libdyld: refactor

firmware/libdyld/src/file.rs

@@ -1,4 +1,4 @@
-use core::{mem, ptr, fmt, slice, str, convert, ops::{Deref, Range}};
+use core::{mem, ptr, ops::{Deref, Range}};
 use super::{
     Arch,
     elf::*,

firmware/libdyld/src/image.rs

@@ -9,64 +9,15 @@ use super::{
     Error,
 };
 
-fn elf_hash(name: &[u8]) -> u32 {
+pub struct DynamicSection {
-    let mut h: u32 = 0;
+    pub strtab: Range<usize>,
-    for c in name {
+    pub symtab: Range<usize>,
-        h = (h << 4) + *c as u32;
+    pub hash: Range<usize>,
-        let g = h & 0xf0000000;
+    pub hash_bucket: Range<usize>,
-        if g != 0 {
+    pub hash_chain: Range<usize>,
-            h ^= g >> 24;
+    pub rel: Range<usize>,
-            h &= !g;
+    pub rela: Range<usize>,
-        }
+    pub pltrel: Range<usize>,
-    }
-    h
-}
-
-pub struct DynamicSection<'a> {
-    pub strtab: &'a [u8],
-    pub symtab: &'a [Elf32_Sym],
-    pub hash_bucket: &'a [Elf32_Word],
-    pub hash_chain: &'a [Elf32_Word],
-    pub rel: &'a [Elf32_Rel],
-    pub rela: &'a [Elf32_Rela],
-    pub pltrel: &'a [Elf32_Rel],
-}
-
-impl<'a> DynamicSection<'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(sym.st_value)
-                    }
-                }
-                _ => (),
-            }
-
-            index = self.hash_chain[index] as usize;
-        }
-    }
-
-    pub fn name_starting_at(&self, offset: usize) -> Result<&'a [u8], Error> {
-        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")?)
-    }
 }
 
 /// target memory image
@@ -90,7 +41,7 @@ impl Image {
     }
 
     /// assumes that self.data is properly aligned
-    pub fn get_ref<T>(&self, offset: usize) -> Option<&T>
+    pub(crate) fn get_ref<T>(&self, offset: usize) -> Option<&T>
     where
         T: Copy,
     {
@@ -104,15 +55,15 @@ impl Image {
         }
     }
 
-    fn get_ref_slice<T: Copy>(&self, offset: usize, len: usize) -> Option<&[T]> {
+    /// assumes that self.data is properly aligned
-        if self.data.len() < offset + mem::size_of::<T>() * len {
+    ///
-            None
+    /// range: in bytes
-        } else if (self.data.as_ptr() as usize + offset) & (mem::align_of::<T>() - 1) != 0 {
+    pub(crate) fn get_ref_slice_unchecked<T: Copy>(&self, range: &Range<usize>) -> &[T] {
-            None
+        let offset = range.start;
-        } else {
+        let len = (range.end - range.start) / mem::size_of::<T>();
+
         let ptr = self.data.as_ptr().wrapping_offset(offset as isize) as *const T;
-            Some(unsafe { slice::from_raw_parts(ptr, len) })
+        unsafe { slice::from_raw_parts(ptr, len) }
-        }
     }
 
     fn dyn_headers<'a>(&'a self, range: Range<usize>) ->
@@ -148,13 +99,13 @@ impl Image {
                 DT_SYMTAB   => symtab_off = val,
                 DT_SYMENT   => sym_ent    = val,
                 DT_REL      => rel_off    = val,
-                DT_RELSZ    => rel_sz     = val / mem::size_of::<Elf32_Rel>(),
+                DT_RELSZ    => rel_sz     = val,
                 DT_RELENT   => rel_ent    = val,
                 DT_RELA     => rela_off   = val,
-                DT_RELASZ   => rela_sz    = val / mem::size_of::<Elf32_Rela>(),
+                DT_RELASZ   => rela_sz    = val,
                 DT_RELAENT  => rela_ent   = val,
                 DT_JMPREL   => pltrel_off = val,
-                DT_PLTRELSZ => pltrel_sz  = val / mem::size_of::<Elf32_Rel>(),
+                DT_PLTRELSZ => pltrel_sz  = val,
                 DT_HASH     => {
                     nbucket  = *self.get_ref::<Elf32_Word>(val + 0)
                         .ok_or("cannot read hash bucket count")? as usize;
@@ -167,44 +118,44 @@ impl Image {
             }
         }
 
