1 // SPDX-License-Identifier: GPL-2.0-only
3 * Based on arch/arm/kernel/signal.c
5 * Copyright (C) 1995-2009 Russell King
6 * Copyright (C) 2012 ARM Ltd.
9 #include <linux/cache.h>
10 #include <linux/compat.h>
11 #include <linux/errno.h>
12 #include <linux/kernel.h>
13 #include <linux/signal.h>
14 #include <linux/personality.h>
15 #include <linux/freezer.h>
16 #include <linux/stddef.h>
17 #include <linux/uaccess.h>
18 #include <linux/sizes.h>
19 #include <linux/string.h>
20 #include <linux/tracehook.h>
21 #include <linux/ratelimit.h>
22 #include <linux/syscalls.h>
24 #include <asm/daifflags.h>
25 #include <asm/debug-monitors.h>
27 #include <asm/cacheflush.h>
28 #include <asm/ucontext.h>
29 #include <asm/unistd.h>
30 #include <asm/fpsimd.h>
31 #include <asm/ptrace.h>
32 #include <asm/syscall.h>
33 #include <asm/signal32.h>
34 #include <asm/traps.h>
38 * Do a signal return; undo the signal stack. These are aligned to 128-bit.
50 struct rt_sigframe_user_layout {
51 struct rt_sigframe __user *sigframe;
52 struct frame_record __user *next_frame;
54 unsigned long size; /* size of allocated sigframe data */
55 unsigned long limit; /* largest allowed size */
57 unsigned long fpsimd_offset;
58 unsigned long esr_offset;
59 unsigned long sve_offset;
60 unsigned long extra_offset;
61 unsigned long end_offset;
64 #define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
65 #define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
66 #define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
68 static void init_user_layout(struct rt_sigframe_user_layout *user)
70 const size_t reserved_size =
71 sizeof(user->sigframe->uc.uc_mcontext.__reserved);
73 memset(user, 0, sizeof(*user));
74 user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);
76 user->limit = user->size + reserved_size;
78 user->limit -= TERMINATOR_SIZE;
79 user->limit -= EXTRA_CONTEXT_SIZE;
80 /* Reserve space for extension and terminator ^ */
83 static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
85 return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
89 * Sanity limit on the approximate maximum size of signal frame we'll
90 * try to generate. Stack alignment padding and the frame record are
91 * not taken into account. This limit is not a guarantee and is
94 #define SIGFRAME_MAXSZ SZ_64K
96 static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
97 unsigned long *offset, size_t size, bool extend)
99 size_t padded_size = round_up(size, 16);
101 if (padded_size > user->limit - user->size &&
102 !user->extra_offset &&
106 user->limit += EXTRA_CONTEXT_SIZE;
107 ret = __sigframe_alloc(user, &user->extra_offset,
108 sizeof(struct extra_context), false);
110 user->limit -= EXTRA_CONTEXT_SIZE;
114 /* Reserve space for the __reserved[] terminator */
115 user->size += TERMINATOR_SIZE;
118 * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
121 user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
124 /* Still not enough space? Bad luck! */
125 if (padded_size > user->limit - user->size)
128 *offset = user->size;
129 user->size += padded_size;
135 * Allocate space for an optional record of <size> bytes in the user
136 * signal frame. The offset from the signal frame base address to the
137 * allocated block is assigned to *offset.
