WIP

src/common/loadable.rs

@@ -7,6 +7,8 @@ use crate::{
     error::LinkError,
 };
 
+use super::SymbolValue;
+
 pub enum SegmentType {
     Text,
     Data,
@@ -62,11 +64,28 @@ impl SegmentSections {
     pub fn data_size(&self) -> u64 {
         self.data_size
     }
+
+    pub fn unresolved_offsets<'s>(
+        &'s self,
+        symbols: &'s Symbols,
+    ) -> impl Iterator<Item = usize> + 's {
+        symbols
+            .unresolved()
+            .map(move |si| {
+                self.sections_info.iter().filter_map(move |section| {
+                    match section.si.section_index == si.section_index {
+                        true => Some(section.output_offset + si.offsets.symbol_offset),
+                        false => None,
+                    }
+                })
+            })
+            .flatten()
+    }
 }
 
 #[derive(Default)]
 pub struct Loadable {
-    start_offset: Option<u64>,
+    start_offset: Option<usize>,
 
     text: SegmentSections,
     rodata: SegmentSections,
@@ -100,12 +119,8 @@ impl Loadable {
         }
 
         let name = object.symbol_name(si.symbol_index)?;
-        eprintln!("NAME: {}/{:?}", name, object.symbol_value(si.symbol_index)?);
-
-        let si = SymbolIndex {
-            object_index: object.object_index(),
-            symbol_index: si.symbol_index,
-        };
+        eprint!("OBJECT: {:?}\nNAME: {}/", object.origin(), name);
+        eprintln!("{:?}", object.symbol_value(si.symbol_index)?);
 
         if let Some(existing) = self.symbol_map.get_mut(name) {
             existing.push(si, objects)
@@ -188,11 +203,11 @@ impl Loadable {
         result
     }
 
-    pub fn set_start_offset(&mut self, offset: u64) {
+    pub fn set_start_offset(&mut self, offset: usize) {
         self.start_offset = Some(offset);
     }
 
-    pub fn start_offset(&self) -> Result<u64, Error> {
+    pub fn start_offset(&self) -> Result<usize, Error> {
         self.start_offset.ok_or_else(|| {
             let link_error = LinkError {
                 message: "Program entrypoint not found".into(),
@@ -202,4 +217,32 @@ impl Loadable {
             Error::LinkingError(link_error)
         })
     }
+
+    pub fn symbol_resolutions<'o, R>(
+        &'o self,
+        objects: &'o [R],
+    ) -> impl Iterator<Item = SymbolResolution<'o>>
+    where
+        R: Relocatable,
+    {
+        self.symbol_map.values().map(move |symbols| {
+            let value = symbols.value(objects).expect("value"); // TODO
+            let offsets = self.unresolved_offsets(symbols).collect();
+
+            SymbolResolution { value, offsets }
+        })
+    }
+
+    fn unresolved_offsets<'s>(&'s self, symbols: &'s Symbols) -> impl Iterator<Item = usize> + 's {
+        self.text
+            .unresolved_offsets(symbols)
+            .chain(self.rodata.unresolved_offsets(symbols))
+            .chain(self.data.unresolved_offsets(symbols))
+            .chain(self.bss.unresolved_offsets(symbols))
+    }
+}
+
+pub struct SymbolResolution<'b> {
+    pub value: SymbolValue<'b>,
+    pub offsets: Vec<usize>, // TODO: box iterator instead
 }

src/common/output.rs

@@ -7,5 +7,9 @@ pub trait Output<R>
 where
     R: Relocatable,
 {
-    fn finalize(self, objects: &[R], loadable: &mut Loadable) -> Result<PathBuf, Error>;
+    fn relocate_sections(&mut self, objects: &[R], loadable: &mut Loadable) -> Result<(), Error>;
+
+    fn resolve_symbols(&mut self, objects: &[R], loadable: &mut Loadable) -> Result<(), Error>;
+
+    fn finalize(self) -> Result<PathBuf, Error>;
 }

src/common/relocatable.rs

@@ -3,7 +3,7 @@ use std::{fmt::Display, path::PathBuf};
 
 use crate::error::Error;
 
-use super::Section;
+use super::{Section, SymbolOffsets, SymbolValue};
 
 pub type SectionIterBox<'iter> = Box<dyn Iterator<Item = Result<Section, Error>> + 'iter>;
 
