */
565 arch_end_context_switch(next_p);
566
567 /* Switch DS and ES.
568 *
569 * Reading them only returns the selectors, but writing them (if
570 * nonzero) loads the full descriptor from the GDT or LDT. The
571 * LDT for next is loaded in switch_mm, and the GDT is loaded
572 * above.
573 *
574 * We therefore need to write new values to the segment
575 * registers on every context switch unless both the new and old
576 * values are zero.
577 *
578 * Note that we don't need to do anything for CS and SS, as
579 * those are saved and restored as part of pt_regs.
580 */
581 savesegment(es, prev->es);
582 if (unlikely(next->es | prev->es))
583 loadsegment(es, next->es);
584
585 savesegment(ds, prev->ds);
586 if (unlikely(next->ds | prev->ds))
587 loadsegment(ds, next->ds);
588
589 x86_fsgsbase_load(prev, next);
590
591 /*
592 * Switch the PDA and FPU contexts.
593 */
594 this_cpu_write(current_task, next_p);
595 this_cpu_write(cpu_current_top_of_stack, task_top_of_stack(next_p));
596
597 switch_fpu_finish(next_fpu);
598
599 /* Reload sp0. */
600 update_task_stack(next_p);
601
602 switch_to_extra(prev_p, next_p);
603
604 if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) {
605 /*
606 * AMD CPUs have a misfeature: SYSRET sets the SS selector but
607 * does not update the cached descriptor. As a result, if we
608 * do SYSRET while SS is NULL, we'll end up in user mode with
609 * SS apparently equal to __USER_DS but actually unusable.
610 *
611 * The straightforward workaround would be to fix it up just
612 * before SYSRET, but that would slow down the system call
613 * fast paths. Instead, we ensure that SS is never NULL in
614 * system call context. We do this by replacing NULL SS
615 * selectors at every context switch. SYSCALL sets up a valid
616 * SS, so the only way to get NULL is to re-enter the kernel
617 * from CPL 3 through an interrupt. Since that can't happen
618 * in the same task as a running syscall, we are guaranteed to
619 * context switch between every interrupt vector entry and a
620 * subsequent SYSRET.
621 *
622 * We read SS first because SS reads are much faster than
623 * writes. Out of caution, we force SS to __KERNEL_DS even if
624 * it previously had a different non-NULL value.
625 */
626 unsigned short ss_sel;
627 savesegment(ss, ss_sel);
628 if (ss_sel != __KERNEL_DS)
629 loadsegment(ss, __KERNEL_DS);
630 }
631
632 /* Load the Intel cache allocation PQR MSR. */
633 resctrl_sched_in();
634
635 return prev_p;
636 }
637
set_personality_64bit(void)638 void set_personality_64bit(void)
639 {
640 /* inherit personality from parent */
641
642 /* Make sure to be in 64bit mode */
643 clear_thread_flag(TIF_ADDR32);
644 /* Pretend that this comes from a 64bit execve */
645 task_pt_regs(current)->orig_ax = __NR_execve;
646 current_thread_info()->status &= ~TS_COMPAT;
647 if (current->mm)
648 current->mm->context.flags = MM_CONTEXT_HAS_VSYSCALL;
649
650 /* TBD: overwrites user setup. Should have two bits.
651 But 64bit processes have always behaved this way,
652 so it's not too bad. The main problem is just that
653 32bit children are affected again. */
654 current->personality &= ~READ_IMPLIES_EXEC;
655 }
656
__set_personality_x32(void)657 static void __set_personality_x32(void)
658 {
659 #ifdef CONFIG_X86_X32
660 if (current->mm)
661 current->mm->context.flags = 0;
662
663 current->personality &= ~READ_IMPLIES_EXEC;
664 /*
665 * in_32bit_syscall() uses the presence of the x32 syscall bit
666 * flag to determine compat status. The x86 mmap() code relies on
667 * the syscall bitness so set x32 syscall bit right here to make
668 * in_32bit_syscall() work during exec().
669 *
670 * Pretend to come from a x32 execve.
671 */
672 task_pt_regs(current)->orig_ax = __NR_x32_execve | __X32_SYSCALL_BIT;
673 current_thread_info()->status &= ~TS_COMPAT;
674 #endif
675 }
676
__set_personality_ia32(void)677 static void __set_personality_ia32(void)
678 {
679 #ifdef CONFIG_IA32_EMULATION
680 if (current->mm) {
681 /*
682 * uprobes applied to this MM need to know this and
683 * cannot use user_64bit_mode() at that time.
