动态修改property ro属性

#include <stdio.h>
#include <sys/ptrace.h>
#include <string.h>
#include <ctype.h>
#include <sys/system_properties.h>

#define nullptr NULL
#define ORI_INST  0x2e6f72
#define HACK_INST 0x2e6f73

static void dump_hex(const char* buf, int len)
{
    const uint8_t *data = (const uint8_t*)buf;
    int i;
    char ascii_buf[17];
    
    ascii_buf[16] = '\0';
    
    for (i = 0; i < len; i++) {
        int val = data[i];
        int off = i % 16;
        
        if (off == 0)
        printf("%08x  ", i);
        printf("%02x ", val);
        ascii_buf[off] = isprint(val) ? val : '.';
        if (off == 15)
        printf(" %-16s\n", ascii_buf);
    }
    
    i %= 16;
    if (i) {
        ascii_buf[i] = '\0';
        while (i++ < 16)
        printf("   ");
        printf(" %-16s\n", ascii_buf);
    }
}

int main(int argc, char **argv) {
    FILE *fp = fopen("/proc/1/maps", "r");
    
    if (fp == nullptr) {
        printf("Unable open /proc/1/maps/.\n");
        return 1;
    }
    
    int rc;
    char line[512];
    unsigned long maps, mape, addr, mlen;
    char perms[5];
    unsigned long real_val, real_vaddr;
    
    memset(line, 0, sizeof(line));
    while (fgets(line, sizeof(line), fp)) {
        int init_exe = (strstr(line, "/init") != nullptr) ? 1:0;
        if (init_exe) {
            rc = sscanf(line, "%lx-%lx %4s ", &maps, &mape, perms);
            if (rc < 3) {
                printf("skip sscanf.\n");
            }
            if (perms[0] == 'r' && perms[1] == '-' && perms[2] == 'x' && perms[3] == 'p') {
                break;
            }
        }
    }
    
    printf("init text: %lx-%lx %4s\n", maps, mape, perms);
    fclose(fp);
    
    mlen = mape - maps;
    
    char *buffer = new char[mlen + 16];
    if (buffer == nullptr) {
        printf("Alloc mem error.\n");
        return 1;
    }
    
    rc = ptrace(PTRACE_ATTACH, 1, 0, 0);
    if (rc < 0) {
        printf("ptrace error.\n");
        return 1;
    }
    
    int tmp;
    for (addr = maps; addr < mape; addr += 4) {
        tmp = ptrace(PTRACE_PEEKTEXT, 1, (void *) addr, 0);
        *((uint32_t *)(buffer + addr - maps)) = tmp;
    }
    
    //dump_hex(buffer, mlen);
    
    //printf("\n\n~~~~~~\n\n");
    
    int m;
    for (m = 0; m < mlen; m++) {
        if (ORI_INST == *(uint32_t *)(buffer+m)) {//ro.
            break;
        }
    }
    
    if (m >= mlen) {
        printf("warnning not found ro. in mem.\n");
        //return 1;
    } else {
        real_vaddr = maps + m;
        real_val = *(uint32_t *)(buffer+m);
        
        tmp = HACK_INST;
        
        rc = ptrace(PTRACE_POKETEXT, 1, (void *)real_vaddr, (void*)tmp);
        if (rc < 0) {
            printf("!! patching failed.\n");
        }
    }
    
    delete[] buffer;
    
    rc = ptrace(PTRACE_DETACH, 1, 0, 0);
    
    __system_property_set(argv[1], argv[2]);
    
    printf("end!\n");
    
    return rc;
}