@@ -23,9 +23,11 @@ pub trait Relocatable: Display + Sized {
 
     fn symbol_name(&self, index: usize) -> Result<&str, Error>;
 
-    fn symbol_value(&self, index: usize) -> Result<&[u8], Error>;
+    fn symbol_value(&self, index: usize) -> Result<SymbolValue, Error>;
 
-    fn symbol_file_offset(&self, index: usize) -> Result<usize, Error>;
+    fn symbol_offsets(&self, index: usize) -> Result<SymbolOffsets, Error>;
+
+    fn symbol_section_index(&self, index: usize) -> Result<usize, Error>;
 
     fn symbol_needs_resolving(&self, index: usize) -> bool;
 

src/common/section.rs

@@ -9,6 +9,7 @@ use super::Relocatable;
 #[derive(Clone)]
 pub struct SectionInfo {
     pub object_index: usize,
+    pub section_index: usize,
     pub file_size: u64,
     pub data_size: u64,
     pub offset: u64,

src/common/symbol.rs

@@ -7,7 +7,28 @@ use super::Relocatable;
 #[derive(Default, Debug, Clone, Copy, PartialEq, Eq)]
 pub struct SymbolIndex {
     pub object_index: usize,
+    pub section_index: usize,
     pub symbol_index: usize,
+    pub offsets: SymbolOffsets,
+}
+
+#[derive(Default, Debug, Clone, Copy, PartialEq, Eq)]
+pub struct SymbolOffsets {
+    pub section_offset: usize, // within the source relocatable
+    pub symbol_offset: usize,  // within the section
+}
+
+impl SymbolOffsets {
+    pub fn file_offset(&self) -> usize {
+        self.section_offset + self.symbol_offset
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SymbolValue<'o> {
+    Undefined,
+    Address(usize),
+    Value(&'o [u8]),
 }
 
 #[derive(Default)]
@@ -28,38 +49,52 @@ impl Symbols {
 
         self.indexes.push(si);
 
-        if value.len() > 0 {
-            if let Some(existing) = self.value_index {
-                let osi = self
-                    .indexes
-                    .get(existing)
-                    .ok_or(Error::InvalidSymbolIndex)?;
-                Self::duplicate_symbol_error(si, *osi, objects)
-            } else {
-                self.value_index = Some(self.indexes.len() - 1);
+        // save "value index" if we found a value
+        match value {
+            SymbolValue::Value(_) | SymbolValue::Address(_) => {
+                if let Some(existing) = self.value_index {
+                    let osi = self
+                        .indexes
+                        .get(existing)
+                        .ok_or(Error::InvalidSymbolIndex)?;
+                    Self::duplicate_symbol_error(si, *osi, objects)
+                } else {
+                    self.value_index = Some(self.indexes.len() - 1);
 
-                Ok(())
+                    Ok(())
+                }
             }
-        } else {
-            Ok(())
+            SymbolValue::Undefined => Ok(()),
         }
     }
 
-    pub fn value<'o, R>(&self, object: &'o R) -> Result<&'o [u8], Error>
+    pub fn value<'o, R>(&self, objects: &'o [R]) -> Result<SymbolValue<'o>, Error>
     where
         R: Relocatable,
     {
-        self.value_index.map_or(Ok(&[]), |v| {
+        self.value_index.map_or(Ok(SymbolValue::Undefined), |v| {
             let si = self.indexes[v];
             // can this be compile time checked??
-            if si.object_index != object.object_index() {
-                Err(Error::InvalidObjectIndex)
-            } else {
+            if let Some(object) = objects.get(si.object_index) {
                 object.symbol_value(si.symbol_index)
+            } else {
+                Err(Error::InvalidObjectIndex)
             }
         })
     }
 
+    pub fn unresolved(&self) -> impl Iterator<Item = &SymbolIndex> {
+        let vi = self.value_index.unwrap_or(std::usize::MAX);
+
+        self.indexes
+            .iter()
+            .enumerate()
+            .filter_map(move |(i, s)| match i == vi {
+                true => None,
+                false => Some(s),
+            })
+    }
+
     fn duplicate_symbol_error<R>(
         si: SymbolIndex,
         osi: SymbolIndex,
@@ -78,12 +113,13 @@ impl Symbols {
 
         traces.push(Trace {
             origin: object.origin().into(),
-            offset: object.symbol_file_offset(si.symbol_index)?,
+            offset: object.symbol_offsets(si.symbol_index)?.file_offset(),
             source_info: None,
         });
+
         traces.push(Trace {
             origin: other.origin().into(),
-            offset: other.symbol_file_offset(osi.symbol_index)?,
+            offset: other.symbol_offsets(osi.symbol_index)?.file_offset(),
             source_info: None,
         });
 

src/formats/elf/object.rs

@@ -4,7 +4,7 @@ use std::{
     path::{Path, PathBuf},
 };
 