139 static int sigframe_alloc(struct rt_sigframe_user_layout *user,
140 unsigned long *offset, size_t size)
142 return __sigframe_alloc(user, offset, size, true);
145 /* Allocate the null terminator record and prevent further allocations */
146 static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
150 /* Un-reserve the space reserved for the terminator: */
151 user->limit += TERMINATOR_SIZE;
153 ret = sigframe_alloc(user, &user->end_offset,
154 sizeof(struct _aarch64_ctx));
158 /* Prevent further allocation: */
159 user->limit = user->size;
163 static void __user *apply_user_offset(
164 struct rt_sigframe_user_layout const *user, unsigned long offset)
166 char __user *base = (char __user *)user->sigframe;
168 return base + offset;
171 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
173 struct user_fpsimd_state const *fpsimd =
174 ¤t->thread.uw.fpsimd_state;
177 /* copy the FP and status/control registers */
178 err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
179 __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
180 __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
182 /* copy the magic/size information */
183 __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
184 __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
186 return err ? -EFAULT : 0;
189 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
191 struct user_fpsimd_state fpsimd;
195 /* check the magic/size information */
196 __get_user_error(magic, &ctx->head.magic, err);
197 __get_user_error(size, &ctx->head.size, err);
200 if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
203 /* copy the FP and status/control registers */
204 err = __copy_from_user(fpsimd.vregs, ctx->vregs,
205 sizeof(fpsimd.vregs));
206 __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
207 __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
209 clear_thread_flag(TIF_SVE);
211 /* load the hardware registers from the fpsimd_state structure */
213 fpsimd_update_current_state(&fpsimd);
215 return err ? -EFAULT : 0;
220 struct fpsimd_context __user *fpsimd;
221 struct sve_context __user *sve;
224 #ifdef CONFIG_ARM64_SVE
226 static int preserve_sve_context(struct sve_context __user *ctx)
229 u16 reserved[ARRAY_SIZE(ctx->__reserved)];
230 unsigned int vl = current->thread.sve_vl;
233 if (test_thread_flag(TIF_SVE))
234 vq = sve_vq_from_vl(vl);
236 memset(reserved, 0, sizeof(reserved));
238 __put_user_error(SVE_MAGIC, &ctx->head.magic, err);
239 __put_user_error(round_up(SVE_SIG_CONTEXT_SIZE(vq), 16),
240 &ctx->head.size, err);
241 __put_user_error(vl, &ctx->vl, err);
242 BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
243 err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
247 * This assumes that the SVE state has already been saved to
248 * the task struct by calling preserve_fpsimd_context().
250 err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
251 current->thread.sve_state,
252 SVE_SIG_REGS_SIZE(vq));
255 return err ? -EFAULT : 0;
258 static int restore_sve_fpsimd_context(struct user_ctxs *user)
262 struct user_fpsimd_state fpsimd;
263 struct sve_context sve;
265 if (__copy_from_user(&sve, user->sve, sizeof(sve)))
268 if (sve.vl != current->thread.sve_vl)
271 if (sve.head.size <= sizeof(*user->sve)) {
272 clear_thread_flag(TIF_SVE);
276 vq = sve_vq_from_vl(sve.vl);
278 if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq))
282 * Careful: we are about __copy_from_user() directly into
283 * thread.sve_state with preemption enabled, so protection is
284 * needed to prevent a racing context switch from writing stale
285 * registers back over the new data.
288 fpsimd_flush_task_state(current);
289 /* From now, fpsimd_thread_switch() won't touch thread.sve_state */
292 err = __copy_from_user(current->thread.sve_state,
293 (char __user const *)user->sve +
295 SVE_SIG_REGS_SIZE(vq));
299 set_thread_flag(TIF_SVE);
302 /* copy the FP and status/control registers */
303 /* restore_sigframe() already checked that user->fpsimd != NULL. */
304 err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
305 sizeof(fpsimd.vregs));
306 __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
307 __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
309 /* load the hardware registers from the fpsimd_state structure */
311 fpsimd_update_current_state(&fpsimd);
313 return err ? -EFAULT : 0;
316 #else /* ! CONFIG_ARM64_SVE */
318 /* Turn any non-optimised out attempts to use these into a link error: */
319 extern int preserve_sve_context(void __user *ctx);
320 extern int restore_sve_fpsimd_context(struct user_ctxs *user);
322 #endif /* ! CONFIG_ARM64_SVE */
325 static int parse_user_sigframe(struct user_ctxs *user,
326 struct rt_sigframe __user *sf)
328 struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
329 struct _aarch64_ctx __user *head;
330 char __user *base = (char __user *)&sc->__reserved;
332 size_t limit = sizeof(sc->__reserved);
333 bool have_extra_context = false;
334 char const __user *const sfp = (char const __user *)sf;
339 if (!IS_ALIGNED((unsigned long)base, 16))
345 char const __user *userp;
346 struct extra_context const __user *extra;
349 struct _aarch64_ctx const __user *end;
350 u32 end_magic, end_size;
352 if (limit - offset < sizeof(*head))
355 if (!IS_ALIGNED(offset, 16))
358 head = (struct _aarch64_ctx __user *)(base + offset);
359 __get_user_error(magic, &head->magic, err);
