Added libpanic_unwind/dwarf from rustc as libdwarf.

src/Cargo.lock

@@ -82,6 +82,16 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7313c0d620d0cb4dbd9d019e461a4beb501071ff46ec0ab933efb4daa76d73e3"
 
+[[package]]
+name = "dwarf"
+version = "0.0.0"
+dependencies = [
+ "cfg-if",
+ "compiler_builtins",
+ "libc",
+ "unwind",
+]
+
 [[package]]
 name = "dyld"
 version = "0.1.0"
@@ -378,6 +388,7 @@ dependencies = [
  "byteorder",
  "core_io",
  "cslice",
+ "dwarf",
  "dyld",
  "fatfs",
  "futures",

src/Cargo.toml

@@ -3,6 +3,7 @@ members = [
   "libc",
   "libdyld",
   "libcoreio",
+  "libdwarf",
   "libunwind",
   "runtime",
   "szl"

src/libdwarf/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+# This package is orignally panic_unwind, but is adapted as a dwarf parser
+authors = ["The Rust Project Developers"]
+name = "dwarf"
+version = "0.0.0"
+edition = "2018"
+
+[lib]
+test = false
+bench = false
+doc = false
+
+[dependencies]
+libc = { path = "../libc" }
+unwind = { path = "../libunwind" }
+compiler_builtins = "0.1.0"
+cfg-if = "0.1.8"

