sbpf_assembler/

program.rs

use {
    crate::{
        debug::{self, DebugData, reuse_debug_sections},
        dynsym::{DynamicSymbol, RelDyn, RelocationType},
        header::{ElfHeader, ProgramHeader},
        parser::ProgramLayout,
        section::{
            DebugSection, DynStrSection, DynSymSection, DynamicSection, NullSection, RelDynSection,
            Section, SectionType, ShStrTabSection,
        },
    },
    std::{fs::File, io::Write, path::Path},
};

#[derive(Debug)]
pub struct Program {
    pub elf_header: ElfHeader,
    pub program_headers: Option<Vec<ProgramHeader>>,
    pub sections: Vec<SectionType>,
}

impl Program {
    pub fn from_parse_result(
        ProgramLayout {
            code_section,
            data_section,
            dynamic_symbols,
            relocation_data,
            prog_is_static,
            arch,
            debug_sections,
        }: ProgramLayout,
        debug_data: Option<DebugData>,
    ) -> Self {
        let mut elf_header = ElfHeader::new();
        let mut program_headers = None;

        let bytecode_size = code_section.size();
        let rodata_size = data_section.size();

        let has_rodata = rodata_size > 0;
        let ph_count = if arch.is_v3() {
            if has_rodata { 2 } else { 1 }
        } else if prog_is_static {
            0
        } else {
            3
        };

        elf_header.e_flags = arch.e_flags();
        elf_header.e_phnum = ph_count;

        // save read + execute size for program header before
        // ownership of code/data sections is transferred
        let text_size = bytecode_size + rodata_size;

        // Calculate base offset after ELF header and program headers
        let base_offset = 64 + (ph_count as u64 * 56); // 64 bytes ELF header, 56 bytes per program header
        let mut current_offset = base_offset;

        let text_offset = if arch.is_v3() && has_rodata {
            rodata_size + base_offset
        } else {
            base_offset
        };

        // Get the entry point offset from dynamic_symbols if available
        let entry_point_offset = dynamic_symbols
            .get_entry_points()
            .first()
            .map(|(_, offset)| *offset)
            .unwrap_or(0);

        elf_header.e_entry = if arch.is_v3() {
            ProgramHeader::V3_BYTECODE_VADDR + entry_point_offset
        } else {
            text_offset + entry_point_offset
        };

        // Create a vector of sections
        let mut sections = Vec::new();
        sections.push(SectionType::Default(NullSection::new()));

        let mut section_names = Vec::new();
        let has_debug_sections = debug_data.is_some() || !debug_sections.is_empty();

        // Add section_names in fixed order for shstrtab
        section_names.push(".text".to_string());
        if has_rodata {
            section_names.push(".rodata".to_string());
        }

        if arch.is_v3() && has_rodata {
            // Data section
            let mut rodata_section = SectionType::Data(data_section);
            rodata_section.set_offset(current_offset);
            rodata_section.set_vaddr(ProgramHeader::V3_RODATA_VADDR);
            current_offset += rodata_section.size();
            sections.push(rodata_section);

            // Code section
            let mut text_section = SectionType::Code(code_section);
            text_section.set_offset(current_offset);
            text_section.set_vaddr(ProgramHeader::V3_BYTECODE_VADDR);
            current_offset += text_section.size();
            sections.push(text_section);
        } else {
            // Code section
            let mut text_section = SectionType::Code(code_section);
            text_section.set_offset(current_offset);
            if arch.is_v3() {
                text_section.set_vaddr(ProgramHeader::V3_BYTECODE_VADDR);
            }
            current_offset += text_section.size();
            sections.push(text_section);

            // Data section (if any)
            if has_rodata {
                let mut rodata_section = SectionType::Data(data_section);
                rodata_section.set_offset(current_offset);
                if arch.is_v3() {
                    rodata_section.set_vaddr(ProgramHeader::V3_RODATA_VADDR);
                }
                current_offset += rodata_section.size();
                sections.push(rodata_section);
            }
        }

        let padding = (8 - (current_offset % 8)) % 8;
        current_offset += padding;

