1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 // Define assembler macros for generating DWARF CFI instructions that use DWARF expressions. 30 // Assemblers don't natively support DWARF expressions, so use the C preprocessor and assembler 31 // macros to lower them to .cfi_escape directives. 32 // 33 // Signal trampolines need to use DWARF expressions to record the locations of saved registers, 34 // because the offsets from the restored SP to the saved registers is variable. e.g. A signal frame 35 // can have optional FP/SIMD extensions, and there may be extra padding if the interrupted SP wasn't 36 // aligned. 37 38 // DWARF constants. 39 #define DW_CFA_def_cfa_expression 0x0f 40 #define DW_CFA_expression 0x10 41 #define DW_OP_breg0 0x70 42 #define DW_OP_deref 0x06 43 44 // Return the size of a small uleb128 value: either 1 or 2 bytes 45 #define ULEB128_14BIT_SIZE(val) \ 46 (1 + (((val) > 0x7f) & 1)) 47 48 // Return the size of a small sleb128 value: either 1 or 2 bytes 49 #define SLEB128_14BIT_SIZE(val) \ 50 (1 + (((val) < -0x40) & 1) + \ 51 (((val) > 0x3f) & 1) ) 52 53 // Output a 1 or 2-byte CFI uleb128 absolute value. 54 .macro m_cfi_uleb128 val 55 .if (\val) < 0 || (\val) > 0x3fff 56 .error "m_cfi_uleb128 value is out of range (\val)" 57 .elseif (\val) > 0x7f 58 .cfi_escape ((\val) & 0x7f) | 0x80 59 .cfi_escape (\val) >> 7 60 .else 61 .cfi_escape (\val) 62 .endif 63 .endm 64 65 // Output a 1 or 2-byte CFI sleb128 absolute value. 66 .macro m_cfi_sleb128 val 67 .if (\val) < -0x2000 || (\val) > 0x1fff 68 .error "m_cfi_sleb128 value is out of range (\val)" 69 .elseif (\val) < -0x40 || (\val) > 0x3f 70 .cfi_escape ((\val) & 0x7f) | 0x80 71 .cfi_escape ((\val) >> 7) & 0x7f 72 .else 73 .cfi_escape (\val) & 0x7f 74 .endif 75 .endm 76 77 .macro check_base_reg reg_no 78 .if (\reg_no) < 0 || (\reg_no) > 31 79 .error "base register is out of range for DW_OP_breg0..DW_OP_breg31 (\reg_no)" 80 .endif 81 .endm 82 83 // Set CFA to the expression, *(base_reg + offset) 84 .macro m_cfi_def_cfa_deref base_reg, offset 85 check_base_reg (\base_reg) 86 .cfi_escape DW_CFA_def_cfa_expression 87 m_cfi_uleb128 (1 + SLEB128_14BIT_SIZE(\offset) + 1) // size of DWARF expression in bytes 88 .cfi_escape DW_OP_breg0 + (\base_reg) // expr: 1 byte 89 m_cfi_sleb128 (\offset) // expr: 1 or 2 bytes 90 .cfi_escape DW_OP_deref // expr: 1 byte 91 .endm 92 93 // Set the address of the register's previous value to the expression, (base_reg + offset) 94 .macro m_cfi_breg_offset dest_reg, base_reg, offset 95 check_base_reg (\base_reg) 96 .cfi_escape DW_CFA_expression 97 m_cfi_uleb128 (\dest_reg) 98 m_cfi_uleb128 (1 + SLEB128_14BIT_SIZE(\offset)) // size of DWARF expression in bytes 99 .cfi_escape DW_OP_breg0 + (\base_reg) // expr: 1 byte 100 m_cfi_sleb128 (\offset) // expr: 1 or 2 bytes 101 .endm 102