elf_loader 0.14.0

//! RISC-V 32-bit architecture-specific ELF relocation and dynamic linking support.
//!
//! This module provides RISC-V 32-bit specific implementations for ELF relocation,
//! dynamic linking, and procedure linkage table (PLT) handling.

use elf::abi::*;

/// The ELF machine type for RISC-V architecture.
pub const EM_ARCH: u16 = EM_RISCV;
/// Offset for TLS Dynamic Thread Vector.
/// In our software-based TLS implementation, we use 0 offset for simplicity.
pub const TLS_DTV_OFFSET: usize = 0;

/// Relative relocation type - add base address to relative offset.
pub const REL_RELATIVE: u32 = R_RISCV_RELATIVE;
/// GOT entry relocation type - set GOT entry to symbol address.
pub const REL_GOT: u32 = R_RISCV_32;
/// TLS DTPMOD relocation type - set to TLS module ID.
pub const REL_DTPMOD: u32 = R_RISCV_TLS_DTPMOD32;
/// Symbolic relocation type - set to absolute symbol address.
pub const REL_SYMBOLIC: u32 = R_RISCV_32;
/// PLT jump slot relocation type - set PLT entry to symbol address.
pub const REL_JUMP_SLOT: u32 = R_RISCV_JUMP_SLOT;
/// TLS DTPOFF relocation type - set to TLS offset relative to DTV.
pub const REL_DTPOFF: u32 = R_RISCV_TLS_DTPREL32;
/// IRELATIVE relocation type - call function to get address.
pub const REL_IRELATIVE: u32 = R_RISCV_IRELATIVE;
/// COPY relocation type - copy data from shared object.
pub const REL_COPY: u32 = R_RISCV_COPY;
/// TLS TPOFF relocation type - set to TLS offset relative to thread pointer.
pub const REL_TPOFF: u32 = R_RISCV_TLS_TPREL32;
/// TLSDESC relocation type - set to a function pointer and an argument.
pub const REL_TLSDESC: u32 = 0;

/// Get the current thread pointer using architecture-specific register.
#[inline(always)]
pub(crate) unsafe fn get_thread_pointer() -> *mut u8 {
    let tp: *mut u8;
    unsafe {
        core::arch::asm!("mv {}, tp", out(reg) tp);
    }
    tp
}

pub(crate) const DYLIB_OFFSET: usize = 1;
pub(crate) const RESOLVE_FUNCTION_OFFSET: usize = 0;

#[unsafe(naked)]
pub(crate) extern "C" fn dl_runtime_resolve() {
    core::arch::naked_asm!(
        "
        // 保存整数参数寄存器
        // ra, a0-a7: 9 * 4 = 36 bytes
        // 栈帧总大小设为 112 字节以保持 16 字节对齐
        addi sp,sp,-112
        sw ra,0(sp)
        sw a0,4(sp)
        sw a1,8(sp)
        sw a2,12(sp)
        sw a3,16(sp)
        sw a4,20(sp)
        sw a5,24(sp)
        sw a6,28(sp)
        sw a7,32(sp)
        ",
        #[cfg(target_feature = "d")]
        "
        fsd fa0,40(sp)
        fsd fa1,48(sp)
        fsd fa2,56(sp)
        fsd fa3,64(sp)
        fsd fa4,72(sp)
        fsd fa5,80(sp)
        fsd fa6,88(sp)
        fsd fa7,96(sp)
        ",
        #[cfg(all(target_feature = "f", not(target_feature = "d")))]
        "
        fsw fa0,40(sp)
        fsw fa1,44(sp)
        fsw fa2,48(sp)
        fsw fa3,52(sp)
        fsw fa4,56(sp)
        fsw fa5,60(sp)
        fsw fa6,64(sp)
        fsw fa7,68(sp)
        ",
        "
        // 这两个是plt代码设置的
        mv a0,t0
        srli a1,t1,3
        // 调用重定位函数
        call {0}
        // 恢复参数寄存器
        mv t1,a0
        lw ra,0(sp)
        lw a0,4(sp)
        lw a1,8(sp)
        lw a2,12(sp)
        lw a3,16(sp)
        lw a4,20(sp)
        lw a5,24(sp)
        lw a6,28(sp)
        lw a7,32(sp)
        ",
        #[cfg(target_feature = "d")]
        "
        fld fa0,40(sp)
        fld fa1,48(sp)
        fld fa2,56(sp)
        fld fa3,64(sp)
        fld fa4,72(sp)
        fld fa5,80(sp)
        fld fa6,88(sp)
        fld fa7,96(sp)
        ",
        #[cfg(all(target_feature = "f", not(target_feature = "d")))]
        "
        flw fa0,40(sp)
        flw fa1,44(sp)
        flw fa2,48(sp)
        flw fa3,52(sp)
        flw fa4,56(sp)
        flw fa5,60(sp)
        flw fa6,64(sp)
        flw fa7,68(sp)
        ",
        "
        addi sp,sp,112
        // 执行真正的函数
        jr t1
        ",
        sym crate::relocation::dl_fixup,
    )
}
/// Static TLSDESC resolver dummy for RISC-V 32.
pub(crate) extern "C" fn tlsdesc_resolver_static() {
    unimplemented!("TLSDESC is not supported on RISC-V 32 yet");
}
/// Dynamic TLSDESC resolver dummy for RISC-V 32.
pub(crate) extern "C" fn tlsdesc_resolver_dynamic() {
    unimplemented!("TLSDESC is not supported on RISC-V 32 yet");
}
/// Map riscv32 relocation types to human readable names
pub(crate) fn rel_type_to_str(r_type: usize) -> &'static str {
    match r_type as u32 {
        R_RISCV_NONE => "R_RISCV_NONE",
        R_RISCV_32 => "R_RISCV_32",
        R_RISCV_RELATIVE => "R_RISCV_RELATIVE",
        R_RISCV_COPY => "R_RISCV_COPY",
        R_RISCV_JUMP_SLOT => "R_RISCV_JUMP_SLOT",
        R_RISCV_IRELATIVE => "R_RISCV_IRELATIVE",
        _ => "UNKNOWN",
    }
}