        if arch.is_v3() {
            // v3 programs are loaded entirely through program headers; the
            // loader never reads the section header table. Unless the program
            // is built in debug mode, we omit section headers along with the
            // .shstrtab and debug sections that exist only to support them,
            // keeping v3 binaries minimal.
            if has_rodata {
                // 2 headers: rodata (PF_R) then bytecode (PF_X)
                let rodata_offset = base_offset;
                let bytecode_offset = base_offset + rodata_size;
                program_headers = Some(vec![
                    ProgramHeader::new_load(rodata_offset, rodata_size, false, arch),
                    ProgramHeader::new_load(bytecode_offset, bytecode_size, true, arch),
                ]);
            } else {
                // 1 header: bytecode only (PF_X)
                program_headers = Some(vec![ProgramHeader::new_load(
                    base_offset,
                    bytecode_size,
                    true,
                    arch,
                )]);
            }

            if has_debug_sections {
                // If debug info is present, generate debug sections
                let debug_sections = Self::generate_debug_sections(
                    debug_sections,
                    &debug_data,
                    ProgramHeader::V3_BYTECODE_VADDR,
                    &mut section_names,
                    &mut current_offset,
                );

                for debug_section in debug_sections {
                    sections.push(debug_section);
                }

                let mut shstrtab_section = SectionType::ShStrTab(ShStrTabSection::new(
                    (section_names
                        .iter()
                        .map(|name| name.len() + 1)
                        .sum::<usize>()
                        + 1) as u32,
                    section_names,
                ));
                shstrtab_section.set_offset(current_offset);
                current_offset += shstrtab_section.size();
                sections.push(shstrtab_section);
            }
        } else if !prog_is_static {
            let mut symbol_names = Vec::new();
            let mut dyn_syms = Vec::new();
            let mut dyn_str_offset = 1;

            dyn_syms.push(DynamicSymbol::new(0, 0, 0, 0, 0, 0));

            // all symbols handled right now are all global symbols
            for (name, _) in dynamic_symbols.get_entry_points() {
                symbol_names.push(name.clone());
                dyn_syms.push(DynamicSymbol::new(
                    dyn_str_offset as u32,
                    0x10,
                    0,
                    1,
                    elf_header.e_entry,
                    0,
                ));
                dyn_str_offset += name.len() + 1;
            }

            for (name, _) in dynamic_symbols.get_call_targets() {
                symbol_names.push(name.clone());
                dyn_syms.push(DynamicSymbol::new(dyn_str_offset as u32, 0x10, 0, 0, 0, 0));
                dyn_str_offset += name.len() + 1;
            }

            let mut rel_count = 0;
            let mut rel_dyns = Vec::new();
            for (offset, rel_type, name) in relocation_data.get_rel_dyns() {
                if rel_type == RelocationType::RSbfSyscall {
                    if let Some(index) = symbol_names.iter().position(|n| *n == name) {
                        rel_dyns.push(RelDyn::new(
                            offset + text_offset,
                            rel_type as u64,
                            index as u64 + 1,
                        ));
                    } else {
                        panic!("Symbol {} not found in symbol_names", name);
                    }
                } else if rel_type == RelocationType::RSbf64Relative {
                    rel_count += 1;
                    rel_dyns.push(RelDyn::new(offset + text_offset, rel_type as u64, 0));
                }
            }
            // create four dynamic related sections
            let mut dynamic_section = SectionType::Dynamic(DynamicSection::new(
                (section_names
                    .iter()
                    .map(|name| name.len() + 1)
                    .sum::<usize>()
                    + 1) as u32,
            ));
            section_names.push(dynamic_section.name().to_string());

            let mut dynsym_section = SectionType::DynSym(DynSymSection::new(
                (section_names
                    .iter()
                    .map(|name| name.len() + 1)
                    .sum::<usize>()
                    + 1) as u32,
                dyn_syms,
            ));
            section_names.push(dynsym_section.name().to_string());

            let mut dynstr_section = SectionType::DynStr(DynStrSection::new(
                (section_names
                    .iter()
                    .map(|name| name.len() + 1)
                    .sum::<usize>()
                    + 1) as u32,
                symbol_names,
            ));
            section_names.push(dynstr_section.name().to_string());

            let mut rel_dyn_section = SectionType::RelDyn(RelDynSection::new(
                (section_names
                    .iter()
                    .map(|name| name.len() + 1)
                    .sum::<usize>()
                    + 1) as u32,
                rel_dyns,
            ));
            section_names.push(rel_dyn_section.name().to_string());

