1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
6 * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson
7 * 2000-06-20 Pentium III FXSR, SSE support by Gareth Hughes
8 * 2000-2002 x86-64 support by Andi Kleen
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 #include <linux/sched.h>
14 #include <linux/sched/task_stack.h>
16 #include <linux/smp.h>
17 #include <linux/kernel.h>
18 #include <linux/kstrtox.h>
19 #include <linux/errno.h>
20 #include <linux/wait.h>
21 #include <linux/unistd.h>
22 #include <linux/stddef.h>
23 #include <linux/personality.h>
24 #include <linux/uaccess.h>
25 #include <linux/user-return-notifier.h>
26 #include <linux/uprobes.h>
27 #include <linux/context_tracking.h>
28 #include <linux/entry-common.h>
29 #include <linux/syscalls.h>
30 #include <linux/rseq.h>
32 #include <asm/processor.h>
33 #include <asm/ucontext.h>
34 #include <asm/fpu/signal.h>
35 #include <asm/fpu/xstate.h>
38 #include <asm/sighandling.h>
41 #include <asm/syscall.h>
42 #include <asm/sigframe.h>
43 #include <asm/signal.h>
44 #include <asm/shstk.h>
46 static inline int is_ia32_compat_frame(struct ksignal *ksig)
48 return IS_ENABLED(CONFIG_IA32_EMULATION) &&
49 ksig->ka.sa.sa_flags & SA_IA32_ABI;
52 static inline int is_ia32_frame(struct ksignal *ksig)
54 return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
57 static inline int is_x32_frame(struct ksignal *ksig)
59 return IS_ENABLED(CONFIG_X86_X32_ABI) &&
60 ksig->ka.sa.sa_flags & SA_X32_ABI;
64 * Set up a signal frame.
67 /* x86 ABI requires 16-byte alignment */
68 #define FRAME_ALIGNMENT 16UL
70 #define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1)
73 * Determine which stack to use..
76 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size,
77 void __user **fpstate)
79 struct k_sigaction *ka = &ksig->ka;
80 int ia32_frame = is_ia32_frame(ksig);
81 /* Default to using normal stack */
82 bool nested_altstack = on_sig_stack(regs->sp);
83 bool entering_altstack = false;
84 unsigned long math_size = 0;
85 unsigned long sp = regs->sp;
86 unsigned long buf_fx = 0;
92 /* This is the X/Open sanctioned signal stack switching. */
93 if (ka->sa.sa_flags & SA_ONSTACK) {
95 * This checks nested_altstack via sas_ss_flags(). Sensible
96 * programs use SS_AUTODISARM, which disables that check, and
97 * programs that don't use SS_AUTODISARM get compatible.
99 if (sas_ss_flags(sp) == 0) {
100 sp = current->sas_ss_sp + current->sas_ss_size;
101 entering_altstack = true;
103 } else if (ia32_frame &&
105 regs->ss != __USER_DS &&
106 !(ka->sa.sa_flags & SA_RESTORER) &&
107 ka->sa.sa_restorer) {
108 /* This is the legacy signal stack switching. */
109 sp = (unsigned long) ka->sa.sa_restorer;
110 entering_altstack = true;
113 sp = fpu__alloc_mathframe(sp, ia32_frame, &buf_fx, &math_size);
114 *fpstate = (void __user *)sp;
120 * Align the stack pointer according to the i386 ABI,
121 * i.e. so that on function entry ((sp + 4) & 15) == 0.
123 sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4;
125 sp = round_down(sp, FRAME_ALIGNMENT) - 8;
128 * If we are on the alternate signal stack and would overflow it, don't.
129 * Return an always-bogus address instead so we will die with SIGSEGV.
131 if (unlikely((nested_altstack || entering_altstack) &&
132 !__on_sig_stack(sp))) {
134 if (show_unhandled_signals && printk_ratelimit())
135 pr_info("%s[%d] overflowed sigaltstack\n",
136 current->comm, task_pid_nr(current));
138 return (void __user *)-1L;
141 /* save i387 and extended state */
142 if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size))
143 return (void __user *)-1L;
145 return (void __user *)sp;
149 * There are four different struct types for signal frame: sigframe_ia32,
150 * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case
151 * -- the largest size. It means the size for 64-bit apps is a bit more
152 * than needed, but this keeps the code simple.
154 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
155 # define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32)
157 # define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe)
161 * The FP state frame contains an XSAVE buffer which must be 64-byte aligned.
162 * If a signal frame starts at an unaligned address, extra space is required.
163 * This is the max alignment padding, conservatively.
