Feature - Strict ELF parser (#624)

* Moves ELF header parsing from load() to load_with_parser().

* Reorders UnsupportedSBPFVersion to be directly checked behind the header OutOfBounds.

* Splits out Executable::load_with_lenient_parser().

* Adds Executable::load_with_strict_parser().

* Adds new linker script and test ELF.

* Adds tests.

src/elf_parser/mod.rs

@@ -573,7 +573,7 @@ impl<'a> Elf64<'a> {
     }
 
     /// Returns the `&[T]` contained at `bytes[range]`
-    fn slice_from_bytes<T: 'static>(
+    pub fn slice_from_bytes<T: 'static>(
         bytes: &[u8],
         range: Range<usize>,
     ) -> Result<&[T], ElfParserError> {

src/program.rs

@@ -15,8 +15,8 @@ pub enum SBPFVersion {
     V1,
     /// The current format
     V2,
-    /// The future format with BTF support
-    V3,
+    /// Used for future versions
+    Reserved,
 }
 
 impl SBPFVersion {
@@ -95,6 +95,11 @@ impl SBPFVersion {
     pub fn move_memory_instruction_classes(self) -> bool {
         self != SBPFVersion::V1
     }
+
+    /// Constrain ELF format to ignore section headers and relocations
+    pub fn enable_stricter_elf_headers(self) -> bool {
+        self != SBPFVersion::V1
+    }
 }
 
 /// Holds the function symbols of an Executable

tests/elfs/elf.ld

@@ -1,26 +1,31 @@
-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
+  .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*)
     }
 }
+
+PHDRS
+{
+  text PT_LOAD FLAGS(1);
+  rodata PT_LOAD FLAGS(4);
+  stack PT_GNU_STACK FLAGS(6);
+  heap PT_LOAD FLAGS(6);
+  dynsym PT_NULL FLAGS(0);
+  other PT_NULL FLAGS(0);
+}

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 +1,21 @@
+#![feature(linkage)]
+
+#[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;
+
+#[inline(never)]
+#[linkage="external"]
+fn foo() -> u64 {
+    return unsafe { core::ptr::read_volatile(&VAL_B) };
+}
+
+#[no_mangle]
+pub fn entrypoint() -> u64 {
+    return foo();
+}

tests/execution.rs

@@ -3049,6 +3049,17 @@ fn test_struct_func_pointer() {
     );
 }
 
+#[test]
+fn test_strict_header() {
+    test_interpreter_and_jit_elf!(
+        "tests/elfs/strict_header.so",
+        [],
+        (),
+        TestContextObject::new(6),
+        ProgramResult::Ok(42),
+    );
+}
+
 // Programs
 
 #[test]