            dynamic_section.set_offset(current_offset);
            if let SectionType::Dynamic(ref mut dynamic_section) = dynamic_section {
                // link to .dynstr
                dynamic_section.set_link(
                    section_names
                        .iter()
                        .position(|name| name == ".dynstr")
                        .expect("missing .dynstr section") as u32
                        + 1,
                );
                dynamic_section.set_rel_count(rel_count);
            }
            current_offset += dynamic_section.size();

            dynsym_section.set_offset(current_offset);
            if let SectionType::DynSym(ref mut dynsym_section) = dynsym_section {
                // link to .dynstr
                dynsym_section.set_link(
                    section_names
                        .iter()
                        .position(|name| name == ".dynstr")
                        .expect("missing .dynstr section") as u32
                        + 1,
                );
            }
            current_offset += dynsym_section.size();

            dynstr_section.set_offset(current_offset);
            current_offset += dynstr_section.size();

            rel_dyn_section.set_offset(current_offset);
            if let SectionType::RelDyn(ref mut rel_dyn_section) = rel_dyn_section {
                // link to .dynsym
                rel_dyn_section.set_link(
                    section_names
                        .iter()
                        .position(|name| name == ".dynsym")
                        .expect("missing .dynsym section") as u32
                        + 1,
                );
            }
            current_offset += rel_dyn_section.size();

            if let SectionType::Dynamic(ref mut dynamic_section) = dynamic_section {
                dynamic_section.set_rel_offset(rel_dyn_section.offset());
                dynamic_section.set_rel_size(rel_dyn_section.size());
                dynamic_section.set_dynsym_offset(dynsym_section.offset());
                dynamic_section.set_dynstr_offset(dynstr_section.offset());
                dynamic_section.set_dynstr_size(dynstr_section.size());
            }

            // Generate debug sections
            let debug_sections = Self::generate_debug_sections(
                debug_sections,
                &debug_data,
                text_offset,
                &mut section_names,
                &mut current_offset,
            );

            let mut shstrtab_section = SectionType::ShStrTab(ShStrTabSection::new(
                (section_names
                    .iter()
                    .map(|name| name.len() + 1)
                    .sum::<usize>()
                    + 1) as u32,
                section_names,
            ));
            shstrtab_section.set_offset(current_offset);
            current_offset += shstrtab_section.size();

            program_headers = Some(vec![
                ProgramHeader::new_load(
                    text_offset,
                    text_size,
                    true, // executable
                    arch,
                ),
                ProgramHeader::new_load(
                    dynsym_section.offset(),
                    dynsym_section.size() + dynstr_section.size() + rel_dyn_section.size(),
                    false,
                    arch,
                ),
                ProgramHeader::new_dynamic(dynamic_section.offset(), dynamic_section.size()),
            ]);

            sections.push(dynamic_section);
            sections.push(dynsym_section);
            sections.push(dynstr_section);
            sections.push(rel_dyn_section);

            for debug_section in debug_sections {
                sections.push(debug_section);
            }

            sections.push(shstrtab_section);
        } else {
            // Create a vector of section names
            let mut section_names = Vec::new();
            for section in &sections {
                section_names.push(section.name().to_string());
            }

            // Generate debug sections
            let debug_sections = Self::generate_debug_sections(
                debug_sections,
                &debug_data,
                text_offset,
                &mut section_names,
                &mut current_offset,
            );

            for debug_section in debug_sections {
                sections.push(debug_section);
            }

            let mut shstrtab_section = ShStrTabSection::new(
                section_names
                    .iter()
                    .map(|name| name.len() + 1)
                    .sum::<usize>() as u32,
                section_names,
            );
            shstrtab_section.set_offset(current_offset);
            current_offset += shstrtab_section.size();
            sections.push(SectionType::ShStrTab(shstrtab_section));
        }

        // Update section header offset in ELF header. v3 binaries carry no
        // section header table unless debug info is present.
        if !arch.is_v3() || has_debug_sections {
            let padding = (8 - (current_offset % 8)) % 8;
            elf_header.e_shoff = current_offset + padding;
            elf_header.e_shnum = sections.len() as u16;
            elf_header.e_shstrndx = sections.len() as u16 - 1;
        }

        Self {
            elf_header,
            program_headers,
            sections,
        }
    }

    pub fn emit_bytecode(&self) -> Vec<u8> {
        let mut bytes = Vec::new();

        // Emit ELF Header bytes
        bytes.extend(self.elf_header.bytecode());

