add libdyld from ARTIQ e8b73876ab60e202bec0a2e5119bd7b740d0c78d

Cargo.lock

@@ -30,6 +30,10 @@ version = "0.1.26"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "036b035e9ebcd705affece16319223d19f229e2358be6e3b7b094e57193312e6"
 
+[[package]]
+name = "dyld"
+version = "0.0.0"
+
 [[package]]
 name = "libasync"
 version = "0.0.0"
@@ -150,6 +154,7 @@ checksum = "bd7a31eed1591dcbc95d92ad7161908e72f4677f8fabf2a32ca49b4237cbf211"
 name = "runtime"
 version = "0.1.0"
 dependencies = [
+ "dyld",
  "libasync",
  "libboard_zynq",
  "libsupport_zynq",

libdyld/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+authors = ["M-Labs"]
+name = "dyld"
+version = "0.0.0"
+
+[lib]
+name = "dyld"
+path = "lib.rs"

libdyld/lib.rs

@@ -0,0 +1,339 @@
+#![no_std]
+
+use core::{mem, ptr, fmt, slice, str, convert};
+use elf::*;
+
+pub mod elf;
+
+fn read_unaligned<T: Copy>(data: &[u8], offset: usize) -> Result<T, ()> {
+    if data.len() < offset + mem::size_of::<T>() {
+        Err(())
+    } else {
+        let ptr = data.as_ptr().wrapping_offset(offset as isize) as *const T;
+        Ok(unsafe { ptr::read_unaligned(ptr) })
+    }
+}
+
+fn get_ref<T: Copy>(data: &[u8], offset: usize) -> Result<&T, ()> {
+    if data.len() < offset + mem::size_of::<T>() {
+        Err(())
+    } else if (data.as_ptr() as usize + offset) & (mem::align_of::<T>() - 1) != 0 {
+        Err(())
+    } else {
+        let ptr = data.as_ptr().wrapping_offset(offset as isize) as *const T;
+        Ok(unsafe { &*ptr })
+    }
+}
+
+fn get_ref_slice<T: Copy>(data: &[u8], offset: usize, len: usize) -> Result<&[T], ()> {
+    if data.len() < offset + mem::size_of::<T>() * len {
+        Err(())
+    } else if (data.as_ptr() as usize + offset) & (mem::align_of::<T>() - 1) != 0 {
+        Err(())
+    } else {
+        let ptr = data.as_ptr().wrapping_offset(offset as isize) as *const T;
+        Ok(unsafe { slice::from_raw_parts(ptr, len) })
+    }
+}
+
+fn elf_hash(name: &[u8]) -> u32 {
+    let mut h: u32 = 0;
+    for c in name {
+        h = (h << 4) + *c as u32;
+        let g = h & 0xf0000000;
+        if g != 0 {
+            h ^= g >> 24;
+            h &= !g;
+        }
+    }
+    h
+}
+
+#[derive(Debug)]
+pub enum Error<'a> {
+    Parsing(&'static str),
+    Lookup(&'a [u8])
+}
+
+impl<'a> convert::From<&'static str> for Error<'a> {
+    fn from(desc: &'static str) -> Error<'a> {
+        Error::Parsing(desc)
+    }
+}
+
+impl<'a> fmt::Display for Error<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            &Error::Parsing(desc) =>
+                write!(f, "parse error: {}", desc),
+            &Error::Lookup(sym) =>
+                match str::from_utf8(sym) {
+                    Ok(sym) => write!(f, "symbol lookup error: {}", sym),
+                    Err(_)  => write!(f, "symbol lookup error: {:?}", sym)
+                }
+        }
+    }
+}
+
+pub struct Library<'a> {
+    image_off:   Elf32_Addr,
+    image_sz:    usize,
+    strtab:      &'a [u8],
+    symtab:      &'a [Elf32_Sym],
+    pltrel:      &'a [Elf32_Rela],
+    hash_bucket: &'a [Elf32_Word],
+    hash_chain:  &'a [Elf32_Word],
+}
+
+impl<'a> Library<'a> {
+    pub fn lookup(&self, name: &[u8]) -> Option<Elf32_Word> {
+        let hash = elf_hash(name);
+        let mut index = self.hash_bucket[hash as usize % self.hash_bucket.len()] as usize;
+
+        loop {
+            if index == STN_UNDEF { return None }
+
+            let sym = &self.symtab[index];
+            let sym_name_off = sym.st_name as usize;
+            match self.strtab.get(sym_name_off..sym_name_off + name.len()) {
+                Some(sym_name) if sym_name == name => {
