elf_loader 0.12.0

A pure-rust library for loading all ELF format files from both memory and files.
Documentation 
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use elf::abi::*;

pub const EM_ARCH: u16 = EM_RISCV;
/* Dynamic thread vector pointers point 0x800 past the start of each
TLS block.  */
pub const TLS_DTV_OFFSET: usize = 0x800;

pub const REL_RELATIVE: u32 = R_RISCV_RELATIVE;
// RISCV does not have this
pub const REL_GOT: u32 = u32::MAX;
pub const REL_DTPMOD: u32 = R_RISCV_TLS_DTPMOD64;
pub const REL_SYMBOLIC: u32 = R_RISCV_32;
pub const REL_JUMP_SLOT: u32 = R_RISCV_JUMP_SLOT;
pub const REL_DTPOFF: u32 = R_RISCV_TLS_DTPREL32;
pub const REL_IRELATIVE: u32 = R_RISCV_IRELATIVE;
pub const REL_COPY: u32 = R_RISCV_COPY;
pub const REL_TPOFF:u32 = R_RISCV_TLS_TPREL32;

#[cfg(feature = "lazy")]
core::arch::global_asm!(
    "
    .text
    .globl dl_runtime_resolve
	.type dl_runtime_resolve, @function
	.align 16
dl_runtime_resolve:
// 保存参数寄存器,因为dl_fixup不会使用浮点参数寄存器,因此不需要保存
    addi sp,sp,-9*8
    sw ra,8*0(sp)
    sw a0,8*1(sp)
    sw a1,8*2(sp)
    sw a2,8*3(sp)
    sw a3,8*4(sp)
    sw a4,8*5(sp)
    sw a5,8*6(sp)
    sw a6,8*7(sp)
    sw a7,8*8(sp)
// 这两个是plt代码设置的
    mv a0,t0
    srli a1,t1,3
    la a2,dl_fixup
// 调用重定位函数
    jalr a2
// 恢复参数寄存器
    mv t1,a0
    lw ra,8*0(sp)
    lw a0,8*1(sp)
    lw a1,8*2(sp)
    lw a2,8*3(sp)
    lw a3,8*4(sp)
    lw a4,8*5(sp)
    lw a5,8*6(sp)
    lw a6,8*7(sp)
    lw a7,8*8(sp)
    addi sp,sp,8*9
// 执行真正的函数
    jr t1
"
);

#[cfg(feature = "lazy")]
pub(crate) fn prepare_lazy_bind(got: *mut usize, dylib: usize) {
    unsafe extern "C" {
        fn dl_runtime_resolve();
    }
    // 这是安全的，延迟绑定时库是存在的
    unsafe {
        got.write(dl_runtime_resolve as usize);
        got.add(1).write(dylib);
    }
}