Initial commit
This commit is contained in:
mid
279
src/boot/x86/1_elf.asm
Normal file
279
src/boot/x86/1_elf.asm
Normal file
@@ -0,0 +1,279 @@
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struc ELFHeader
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.e_ident resb 16
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.e_type resw 1
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.e_machine resw 1
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.e_version resd 1
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.e_entry resd 1
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.e_phoff resd 1
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.e_shoff resd 1
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.e_flags resd 1
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.e_ehsize resw 1
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.e_phentsize resw 1
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.e_phnum resw 1
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.e_shentsize resw 1
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.e_shnum resw 1
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.e_shstrndx resw 1
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endstruc
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struc ELFSection
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.sh_name resd 1
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.sh_type resd 1
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.sh_flags resd 1
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.sh_addr resd 1
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.sh_offset resd 1
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.sh_size resd 1
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.sh_link resd 1
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.sh_info resd 1
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.sh_addralign resd 1
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.sh_entsize resd 1
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endstruc
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struc ELFProgram
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.p_type resd 1
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.p_offset resd 1
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.p_vaddr resd 1
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.p_paddr resd 1
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.p_filesz resd 1
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.p_memsz resd 1
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.p_flags resd 1
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.p_align resd 1
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endstruc
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struc ELFSym
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.st_name resd 1
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.st_value resd 1
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.st_size resd 1
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.st_info resb 1
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.st_other resb 1
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.st_shndx resw 1
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endstruc
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; in eax = kernel file inode
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load_kernel:
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pushad
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mov edi, ext2_get_inode_data_SCRATCH
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call ext2_get_inode_data
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mov esi, ext2_get_inode_data_SCRATCH
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mov eax, 0
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mov ecx, [ext2_get_inode_data_SCRATCH + 4] ; filesize
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mov edi, KERNEL_INITIAL_LOAD
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call ext2_read_inode_bytes
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cmp dword [KERNEL_INITIAL_LOAD], 0x464C457F ;ELF signature
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je .pass_signature
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popad
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stc
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ret
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.pass_signature:
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; follow the LOAD program header instructions
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movzx ecx, word [KERNEL_INITIAL_LOAD + ELFHeader.e_phnum]
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movzx ebp, word [KERNEL_INITIAL_LOAD + ELFHeader.e_phentsize]
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mov eax, KERNEL_INITIAL_LOAD
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add eax, [eax + ELFHeader.e_phoff]
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.lup0:
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cmp dword [eax + ELFProgram.p_type], 1 ; PT_LOAD
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jne .skip0
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pushad
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mov esi, [eax + ELFProgram.p_offset]
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mov ecx, [eax + ELFProgram.p_memsz]
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add ecx, esi
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add ecx, 4095
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and ecx, ~4095
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and esi, ~4095
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sub ecx, esi
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add esi, KERNEL_INITIAL_LOAD
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mov edi, [eax + ELFProgram.p_vaddr]
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and edi, ~4095
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add edi, KERNEL_BASE
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test ecx, ecx
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jz .skipcopy
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rep movsb
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.skipcopy:
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mov edi, [eax + ELFProgram.p_vaddr]
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add edi, KERNEL_BASE
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add edi, [eax + ELFProgram.p_filesz]
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mov ecx, [eax + ELFProgram.p_memsz]
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sub ecx, [eax + ELFProgram.p_filesz]
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test ecx, ecx
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jz .skipbss
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mov eax, 0
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rep stosb
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.skipbss:
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cmp edi, [KERNEL_END]
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jbe .maxkernelend
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mov [KERNEL_END], edi
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.maxkernelend:
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popad
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.skip0:
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add eax, ebp
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dec ecx
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jnz .lup0
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; fix up the relocations
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mov esi, KERNEL_INITIAL_LOAD
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mov eax, string_reldyn
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call elf_find_array_section_by_name
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.lup2:
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mov ebx, [eax]
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add dword [KERNEL_BASE + ebx], KERNEL_BASE
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add eax, ebp
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dec ecx
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jnz .lup2
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; Save .dynstr for elf_find_symbol to use
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mov esi, KERNEL_INITIAL_LOAD
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mov eax, string_dynstr
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call elf_find_array_section_by_name
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mov [elf_DYNSTR_TABLE], eax
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; Save .dynsym for elf_find_symbol to use
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mov esi, KERNEL_INITIAL_LOAD
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mov eax, string_dynsym
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call elf_find_array_section_by_name
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mov [elf_DYNSYM_TABLE], eax
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mov [elf_DYNSYMS], ecx
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popad
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clc
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ret
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; in esi = ptr to elf file
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; in eax = section name ptr
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; out eax = ptr to section data (or 0)
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; out ebp = section entry size
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; out ecx = section entry count
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elf_find_array_section_by_name:
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push ebx
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push edx
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; ebx = section name ptr
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mov ebx, eax
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; ebp = section table entry size
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movzx ebp, word [esi + ELFHeader.e_shentsize]
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movzx eax, word [esi + ELFHeader.e_shstrndx]
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mul ebp
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; edx = section table
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mov edx, [esi + ELFHeader.e_shoff]
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add edx, esi
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; eax = string table
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add eax, edx
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mov eax, [eax + ELFSection.sh_offset]
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add eax, esi
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; ecx = section index counter
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mov ecx, 0
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.lup:
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push eax
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push ebx
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add eax, [edx + ELFSection.sh_name]
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call streq
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pop ebx
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pop eax
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je .found
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add edx, ebp
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inc ecx
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cmp cx, word [esi + ELFHeader.e_shnum]
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jb .lup
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mov eax, 0
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jmp .notfound
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.found:
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; eax = section header
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mov eax, ecx
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mul ebp
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add eax, [esi + ELFHeader.e_shoff]
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add eax, esi
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; ebp = section entry size
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mov ebp, [eax + ELFSection.sh_entsize]
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; ecx = entry count
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mov ecx, 0
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test ebp, ebp
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jz .zeroentitysize
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push eax
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mov eax, [eax + ELFSection.sh_size]
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mov edx, 0
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div ebp
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mov ecx, eax
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pop eax
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.zeroentitysize:
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mov eax, [eax + ELFSection.sh_offset]
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add eax, esi
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.notfound:
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pop edx
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pop ebx
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ret
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elf_find_symbol:
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cmp dword [elf_DYNSTR_TABLE], 0
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jnz .inited1
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; table not loaded
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ret
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.inited1:
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cmp dword [elf_DYNSYM_TABLE], 0
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jnz .inited2
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; table not loaded
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ret
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.inited2:
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push edx
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push ecx
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push ebx
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mov edx, [elf_DYNSYM_TABLE]
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mov ecx, 0
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.lup:
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mov ebx, [elf_DYNSTR_TABLE]
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add ebx, [edx + ELFSym.st_name]
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push eax
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call streq
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pop eax
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je .found
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add edx, 16 ; symbol size
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inc ecx
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cmp ecx, [elf_DYNSYMS]
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jne .lup
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; symbol not found
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mov edx, 0
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.found:
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mov eax, edx
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pop ebx
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pop ecx
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pop edx
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ret
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