+                    if ELF32_ST_BIND(sym.st_info) & STB_GLOBAL == 0 {
+                        return None
+                    }
+
+                    match sym.st_shndx {
+                        SHN_UNDEF => return None,
+                        SHN_ABS => return Some(sym.st_value),
+                        _ => return Some(self.image_off + sym.st_value)
+                    }
+                }
+                _ => (),
+            }
+
+            index = self.hash_chain[index] as usize;
+        }
+    }
+
+    fn name_starting_at(&self, offset: usize) -> Result<&'a [u8], Error<'a>> {
+        let size = self.strtab.iter().skip(offset).position(|&x| x == 0)
+                              .ok_or("symbol in symbol table not null-terminated")?;
+        Ok(self.strtab.get(offset..offset + size)
+                      .ok_or("cannot read symbol name")?)
+    }
+
+    fn update_rela(&self, rela: &Elf32_Rela, value: Elf32_Word) -> Result<(), Error<'a>> {
+        if rela.r_offset as usize + mem::size_of::<Elf32_Addr>() > self.image_sz {
+            return Err("relocation out of image bounds")?
+        }
+
+        let ptr = (self.image_off + rela.r_offset) as *mut Elf32_Addr;
+        Ok(unsafe { *ptr = value })
+    }
+
+    // This is unsafe because it mutates global data (the PLT).
+    pub unsafe fn rebind(&self, name: &[u8], addr: Elf32_Word) -> Result<(), Error<'a>> {
+        for rela in self.pltrel.iter() {
+            match ELF32_R_TYPE(rela.r_info) {
+                R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT => {
+                    let sym = self.symtab.get(ELF32_R_SYM(rela.r_info) as usize)
+                                         .ok_or("symbol out of bounds of symbol table")?;
+                    let sym_name = self.name_starting_at(sym.st_name as usize)?;
+
+                    if sym_name == name {
+                        self.update_rela(rela, addr)?
+                    }
+                }
+
+                // No associated symbols for other relocation types.
+                _ => ()
+            }
+        }
+        Ok(())
+    }
+
+    fn resolve_rela(&self, rela: &Elf32_Rela, resolve: &Fn(&[u8]) -> Option<Elf32_Word>)
+            -> Result<(), Error<'a>> {
+        let sym;
+        if ELF32_R_SYM(rela.r_info) == 0 {
+            sym = None;
+        } else {
+            sym = Some(self.symtab.get(ELF32_R_SYM(rela.r_info) as usize)
+                                  .ok_or("symbol out of bounds of symbol table")?)
+        }
+
+        let value;
+        match ELF32_R_TYPE(rela.r_info) {
+            R_OR1K_NONE =>
+                return Ok(()),
+
+            R_OR1K_RELATIVE =>
+                value = self.image_off + rela.r_addend as Elf32_Word,
+
+            R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT => {
+                let sym = sym.ok_or("relocation requires an associated symbol")?;
+                let sym_name = self.name_starting_at(sym.st_name as usize)?;
+
+                // First, try to resolve against itself.
+                match self.lookup(sym_name) {
+                    Some(addr) => value = addr,
+                    None => {
+                        // Second, call the user-provided function.
+                        match resolve(sym_name) {
+                            Some(addr) => value = addr,
+                            None => {
+                                // We couldn't find it anywhere.
+                                return Err(Error::Lookup(sym_name))
+                            }
+                        }
+                    }
+                }
+            }
+