360 __get_user_error(size, &head->size, err);
364 if (limit - offset < size)
378 if (size < sizeof(*user->fpsimd))
381 user->fpsimd = (struct fpsimd_context __user *)head;
389 if (!system_supports_sve())
395 if (size < sizeof(*user->sve))
398 user->sve = (struct sve_context __user *)head;
402 if (have_extra_context)
405 if (size < sizeof(*extra))
408 userp = (char const __user *)head;
410 extra = (struct extra_context const __user *)userp;
413 __get_user_error(extra_datap, &extra->datap, err);
414 __get_user_error(extra_size, &extra->size, err);
418 /* Check for the dummy terminator in __reserved[]: */
420 if (limit - offset - size < TERMINATOR_SIZE)
423 end = (struct _aarch64_ctx const __user *)userp;
424 userp += TERMINATOR_SIZE;
426 __get_user_error(end_magic, &end->magic, err);
427 __get_user_error(end_size, &end->size, err);
431 if (end_magic || end_size)
434 /* Prevent looping/repeated parsing of extra_context */
435 have_extra_context = true;
437 base = (__force void __user *)extra_datap;
438 if (!IS_ALIGNED((unsigned long)base, 16))
441 if (!IS_ALIGNED(extra_size, 16))
447 /* Reject "unreasonably large" frames: */
448 if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
452 * Ignore trailing terminator in __reserved[]
453 * and start parsing extra data:
458 if (!access_ok(base, limit))
467 if (size < sizeof(*head))
470 if (limit - offset < size)
483 static int restore_sigframe(struct pt_regs *regs,
484 struct rt_sigframe __user *sf)
488 struct user_ctxs user;
490 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
492 set_current_blocked(&set);
494 for (i = 0; i < 31; i++)
495 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
497 __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
498 __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
499 __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
502 * Avoid sys_rt_sigreturn() restarting.
504 forget_syscall(regs);
506 err |= !valid_user_regs(®s->user_regs, current);
508 err = parse_user_sigframe(&user, sf);
515 if (!system_supports_sve())
518 err = restore_sve_fpsimd_context(&user);
520 err = restore_fpsimd_context(user.fpsimd);
527 SYSCALL_DEFINE0(rt_sigreturn)
529 struct pt_regs *regs = current_pt_regs();
530 struct rt_sigframe __user *frame;
532 /* Always make any pending restarted system calls return -EINTR */
533 current->restart_block.fn = do_no_restart_syscall;
536 * Since we stacked the signal on a 128-bit boundary, then 'sp' should
537 * be word aligned here.
542 frame = (struct rt_sigframe __user *)regs->sp;
544 if (!access_ok(frame, sizeof (*frame)))
547 if (restore_sigframe(regs, frame))
550 if (restore_altstack(&frame->uc.uc_stack))
553 return regs->regs[0];
556 arm64_notify_segfault(regs->sp);
561 * Determine the layout of optional records in the signal frame
563 * add_all: if true, lays out the biggest possible signal frame for
564 * this task; otherwise, generates a layout for the current state
567 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
572 err = sigframe_alloc(user, &user->fpsimd_offset,
573 sizeof(struct fpsimd_context));
577 /* fault information, if valid */
578 if (add_all || current->thread.fault_code) {
579 err = sigframe_alloc(user, &user->esr_offset,
580 sizeof(struct esr_context));
585 if (system_supports_sve()) {
588 if (add_all || test_thread_flag(TIF_SVE)) {
592 vl = current->thread.sve_vl;
594 vq = sve_vq_from_vl(vl);
597 err = sigframe_alloc(user, &user->sve_offset,
598 SVE_SIG_CONTEXT_SIZE(vq));
603 return sigframe_alloc_end(user);
606 static int setup_sigframe(struct rt_sigframe_user_layout *user,
607 struct pt_regs *regs, sigset_t *set)
610 struct rt_sigframe __user *sf = user->sigframe;
612 /* set up the stack frame for unwinding */
613 __put_user_error(regs->regs[29], &user->next_frame->fp, err);
614 __put_user_error(regs->regs[30], &user->next_frame->lr, err);
616 for (i = 0; i < 31; i++)
617 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
619 __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
620 __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
621 __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
623 __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
625 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
628 struct fpsimd_context __user *fpsimd_ctx =
629 apply_user_offset(user, user->fpsimd_offset);
630 err |= preserve_fpsimd_context(fpsimd_ctx);
633 /* fault information, if valid */
634 if (err == 0 && user->esr_offset) {
635 struct esr_context __user *esr_ctx =
636 apply_user_offset(user, user->esr_offset);
638 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
639 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
640 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
643 /* Scalable Vector Extension state, if present */
644 if (system_supports_sve() && err == 0 && user->sve_offset) {
645 struct sve_context __user *sve_ctx =
646 apply_user_offset(user, user->sve_offset);
647 err |= preserve_sve_context(sve_ctx);
650 if (err == 0 && user->extra_offset) {
651 char __user *sfp = (char __user *)user->sigframe;
653 apply_user_offset(user, user->extra_offset);
655 struct extra_context __user *extra;
656 struct _aarch64_ctx __user *end;
660 extra = (struct extra_context __user *)userp;
661 userp += EXTRA_CONTEXT_SIZE;
663 end = (struct _aarch64_ctx __user *)userp;
664 userp += TERMINATOR_SIZE;
667 * extra_datap is just written to the signal frame.
