/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (C) 2019 ARM Limited */

#include <asm/unistd.h>

.section        .rodata, "a"
call_fmt:
        .asciz "Calling sigreturn with fake sigframe sized:%zd at SP @%08lX\n"

.text

.globl fake_sigreturn

/*      fake_sigreturn  x0:&sigframe,  x1:sigframe_size,  x2:misalign_bytes */
fake_sigreturn:
        stp     x29, x30, [sp, #-16]!
        mov     x29, sp

        mov     x20, x0
        mov     x21, x1
        mov     x22, x2

        /* create space on the stack for fake sigframe 16 bytes-aligned */
        add     x0, x21, x22
        add     x0, x0, #15
        bic     x0, x0, #15 /* round_up(sigframe_size + misalign_bytes, 16) */
        sub     sp, sp, x0
        add     x23, sp, x22 /* new sigframe base with misaligment if any */

        ldr     x0, =call_fmt
        mov     x1, x21
        mov     x2, x23
        bl      printf

        /* memcpy the provided content, while still keeping SP aligned */
        mov     x0, x23
        mov     x1, x20
        mov     x2, x21
        bl      memcpy

        /*
         * Here saving a last minute SP to current->token acts as a marker:
         * if we got here, we are successfully faking a sigreturn; in other
         * words we are sure no bad fatal signal has been raised till now
         * for unrelated reasons, so we should consider the possibly observed
         * fatal signal like SEGV coming from Kernel restore_sigframe() and
         * triggered as expected from our test-case.
         * For simplicity this assumes that current field 'token' is laid out
         * as first in struct tdescr
         */
        ldr     x0, current
        str     x23, [x0]
        /* finally move SP to misaligned address...if any requested */
        mov     sp, x23

        mov     x8, #__NR_rt_sigreturn
        svc     #0

        /*
         * Above sigreturn should not return...looping here leads to a timeout
         * and ensure proper and clean test failure, instead of jumping around
         * on a potentially corrupted stack.
         */
        b       .