第 14 题 Matrix-A-4.cpp

src/群友提交/第14题/Matrix-A-4.cpp

@@ -0,0 +1,121 @@
+//!msvc
+#include <iostream>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <link.h>
+#include <string.h>
+
+namespace ss {
+    int a = 0;
+}
+
+uintptr_t base_address = 0;
+
+const char* symbol_name="_ZN2ss1aE";
+
+uintptr_t get_self_base_address() {
+    dl_iterate_phdr([](struct dl_phdr_info *info, size_t size, void *data) {
+        base_address = info->dlpi_addr;
+        return 1; 
+    }, NULL);
+    return base_address;
+}
+
+// 解析 ELF 文件，查找符号内存地址
+void find_symbol_in_self(const char *file_name) {
+    FILE *file = fopen(file_name, "rb");
+    if (!file) {
+        perror("fopen");
+        return;
+    }
+
+    // 读取 ELF Header
+    Elf64_Ehdr ehdr;
+    fseek(file, 0, SEEK_SET);
+    fread(&ehdr, sizeof(Elf64_Ehdr), 1, file);
+
+    // 跳转到节头表
+    fseek(file, ehdr.e_shoff, SEEK_SET);
+
+    // 读取所有节头表
+    Elf64_Shdr *sh_table = (Elf64_Shdr*)malloc(ehdr.e_shentsize * ehdr.e_shnum);
+    fread(sh_table, ehdr.e_shentsize, ehdr.e_shnum, file);
+
+    // 读取节头字符串表
+    Elf64_Shdr shstrtab = sh_table[ehdr.e_shstrndx];
+    char *shstrtab_data = (char*)malloc(shstrtab.sh_size);
+    fseek(file, shstrtab.sh_offset, SEEK_SET);
+    fread(shstrtab_data, 1, shstrtab.sh_size, file);
+
+    // 查找 .symtab 和 .strtab
+    Elf64_Shdr symtab, strtab;
+    int found_symtab = 0, found_strtab = 0;
+    for (int i = 0; i < ehdr.e_shnum; i++) {
+        const char *name = &shstrtab_data[sh_table[i].sh_name];
+        if (strcmp(name, ".symtab") == 0) {
+            symtab = sh_table[i];
+            found_symtab = 1;
+        } else if (strcmp(name, ".strtab") == 0) {
+            strtab = sh_table[i];
+            found_strtab = 1;
+        }
+    }
+
+    if (!found_symtab || !found_strtab) {
+        fprintf(stderr, "Failed to find .symtab or .strtab\n");
+        free(sh_table);
+        free(shstrtab_data);
+        fclose(file);
+        return;
+    }
+
+    // 读取符号表
+    Elf64_Sym *symtab_data = (Elf64_Sym*)malloc(symtab.sh_size);
+    fseek(file, symtab.sh_offset, SEEK_SET);
+    fread(symtab_data, symtab.sh_entsize, symtab.sh_size / symtab.sh_entsize, file);
+
+    // 读取字符串表
+    char *strtab_data = (char*)malloc(strtab.sh_size);
+    fseek(file, strtab.sh_offset, SEEK_SET);
+    fread(strtab_data, 1, strtab.sh_size, file);
+
+    // 查找目标符号
+    uintptr_t target_address = 0;
+    for (size_t i = 0; i < symtab.sh_size / symtab.sh_entsize; i++) {
+        const char *sym_name = &strtab_data[symtab_data[i].st_name];
+        if (strcmp(sym_name, symbol_name) == 0) {
+            target_address = symtab_data[i].st_value;
+            break;
+        }
+    }
+
+    if (target_address == 0) {
+        fprintf(stderr, "Symbol %s not found\n", symbol_name);
+        free(sh_table);
+        free(shstrtab_data);
+        free(symtab_data);
+        free(strtab_data);
+        fclose(file);
+        return;
+    }
+
+    // 计算实际内存地址
+    uintptr_t base_address = get_self_base_address();
+    uintptr_t actual_address = base_address + target_address;
+
+    // 修改
+    *(int*)actual_address = 100;
+
+    // 清理资源
+    free(sh_table);
+    free(shstrtab_data);
+    free(symtab_data);
+    free(strtab_data);
+    fclose(file);
+}
+
+int main(int argc, char **argv) {
+    find_symbol_in_self(argv[0]);
+    std::cout << ss::a << '\n'; 
+}