668 * The value gets cast back to a void __user *
671 extra_datap = (__force u64)userp;
672 extra_size = sfp + round_up(user->size, 16) - userp;
674 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
675 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
676 __put_user_error(extra_datap, &extra->datap, err);
677 __put_user_error(extra_size, &extra->size, err);
679 /* Add the terminator */
680 __put_user_error(0, &end->magic, err);
681 __put_user_error(0, &end->size, err);
684 /* set the "end" magic */
686 struct _aarch64_ctx __user *end =
687 apply_user_offset(user, user->end_offset);
689 __put_user_error(0, &end->magic, err);
690 __put_user_error(0, &end->size, err);
696 static int get_sigframe(struct rt_sigframe_user_layout *user,
697 struct ksignal *ksig, struct pt_regs *regs)
699 unsigned long sp, sp_top;
702 init_user_layout(user);
703 err = setup_sigframe_layout(user, false);
707 sp = sp_top = sigsp(regs->sp, ksig);
709 sp = round_down(sp - sizeof(struct frame_record), 16);
710 user->next_frame = (struct frame_record __user *)sp;
712 sp = round_down(sp, 16) - sigframe_size(user);
713 user->sigframe = (struct rt_sigframe __user *)sp;
716 * Check that we can actually write to the signal frame.
718 if (!access_ok(user->sigframe, sp_top - sp))
724 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
725 struct rt_sigframe_user_layout *user, int usig)
727 __sigrestore_t sigtramp;
729 regs->regs[0] = usig;
730 regs->sp = (unsigned long)user->sigframe;
731 regs->regs[29] = (unsigned long)&user->next_frame->fp;
732 regs->pc = (unsigned long)ka->sa.sa_handler;
734 if (ka->sa.sa_flags & SA_RESTORER)
735 sigtramp = ka->sa.sa_restorer;
737 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
739 regs->regs[30] = (unsigned long)sigtramp;
742 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
743 struct pt_regs *regs)
745 struct rt_sigframe_user_layout user;
746 struct rt_sigframe __user *frame;
749 fpsimd_signal_preserve_current_state();
751 if (get_sigframe(&user, ksig, regs))
754 frame = user.sigframe;
756 __put_user_error(0, &frame->uc.uc_flags, err);
757 __put_user_error(NULL, &frame->uc.uc_link, err);
759 err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
760 err |= setup_sigframe(&user, regs, set);
762 setup_return(regs, &ksig->ka, &user, usig);
763 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
764 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
765 regs->regs[1] = (unsigned long)&frame->info;
766 regs->regs[2] = (unsigned long)&frame->uc;
773 static void setup_restart_syscall(struct pt_regs *regs)
775 if (is_compat_task())
776 compat_setup_restart_syscall(regs);
778 regs->regs[8] = __NR_restart_syscall;
782 * OK, we're invoking a handler
784 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
786 sigset_t *oldset = sigmask_to_save();
787 int usig = ksig->sig;
790 rseq_signal_deliver(ksig, regs);
793 * Set up the stack frame
795 if (is_compat_task()) {
796 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
797 ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
799 ret = compat_setup_frame(usig, ksig, oldset, regs);
801 ret = setup_rt_frame(usig, ksig, oldset, regs);
805 * Check that the resulting registers are actually sane.