-use crate::common::{Relocatable, Section, SectionInfo};
+use crate::common::{Relocatable, Section, SectionInfo, SymbolOffsets, SymbolValue};
 use crate::{common::SectionIterBox, error::Error};
 use elf_utilities::{
     header::Ehdr64,
@@ -13,13 +13,19 @@ use elf_utilities::{
 };
 use memmap::Mmap;
 
+struct ElfSymbol {
+    s64: Symbol64,
+    sh_index: usize,
+    rel_offset: usize,
+}
+
 pub struct ElfObject {
     object_index: usize,
     origin: PathBuf,
     data: Mmap,
     ehdr: Ehdr64,
     shdrs: Vec<Shdr64>,
-    symbols: Vec<(usize, Symbol64)>,
+    symbols: Vec<ElfSymbol>,
 }
 
 impl ElfObject {
@@ -48,15 +54,22 @@ impl ElfObject {
         Ok(result)
     }
 
-    fn resolve_symbol_value(&self, symbol_index: usize) -> Result<&[u8], Error> {
-        if let Some((_, s64)) = self.symbols.get(symbol_index) {
-            if s64.st_size == 0 {
-                Ok(&[])
-            } else if let Some(shdr) = self.shdrs.get(s64.st_shndx as usize) {
-                let start: usize = (shdr.sh_offset + s64.st_value) as usize;
-                let end: usize = start + s64.st_size as usize;
-
-                Ok(&self.data[start..end])
+    fn resolve_symbol_value(&self, symbol_index: usize) -> Result<SymbolValue, Error> {
+        if let Some(symbol) = self.symbols.get(symbol_index) {
+            let idx = symbol.s64.st_shndx as usize;
+            if idx == 0 {
+                Ok(SymbolValue::Undefined)
+            } else if let Some(shdr) = self.shdrs.get(idx) {
+                let sym_size = symbol.s64.st_size as usize;
+                let start: usize = (shdr.sh_offset + symbol.s64.st_value) as usize;
+
+                if sym_size > 0 {
+                    let end: usize = start + sym_size;
+
+                    Ok(SymbolValue::Value(&self.data[start..end]))
+                } else {
+                    Ok(SymbolValue::Address(start))
+                }
             } else {
                 Err(Error::InvalidSectionIndex)
             }
@@ -104,7 +117,8 @@ impl ElfObject {
     }
 
     fn populate(&mut self) -> Result<(), Error> {
-        for i in 0..self.ehdr.e_shnum {
+        for i in 1..self.ehdr.e_shnum {
+            // skip null section
             let i_usize: usize = i.into();
             let sh_start = self.ehdr.e_shoff as usize;
             let sh_size = usize::from(self.ehdr.e_shentsize);
@@ -113,24 +127,10 @@ impl ElfObject {
             let shdr: Shdr64 = bincode::deserialize(&self.data[offset..offset + sh_size])
                 .map_err(|err| Error::ParseError(err))?;
 
-            if shdr.get_type() == Type::SymTab {
-                let ent_size = shdr.sh_entsize as usize;
-                let offset = shdr.sh_offset as usize;
-                let count = shdr.sh_size as usize / ent_size;
-
-                for s_i in 1..count {
-                    // skip null-symbol
-                    let start = offset + s_i * ent_size;
-                    let s64 = Symbol64::deserialize(&self.data, start)
-                        .map_err(|err| Error::ParseError(err))?;
-
-                    match s64.get_type() {
-                        SymType::Object | SymType::Func | SymType::NoType => {
-                            self.symbols.push((shdr.sh_link as usize, s64))
-                        }
-                        _ => {}
-                    }
-                }
+            match shdr.get_type() {
+                Type::SymTab => self.populate_symtab(&shdr, i as usize)?,
+                Type::Rel | Type::Rela => self.populate_rela(&shdr)?,
+                _ => {}
             }
 
             self.shdrs.push(shdr);
@@ -139,7 +139,36 @@ impl ElfObject {
         Ok(())
     }
 