684 */
685 current->mm->context.flags = MM_CONTEXT_UPROBE_IA32;
686 }
687
688 current->personality |= force_personality32;
689 /* Prepare the first "return" to user space */
690 task_pt_regs(current)->orig_ax = __NR_ia32_execve;
691 current_thread_info()->status |= TS_COMPAT;
692 #endif
693 }
694
set_personality_ia32(bool x32)695 void set_personality_ia32(bool x32)
696 {
697 /* Make sure to be in 32bit mode */
698 set_thread_flag(TIF_ADDR32);
699
700 if (x32)
701 __set_personality_x32();
702 else
703 __set_personality_ia32();
704 }
705 EXPORT_SYMBOL_GPL(set_personality_ia32);
706
707 #ifdef CONFIG_CHECKPOINT_RESTORE
prctl_map_vdso(const struct vdso_image * image,unsigned long addr)708 static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr)
709 {
710 int ret;
711
712 ret = map_vdso_once(image, addr);
713 if (ret)
714 return ret;
715
716 return (long)image->size;
717 }
718 #endif
719
do_arch_prctl_64(struct task_struct * task,int option,unsigned long arg2)720 long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
721 {
722 int ret = 0;
723
724 switch (option) {
725 case ARCH_SET_GS: {
726 if (unlikely(arg2 >= TASK_SIZE_MAX))
727 return -EPERM;
728
729 preempt_disable();
730 /*
731 * ARCH_SET_GS has always overwritten the index
732 * and the base. Zero is the most sensible value
733 * to put in the index, and is the only value that
734 * makes any sense if FSGSBASE is unavailable.
735 */
736 if (task == current) {
737 loadseg(GS, 0);
738 x86_gsbase_write_cpu_inactive(arg2);
739
740 /*
741 * On non-FSGSBASE systems, save_base_legacy() expects
742 * that we also fill in thread.gsbase.
743 */
744 task->thread.gsbase = arg2;
745
746 } else {
747 task->thread.gsindex = 0;
748 x86_gsbase_write_task(task, arg2);
749 }
750 preempt_enable();
751 break;
752 }
753 case ARCH_SET_FS: {
754 /*
755 * Not strictly needed for %fs, but do it for symmetry
756 * with %gs
757 */
758 if (unlikely(arg2 >= TASK_SIZE_MAX))
759 return -EPERM;
760
761 preempt_disable();
762 /*
763 * Set the selector to 0 for the same reason
764 * as %gs above.
765 */
766 if (task == current) {
767 loadseg(FS, 0);
768 x86_fsbase_write_cpu(arg2);
769
770 /*
771 * On non-FSGSBASE systems, save_base_legacy() expects
772 * that we also fill in thread.fsbase.
773 */
774 task->thread.fsbase = arg2;
775 } else {
776 task->thread.fsindex = 0;
777 x86_fsbase_write_task(task, arg2);
778 }
779 preempt_enable();
780 break;
781 }
782 case ARCH_GET_FS: {
783 unsigned long base = x86_fsbase_read_task(task);
784
785 ret = put_user(base, (unsigned long __user *)arg2);
786 break;
787 }
788 case ARCH_GET_GS: {
789 unsigned long base = x86_gsbase_read_task(task);
790
791 ret = put_user(base, (unsigned long __user *)arg2);
792 break;
793 }
794
795 #ifdef CONFIG_CHECKPOINT_RESTORE
796 # ifdef CONFIG_X86_X32_ABI
797 case ARCH_MAP_VDSO_X32:
798 return prctl_map_vdso(&vdso_image_x32, arg2);
799 # endif
800 # if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
801 case ARCH_MAP_VDSO_32:
802 return prctl_map_vdso(&vdso_image_32, arg2);
803 # endif
804 case ARCH_MAP_VDSO_64:
805 return prctl_map_vdso(&vdso_image_64, arg2);
806 #endif
807
808 default:
809 ret = -EINVAL;
810 break;
811 }
812
813 return ret;
814 }
815
SYSCALL_DEFINE2(arch_prctl,int,option,unsigned long,arg2)816 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
817 {
818 long ret;
819
820 ret = do_arch_prctl_64(current, option, arg2);
821 if (ret == -EINVAL)
822 ret = do_arch_prctl_common(current, option, arg2);
823
824 return ret;
825 }
826
827 #ifdef CONFIG_IA32_EMULATION
COMPAT_SYSCALL_DEFINE2(arch_prctl,int,option,unsigned long,arg2)828 COMPAT_SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
829 {
830 return do_arch_prctl_common(current, option, arg2);
831 }
832 #endif
833
KSTK_ESP(struct task_struct * task)834 unsigned long KSTK_ESP(struct task_struct *task)
835 {
836 return task_pt_regs(task)->sp;
837 }
838