The way to extend qemu TCG plugin functionality

Hi, if want to to provide other function-calls to TCG plugin, such as reading guest memory, follow these steps:

in include/qemu/qemu-plugin.h, add function header, such as

/**
 * qemu_plugin_read_guest_virt_mem() - Read a buffer of guest memory
 * @gva: Guest virtual address
 * @buf: Buffer to copy guest memory into
 * @length: Size of buf
 *
 * Returns: True if the memory was successfully copied into buf
 */
bool qemu_plugin_read_guest_virt_mem(uint64_t gva, char* buf, size_t length);

in plugins/api.c, add function body, such as

bool qemu_plugin_read_guest_virt_mem(uint64_t gva, char* buf, size_t length) {
#ifdef CONFIG_USER_ONLY
  return false;
#else
    // Convert virtual address to physical, then read it
    CPUState *cpu = current_cpu;
    uint64_t page = gva & TARGET_PAGE_MASK;
    hwaddr gpa = cpu_get_phys_page_debug(cpu, page);
    if (gpa == (hwaddr)-1) {
        return false;
    }
 
    gpa += (gva & ~TARGET_PAGE_MASK);
	// cpu_physical_memory_read(gpa, buf, length);
    cpu_memory_rw_debug(cpu, gva, buf, length, false);
    return true;
#endif
}

in plugins/qemu-plugins.symbols, add

qemu_plugin_read_guest_virt_mem;

in your tcg plugin tests/tcg/plugins/mem.c, just call to it, such as

https://peter.quantr.hk/2024/01/qemu-risc-v-log-all-memory-operations/

5. Run in qemu

./configure --target-list=riscv64-softmmu --enable-plugins

6. Edit xv6-riscv Makefile:

qemu2: $K/kernel fs.img
        $(QEMU) $(QEMUOPTS) -singlestep -d exec,cpu,nochain,in_asm,int,plugin -plugin ~/workspace/qemu/build/tests/tcg/plugins/libmem.so,callback=true -D qemu.log

References:

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2024/02/10 by admin