forked from M-Labs/artiq-zynq
79 lines
2.1 KiB
Rust
79 lines
2.1 KiB
Rust
//! Utilities for parsing DWARF-encoded data streams.
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//! See <http://www.dwarfstd.org>,
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//! DWARF-4 standard, Section 7 - "Data Representation"
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#![no_std]
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// This module is used only by x86_64-pc-windows-gnu for now, but we
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// are compiling it everywhere to avoid regressions.
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#![allow(unused)]
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#[cfg(test)]
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mod tests;
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pub mod eh;
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use core::mem;
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pub struct DwarfReader {
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pub ptr: *const u8,
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}
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#[repr(C, packed)]
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struct Unaligned<T>(T);
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impl DwarfReader {
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pub fn new(ptr: *const u8) -> DwarfReader {
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DwarfReader { ptr }
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}
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pub unsafe fn offset(&mut self, offset: isize) {
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self.ptr = self.ptr.offset(offset);
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}
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// DWARF streams are packed, so e.g., a u32 would not necessarily be aligned
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// on a 4-byte boundary. This may cause problems on platforms with strict
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// alignment requirements. By wrapping data in a "packed" struct, we are
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// telling the backend to generate "misalignment-safe" code.
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pub unsafe fn read<T: Copy>(&mut self) -> T {
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let Unaligned(result) = *(self.ptr as *const Unaligned<T>);
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self.ptr = self.ptr.add(mem::size_of::<T>());
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result
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}
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// ULEB128 and SLEB128 encodings are defined in Section 7.6 - "Variable
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// Length Data".
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pub unsafe fn read_uleb128(&mut self) -> u64 {
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let mut shift: usize = 0;
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let mut result: u64 = 0;
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let mut byte: u8;
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loop {
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byte = self.read::<u8>();
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result |= ((byte & 0x7F) as u64) << shift;
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shift += 7;
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if byte & 0x80 == 0 {
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break;
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}
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}
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result
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}
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pub unsafe fn read_sleb128(&mut self) -> i64 {
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let mut shift: usize = 0;
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let mut result: u64 = 0;
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let mut byte: u8;
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loop {
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byte = self.read::<u8>();
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result |= ((byte & 0x7F) as u64) << shift;
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shift += 7;
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if byte & 0x80 == 0 {
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break;
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}
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}
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// sign-extend
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if shift < 8 * mem::size_of::<u64>() && (byte & 0x40) != 0 {
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result |= (!0 as u64) << shift;
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}
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result as i64
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}
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}
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