-    fn make_section(&self, shdr: &Shdr64) -> Option<Result<Section, Error>> {
+    fn populate_symtab(&mut self, shdr: &Shdr64, sh_index: usize) -> Result<(), Error> {
+        let ent_size = shdr.sh_entsize as usize;
+        let offset = shdr.sh_offset as usize;
+        let count = shdr.sh_size as usize / ent_size;
+
+        for s_i in 1..count {
+            // skip null-symbol
+            let start = offset + s_i * ent_size;
+            let s64 =
+                Symbol64::deserialize(&self.data, start).map_err(|err| Error::ParseError(err))?;
+
+            match s64.get_type() {
+                SymType::Object | SymType::Func | SymType::NoType => self.symbols.push(ElfSymbol {
+                    sh_index,
+                    s64,
+                    rel_offset: 0,
+                }),
+                _ => {}
+            }
+        }
+
+        Ok(())
+    }
+
+    fn populate_rela(&mut self, shdr: &Shdr64) -> Result<(), Error> {
+        // TODO
+        Ok(())
+    }
+
+    fn make_section(&self, shdr: &Shdr64, section_index: usize) -> Option<Result<Section, Error>> {
         let sh_index: usize = self.ehdr.e_shstrndx.into();
         let name = match self.resolve_name(shdr.sh_name as usize, sh_index) {
             Ok(n) => n,
@@ -148,6 +177,7 @@ impl ElfObject {
 
         let mut si = SectionInfo {
             object_index: self.object_index,
+            section_index,
             file_size: shdr.sh_size,
             data_size: shdr.sh_size,
             offset: shdr.sh_offset,
@@ -182,13 +212,14 @@ impl Relocatable for ElfObject {
     }
 
     fn sections(&self) -> SectionIterBox {
-        let iter = self
-            .shdrs
-            .iter()
-            .filter_map(move |shdr| match shdr.get_type() {
-                Type::ProgBits | Type::NoBits => self.make_section(shdr),
-                _ => None,
-            });
+        let iter =
+            self.shdrs
+                .iter()
+                .enumerate()
+                .filter_map(move |(i, shdr)| match shdr.get_type() {
+                    Type::ProgBits | Type::NoBits => self.make_section(shdr, i),
+                    _ => None,
+                });
 
         Box::new(iter)
     }
@@ -205,30 +236,39 @@ impl Relocatable for ElfObject {
 
     fn symbol_name(&self, index: usize) -> Result<&str, Error> {
         if let Some(symbol) = self.symbols.get(index) {
-            self.resolve_name(symbol.1.st_name as usize, symbol.0)
+            self.resolve_name(symbol.s64.st_name as usize, symbol.sh_index)
         } else {
             Err(Error::InvalidSymbolIndex)
         }
     }
 
-    fn symbol_value(&self, index: usize) -> Result<&[u8], Error> {
+    fn symbol_value(&self, index: usize) -> Result<SymbolValue, Error> {
         self.resolve_symbol_value(index)
     }
 
-    fn symbol_file_offset(&self, index: usize) -> Result<usize, Error> {
-        let (sh_index, s64) = self.symbols.get(index).ok_or(Error::InvalidSymbolIndex)?;
+    fn symbol_section_index(&self, index: usize) -> Result<usize, Error> {
+        let symbol = self.symbols.get(index).ok_or(Error::InvalidSymbolIndex)?;
+
+        Ok(symbol.sh_index)
+    }
+
+    fn symbol_offsets(&self, index: usize) -> Result<SymbolOffsets, Error> {
+        let symbol = self.symbols.get(index).ok_or(Error::InvalidSymbolIndex)?;
 
         let shdr = self
             .shdrs
-            .get(*sh_index)
+            .get(symbol.sh_index)
             .ok_or(Error::InvalidSectionIndex)?;
         let sh_offset: usize = shdr.sh_offset as usize;
 