+        if strtab_off + strtab_sz > self.data.len() {
+            return Err("invalid strtab offset/size")?
+        }
+        if symtab_off + symtab_sz > self.data.len() {
+            return Err("invalid symtab offset/size")?
+        }
         if sym_ent != mem::size_of::<Elf32_Sym>() {
             return Err("incorrect symbol entry size")?
         }
+        if rel_off + rel_sz > self.data.len() {
+            return Err("invalid rel offset/size")?
+        }
         if rel_ent != 0 && rel_ent != mem::size_of::<Elf32_Rel>() {
             return Err("incorrect relocation entry size")?
         }
+        if rela_off + rela_sz > self.data.len() {
+            return Err("invalid rela offset/size")?
+        }
         if rela_ent != 0 && rela_ent != mem::size_of::<Elf32_Rela>() {
             return Err("incorrect relocation entry size")?
         }
+        if pltrel_off + pltrel_sz > self.data.len() {
+            return Err("invalid pltrel offset/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;
 
-        let hash   = self.get_ref_slice::<Elf32_Word>(hash_off, hash_sz)
-            .ok_or("cannot read hash entries")?;
-        let strtab = self.get_ref_slice(strtab_off, strtab_sz)
-                .ok_or("cannot read string table")?;
-        let symtab = self.get_ref_slice::<Elf32_Sym>(symtab_off, symtab_sz)
-                .ok_or("cannot read symbol table")?;
-        let hash_bucket = &hash[..nbucket];
-        let hash_chain = &hash[nbucket..nbucket + nchain];
-        let rel   =  self.get_ref_slice::<Elf32_Rel>(rel_off, rel_sz)
-            .ok_or("cannot read rel entries")?;
-        let rela   = self.get_ref_slice::<Elf32_Rela>(rela_off, rela_sz)
-            .ok_or("cannot read rela entries")?;
-        let pltrel = self.get_ref_slice::<Elf32_Rel>(pltrel_off, pltrel_sz)
-            .ok_or("cannot read pltrel entries")?;
-        // debug!("ELF: {} rela, {} rel, {} pltrel entries", rela_sz, rel_sz, pltrel_sz);
-
         Ok(DynamicSection {
-            strtab,
+            strtab: strtab_off..strtab_off + strtab_sz,
-            symtab,
+            symtab: symtab_off..symtab_off + symtab_sz,
-            hash_bucket,
+            hash: hash_off..hash_off + hash_sz,
-            hash_chain,
+            hash_bucket: 0..nbucket,
-            rel,
+            hash_chain: nbucket..nbucket + nchain,
-            rela,
+            rel: rel_off..rel_off + rel_sz,
-            pltrel,
+            rela: rela_off..rela_off + rela_sz,
+            pltrel: pltrel_off..pltrel_off + rela_sz,
         })
     }
 

firmware/libdyld/src/lib.rs

@@ -3,9 +3,9 @@
 extern crate alloc;
 extern crate log;
 
-use core::{mem, ptr, fmt, slice, str, convert, ops::Range};
+use core::{fmt, str, convert};
 use alloc::string::String;
-use log::{info, trace, error};
+use log::{info, trace};
 use elf::*;
 
 pub mod elf;
@@ -44,16 +44,90 @@ impl fmt::Display for Error {
     }
 }
 
+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
+}
+
 pub struct Library {
     image: Image,
-    dyn_range: Range<usize>,
+    dyn_section: DynamicSection,
-    dyn_section: DynamicSection<'static>,
 }
 
 impl Library {
-    pub fn lookup(&self, name: &[u8]) -> Option<u32> {
+    fn strtab(&self) -> &[u8] {
-        self.dyn_section.lookup(name)
+        self.image.get_ref_slice_unchecked(&self.dyn_section.strtab)
-            .map(|addr| self.image.ptr() as u32 + addr)
+    }
+
+    fn symtab(&self) -> &[Elf32_Sym] {
+        self.image.get_ref_slice_unchecked(&self.dyn_section.symtab)
+    }
+
+    fn hash(&self) -> &[Elf32_Word] {
+        self.image.get_ref_slice_unchecked(&self.dyn_section.hash)
+    }
+
+    fn hash_bucket(&self) -> &[Elf32_Word] {
+        &self.hash()[self.dyn_section.hash_bucket.clone()]
+    }
+
+    fn hash_chain(&self) -> &[Elf32_Word] {
+        &self.hash()[self.dyn_section.hash_chain.clone()]
+    }
+
+    fn rel(&self) -> &[Elf32_Rel] {
+        self.image.get_ref_slice_unchecked(&self.dyn_section.rel)
+    }
+
+    fn rela(&self) -> &[Elf32_Rela] {
+        self.image.get_ref_slice_unchecked(&self.dyn_section.rela)
+    }
+
+    fn pltrel(&self) -> &[Elf32_Rel] {
+        self.image.get_ref_slice_unchecked(&self.dyn_section.pltrel)
+    }
+
+    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(self.image.ptr() as u32 + sym.st_value),
+                        _ => return Some(self.image.ptr() as u32 + sym.st_value)
+                    }
+                }
+                _ => (),
+            }
+
+            index = self.hash_chain()[index] as usize;
+        }
+    }
+
+    pub fn name_starting_at(&self, offset: usize) -> Result<&[u8], Error> {
+        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")?)
     }
 }
 
