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firmware: implement dyld::Library::rebind.

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This commit is contained in:
whitequark 2017-02-25 00:10:40 +00:00
parent 04ad267055
commit 13c6e96760
1 changed files with 46 additions and 19 deletions
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65
artiq/firmware/libdyld/lib.rs
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@ -81,6 +81,8 @@ pub struct Library<'a> {
image_sz: usize,
strtab: &'a [u8],
symtab: &'a [Elf32_Sym],
rela: &'a [Elf32_Rela],
pltrel: &'a [Elf32_Rela],
hash_bucket: &'a [Elf32_Word],
hash_chain: &'a [Elf32_Word],
}
@ -114,7 +116,43 @@ impl<'a> Library<'a> {
}
}
fn fixup_rela(&self, rela: &Elf32_Rela, resolve: &Fn(&[u8]) -> Option<Elf32_Word>)
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 })
}
pub fn rebind(&self, name: &[u8], addr: Elf32_Word) -> Result<(), Error<'a>> {
for rela in self.rela.iter().chain(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 {
@ -134,14 +172,7 @@ impl<'a> Library<'a> {
R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT => {
let sym = sym.ok_or("relocation requires an associated symbol")?;
let sym_name_off = sym.st_name as usize;
let sym_name_end =
self.strtab.iter().skip(sym_name_off).position(|&x| x == 0)
.ok_or("symbol in symbol table not null-terminated")?;
let sym_name =
self.strtab.get(sym_name_off..sym_name_off + sym_name_end)
.ok_or("cannot read symbol name")?;
let sym_name = self.name_starting_at(sym.st_name as usize)?;
// First, try to resolve against itself.
match self.lookup(sym_name) {
@ -162,14 +193,7 @@ impl<'a> Library<'a> {
_ => return Err("unsupported relocation type")?
}
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;
unsafe { *ptr = value }
Ok(())
self.update_rela(rela, value)
}
pub fn load(data: &[u8], image: &'a mut [u8], resolve: &Fn(&[u8]) -> Option<Elf32_Word>)
@ -291,6 +315,8 @@ impl<'a> Library<'a> {
image_sz: image.len(),
strtab: strtab,
symtab: symtab,
rela: rela,
pltrel: pltrel,
hash_bucket: &hash[..nbucket],
hash_chain: &hash[nbucket..nbucket + nchain],
};
@ -305,8 +331,9 @@ impl<'a> Library<'a> {
// we never write to the memory they refer to, so it's safe.
mem::drop(image);
for r in rela { library.fixup_rela(r, resolve)? }
for r in pltrel { library.fixup_rela(r, resolve)? }
for r in rela.iter().chain(pltrel.iter()) {
library.resolve_rela(r, resolve)?
}
Ok(library)
}