-        Ok(sh_offset + s64.st_value as usize)
+        Ok(SymbolOffsets {
+            section_offset: sh_offset,
+            symbol_offset: symbol.rel_offset,
+        })
     }
 
     fn symbol_needs_resolving(&self, index: usize) -> bool {
-        match self.symbols[index].1.get_bind() {
+        match self.symbols[index].s64.get_bind() {
             Bind::Global | Bind::Weak => true,
             _ => false,
         }

src/formats/elf/output.rs

@@ -1,4 +1,10 @@
-use std::{fs::File, io::BufWriter, io::Write, mem::size_of, path::PathBuf};
+use std::{
+    fs::File,
+    io::BufWriter,
+    io::{Seek, SeekFrom, Write},
+    mem::size_of,
+    path::PathBuf,
+};
 
 use elf_utilities::{
     header::Ehdr64,
@@ -7,7 +13,9 @@ use elf_utilities::{
 };
 
 use crate::{
-    common::{expand_path, pad_to_next_page, Loadable, Output, Relocatable, SegmentType},
+    common::{
+        expand_path, pad_to_next_page, Loadable, Output, Relocatable, SegmentType, SymbolValue,
+    },
     error::Error,
 };
 
@@ -58,11 +66,11 @@ impl ElfOutput {
 }
 
 impl Output<ElfObject> for ElfOutput {
-    fn finalize(
-        mut self,
+    fn relocate_sections(
+        &mut self,
         objects: &[ElfObject],
         loadable: &mut Loadable,
-    ) -> Result<PathBuf, Error> {
+    ) -> Result<(), Error> {
         const EHS: u64 = size_of::<Ehdr64>() as u64;
         const PHS: u16 = size_of::<Phdr64>() as u16;
         const SHS: u16 = size_of::<Shdr64>() as u16;
@@ -72,7 +80,7 @@ impl Output<ElfObject> for ElfOutput {
         ehdr.e_shnum = SECTION_NAMES.len() as u16;
         ehdr.e_phnum = 3u16; // .text, .rodata + .data, .bss
         ehdr.e_shstrndx = ehdr.e_shnum - 1; // .shstrab is always last
-        ehdr.e_entry = loadable.start_offset()?;
+        ehdr.e_entry = loadable.start_offset()? as u64;
         ehdr.e_phentsize = PHS;
         ehdr.e_shentsize = SHS;
         ehdr.e_phoff = EHS;
@@ -124,9 +132,7 @@ impl Output<ElfObject> for ElfOutput {
             let bytes = object.bytes(si.offset, si.file_size)?;
             offset += self.writer.write(bytes)?;
         }
-        // for bytes in loadable.program_bytes(objects) {
-        //     offset += self.writer.write(bytes?)?;
-        // }
+
         offset += pad_to_next_page(&mut self.writer, offset)?;
 
         eprintln!("Data start: {}", offset);
@@ -139,6 +145,36 @@ impl Output<ElfObject> for ElfOutput {
             offset += self.writer.write(bytes)?;
         }
 
+        Ok(())
+    }
+
+    fn resolve_symbols(
+        &mut self,
+        objects: &[ElfObject],
+        loadable: &mut Loadable,
+    ) -> Result<(), Error> {
+        for resolution in loadable.symbol_resolutions(objects) {
+            for offset in resolution.offsets {
+                match resolution.value {
+                    SymbolValue::Value(v) => {
+                        eprintln!("Writing value {:?} to {}", resolution.value, offset);
+                        self.writer.seek(SeekFrom::Start(offset as u64))?;
+                        self.writer.write(v)?;
+                    }
+                    SymbolValue::Address(a) => {
+                        eprintln!("TODO");
+                    }
+                    SymbolValue::Undefined => {
+                        eprintln!("TODO2");
+                    }
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    fn finalize(mut self) -> Result<PathBuf, Error> {
         self.writer.flush()?;
 
         Ok(self.destination)

src/linker.rs

@@ -44,8 +44,14 @@ where
     pub fn link(mut self) -> Result<PathBuf, Error> {
         self.process_symbols()?;
 
-        self.loadable.set_start_offset(4096); // TODO: get from .start symbol location
-        self.output.finalize(&self.objects, &mut self.loadable)
+        self.loadable.set_start_offset(4096); // TODO
+
+        self.output
+            .relocate_sections(&self.objects, &mut self.loadable)?;
+        self.output
+            .resolve_symbols(&self.objects, &mut self.loadable)?;
+
+        self.output.finalize()
     }
 
     fn process_symbols(&mut self) -> Result<(), Error> {
@@ -55,7 +61,9 @@ where
             for i in 0..symbol_count {
                 let si = SymbolIndex {
                     object_index: r.object_index(),
+                    section_index: r.symbol_section_index(i)?,
                     symbol_index: i,
+                    offsets: r.symbol_offsets(i)?,
                 };
                 self.loadable.process_symbol(si, &self.objects)?;
             }