Implements strict ELF loader.

src/elf.rs

@@ -11,10 +11,11 @@ use crate::{
     ebpf::{self, EF_SBPF_V2, HOST_ALIGN, INSN_SIZE},
     elf_parser::{
         consts::{
-            ELFCLASS64, ELFDATA2LSB, ELFOSABI_NONE, EM_BPF, EM_SBPF, ET_DYN, R_X86_64_32,
-            R_X86_64_64, R_X86_64_NONE, R_X86_64_RELATIVE,
+            ELFCLASS64, ELFDATA2LSB, ELFOSABI_NONE, EM_BPF, EM_SBPF, ET_DYN, PF_R, PF_W, PF_X,
+            PT_GNU_STACK, PT_LOAD, R_X86_64_32, R_X86_64_64, R_X86_64_NONE, R_X86_64_RELATIVE,
+            STT_FUNC,
         },
-        types::{Elf64Phdr, Elf64Shdr, Elf64Word},
+        types::{Elf64Phdr, Elf64Shdr, Elf64Sym, Elf64Word},
         Elf64, ElfParserError,
     },
     error::EbpfError,
@@ -116,7 +117,7 @@ impl From<ElfParserError> for ElfError {
             | ElfParserError::InvalidString
             | ElfParserError::InvalidSize
             | ElfParserError::Overlap
-            | ElfParserError::SectionNotInOrder
+            | ElfParserError::NotInOrder
             | ElfParserError::NoSectionNameStringTable
             | ElfParserError::InvalidDynamicSectionTable
             | ElfParserError::InvalidRelocationTable
@@ -382,10 +383,158 @@ impl<C: ContextObject> Executable<C> {
             aligned = AlignedMemory::<{ HOST_ALIGN }>::from_slice(bytes);
             aligned.as_slice()
         };
-        Self::load_with_parser(&Elf64::parse(bytes)?, bytes, loader)
+        let mut elf = Elf64::parse(bytes)?;
+        let enabled_sbpf_versions = loader.get_config().enabled_sbpf_versions.clone();
+        let sbpf_version = if *enabled_sbpf_versions.end() == SBPFVersion::V1 {
+            // Emulates a bug in the version dispatcher until we enable the first other version
+            if elf.file_header().e_flags == 0x20 {
+                SBPFVersion::V2
+            } else {
+                SBPFVersion::V1
+            }
+        } else {
+            match elf.file_header().e_flags {
+                0 => SBPFVersion::V1,
+                EF_SBPF_V2 => SBPFVersion::V2,
+                _ => SBPFVersion::V3,
+            }
+        };
+        if !enabled_sbpf_versions.contains(&sbpf_version) {
+            return Err(ElfError::UnsupportedSBPFVersion);
+        }
+        if sbpf_version == SBPFVersion::V1 {
+            elf.parse_sections()?;
+            elf.parse_dynamic()?;
+            Self::load_with_lenient_parser(&elf, bytes, loader)
+        } else {
+            Self::load_with_strict_parser(&elf, bytes, loader).map_err(|err| err.into())
+        }
+    }
+
+    fn load_with_strict_parser(
+        elf: &Elf64,
+        bytes: &[u8],
+        loader: Arc<BuiltinProgram<C>>,
+    ) -> Result<Self, ElfParserError> {
+        const EXPECTED_PROGRAM_HEADERS: [(u32, u32, u64); 5] = [
+            (PT_LOAD, PF_R | PF_X, ebpf::MM_BYTECODE_START), // byte code
+            (PT_LOAD, PF_R, ebpf::MM_RODATA_START),          // read only data
+            (PT_GNU_STACK, PF_R | PF_W, ebpf::MM_STACK_START), // stack
+            (PT_LOAD, PF_R | PF_W, ebpf::MM_HEAP_START),     // heap
+            (PT_LOAD, PF_R, 0xFFFFFFFF00000000),             // dynamic symbol table
+        ];
+        if elf.file_header().e_type != ET_DYN
+            || elf.file_header().e_ident.ei_osabi != 0x00
+            || elf.file_header().e_ident.ei_abiversion != 0x00
+            || elf.program_header_table().len() < EXPECTED_PROGRAM_HEADERS.len()
+        {
+            return Err(ElfParserError::InvalidFileHeader);
+        }
+        for (program_header, (p_type, p_flags, p_vaddr)) in elf
+            .program_header_table()
+            .iter()
+            .zip(EXPECTED_PROGRAM_HEADERS.iter())
+        {
+            let p_filesz = if (*p_flags & PF_W) != 0 {
+                0
+            } else {
+                program_header.p_memsz
+            };
+            if program_header.p_type != *p_type