src/libdwarf/src/eh.rs

@@ -0,0 +1,200 @@
+//! Parsing of GCC-style Language-Specific Data Area (LSDA)
+//! For details see:
+//!   http://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-PDA/LSB-PDA/ehframechpt.html
+//!   http://mentorembedded.github.io/cxx-abi/exceptions.pdf
+//!   http://www.airs.com/blog/archives/460
+//!   http://www.airs.com/blog/archives/464
+//!
+//! A reference implementation may be found in the GCC source tree
+//! (`<root>/libgcc/unwind-c.c` as of this writing).
+
+#![allow(non_upper_case_globals)]
+#![allow(unused)]
+
+use crate::DwarfReader;
+use core::mem;
+
+pub const DW_EH_PE_omit: u8 = 0xFF;
+pub const DW_EH_PE_absptr: u8 = 0x00;
+
+pub const DW_EH_PE_uleb128: u8 = 0x01;
+pub const DW_EH_PE_udata2: u8 = 0x02;
+pub const DW_EH_PE_udata4: u8 = 0x03;
+pub const DW_EH_PE_udata8: u8 = 0x04;
+pub const DW_EH_PE_sleb128: u8 = 0x09;
+pub const DW_EH_PE_sdata2: u8 = 0x0A;
+pub const DW_EH_PE_sdata4: u8 = 0x0B;
+pub const DW_EH_PE_sdata8: u8 = 0x0C;
+
+pub const DW_EH_PE_pcrel: u8 = 0x10;
+pub const DW_EH_PE_textrel: u8 = 0x20;
+pub const DW_EH_PE_datarel: u8 = 0x30;
+pub const DW_EH_PE_funcrel: u8 = 0x40;
+pub const DW_EH_PE_aligned: u8 = 0x50;
+
+pub const DW_EH_PE_indirect: u8 = 0x80;
+
+#[derive(Copy, Clone)]
+pub struct EHContext<'a> {
+    pub ip: usize,                             // Current instruction pointer
+    pub func_start: usize,                     // Address of the current function
+    pub get_text_start: &'a dyn Fn() -> usize, // Get address of the code section
+    pub get_data_start: &'a dyn Fn() -> usize, // Get address of the data section
+}
+
+pub enum EHAction {
+    None,
+    Cleanup(usize),
+    Catch(usize),
+    Terminate,
+}
+
+pub const USING_SJLJ_EXCEPTIONS: bool = cfg!(all(target_os = "ios", target_arch = "arm"));
+
+pub unsafe fn find_eh_action(
+    lsda: *const u8,
+    context: &EHContext<'_>,
+    foreign_exception: bool,
+) -> Result<EHAction, ()> {
+    if lsda.is_null() {
+        return Ok(EHAction::None);
+    }
+
+    let func_start = context.func_start;
+    let mut reader = DwarfReader::new(lsda);
+
+    let start_encoding = reader.read::<u8>();
+    // base address for landing pad offsets
+    let lpad_base = if start_encoding != DW_EH_PE_omit {
+        read_encoded_pointer(&mut reader, context, start_encoding)?
+    } else {
+        func_start
+    };
+
+    let ttype_encoding = reader.read::<u8>();
+    if ttype_encoding != DW_EH_PE_omit {
+        // Rust doesn't analyze exception types, so we don't care about the type table
+        reader.read_uleb128();
+    }
+
+    let call_site_encoding = reader.read::<u8>();
+    let call_site_table_length = reader.read_uleb128();
+    let action_table = reader.ptr.offset(call_site_table_length as isize);
+    let ip = context.ip;
+
+    if !USING_SJLJ_EXCEPTIONS {
+        while reader.ptr < action_table {
+            let cs_start = read_encoded_pointer(&mut reader, context, call_site_encoding)?;
+            let cs_len = read_encoded_pointer(&mut reader, context, call_site_encoding)?;
+            let cs_lpad = read_encoded_pointer(&mut reader, context, call_site_encoding)?;
+            let cs_action = reader.read_uleb128();
+            // Callsite table is sorted by cs_start, so if we've passed the ip, we
+            // may stop searching.
+            if ip < func_start + cs_start {
+                break;
+            }
+            if ip < func_start + cs_start + cs_len {
+                if cs_lpad == 0 {
+                    return Ok(EHAction::None);
+                } else {
+                    let lpad = lpad_base + cs_lpad;
+                    return Ok(interpret_cs_action(cs_action, lpad, foreign_exception));
+                }
+            }
+        }
+        // Ip is not present in the table.  This should not happen... but it does: issue #35011.
+        // So rather than returning EHAction::Terminate, we do this.
+        Ok(EHAction::None)
+    } else {
+        // SjLj version:
+        // The "IP" is an index into the call-site table, with two exceptions:
+        // -1 means 'no-action', and 0 means 'terminate'.
+        match ip as isize {
+            -1 => return Ok(EHAction::None),
+            0 => return Ok(EHAction::Terminate),
+            _ => (),
+        }
+        let mut idx = ip;
+        loop {
+            let cs_lpad = reader.read_uleb128();
+            let cs_action = reader.read_uleb128();
+            idx -= 1;
+            if idx == 0 {
+                // Can never have null landing pad for sjlj -- that would have
+                // been indicated by a -1 call site index.
+                let lpad = (cs_lpad + 1) as usize;
+                return Ok(interpret_cs_action(cs_action, lpad, foreign_exception));
+            }
+        }
+    }
+}
+
+fn interpret_cs_action(cs_action: u64, lpad: usize, foreign_exception: bool) -> EHAction {
+    if cs_action == 0 {
+        // If cs_action is 0 then this is a cleanup (Drop::drop). We run these
+        // for both Rust panics and foreign exceptions.
+        EHAction::Cleanup(lpad)
+    } else if foreign_exception {
+        // catch_unwind should not catch foreign exceptions, only Rust panics.
+        // Instead just continue unwinding.
+        EHAction::None
+    } else {
+        // Stop unwinding Rust panics at catch_unwind.
+        EHAction::Catch(lpad)
+    }
+}
+
+#[inline]
+fn round_up(unrounded: usize, align: usize) -> Result<usize, ()> {
+    if align.is_power_of_two() { Ok((unrounded + align - 1) & !(align - 1)) } else { Err(()) }
+}
+
+unsafe fn read_encoded_pointer(
+    reader: &mut DwarfReader,
+    context: &EHContext<'_>,
+    encoding: u8,
+) -> Result<usize, ()> {
+    if encoding == DW_EH_PE_omit {
+        return Err(());
+    }
+
+    // DW_EH_PE_aligned implies it's an absolute pointer value
+    if encoding == DW_EH_PE_aligned {
+        reader.ptr = round_up(reader.ptr as usize, mem::size_of::<usize>())? as *const u8;
+        return Ok(reader.read::<usize>());
+    }
+
+    let mut result = match encoding & 0x0F {
+        DW_EH_PE_absptr => reader.read::<usize>(),
+        DW_EH_PE_uleb128 => reader.read_uleb128() as usize,
+        DW_EH_PE_udata2 => reader.read::<u16>() as usize,
+        DW_EH_PE_udata4 => reader.read::<u32>() as usize,
+        DW_EH_PE_udata8 => reader.read::<u64>() as usize,
+        DW_EH_PE_sleb128 => reader.read_sleb128() as usize,
+        DW_EH_PE_sdata2 => reader.read::<i16>() as usize,
+        DW_EH_PE_sdata4 => reader.read::<i32>() as usize,
+        DW_EH_PE_sdata8 => reader.read::<i64>() as usize,
+        _ => return Err(()),
+    };
+
+    result += match encoding & 0x70 {
+        DW_EH_PE_absptr => 0,
+        // relative to address of the encoded value, despite the name
+        DW_EH_PE_pcrel => reader.ptr as usize,
+        DW_EH_PE_funcrel => {
+            if context.func_start == 0 {
+                return Err(());
+            }
+            context.func_start
+        }
+        DW_EH_PE_textrel => (*context.get_text_start)(),
+        DW_EH_PE_datarel => (*context.get_data_start)(),
+        _ => return Err(()),
+    };
+
+    if encoding & DW_EH_PE_indirect != 0 {
+        result = *(result as *const usize);
+    }
+
+    Ok(result)
+}

src/libdwarf/src/lib.rs

@@ -0,0 +1,74 @@
+//! Utilities for parsing DWARF-encoded data streams.
+//! See <http://www.dwarfstd.org>,
+//! DWARF-4 standard, Section 7 - "Data Representation"
+
+#![no_std]
+// This module is used only by x86_64-pc-windows-gnu for now, but we
+// are compiling it everywhere to avoid regressions.
+#![allow(unused)]
+
+#[cfg(test)]
+mod tests;
+
+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
+    }
+}

src/libdwarf/src/tests.rs

@@ -0,0 +1,19 @@
+use super::*;
+
+#[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));
+    }
+}

src/runtime/Cargo.toml

@@ -24,6 +24,7 @@ libsupport_zynq = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 libcortex_a9 = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 libasync = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 dyld = { path = "../libdyld" }
+dwarf = { path = "../libdwarf" }
 unwind = { path = "../libunwind" }
 libc = { path = "../libc" }
 fatfs = { version = "0.3", features = ["core_io"], default-features = false }