shdr.cpp

#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <string_view>
#include <elf.h>

struct symbol {
	std::string_view name;
	uintptr_t base;
	size_t size;
};

struct symbol_table {
	symbol_table()
	: symbols_{} {
		[[gnu::weak]] extern char __ehdr_start[];
		auto ehdr_addr = reinterpret_cast<uintptr_t>(&__ehdr_start);

		auto ehdr = reinterpret_cast<Elf64_Ehdr *>(ehdr_addr);
		if (!ehdr) return;
		if (!ehdr->e_shnum) return;

		Elf64_Shdr *symtab{}, *strtab{};
		auto shdrs = reinterpret_cast<Elf64_Shdr *>(ehdr_addr + ehdr->e_shoff);
		for (int i = 0; i < ehdr->e_shnum; i++) {
			auto &shdr = shdrs[i];

			if (!symtab && shdr.sh_type == SHT_SYMTAB)
				symtab = &shdr;

			if (!strtab && shdr.sh_type == SHT_STRTAB && i != ehdr->e_shstrndx)
				strtab = &shdr;
		}

		size_t n_symbols = symtab->sh_size / symtab->sh_entsize;
		symbols_.reserve(n_symbols);

		for (size_t i = 0; i < n_symbols; i++) {
			Elf64_Sym &sym = reinterpret_cast<Elf64_Sym *>(symtab->sh_addr)[i];

			if ((sym.st_info & 0xf) != STT_FUNC)
				continue;

			symbols_.push_back({reinterpret_cast<char *>(strtab->sh_addr + sym.st_name), sym.st_value, sym.st_size});
		}
	}

	std::vector<symbol> symbols_;
};

int main() {
	symbol_table st;

	for (auto &sym : st.symbols_) {
		std::cout << sym.name << " " << std::hex << sym.base << " " << std::dec << sym.size << std::endl;
	}
}