signal32.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Based on arch/arm/kernel/signal.c
 *
 * Copyright (C) 1995-2009 Russell King
 * Copyright (C) 2012 ARM Ltd.
 * Modified by Will Deacon <will.deacon@arm.com>
 */

#include <linux/compat.h>
#include <linux/signal.h>
#include <linux/syscalls.h>
#include <linux/ratelimit.h>

#include <asm/esr.h>
#include <asm/fpsimd.h>
#include <asm/signal32.h>
#include <asm/traps.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
#include <asm/vdso.h>

struct compat_vfp_sigframe {
	compat_ulong_t	magic;
	compat_ulong_t	size;
	struct compat_user_vfp {
		compat_u64	fpregs[32];
		compat_ulong_t	fpscr;
	} ufp;
	struct compat_user_vfp_exc {
		compat_ulong_t	fpexc;
		compat_ulong_t	fpinst;
		compat_ulong_t	fpinst2;
	} ufp_exc;
} __attribute__((__aligned__(8)));

#define VFP_MAGIC		0x56465001
#define VFP_STORAGE_SIZE	sizeof(struct compat_vfp_sigframe)

#define FSR_WRITE_SHIFT		(11)

struct compat_aux_sigframe {
	struct compat_vfp_sigframe	vfp;

	/* Something that isn't a valid magic number for any coprocessor.  */
	unsigned long			end_magic;
} __attribute__((__aligned__(8)));

static inline int put_sigset_t(compat_sigset_t __user *uset, sigset_t *set)
{
	compat_sigset_t	cset;

	cset.sig[0] = set->sig[0] & 0xffffffffull;
	cset.sig[1] = set->sig[0] >> 32;

	return copy_to_user(uset, &cset, sizeof(*uset));
}

static inline int get_sigset_t(sigset_t *set,
			       const compat_sigset_t __user *uset)
{
	compat_sigset_t s32;

	if (copy_from_user(&s32, uset, sizeof(*uset)))
		return -EFAULT;

	set->sig[0] = s32.sig[0] | (((long)s32.sig[1]) << 32);
	return 0;
}

/*
 * VFP save/restore code.
 *
 * We have to be careful with endianness, since the fpsimd context-switch
 * code operates on 128-bit (Q) register values whereas the compat ABI
 * uses an array of 64-bit (D) registers. Consequently, we need to swap
 * the two halves of each Q register when running on a big-endian CPU.
 */
union __fpsimd_vreg {
	__uint128_t	raw;
	struct {
#ifdef __AARCH64EB__
		u64	hi;
		u64	lo;
#else
		u64	lo;
		u64	hi;
#endif
	};
};

static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame)
{
	struct user_fpsimd_state const *fpsimd =
		&current->thread.uw.fpsimd_state;
	compat_ulong_t magic = VFP_MAGIC;
	compat_ulong_t size = VFP_STORAGE_SIZE;
	compat_ulong_t fpscr, fpexc;
	int i, err = 0;

	/*
	 * Save the hardware registers to the fpsimd_state structure.
	 * Note that this also saves V16-31, which aren't visible
	 * in AArch32.
	 */
	fpsimd_signal_preserve_current_state();

	/* Place structure header on the stack */
	__put_user_error(magic, &frame->magic, err);
	__put_user_error(size, &frame->size, err);

	/*
	 * Now copy the FP registers. Since the registers are packed,
	 * we can copy the prefix we want (V0-V15) as it is.
	 */
	for (i = 0; i < ARRAY_SIZE(frame->ufp.fpregs); i += 2) {
		union __fpsimd_vreg vreg = {
			.raw = fpsimd->vregs[i >> 1],
		};

		__put_user_error(vreg.lo, &frame->ufp.fpregs[i], err);
		__put_user_error(vreg.hi, &frame->ufp.fpregs[i + 1], err);
	}

	/* Create an AArch32 fpscr from the fpsr and the fpcr. */
	fpscr = (fpsimd->fpsr & VFP_FPSCR_STAT_MASK) |
		(fpsimd->fpcr & VFP_FPSCR_CTRL_MASK);
	__put_user_error(fpscr, &frame->ufp.fpscr, err);

	/*
	 * The exception register aren't available so we fake up a
	 * basic FPEXC and zero everything else.
	 */
	fpexc = (1 << 30);
	__put_user_error(fpexc, &frame->ufp_exc.fpexc, err);
	__put_user_error(0, &frame->ufp_exc.fpinst, err);
	__put_user_error(0, &frame->ufp_exc.fpinst2, err);

	return err ? -EFAULT : 0;
}

static int compat_restore_vfp_context(struct compat_vfp_sigframe __user *frame)
{
	struct user_fpsimd_state fpsimd;
	compat_ulong_t magic = VFP_MAGIC;
	compat_ulong_t size = VFP_STORAGE_SIZE;
	compat_ulong_t fpscr;
	int i, err = 0;