+                || program_header.p_flags != *p_flags
+                || program_header.p_paddr != *p_vaddr
+                || program_header.p_vaddr != *p_vaddr
+                || program_header.p_memsz >= ebpf::MM_REGION_SIZE
+                || program_header.p_filesz != p_filesz
+            {
+                return Err(ElfParserError::InvalidProgramHeader);
+            }
+        }
+        let config = loader.get_config();
+        let bytecode_header = &elf.program_header_table()[0];
+        let rodata_header = &elf.program_header_table()[1];
+        let dynamic_symbol_table: &[Elf64Sym] =
+            elf.slice_from_program_header(&elf.program_header_table()[4])?;
+        let mut function_registry = FunctionRegistry::<usize>::default();
+        let mut expected_symbol_address = bytecode_header.p_vaddr;
+        for symbol in dynamic_symbol_table {
+            if symbol.st_info & STT_FUNC == 0 {
+                continue;
+            }
+            if symbol.st_size == 0 {
+                return Err(ElfParserError::InvalidSize);
+            }
+            if symbol.st_value != expected_symbol_address {
+                return Err(ElfParserError::NotInOrder);
+            }
+            if symbol.st_value.checked_rem(ebpf::INSN_SIZE as u64) != Some(0) {
+                return Err(ElfParserError::InvalidAlignment);
+            }
+            expected_symbol_address = symbol.st_value.saturating_add(symbol.st_size);
+            let target_pc = symbol
+                .st_value
+                .saturating_sub(bytecode_header.p_vaddr)
+                .checked_div(ebpf::INSN_SIZE as u64)
+                .unwrap_or_default() as usize;
+            function_registry
+                .register_function(
+                    target_pc as u32,
+                    if config.enable_symbol_and_section_labels {
+                        elf.symbol_name(symbol.st_name as Elf64Word)?
+                    } else {
+                        &[]
+                    },
+                    target_pc,
+                )
+                .unwrap();
+        }
+        if expected_symbol_address != bytecode_header.vm_range().end {
+            return Err(ElfParserError::OutOfBounds);
+        }
+        if expected_symbol_address.checked_rem(ebpf::INSN_SIZE as u64) != Some(0) {
+            return Err(ElfParserError::InvalidAlignment);
+        }
+        if !bytecode_header
+            .vm_range()
+            .contains(&elf.file_header().e_entry)
+        {
+            return Err(ElfParserError::OutOfBounds);
+        }
+        if elf
+            .file_header()
+            .e_entry
+            .checked_rem(ebpf::INSN_SIZE as u64)
+            != Some(0)
+        {
+            return Err(ElfParserError::InvalidAlignment);
+        }
+        let entry_pc = elf
+            .file_header()
+            .e_entry
+            .saturating_sub(bytecode_header.p_vaddr)
+            .checked_div(ebpf::INSN_SIZE as u64)
+            .unwrap_or_default() as usize;
+        if function_registry.lookup_by_key(entry_pc as u32).is_none() {
+            return Err(ElfParserError::InvalidFileHeader);
+        }
+        Ok(Self {
+            elf_bytes: AlignedMemory::from_slice(bytes), // TODO: borrow
+            sbpf_version: SBPFVersion::V2,
+            ro_section: Section::Borrowed(
+                rodata_header.p_vaddr as usize,
+                rodata_header.file_range().unwrap_or_default(),
+            ),
+            text_section_vaddr: bytecode_header.p_vaddr,
+            text_section_range: bytecode_header.file_range().unwrap_or_default(),
+            entry_pc,
+            function_registry,
+            loader,
+            #[cfg(all(feature = "jit", not(target_os = "windows"), target_arch = "x86_64"))]
+            compiled_program: None,
+        })
     }
 