807 ret |= !valid_user_regs(®s->user_regs, current);
809 /* Step into the signal handler if we are stepping */
810 signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
814 * Note that 'init' is a special process: it doesn't get signals it doesn't
815 * want to handle. Thus you cannot kill init even with a SIGKILL even by
818 * Note that we go through the signals twice: once to check the signals that
819 * the kernel can handle, and then we build all the user-level signal handling
820 * stack-frames in one go after that.
822 static void do_signal(struct pt_regs *regs)
824 unsigned long continue_addr = 0, restart_addr = 0;
827 bool syscall = in_syscall(regs);
830 * If we were from a system call, check for system call restarting...
833 continue_addr = regs->pc;
834 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
835 retval = regs->regs[0];
838 * Avoid additional syscall restarting via ret_to_user.
840 forget_syscall(regs);
843 * Prepare for system call restart. We do this here so that a
844 * debugger will see the already changed PC.
847 case -ERESTARTNOHAND:
849 case -ERESTARTNOINTR:
850 case -ERESTART_RESTARTBLOCK:
851 regs->regs[0] = regs->orig_x0;
852 regs->pc = restart_addr;
858 * Get the signal to deliver. When running under ptrace, at this point
859 * the debugger may change all of our registers.
861 if (get_signal(&ksig)) {
863 * Depending on the signal settings, we may need to revert the
864 * decision to restart the system call, but skip this if a
865 * debugger has chosen to restart at a different PC.
867 if (regs->pc == restart_addr &&
868 (retval == -ERESTARTNOHAND ||
869 retval == -ERESTART_RESTARTBLOCK ||
870 (retval == -ERESTARTSYS &&
871 !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
872 syscall_set_return_value(current, regs, -EINTR, 0);
873 regs->pc = continue_addr;
876 handle_signal(&ksig, regs);
881 * Handle restarting a different system call. As above, if a debugger
882 * has chosen to restart at a different PC, ignore the restart.
884 if (syscall && regs->pc == restart_addr) {
885 if (retval == -ERESTART_RESTARTBLOCK)
886 setup_restart_syscall(regs);
887 user_rewind_single_step(current);
890 restore_saved_sigmask();
893 asmlinkage void do_notify_resume(struct pt_regs *regs,
894 unsigned long thread_flags)
897 * The assembly code enters us with IRQs off, but it hasn't
898 * informed the tracing code of that for efficiency reasons.
899 * Update the trace code with the current status.
901 trace_hardirqs_off();
904 /* Check valid user FS if needed */
905 addr_limit_user_check();
907 if (thread_flags & _TIF_NEED_RESCHED) {
908 /* Unmask Debug and SError for the next task */
909 local_daif_restore(DAIF_PROCCTX_NOIRQ);
913 local_daif_restore(DAIF_PROCCTX);
915 if (thread_flags & _TIF_UPROBE)
916 uprobe_notify_resume(regs);
918 if (thread_flags & _TIF_SIGPENDING)
921 if (thread_flags & _TIF_NOTIFY_RESUME) {
922 clear_thread_flag(TIF_NOTIFY_RESUME);
923 tracehook_notify_resume(regs);
924 rseq_handle_notify_resume(NULL, regs);
927 if (thread_flags & _TIF_FOREIGN_FPSTATE)
928 fpsimd_restore_current_state();
932 thread_flags = READ_ONCE(current_thread_info()->flags);
933 } while (thread_flags & _TIF_WORK_MASK);
936 unsigned long __ro_after_init signal_minsigstksz;
939 * Determine the stack space required for guaranteed signal devliery.
940 * This function is used to populate AT_MINSIGSTKSZ at process startup.
941 * cpufeatures setup is assumed to be complete.
943 void __init minsigstksz_setup(void)
945 struct rt_sigframe_user_layout user;
947 init_user_layout(&user);
950 * If this fails, SIGFRAME_MAXSZ needs to be enlarged. It won't
951 * be big enough, but it's our best guess:
953 if (WARN_ON(setup_sigframe_layout(&user, true)))
956 signal_minsigstksz = sigframe_size(&user) +
957 round_up(sizeof(struct frame_record), 16) +
958 16; /* max alignment padding */