165 #define MAX_XSAVE_PADDING 63UL
168 * The frame data is composed of the following areas and laid out as:
170 * -------------------------
171 * | alignment padding |
172 * -------------------------
174 * -------------------------
176 * -------------------------
177 * | alignment padding |
178 * -------------------------
179 * | siginfo + ucontext |
180 * -------------------------
183 /* max_frame_size tells userspace the worst case signal stack size. */
184 static unsigned long __ro_after_init max_frame_size;
185 static unsigned int __ro_after_init fpu_default_state_size;
187 static int __init init_sigframe_size(void)
189 fpu_default_state_size = fpu__get_fpstate_size();
191 max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING;
193 max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING;
195 /* Userspace expects an aligned size. */
196 max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT);
198 pr_info("max sigframe size: %lu\n", max_frame_size);
201 early_initcall(init_sigframe_size);
203 unsigned long get_sigframe_size(void)
205 return max_frame_size;
209 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
211 /* Perform fixup for the pre-signal frame. */
212 rseq_signal_deliver(ksig, regs);
214 /* Set up the stack frame */
215 if (is_ia32_frame(ksig)) {
216 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
217 return ia32_setup_rt_frame(ksig, regs);
219 return ia32_setup_frame(ksig, regs);
220 } else if (is_x32_frame(ksig)) {
221 return x32_setup_rt_frame(ksig, regs);
223 return x64_setup_rt_frame(ksig, regs);
228 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
230 bool stepping, failed;
231 struct fpu *fpu = ¤t->thread.fpu;
233 if (v8086_mode(regs))
234 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
236 /* Are we from a system call? */
237 if (syscall_get_nr(current, regs) != -1) {
238 /* If so, check system call restarting.. */
239 switch (syscall_get_error(current, regs)) {
240 case -ERESTART_RESTARTBLOCK:
241 case -ERESTARTNOHAND:
246 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
251 case -ERESTARTNOINTR:
252 regs->ax = regs->orig_ax;
259 * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
260 * so that register information in the sigcontext is correct and
261 * then notify the tracer before entering the signal handler.
263 stepping = test_thread_flag(TIF_SINGLESTEP);
265 user_disable_single_step(current);
267 failed = (setup_rt_frame(ksig, regs) < 0);
270 * Clear the direction flag as per the ABI for function entry.
272 * Clear RF when entering the signal handler, because
273 * it might disable possible debug exception from the
276 * Clear TF for the case when it wasn't set by debugger to
277 * avoid the recursive send_sigtrap() in SIGTRAP handler.
279 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
281 * Ensure the signal handler starts with the new fpu state.
283 fpu__clear_user_states(fpu);
285 signal_setup_done(failed, ksig, stepping);
288 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
290 #ifdef CONFIG_IA32_EMULATION
291 if (current->restart_block.arch_data & TS_COMPAT)
292 return __NR_ia32_restart_syscall;
294 #ifdef CONFIG_X86_X32_ABI
295 return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
297 return __NR_restart_syscall;
302 * Note that 'init' is a special process: it doesn't get signals it doesn't
303 * want to handle. Thus you cannot kill init even with a SIGKILL even by
306 void arch_do_signal_or_restart(struct pt_regs *regs)
310 if (get_signal(&ksig)) {
311 /* Whee! Actually deliver the signal. */
312 handle_signal(&ksig, regs);
316 /* Did we come from a system call? */
317 if (syscall_get_nr(current, regs) != -1) {
318 /* Restart the system call - no handlers present */
319 switch (syscall_get_error(current, regs)) {
320 case -ERESTARTNOHAND:
322 case -ERESTARTNOINTR:
323 regs->ax = regs->orig_ax;
327 case -ERESTART_RESTARTBLOCK:
328 regs->ax = get_nr_restart_syscall(regs);
335 * If there's no signal to deliver, we just put the saved sigmask
338 restore_saved_sigmask();
341 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
343 struct task_struct *me = current;
345 if (show_unhandled_signals && printk_ratelimit()) {
347 "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
348 task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
349 me->comm, me->pid, where, frame,
350 regs->ip, regs->sp, regs->orig_ax);
351 print_vma_addr(KERN_CONT " in ", regs->ip);
358 #ifdef CONFIG_DYNAMIC_SIGFRAME
359 #ifdef CONFIG_STRICT_SIGALTSTACK_SIZE
360 static bool strict_sigaltstack_size __ro_after_init = true;
362 static bool strict_sigaltstack_size __ro_after_init = false;
365 static int __init strict_sas_size(char *arg)
367 return kstrtobool(arg, &strict_sigaltstack_size) == 0;
369 __setup("strict_sas_size", strict_sas_size);
372 * MINSIGSTKSZ is 2048 and can't be changed despite the fact that AVX512
373 * exceeds that size already. As such programs might never use the
374 * sigaltstack they just continued to work. While always checking against
375 * the real size would be correct, this might be considered a regression.
377 * Therefore avoid the sanity check, unless enforced by kernel
378 * configuration or command line option.
380 * When dynamic FPU features are supported, the check is also enforced when
381 * the task has permissions to use dynamic features. Tasks which have no
382 * permission are checked against the size of the non-dynamic feature set
383 * if strict checking is enabled. This avoids forcing all tasks on the
384 * system to allocate large sigaltstacks even if they are never going
385 * to use a dynamic feature. As this is serialized via sighand::siglock
386 * any permission request for a dynamic feature either happened already
387 * or will see the newly install sigaltstack size in the permission checks.
389 bool sigaltstack_size_valid(size_t ss_size)
391 unsigned long fsize = max_frame_size - fpu_default_state_size;
394 lockdep_assert_held(¤t->sighand->siglock);
396 if (!fpu_state_size_dynamic() && !strict_sigaltstack_size)
399 fsize += current->group_leader->thread.fpu.perm.__user_state_size;
400 if (likely(ss_size > fsize))
403 if (strict_sigaltstack_size)
404 return ss_size > fsize;
406 mask = current->group_leader->thread.fpu.perm.__state_perm;
407 if (mask & XFEATURE_MASK_USER_DYNAMIC)
408 return ss_size > fsize;
412 #endif /* CONFIG_DYNAMIC_SIGFRAME */