        // Emit program headers
        if let Some(program_headers) = &self.program_headers {
            for ph in program_headers {
                bytes.extend(ph.bytecode());
            }
        }

        // Emit sections
        for section in &self.sections {
            bytes.extend(section.bytecode());
        }

        // Emit section headers (omitted when there is no section header table,
        // e.g. v3 binaries).
        if self.elf_header.e_shoff != 0 {
            for section in &self.sections {
                bytes.extend(section.section_header_bytecode());
            }
        }

        bytes
    }

    fn generate_debug_sections(
        parsed_debug_sections: Vec<DebugSection>,
        debug_data: &Option<DebugData>,
        text_offset: u64,
        section_names: &mut Vec<String>,
        current_offset: &mut u64,
    ) -> Vec<SectionType> {
        if let Some(data) = debug_data {
            debug::generate_debug_sections(data, text_offset, section_names, current_offset)
                .into_iter()
                .enumerate()
                .map(|(i, s)| match i {
                    0 => SectionType::DebugAbbrev(s),
                    1 => SectionType::DebugInfo(s),
                    2 => SectionType::DebugLine(s),
                    3 => SectionType::DebugLineStr(s),
                    _ => unreachable!(),
                })
                .collect()
        } else {
            reuse_debug_sections(parsed_debug_sections, section_names, current_offset)
        }
    }

    pub fn has_rodata(&self) -> bool {
        self.sections.iter().any(|s| s.name() == ".rodata")
    }

    pub fn parse_rodata(&self) -> Vec<(String, usize, String)> {
        let rodata = self
            .sections
            .iter()
            .find(|s| s.name() == ".rodata")
            .unwrap();
        if let SectionType::Data(data_section) = rodata {
            data_section.rodata()
        } else {
            panic!("ROData section not found");
        }
    }

    pub fn save_to_file(&self, input_path: &str) -> std::io::Result<()> {
        // Get the file stem (name without extension) from input path
        let path = Path::new(input_path);
        let file_stem = path
            .file_stem()
            .and_then(|s| s.to_str())
            .unwrap_or("output");

        // Create the output file name with .so extension
        let output_path = format!("{}.so", file_stem);

        // Get the bytecode
        let bytes = self.emit_bytecode();

        // Write bytes to file
        let mut file = File::create(output_path)?;
        file.write_all(&bytes)?;

        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use {
        super::*,
        crate::{SbpfArch, parser::parse},
    };

    #[test]
    fn test_program_from_simple_source() {
        let source = "exit";
        for arch in [SbpfArch::V0, SbpfArch::V3] {
            let parse_result = parse(source, arch).unwrap();
            let program = Program::from_parse_result(parse_result, None);

            // Verify basic structure
            assert!(!program.sections.is_empty());
            assert!(program.sections.len() >= 2);
        }
    }

    #[test]
    fn test_program_without_rodata() {
        let source = "exit";
        for arch in [SbpfArch::V0, SbpfArch::V3] {
            let parse_result = parse(source, arch).unwrap();
            let program = Program::from_parse_result(parse_result, None);

            assert!(!program.has_rodata());
        }
    }

    #[test]
    fn test_program_emit_bytecode() {
        let source = "exit";
        for arch in [SbpfArch::V0, SbpfArch::V3] {
            let parse_result = parse(source, arch).unwrap();
            let program = Program::from_parse_result(parse_result, None);

            let bytecode = program.emit_bytecode();
            assert!(!bytecode.is_empty());
            // Should start with ELF magic
            assert_eq!(&bytecode[0..4], b"\x7fELF");
        }
    }

    #[test]
    fn test_v0_program_static_no_program_headers() {
        // Create a static program (no dynamic symbols)
        let source = "exit";
        let mut parse_result = parse(source, SbpfArch::V0).unwrap();
        parse_result.prog_is_static = true;

        let program = Program::from_parse_result(parse_result, None);
        assert!(program.program_headers.is_none());
        assert_eq!(program.elf_header.e_phnum, 0);
    }

    #[test]
    fn test_program_sections_ordering() {
        let source = r"exit";
        for arch in [SbpfArch::V0, SbpfArch::V3] {
            let parse_result = parse(source, arch).unwrap();
            let program = Program::from_parse_result(parse_result, None);

            // First section should be null
            assert_eq!(program.sections[0].name(), "");
            // Second should be .text
            assert_eq!(program.sections[1].name(), ".text");
        }
    }

