| // Copyright 2015 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //! Utilities for parsing DWARF-encoded data streams. |
| //! See http://www.dwarfstd.org, |
| //! DWARF-4 standard, Section 7 - "Data Representation" |
| |
| // This module is used only by x86_64-pc-windows-gnu for now, but we |
| // are compiling it everywhere to avoid regressions. |
| #![allow(unused)] |
| |
| pub mod eh; |
| |
| use core::mem; |
| |
| pub struct DwarfReader { |
| pub ptr: *const u8, |
| } |
| |
| #[repr(C,packed)] |
| struct Unaligned<T>(T); |
| |
| impl DwarfReader { |
| pub fn new(ptr: *const u8) -> DwarfReader { |
| DwarfReader { ptr } |
| } |
| |
| // DWARF streams are packed, so e.g. a u32 would not necessarily be aligned |
| // on a 4-byte boundary. This may cause problems on platforms with strict |
| // alignment requirements. By wrapping data in a "packed" struct, we are |
| // telling the backend to generate "misalignment-safe" code. |
| pub unsafe fn read<T: Copy>(&mut self) -> T { |
| let Unaligned(result) = *(self.ptr as *const Unaligned<T>); |
| self.ptr = self.ptr.add(mem::size_of::<T>()); |
| result |
| } |
| |
| // ULEB128 and SLEB128 encodings are defined in Section 7.6 - "Variable |
| // Length Data". |
| pub unsafe fn read_uleb128(&mut self) -> u64 { |
| let mut shift: usize = 0; |
| let mut result: u64 = 0; |
| let mut byte: u8; |
| loop { |
| byte = self.read::<u8>(); |
| result |= ((byte & 0x7F) as u64) << shift; |
| shift += 7; |
| if byte & 0x80 == 0 { |
| break; |
| } |
| } |
| result |
| } |
| |
| pub unsafe fn read_sleb128(&mut self) -> i64 { |
| let mut shift: usize = 0; |
| let mut result: u64 = 0; |
| let mut byte: u8; |
| loop { |
| byte = self.read::<u8>(); |
| result |= ((byte & 0x7F) as u64) << shift; |
| shift += 7; |
| if byte & 0x80 == 0 { |
| break; |
| } |
| } |
| // sign-extend |
| if shift < 8 * mem::size_of::<u64>() && (byte & 0x40) != 0 { |
| result |= (!0 as u64) << shift; |
| } |
| result as i64 |
| } |
| } |
| |
| #[test] |
| fn dwarf_reader() { |
| let encoded: &[u8] = &[1, 2, 3, 4, 5, 6, 7, 0xE5, 0x8E, 0x26, 0x9B, 0xF1, 0x59, 0xFF, 0xFF]; |
| |
| let mut reader = DwarfReader::new(encoded.as_ptr()); |
| |
| unsafe { |
| assert!(reader.read::<u8>() == u8::to_be(1u8)); |
| assert!(reader.read::<u16>() == u16::to_be(0x0203)); |
| assert!(reader.read::<u32>() == u32::to_be(0x04050607)); |
| |
| assert!(reader.read_uleb128() == 624485); |
| assert!(reader.read_sleb128() == -624485); |
| |
| assert!(reader.read::<i8>() == i8::to_be(-1)); |
| } |
| } |