| /* | |
| * Copyright (C) 2020 The Android Open Source Project | |
| * All rights reserved. | |
| * | |
| * Redistribution and use in source and binary forms, with or without | |
| * modification, are permitted provided that the following conditions | |
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| * * Redistributions of source code must retain the above copyright | |
| * notice, this list of conditions and the following disclaimer. | |
| * * Redistributions in binary form must reproduce the above copyright | |
| * notice, this list of conditions and the following disclaimer in | |
| * the documentation and/or other materials provided with the | |
| * distribution. | |
| * | |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS | |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE | |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, | |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, | |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS | |
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| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| * SUCH DAMAGE. | |
| */ | |
| // Define assembler macros for generating DWARF CFI instructions that use DWARF expressions. | |
| // Assemblers don't natively support DWARF expressions, so use the C preprocessor and assembler | |
| // macros to lower them to .cfi_escape directives. | |
| // | |
| // Signal trampolines need to use DWARF expressions to record the locations of saved registers, | |
| // because the offsets from the restored SP to the saved registers is variable. e.g. A signal frame | |
| // can have optional FP/SIMD extensions, and there may be extra padding if the interrupted SP wasn't | |
| // aligned. | |
| // DWARF constants. | |
| #define DW_CFA_def_cfa_expression 0x0f | |
| #define DW_CFA_expression 0x10 | |
| #define DW_OP_breg0 0x70 | |
| #define DW_OP_deref 0x06 | |
| // Return the size of a small uleb128 value: either 1 or 2 bytes | |
| #define ULEB128_14BIT_SIZE(val) \ | |
| (1 + (((val) > 0x7f) & 1)) | |
| // Return the size of a small sleb128 value: either 1 or 2 bytes | |
| #define SLEB128_14BIT_SIZE(val) \ | |
| (1 + (((val) < -0x40) & 1) + \ | |
| (((val) > 0x3f) & 1) ) | |
| // Output a 1 or 2-byte CFI uleb128 absolute value. | |
| .macro m_cfi_uleb128 val | |
| .if (\val) < 0 || (\val) > 0x3fff | |
| .error "m_cfi_uleb128 value is out of range (\val)" | |
| .elseif (\val) > 0x7f | |
| .cfi_escape ((\val) & 0x7f) | 0x80 | |
| .cfi_escape (\val) >> 7 | |
| .else | |
| .cfi_escape (\val) | |
| .endif | |
| .endm | |
| // Output a 1 or 2-byte CFI sleb128 absolute value. | |
| .macro m_cfi_sleb128 val | |
| .if (\val) < -0x2000 || (\val) > 0x1fff | |
| .error "m_cfi_sleb128 value is out of range (\val)" | |
| .elseif (\val) < -0x40 || (\val) > 0x3f | |
| .cfi_escape ((\val) & 0x7f) | 0x80 | |
| .cfi_escape ((\val) >> 7) & 0x7f | |
| .else | |
| .cfi_escape (\val) & 0x7f | |
| .endif | |
| .endm | |
| .macro check_base_reg reg_no | |
| .if (\reg_no) < 0 || (\reg_no) > 31 | |
| .error "base register is out of range for DW_OP_breg0..DW_OP_breg31 (\reg_no)" | |
| .endif | |
| .endm | |
| // Set CFA to the expression, *(base_reg + offset) | |
| .macro m_cfi_def_cfa_deref base_reg, offset | |
| check_base_reg (\base_reg) | |
| .cfi_escape DW_CFA_def_cfa_expression | |
| m_cfi_uleb128 (1 + SLEB128_14BIT_SIZE(\offset) + 1) // size of DWARF expression in bytes | |
| .cfi_escape DW_OP_breg0 + (\base_reg) // expr: 1 byte | |
| m_cfi_sleb128 (\offset) // expr: 1 or 2 bytes | |
| .cfi_escape DW_OP_deref // expr: 1 byte | |
| .endm | |
| // Set the address of the register's previous value to the expression, (base_reg + offset) | |
| .macro m_cfi_breg_offset dest_reg, base_reg, offset | |
| check_base_reg (\base_reg) | |
| .cfi_escape DW_CFA_expression | |
| m_cfi_uleb128 (\dest_reg) | |
| m_cfi_uleb128 (1 + SLEB128_14BIT_SIZE(\offset)) // size of DWARF expression in bytes | |
| .cfi_escape DW_OP_breg0 + (\base_reg) // expr: 1 byte | |
| m_cfi_sleb128 (\offset) // expr: 1 or 2 bytes | |
| .endm |