	__get_user_error(magic, &frame->magic, err);
	__get_user_error(size, &frame->size, err);

	if (err)
		return -EFAULT;
	if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
		return -EINVAL;

	/* Copy the FP registers into the start of the fpsimd_state. */
	for (i = 0; i < ARRAY_SIZE(frame->ufp.fpregs); i += 2) {
		union __fpsimd_vreg vreg;

		__get_user_error(vreg.lo, &frame->ufp.fpregs[i], err);
		__get_user_error(vreg.hi, &frame->ufp.fpregs[i + 1], err);
		fpsimd.vregs[i >> 1] = vreg.raw;
	}

	/* Extract the fpsr and the fpcr from the fpscr */
	__get_user_error(fpscr, &frame->ufp.fpscr, err);
	fpsimd.fpsr = fpscr & VFP_FPSCR_STAT_MASK;
	fpsimd.fpcr = fpscr & VFP_FPSCR_CTRL_MASK;

	/*
	 * We don't need to touch the exception register, so
	 * reload the hardware state.
	 */
	if (!err)
		fpsimd_update_current_state(&fpsimd);

	return err ? -EFAULT : 0;
}

static int compat_restore_sigframe(struct pt_regs *regs,
				   struct compat_sigframe __user *sf)
{
	int err;
	sigset_t set;
	struct compat_aux_sigframe __user *aux;
	unsigned long psr;

	err = get_sigset_t(&set, &sf->uc.uc_sigmask);
	if (err == 0)
		set_current_blocked(&set);

	__get_user_error(regs->regs[0], &sf->uc.uc_mcontext.arm_r0, err);
	__get_user_error(regs->regs[1], &sf->uc.uc_mcontext.arm_r1, err);
	__get_user_error(regs->regs[2], &sf->uc.uc_mcontext.arm_r2, err);
	__get_user_error(regs->regs[3], &sf->uc.uc_mcontext.arm_r3, err);
	__get_user_error(regs->regs[4], &sf->uc.uc_mcontext.arm_r4, err);
	__get_user_error(regs->regs[5], &sf->uc.uc_mcontext.arm_r5, err);
	__get_user_error(regs->regs[6], &sf->uc.uc_mcontext.arm_r6, err);
	__get_user_error(regs->regs[7], &sf->uc.uc_mcontext.arm_r7, err);
	__get_user_error(regs->regs[8], &sf->uc.uc_mcontext.arm_r8, err);
	__get_user_error(regs->regs[9], &sf->uc.uc_mcontext.arm_r9, err);
	__get_user_error(regs->regs[10], &sf->uc.uc_mcontext.arm_r10, err);
	__get_user_error(regs->regs[11], &sf->uc.uc_mcontext.arm_fp, err);
	__get_user_error(regs->regs[12], &sf->uc.uc_mcontext.arm_ip, err);
	__get_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
	__get_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
	__get_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
	__get_user_error(psr, &sf->uc.uc_mcontext.arm_cpsr, err);

	regs->pstate = compat_psr_to_pstate(psr);

	/*
	 * Avoid compat_sys_sigreturn() restarting.
	 */
	forget_syscall(regs);

	err |= !valid_user_regs(&regs->user_regs, current);

	aux = (struct compat_aux_sigframe __user *) sf->uc.uc_regspace;
	if (err == 0 && system_supports_fpsimd())
		err |= compat_restore_vfp_context(&aux->vfp);

	return err;
}

COMPAT_SYSCALL_DEFINE0(sigreturn)
{
	struct pt_regs *regs = current_pt_regs();
	struct compat_sigframe __user *frame;

	/* Always make any pending restarted system calls return -EINTR */
	current->restart_block.fn = do_no_restart_syscall;

	/*
	 * Since we stacked the signal on a 64-bit boundary,
	 * then 'sp' should be word aligned here.  If it's
	 * not, then the user is trying to mess with us.
	 */
	if (regs->compat_sp & 7)
		goto badframe;

	frame = (struct compat_sigframe __user *)regs->compat_sp;

	if (!access_ok(frame, sizeof (*frame)))
		goto badframe;

	if (compat_restore_sigframe(regs, frame))
		goto badframe;

	return regs->regs[0];

badframe:
	arm64_notify_segfault(regs->compat_sp);
	return 0;
}

COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
{
	struct pt_regs *regs = current_pt_regs();
	struct compat_rt_sigframe __user *frame;

	/* Always make any pending restarted system calls return -EINTR */
	current->restart_block.fn = do_no_restart_syscall;