+            _ => return Err("unsupported relocation type")?
+        }
+
+        self.update_rela(rela, value)
+    }
+
+    pub fn load(data: &[u8], image: &'a mut [u8], resolve: &Fn(&[u8]) -> Option<Elf32_Word>)
+            -> Result<Library<'a>, Error<'a>> {
+        #![allow(unused_assignments)]
+
+        let ehdr = read_unaligned::<Elf32_Ehdr>(data, 0)
+                                  .map_err(|()| "cannot read ELF header")?;
+
+        const IDENT: [u8; EI_NIDENT] = [
+            ELFMAG0,    ELFMAG1,     ELFMAG2,    ELFMAG3,
+            ELFCLASS32, ELFDATA2MSB, EV_CURRENT, ELFOSABI_NONE,
+            /* ABI version */ 0, /* padding */ 0, 0, 0, 0, 0, 0, 0
+        ];
+
+        #[cfg(target_arch = "or1k")]
+        const ARCH: u16 = EM_OPENRISC;
+        #[cfg(not(target_arch = "or1k"))]
+        const ARCH: u16 = EM_NONE;
+
+        if ehdr.e_ident != IDENT || ehdr.e_type != ET_DYN || ehdr.e_machine != ARCH {
+            return Err("not a shared library for current architecture")?
+        }
+
+        let mut dyn_off = None;
+        for i in 0..ehdr.e_phnum {
+            let phdr_off = ehdr.e_phoff as usize + mem::size_of::<Elf32_Phdr>() * i as usize;
+            let phdr = read_unaligned::<Elf32_Phdr>(data, phdr_off)
+                                      .map_err(|()| "cannot read program header")?;
+
+            match phdr.p_type {
+                PT_LOAD => {
+                    if (phdr.p_vaddr + phdr.p_filesz) as usize > image.len() ||
+                            (phdr.p_offset + phdr.p_filesz) as usize > data.len() {
+                        return Err("program header requests an out of bounds load")?
+                    }
+                    let dst = image.get_mut(phdr.p_vaddr as usize..
+                                            (phdr.p_vaddr + phdr.p_filesz) as usize)
+                                   .ok_or("cannot write to program header destination")?;
+                    let src = data.get(phdr.p_offset as usize..
+                                       (phdr.p_offset + phdr.p_filesz) as usize)
+                                  .ok_or("cannot read from program header source")?;
+                    dst.copy_from_slice(src);
+                }
+
+                PT_DYNAMIC =>
+                    dyn_off = Some(phdr.p_vaddr),
+
+                _ => ()
+            }
+        }
+
+        let (mut strtab_off, mut strtab_sz) = (0, 0);
+        let (mut symtab_off, mut symtab_sz) = (0, 0);
+        let (mut rela_off,   mut rela_sz)   = (0, 0);
+        let (mut pltrel_off, mut pltrel_sz) = (0, 0);
+        let (mut hash_off,   mut hash_sz)   = (0, 0);
+        let mut sym_ent  = 0;
+        let mut rela_ent = 0;
+        let mut nbucket  = 0;
+        let mut nchain   = 0;
+
+        let dyn_off = dyn_off.ok_or("cannot find a dynamic header")?;
+        for i in 0.. {
+            let dyn_off = dyn_off as usize + i * mem::size_of::<Elf32_Dyn>();
+            let dyn = get_ref::<Elf32_Dyn>(image, dyn_off)
+                              .map_err(|()| "cannot read dynamic header")?;
+
+            let val = unsafe { dyn.d_un.d_val } as usize;
+            match dyn.d_tag {
+                DT_NULL     => break,
+                DT_REL      => return Err("relocations with implicit addend are not supported")?,
+                DT_STRTAB   => strtab_off = val,
+                DT_STRSZ    => strtab_sz  = val,
+                DT_SYMTAB   => symtab_off = val,
+                DT_SYMENT   => sym_ent    = val,
+                DT_RELA     => rela_off   = val,
+                DT_RELASZ   => rela_sz    = val / mem::size_of::<Elf32_Rela>(),
+                DT_RELAENT  => rela_ent   = val,