    #[test]
    fn test_program_sections_debug() {
        let source = "exit";
        for arch in [SbpfArch::V0, SbpfArch::V3] {
            let parse_result = parse(source, arch).unwrap();
            let debug_data = Some(DebugData {
                filename: "test.s".to_string(),
                directory: "/test".to_string(),
                lines: vec![],
                labels: vec![],
                code_start: 0,
                code_end: 8,
            });
            let program = Program::from_parse_result(parse_result, debug_data);

            let debug_section_names: Vec<&str> = program
                .sections
                .iter()
                .map(|s| s.name())
                .filter(|name| name.starts_with(".debug_"))
                .collect();

            assert!(debug_section_names.contains(&".debug_abbrev"));
            assert!(debug_section_names.contains(&".debug_info"));
            assert!(debug_section_names.contains(&".debug_line"));
            assert!(debug_section_names.contains(&".debug_line_str"));
        }
    }

    #[test]
    fn test_v3_e_flags() {
        let source = "exit";
        let parse_result = parse(source, SbpfArch::V3).unwrap();
        let program = Program::from_parse_result(parse_result, None);
        assert_eq!(program.elf_header.e_flags, 3);
    }

    #[test]
    fn test_v3_no_rodata_one_header() {
        let source = "exit";
        let parse_result = parse(source, SbpfArch::V3).unwrap();
        let program = Program::from_parse_result(parse_result, None);

        let headers = program.program_headers.as_ref().unwrap();
        assert_eq!(headers.len(), 1);
        assert_eq!(headers[0].p_flags, ProgramHeader::PF_X);
        assert_eq!(headers[0].p_vaddr, ProgramHeader::V3_BYTECODE_VADDR);
    }

    #[test]
    fn test_v3_with_rodata_two_headers() {
        let source = r#"
.rodata
msg: .ascii "test"
.text
.globl entrypoint
entrypoint:
    exit
        "#;
        let parse_result = parse(source, SbpfArch::V3).unwrap();
        let program = Program::from_parse_result(parse_result, None);

        let headers = program.program_headers.as_ref().unwrap();
        assert_eq!(headers.len(), 2);
        // first header: rodata (PF_R, vaddr=0)
        assert_eq!(headers[0].p_flags, ProgramHeader::PF_R);
        assert_eq!(headers[0].p_vaddr, ProgramHeader::V3_RODATA_VADDR);
        // second header: bytecode (PF_X, vaddr=1<<32)
        assert_eq!(headers[1].p_flags, ProgramHeader::PF_X);
        assert_eq!(headers[1].p_vaddr, ProgramHeader::V3_BYTECODE_VADDR);
    }

    #[test]
    fn test_v3_e_entry() {
        let source = r#"
.globl entrypoint
entrypoint:
    exit
        "#;
        let parse_result = parse(source, SbpfArch::V3).unwrap();
        let program = Program::from_parse_result(parse_result, None);

        // v3: e_entry must be >= V3_BYTECODE_VADDR (1 << 32)
        assert!(program.elf_header.e_entry >= ProgramHeader::V3_BYTECODE_VADDR,);
    }

    #[test]
    fn test_v3_p_offset() {
        let source = r#"
.rodata
msg: .ascii "test"
.text
.globl entrypoint
entrypoint:
    exit
        "#;
        let parse_result = parse(source, SbpfArch::V3).unwrap();
        let program = Program::from_parse_result(parse_result, None);

        let headers = program.program_headers.as_ref().unwrap();
        let expected_first_offset = 64 + (program.elf_header.e_phnum as u64) * 56;
        assert_eq!(headers[0].p_offset, expected_first_offset);
        assert_eq!(
            headers[1].p_offset,
            headers[0].p_offset + headers[0].p_filesz
        );
    }

    #[test]
    fn test_v3_no_dynamic_sections() {
        let source = r#"
.globl entrypoint
entrypoint:
    call sol_log_64_
    exit
        "#;
        let parse_result = parse(source, SbpfArch::V3).unwrap();
        let program = Program::from_parse_result(parse_result, None);

        // v3 should not have any dynamic sections
        let section_names: Vec<&str> = program.sections.iter().map(|s| s.name()).collect();
        assert!(!section_names.contains(&".dynamic"));
        assert!(!section_names.contains(&".dynsym"));
        assert!(!section_names.contains(&".dynstr"));
        assert!(!section_names.contains(&".rel.dyn"));
    }
}