forked from M-Labs/artiq
firmware: implement dyld::Library::rebind.
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04ad267055
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13c6e96760
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@ -81,6 +81,8 @@ pub struct Library<'a> {
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image_sz: usize,
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strtab: &'a [u8],
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symtab: &'a [Elf32_Sym],
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rela: &'a [Elf32_Rela],
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pltrel: &'a [Elf32_Rela],
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hash_bucket: &'a [Elf32_Word],
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hash_chain: &'a [Elf32_Word],
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}
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@ -114,7 +116,43 @@ impl<'a> Library<'a> {
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}
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}
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fn fixup_rela(&self, rela: &Elf32_Rela, resolve: &Fn(&[u8]) -> Option<Elf32_Word>)
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fn name_starting_at(&self, offset: usize) -> Result<&'a [u8], Error<'a>> {
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let size = self.strtab.iter().skip(offset).position(|&x| x == 0)
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.ok_or("symbol in symbol table not null-terminated")?;
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Ok(self.strtab.get(offset..offset + size)
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.ok_or("cannot read symbol name")?)
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}
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fn update_rela(&self, rela: &Elf32_Rela, value: Elf32_Word) -> Result<(), Error<'a>> {
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if rela.r_offset as usize + mem::size_of::<Elf32_Addr>() > self.image_sz {
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return Err("relocation out of image bounds")?
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}
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let ptr = (self.image_off + rela.r_offset) as *mut Elf32_Addr;
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Ok(unsafe { *ptr = value })
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}
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pub fn rebind(&self, name: &[u8], addr: Elf32_Word) -> Result<(), Error<'a>> {
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for rela in self.rela.iter().chain(self.pltrel.iter()) {
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match ELF32_R_TYPE(rela.r_info) {
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R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT => {
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let sym = self.symtab.get(ELF32_R_SYM(rela.r_info) as usize)
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.ok_or("symbol out of bounds of symbol table")?;
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let sym_name = self.name_starting_at(sym.st_name as usize)?;
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if sym_name == name {
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self.update_rela(rela, addr)?
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}
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}
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// No associated symbols for other relocation types.
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_ => ()
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}
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}
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Ok(())
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}
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fn resolve_rela(&self, rela: &Elf32_Rela, resolve: &Fn(&[u8]) -> Option<Elf32_Word>)
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-> Result<(), Error<'a>> {
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let sym;
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if ELF32_R_SYM(rela.r_info) == 0 {
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@ -134,14 +172,7 @@ impl<'a> Library<'a> {
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R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT => {
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let sym = sym.ok_or("relocation requires an associated symbol")?;
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let sym_name_off = sym.st_name as usize;
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let sym_name_end =
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self.strtab.iter().skip(sym_name_off).position(|&x| x == 0)
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.ok_or("symbol in symbol table not null-terminated")?;
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let sym_name =
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self.strtab.get(sym_name_off..sym_name_off + sym_name_end)
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.ok_or("cannot read symbol name")?;
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let sym_name = self.name_starting_at(sym.st_name as usize)?;
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// First, try to resolve against itself.
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match self.lookup(sym_name) {
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@ -162,14 +193,7 @@ impl<'a> Library<'a> {
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_ => return Err("unsupported relocation type")?
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}
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if rela.r_offset as usize + mem::size_of::<Elf32_Addr>() > self.image_sz {
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return Err("relocation out of image bounds")?
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}
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let ptr = (self.image_off + rela.r_offset) as *mut Elf32_Addr;
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unsafe { *ptr = value }
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Ok(())
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self.update_rela(rela, value)
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}
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pub fn load(data: &[u8], image: &'a mut [u8], resolve: &Fn(&[u8]) -> Option<Elf32_Word>)
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@ -291,6 +315,8 @@ impl<'a> Library<'a> {
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image_sz: image.len(),
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strtab: strtab,
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symtab: symtab,
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rela: rela,
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pltrel: pltrel,
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hash_bucket: &hash[..nbucket],
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hash_chain: &hash[nbucket..nbucket + nchain],
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};
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@ -305,8 +331,9 @@ impl<'a> Library<'a> {
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// we never write to the memory they refer to, so it's safe.
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mem::drop(image);
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for r in rela { library.fixup_rela(r, resolve)? }
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for r in pltrel { library.fixup_rela(r, resolve)? }
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for r in rela.iter().chain(pltrel.iter()) {
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library.resolve_rela(r, resolve)?
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}
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Ok(library)
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}
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