	/*
	 * Since we stacked the signal on a 64-bit boundary,
	 * then 'sp' should be word aligned here.  If it's
	 * not, then the user is trying to mess with us.
	 */
	if (regs->compat_sp & 7)
		goto badframe;

	frame = (struct compat_rt_sigframe __user *)regs->compat_sp;

	if (!access_ok(frame, sizeof (*frame)))
		goto badframe;

	if (compat_restore_sigframe(regs, &frame->sig))
		goto badframe;

	if (compat_restore_altstack(&frame->sig.uc.uc_stack))
		goto badframe;

	return regs->regs[0];

badframe:
	arm64_notify_segfault(regs->compat_sp);
	return 0;
}

static void __user *compat_get_sigframe(struct ksignal *ksig,
					struct pt_regs *regs,
					int framesize)
{
	compat_ulong_t sp = sigsp(regs->compat_sp, ksig);
	void __user *frame;

	/*
	 * ATPCS B01 mandates 8-byte alignment
	 */
	frame = compat_ptr((compat_uptr_t)((sp - framesize) & ~7));

	/*
	 * Check that we can actually write to the signal frame.
	 */
	if (!access_ok(frame, framesize))
		frame = NULL;

	return frame;
}

static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
				compat_ulong_t __user *rc, void __user *frame,
				int usig)
{
	compat_ulong_t handler = ptr_to_compat(ka->sa.sa_handler);
	compat_ulong_t retcode;
	compat_ulong_t spsr = regs->pstate & ~(PSR_f | PSR_AA32_E_BIT);
	int thumb;

	/* Check if the handler is written for ARM or Thumb */
	thumb = handler & 1;

	if (thumb)
		spsr |= PSR_AA32_T_BIT;
	else
		spsr &= ~PSR_AA32_T_BIT;

	/* The IT state must be cleared for both ARM and Thumb-2 */
	spsr &= ~PSR_AA32_IT_MASK;

	/* Restore the original endianness */
	spsr |= PSR_AA32_ENDSTATE;

	if (ka->sa.sa_flags & SA_RESTORER) {
		retcode = ptr_to_compat(ka->sa.sa_restorer);
	} else {
		/* Set up sigreturn pointer */
		unsigned int idx = thumb << 1;

		if (ka->sa.sa_flags & SA_SIGINFO)
			idx += 3;

		retcode = (unsigned long)current->mm->context.sigpage +
			  (idx << 2) + thumb;
	}

	regs->regs[0]	= usig;
	regs->compat_sp	= ptr_to_compat(frame);
	regs->compat_lr	= retcode;
	regs->pc	= handler;
	regs->pstate	= spsr;
}

static int compat_setup_sigframe(struct compat_sigframe __user *sf,
				 struct pt_regs *regs, sigset_t *set)
{
	struct compat_aux_sigframe __user *aux;
	unsigned long psr = pstate_to_compat_psr(regs->pstate);
	int err = 0;

	__put_user_error(regs->regs[0], &sf->uc.uc_mcontext.arm_r0, err);
	__put_user_error(regs->regs[1], &sf->uc.uc_mcontext.arm_r1, err);
	__put_user_error(regs->regs[2], &sf->uc.uc_mcontext.arm_r2, err);
	__put_user_error(regs->regs[3], &sf->uc.uc_mcontext.arm_r3, err);
	__put_user_error(regs->regs[4], &sf->uc.uc_mcontext.arm_r4, err);
	__put_user_error(regs->regs[5], &sf->uc.uc_mcontext.arm_r5, err);
	__put_user_error(regs->regs[6], &sf->uc.uc_mcontext.arm_r6, err);
	__put_user_error(regs->regs[7], &sf->uc.uc_mcontext.arm_r7, err);
	__put_user_error(regs->regs[8], &sf->uc.uc_mcontext.arm_r8, err);
	__put_user_error(regs->regs[9], &sf->uc.uc_mcontext.arm_r9, err);
	__put_user_error(regs->regs[10], &sf->uc.uc_mcontext.arm_r10, err);
	__put_user_error(regs->regs[11], &sf->uc.uc_mcontext.arm_fp, err);
	__put_user_error(regs->regs[12], &sf->uc.uc_mcontext.arm_ip, err);
	__put_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
	__put_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
	__put_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
	__put_user_error(psr, &sf->uc.uc_mcontext.arm_cpsr, err);

