68 lines
2.4 KiB
C
68 lines
2.4 KiB
C
#ifndef FORMAT_H
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#define FORMAT_H
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#include <stddef.h>
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#include <stdint.h>
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#include <stdio.h>
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typedef uint32_t symbol;
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/// Begin a new ELF executable.
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void elf_executable(void);
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/// All definitions are complete. Finish processing the executable.
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void finish_executable(symbol entry_point);
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/// Create a new symbol. You will later have to define this with
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/// `define_executable_symbol`, `define_readonly_symbol`,
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/// or import it from an external library.
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symbol new_symbol(void);
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void define_executable_symbol(symbol sym);
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void define_readonly_symbol(symbol sym);
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void append_data(size_t size, const void* buf);
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void append_u8(uint8_t x);
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void append_u32(uint32_t x);
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void append_u64(uint64_t x);
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/// Assuming the symbol is located in the same segment as this code,
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/// insert a 32-bit offset for the symbol relative to the virtual address
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/// of the current address (Program Counter (PC)).
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///
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/// This is used for generating relative jumps.
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///
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/// If the symbol is defined in this object, then it will be computed
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/// at compile-time and not emitted as an actual relocation in the executable.
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void relocate_pc32(symbol sym);
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/// Like pc32 for DIY relocations. This returns INT32_MAX if the symbol
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/// has not been defined yet. This exists so that the assembler can manually
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/// emit 8-bit short jumps when the distance is short enough.
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///
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/// The offset exists to account for the offset being relative to the
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/// *end* of an instruction, whereas the symbol offset is computed
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/// relative to `here`. This makes bounds-checking slightly easier.
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int32_t symbol_offset(symbol sym, int8_t offset);
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/// If the symbol is not in the same segment as this code,
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/// for example when linking against a dynamic library or accessing read-only data,
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/// then a 32-bit offset may not be sufficient to access a symbol with pc32.
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/// This necessitates a Global Offset Table (GOT) which contains the 64-bit
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/// absolute addresses of the symbols which *is* located in this segment.
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/// Thus, this relocation inserts a 32-bit PC-relative address which points
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/// into the location in the GOT which contains the 64-bit absolute address
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/// of the symbol.
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///
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/// This is used for generating jumps to dynamic library code
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/// and for accessing data in a different segment (e.g. read-only symbols).
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void relocate_gotpcrel(symbol sym);
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/// Insert the 32-bit truncated size of a symbol.
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void relocate_size32(symbol sym);
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/// Insert the 64-bit size of a symbol.
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void relocate_size64(symbol sym);
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#endif
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