@@ -113,23 +187,20 @@ pub fn load(
     let dyn_section = image.dyn_section(dyn_range.clone())?;
     info!("Relocating {} rela, {} rel, {} pltrel",
           dyn_section.rela.len(), dyn_section.rel.len(), dyn_section.pltrel.len());
-
+    let lib = Library {
-    for rela in dyn_section.rela {
-        reloc::relocate(arch, &image, &dyn_section, rela, resolve)?;
-    }
-    for rel in dyn_section.rela {
-        reloc::relocate(arch, &image, &dyn_section, rel, resolve)?;
-    }
-    for pltrel in dyn_section.pltrel {
-        reloc::relocate(arch, &image, &dyn_section, pltrel, resolve)?;
-    }
-
-    let dyn_section = unsafe {
-        core::mem::transmute(dyn_section)
-    };
-    Ok(Library {
         image,
-        dyn_range,
         dyn_section,
-    })
+    };
+
+    for rela in lib.rela() {
+        reloc::relocate(arch, &lib, rela, resolve)?;
+    }
+    for rel in lib.rel() {
+        reloc::relocate(arch, &lib, rel, resolve)?;
+    }
+    for pltrel in lib.pltrel() {
+        reloc::relocate(arch, &lib, pltrel, resolve)?;
+    }
+
+    Ok(lib)
 }

firmware/libdyld/src/reloc.rs

@@ -4,7 +4,8 @@ use super::{
     Arch,
     elf::*,
     Error,
-    image::{DynamicSection, Image},
+    image::Image,
+    Library,
 };
 
 pub trait Relocatable {
@@ -87,16 +88,16 @@ fn format_sym_name(sym_name: &[u8]) -> String {
         .unwrap_or(String::from("<invalid symbol name>"))
 }
 
-pub fn relocate<'a, R: Relocatable>(
+pub fn relocate<R: Relocatable>(
-    arch: Arch, image: &'a Image, dynamic_section: &'a DynamicSection<'a>,
+    arch: Arch, lib: &Library,
-    rel: &'a R, resolve: &dyn Fn(&[u8]) -> Option<Elf32_Word>
+    rel: &R, resolve: &dyn Fn(&[u8]) -> Option<Elf32_Word>
 ) -> Result<(), Error> {
     // debug!("rel r_offset={:08X} r_info={:08X} r_addend={:08X}", rel.offset(), rel.r_info, rela.r_addend);
     let sym;
     if rel.sym_info() == 0 {
         sym = None;
     } else {
-        sym = Some(dynamic_section.symtab.get(rel.sym_info() as usize)
+        sym = Some(lib.symtab().get(rel.sym_info() as usize)
                    .ok_or("symbol out of bounds of symbol table")?)
     }
 
@@ -108,18 +109,18 @@ pub fn relocate<'a, R: Relocatable>(
             return Ok(()),
 
         RelType::Relative => {
-            let addend = rel.addend(image);
+            let addend = rel.addend(&lib.image);
-            value = image.ptr().wrapping_offset(addend as isize) as Elf32_Word;
+            value = lib.image.ptr().wrapping_offset(addend as isize) as Elf32_Word;
         }
 
         RelType::Lookup => {
             let sym = sym.ok_or("relocation requires an associated symbol")?;
-            let sym_name = dynamic_section.name_starting_at(sym.st_name as usize)?;
+            let sym_name = lib.name_starting_at(sym.st_name as usize)?;
 
-            if let Some(addr) = dynamic_section.lookup(sym_name) {
+            if let Some(addr) = lib.lookup(sym_name) {
                 // First, try to resolve against itself.
                 trace!("looked up symbol {} in image", format_sym_name(sym_name));
-                value = image.ptr() as u32 + addr;
+                value = lib.image.ptr() as u32 + addr;
             } else if let Some(addr) = resolve(sym_name) {
                 // Second, call the user-provided function.
                 trace!("resolved symbol {:?}", format_sym_name(sym_name));
@@ -132,5 +133,5 @@ pub fn relocate<'a, R: Relocatable>(
     }
 
     debug!("rel_type={:?} write at {:08X} value {:08X}", rel_type, rel.offset(), value);
-    image.write(rel.offset(), value)
+    lib.image.write(rel.offset(), value)
 }