-    fn load_with_parser(
+    fn load_with_lenient_parser(
         elf: &Elf64,
         bytes: &[u8],
         loader: Arc<BuiltinProgram<C>>,
@@ -1941,14 +2090,29 @@ mod test {
 
     #[test]
     fn test_long_section_name() {
+        let loader = BuiltinProgram::new_loader(
+            Config {
+                enabled_sbpf_versions: SBPFVersion::V1..=SBPFVersion::V1,
+                reject_broken_elfs: true,
+                ..Config::default()
+            },
+            FunctionRegistry::default(),
+        );
         let elf_bytes = std::fs::read("tests/elfs/long_section_name.so").unwrap();
         assert_error!(
-            Elf64::parse(&elf_bytes),
-            "StringTooLong({:?}, {})",
+            ElfExecutable::load(&elf_bytes, Arc::new(loader)),
+            "FailedToParse(\"Section or symbol name `{}` is longer than `{}` bytes\")",
             ".bss.__rust_no_alloc_shim_is_unstable"
                 .get(0..SECTION_NAME_LENGTH_MAXIMUM)
                 .unwrap(),
             SECTION_NAME_LENGTH_MAXIMUM
         );
     }
+
+    #[test]
+    fn test_strict_header() {
+        let elf_bytes =
+            std::fs::read("tests/elfs/strict_header.so").expect("failed to read elf file");
+        ElfExecutable::load(&elf_bytes, loader()).expect("validation failed");
+    }
 }

src/elf_parser/mod.rs

@@ -39,9 +39,9 @@ pub enum ElfParserError {
     /// Headers, tables or sections do overlap in the file
     #[error("values overlap")]
     Overlap,
-    /// Sections are not sorted in ascending order
-    #[error("sections not in ascending order")]
-    SectionNotInOrder,
+    /// Tables or sections are not sorted in ascending order
+    #[error("values not in ascending order")]
+    NotInOrder,
     /// No section name string table present in the file
     #[error("no section name string table found")]
     NoSectionNameStringTable,
@@ -63,6 +63,14 @@ pub enum ElfParserError {
 }
 
 impl Elf64Phdr {
+    /// Returns the byte range the section spans in the file.
+    pub fn file_range(&self) -> Option<Range<usize>> {
+        (self.p_type == PT_LOAD).then(|| {
+            let offset = self.p_offset as usize;
+            offset..offset.saturating_add(self.p_filesz as usize)
+        })
+    }
+
     /// Returns the segment virtual address range.
     pub fn vm_range(&self) -> Range<Elf64Addr> {
         let addr = self.p_vaddr;
@@ -222,7 +230,7 @@ impl<'a> Elf64<'a> {
             check_that_there_is_no_overlap(&section_range, &program_header_table_range)?;
             check_that_there_is_no_overlap(&section_range, &section_header_table_range)?;
             if section_range.start < offset {
-                return Err(ElfParserError::SectionNotInOrder);
+                return Err(ElfParserError::NotInOrder);
             }
             if section_range.end > elf_bytes.len() {
                 return Err(ElfParserError::OutOfBounds);
@@ -238,7 +246,7 @@ impl<'a> Elf64<'a> {
             })
             .transpose()?;
 
-        let mut parser = Self {
+        let parser = Self {
             elf_bytes,
             file_header,
             program_header_table,
@@ -252,9 +260,6 @@ impl<'a> Elf64<'a> {
             dynamic_symbol_names_section_header: None,
         };
 
-        parser.parse_sections()?;
-        parser.parse_dynamic()?;
-
         Ok(parser)
     }
 
@@ -283,7 +288,8 @@ impl<'a> Elf64<'a> {
         self.dynamic_relocations_table
     }
 
-    fn parse_sections(&mut self) -> Result<(), ElfParserError> {
+    /// Parses the section header table.
+    pub fn parse_sections(&mut self) -> Result<(), ElfParserError> {
         macro_rules! section_header_by_name {
             ($self:expr, $section_header:expr, $section_name:expr,
              $($name:literal => $field:ident,)*) => {
@@ -318,7 +324,8 @@ impl<'a> Elf64<'a> {
         Ok(())
     }
 
-    fn parse_dynamic(&mut self) -> Result<(), ElfParserError> {
+    /// Parses the dynamic section.
+    pub fn parse_dynamic(&mut self) -> Result<(), ElfParserError> {
         let mut dynamic_table: Option<&[Elf64Dyn]> = None;
 
         // try to parse PT_DYNAMIC

tests/elfs/elf.ld

@@ -1,26 +1,31 @@
 PHDRS
 {
-  text PT_LOAD  ;
+  text PT_LOAD ;
   rodata PT_LOAD ;
-  data PT_LOAD ;
-  dynamic PT_DYNAMIC ;
+  stack PT_GNU_STACK ;
+  heap PT_LOAD ;
+  dynsym PT_LOAD ;
+  other PT_NULL ;
 }
 