	__put_user_error((compat_ulong_t)0, &sf->uc.uc_mcontext.trap_no, err);
	/* set the compat FSR WnR */
	__put_user_error(!!(current->thread.fault_code & ESR_ELx_WNR) <<
			 FSR_WRITE_SHIFT, &sf->uc.uc_mcontext.error_code, err);
	__put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
	__put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);

	err |= put_sigset_t(&sf->uc.uc_sigmask, set);

	aux = (struct compat_aux_sigframe __user *) sf->uc.uc_regspace;

	if (err == 0 && system_supports_fpsimd())
		err |= compat_preserve_vfp_context(&aux->vfp);
	__put_user_error(0, &aux->end_magic, err);

	return err;
}

/*
 * 32-bit signal handling routines called from signal.c
 */
int compat_setup_rt_frame(int usig, struct ksignal *ksig,
			  sigset_t *set, struct pt_regs *regs)
{
	struct compat_rt_sigframe __user *frame;
	int err = 0;

	frame = compat_get_sigframe(ksig, regs, sizeof(*frame));

	if (!frame)
		return 1;

	err |= copy_siginfo_to_user32(&frame->info, &ksig->info);

	__put_user_error(0, &frame->sig.uc.uc_flags, err);
	__put_user_error(0, &frame->sig.uc.uc_link, err);

	err |= __compat_save_altstack(&frame->sig.uc.uc_stack, regs->compat_sp);

	err |= compat_setup_sigframe(&frame->sig, regs, set);

	if (err == 0) {
		compat_setup_return(regs, &ksig->ka, frame->sig.retcode, frame, usig);
		regs->regs[1] = (compat_ulong_t)(unsigned long)&frame->info;
		regs->regs[2] = (compat_ulong_t)(unsigned long)&frame->sig.uc;
	}

	return err;
}

int compat_setup_frame(int usig, struct ksignal *ksig, sigset_t *set,
		       struct pt_regs *regs)
{
	struct compat_sigframe __user *frame;
	int err = 0;

	frame = compat_get_sigframe(ksig, regs, sizeof(*frame));

	if (!frame)
		return 1;

	__put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err);

	err |= compat_setup_sigframe(frame, regs, set);
	if (err == 0)
		compat_setup_return(regs, &ksig->ka, frame->retcode, frame, usig);

	return err;
}

void compat_setup_restart_syscall(struct pt_regs *regs)
{
       regs->regs[7] = __NR_compat_restart_syscall;
}

/*
 * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as
 * changes likely come with new fields that should be added below.
 */
static_assert(NSIGILL	== 11);
static_assert(NSIGFPE	== 15);
static_assert(NSIGSEGV	== 9);
static_assert(NSIGBUS	== 5);
static_assert(NSIGTRAP	== 6);
static_assert(NSIGCHLD	== 6);
static_assert(NSIGSYS	== 2);
static_assert(sizeof(compat_siginfo_t) == 128);
static_assert(__alignof__(compat_siginfo_t) == 4);
static_assert(offsetof(compat_siginfo_t, si_signo)	== 0x00);
static_assert(offsetof(compat_siginfo_t, si_errno)	== 0x04);
static_assert(offsetof(compat_siginfo_t, si_code)	== 0x08);
static_assert(offsetof(compat_siginfo_t, si_pid)	== 0x0c);
static_assert(offsetof(compat_siginfo_t, si_uid)	== 0x10);
static_assert(offsetof(compat_siginfo_t, si_tid)	== 0x0c);
static_assert(offsetof(compat_siginfo_t, si_overrun)	== 0x10);
static_assert(offsetof(compat_siginfo_t, si_status)	== 0x14);
static_assert(offsetof(compat_siginfo_t, si_utime)	== 0x18);
static_assert(offsetof(compat_siginfo_t, si_stime)	== 0x1c);
static_assert(offsetof(compat_siginfo_t, si_value)	== 0x14);
static_assert(offsetof(compat_siginfo_t, si_int)	== 0x14);
static_assert(offsetof(compat_siginfo_t, si_ptr)	== 0x14);
static_assert(offsetof(compat_siginfo_t, si_addr)	== 0x0c);
static_assert(offsetof(compat_siginfo_t, si_addr_lsb)	== 0x10);
static_assert(offsetof(compat_siginfo_t, si_lower)	== 0x14);
static_assert(offsetof(compat_siginfo_t, si_upper)	== 0x18);
static_assert(offsetof(compat_siginfo_t, si_pkey)	== 0x14);
static_assert(offsetof(compat_siginfo_t, si_perf_data)	== 0x10);
static_assert(offsetof(compat_siginfo_t, si_perf_type)	== 0x14);
static_assert(offsetof(compat_siginfo_t, si_perf_flags)	== 0x18);
static_assert(offsetof(compat_siginfo_t, si_band)	== 0x0c);
static_assert(offsetof(compat_siginfo_t, si_fd)		== 0x10);
static_assert(offsetof(compat_siginfo_t, si_call_addr)	== 0x0c);
static_assert(offsetof(compat_siginfo_t, si_syscall)	== 0x10);
static_assert(offsetof(compat_siginfo_t, si_arch)	== 0x14);