+                DT_JMPREL   => pltrel_off = val,
+                DT_PLTRELSZ => pltrel_sz  = val / mem::size_of::<Elf32_Rela>(),
+                DT_HASH     => {
+                    nbucket  = *get_ref::<Elf32_Word>(image, val + 0)
+                                        .map_err(|()| "cannot read hash bucket count")? as usize;
+                    nchain   = *get_ref::<Elf32_Word>(image, val + 4)
+                                        .map_err(|()| "cannot read hash chain count")? as usize;
+                    hash_off = val + 8;
+                    hash_sz  = nbucket + nchain;
+                }
+                _ => ()
+            }
+        }
+
+        if sym_ent != mem::size_of::<Elf32_Sym>() {
+            return Err("incorrect symbol entry size")?
+        }
+        if rela_ent != 0 && rela_ent != mem::size_of::<Elf32_Rela>() {
+            return Err("incorrect relocation entry size")?
+        }
+
+        // These are the same--there are as many chains as buckets, and the chains only contain
+        // the symbols that overflowed the bucket.
+        symtab_sz = nchain;
+
+        // Drop the mutability. See also the comment below.
+        let image = &*image;
+
+        let strtab = get_ref_slice::<u8>(image, strtab_off, strtab_sz)
+                                   .map_err(|()| "cannot read string table")?;
+        let symtab = get_ref_slice::<Elf32_Sym>(image, symtab_off, symtab_sz)
+                                   .map_err(|()| "cannot read symbol table")?;
+        let rela   = get_ref_slice::<Elf32_Rela>(image, rela_off, rela_sz)
+                                   .map_err(|()| "cannot read rela entries")?;
+        let pltrel = get_ref_slice::<Elf32_Rela>(image, pltrel_off, pltrel_sz)
+                                   .map_err(|()| "cannot read pltrel entries")?;
+        let hash   = get_ref_slice::<Elf32_Word>(image, hash_off, hash_sz)
+                                   .map_err(|()| "cannot read hash entries")?;
+
+        let library = Library {
+            image_off:   image.as_ptr() as Elf32_Word,
+            image_sz:    image.len(),
+            strtab:      strtab,
+            symtab:      symtab,
+            pltrel:      pltrel,
+            hash_bucket: &hash[..nbucket],
+            hash_chain:  &hash[nbucket..nbucket + nchain],
+        };
+
+        // If a borrow exists anywhere, the borrowed memory cannot be mutated except
+        // through that pointer or it's UB. However, we need to retain pointers
+        // to the symbol tables and relocations, and at the same time mutate the code
+        // to resolve the relocations.
+        //
+        // To avoid invoking UB, we drop the only pointer to the entire area (which is
+        // unique since it's a &mut); we retain pointers to the various tables, but
+        // we never write to the memory they refer to, so it's safe.
+        mem::drop(image);
+
+        for r in rela   { library.resolve_rela(r, resolve)? }
+        for r in pltrel { library.resolve_rela(r, resolve)? }
+
+        Ok(library)
+    }
+}

runtime/Cargo.toml

@@ -10,11 +10,9 @@ target_zc706 = ["libboard_zynq/target_zc706", "libsupport_zynq/target_zc706"]
 default = ["target_zc706"]
 
 [dependencies]
+num-traits = { version = "0.2", default-features = false }
+num-derive = "0.3"
 libboard_zynq = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 libsupport_zynq = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
 libasync = { git = "https://git.m-labs.hk/M-Labs/zc706.git" }
-num-derive = "0.3"
-
-[dependencies.num-traits]
-version = "0.2"
-default-features = false
+dyld = { path = "../libdyld" }