Demo QEMU plugin that dumps the first 256 bytes of firmware when booting a BIOS on RISC-V

dump-riscv-firmware.c

/*
 * Copyright (C) 2018, Emilio G. Cota <[email protected]>
 *
 * License: GNU GPL, version 2 or later.
 *   See the COPYING file in the top-level directory.
 */
#include <inttypes.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>

#include <qemu-plugin.h>

QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
static bool did_dump = false;

/*
 * Hex-dump a GByteArray to the QEMU plugin output in the format:
 * 61 63 63 65 6c 09 09 20 20 20 66 70 75 09 09 09  | accel.....fpu...
 * 20 6d 6f 64 75 6c 65 2d 63 6f 6d 6d 6f 6e 2e 63  | .module-common.c
 */
static void hexdump(const GByteArray *data)
{
    g_autoptr(GString) out = g_string_new("");

    for (guint index = 0; index < data->len; index += 16) {
        for (guint col = 0; col < 16; col++) {
            if (index + col < data->len) {
                g_string_append_printf(out, "%02x ", data->data[index + col]);
            } else {
                g_string_append(out, "   ");
            }
        }

        g_string_append(out, " | ");

        for (guint col = 0; col < 16; col++) {
            if (index + col >= data->len) {
                break;
            }

            if (g_ascii_isgraph(data->data[index + col])) {
                g_string_append_printf(out, "%c", data->data[index + col]);
            } else {
                g_string_append(out, ".");
            }
        }

        g_string_append(out, "\n");
    }

    qemu_plugin_outs(out->str);
}

static void vcpu_insn_exec_before(unsigned int cpu_index, void *udata)
{
    g_autoptr(GByteArray) mem = g_byte_array_new();
    if (!did_dump && qemu_plugin_read_cpu_memory_hwaddr(0x80000000, mem, 256)) {
        hexdump(mem);
        did_dump = true;
    }
}

static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
{
    size_t n = qemu_plugin_tb_n_insns(tb);

    for (size_t i = 0; i < n; i++) {
        struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i);
        qemu_plugin_register_vcpu_insn_exec_cb(insn, vcpu_insn_exec_before, QEMU_PLUGIN_CB_NO_REGS, NULL);
    }
}

QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
                                           const qemu_info_t *info,
                                           int argc, char **argv)
{
    qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
    return 0;
}