 SECTIONS
 {
-  . = SIZEOF_HEADERS;
-  .text : { *(.text*) } :text
-  .rodata : { *(.rodata*) } :rodata
-  .data.rel.ro : { *(.data.rel.ro*) } :rodata
-  .dynamic : { *(.dynamic) } :dynamic
-  .dynsym : { *(.dynsym) } :data
-  .dynstr : { *(.dynstr) } :data
-  .rel.dyn : { *(.rel.dyn) } :data
-  .data : { *(.data*) } :data
-  .bss : { *(.bss*) } :data
+  .text 0x000000000 : { *(.text*) } :text
+  .rodata 0x100000000 : { *(.rodata*) } :rodata
+  .bss.stack 0x200000000 : { *(.bss.stack*) } :stack
+  .bss.heap 0x300000000 : { *(.bss.heap*) } :heap
+  .dynsym 0xFFFFFFFF00000000 : { *(.dynsym) } :dynsym
+  .dynstr : { *(.dynstr) } :other
+  .dynamic : { *(.dynamic) } :other
+  .symtab : { *(.symtab) } :other
+  .shstrtab : { *(.shstrtab) } :other
+  .strtab : { *(.strtab) } :other
   /DISCARD/ : {
+      *(.comment*)
       *(.eh_frame*)
-      *(.gnu.hash*)
-      *(.hash*)
+      *(*hash*)
+      *(.bss*)
+      *(.data*)
+      *(.rel.dyn*)
     }
 }

tests/elfs/elf_sbpfv1.ld

@@ -0,0 +1,26 @@
+PHDRS
+{
+  text PT_LOAD ;
+  rodata PT_LOAD ;
+  data PT_LOAD ;
+  dynamic PT_DYNAMIC ;
+}
+
+SECTIONS
+{
+  . = SIZEOF_HEADERS;
+  .text : { *(.text*) } :text
+  .rodata : { *(.rodata*) } :rodata
+  .data.rel.ro : { *(.data.rel.ro*) } :rodata
+  .dynamic : { *(.dynamic) } :dynamic
+  .dynsym : { *(.dynsym) } :data
+  .dynstr : { *(.dynstr) } :data
+  .rel.dyn : { *(.rel.dyn) } :data
+  .data : { *(.data*) } :data
+  .bss : { *(.bss*) } :data
+  /DISCARD/ : {
+      *(.eh_frame*)
+      *(.gnu.hash*)
+      *(.hash*)
+    }
+}

tests/elfs/elfs.sh

@@ -7,9 +7,12 @@ TOOLCHAIN=../../../agave/sdk/sbf/dependencies/platform-tools
 RC_COMMON="$TOOLCHAIN/rust/bin/rustc --target sbf-solana-solana --crate-type lib -C panic=abort -C opt-level=2"
 RC="$RC_COMMON -C target_cpu=sbfv2"
 RC_V1="$RC_COMMON -C target_cpu=generic"
-LD_COMMON="$TOOLCHAIN/llvm/bin/ld.lld -z notext -shared --Bdynamic -entry entrypoint --script elf.ld"
-LD="$LD_COMMON --section-start=.text=0x100000000"
-LD_V1=$LD_COMMON
+LD_COMMON="$TOOLCHAIN/llvm/bin/ld.lld -z notext -shared --Bdynamic -entry entrypoint"
+LD="$LD_COMMON --script elf.ld"
+LD_V1="$LD_COMMON --script elf_sbpfv1.ld"
+
+$RC -o strict_header.o strict_header.rs
+$LD -o strict_header.so strict_header.o
 
 $RC_V1 -o relative_call.o relative_call.rs
 $LD_V1 -o relative_call_sbpfv1.so relative_call.o

tests/elfs/strict_header.rs

@@ -0,0 +1,13 @@
+#[link_section = ".bss.stack"]
+pub static _STACK: [u8; 0x1000] = [0; 0x1000];
+#[link_section = ".bss.heap"]
+pub static _HEAP: [u8; 0x1000] = [0; 0x1000];
+
+static _VAL_A: u64 = 41;
+static VAL_B: u64 = 42;
+static _VAL_C: u64 = 43;
+
+#[no_mangle]
+pub fn entrypoint() -> u64 {
+    return unsafe { core::ptr::read_volatile(&VAL_B) };
+}