Watch this: $ gdb --args ../qemu/bld/qemu-system-aarch64 -S -M virt -display none -qmp stdio [...] (gdb) r [...] {"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major": 7}, "package": "v7.2.0-2331-gda89f78a7d"}, "capabilities": ["oob"]}} [New Thread 0x7fffed62c6c0 (LWP 1021967)] {"execute": "qmp_capabilities", "arguments": {"enable": ["oob"]}} {"return": {}} {"execute": "dumpdtb", "arguments": {"filename": "fdt.dtb"}}
Thread 1 "qemu-system-aar" received signal SIGSEGV, Segmentation fault. qmp_dumpdtb (filename=0x5555581c5170 "fdt.dtb", errp=errp@entry=0x7fffffffdae8) at ../softmmu/device_tree.c:661 661 size = fdt_totalsize(current_machine->fdt); current_machine->fdt is non-null here. The crash is within fdt_totalsize(). I suspect ... void qmp_dumpdtb(const char *filename, Error **errp) { g_autoptr(GError) err = NULL; uint32_t size; if (!current_machine->fdt) { error_setg(errp, "This machine doesn't have a FDT"); return; } ... we're missing an "FDT isn't ready" guard here. size = fdt_totalsize(current_machine->fdt); g_assert(size > 0); if (!g_file_set_contents(filename, current_machine->fdt, size, &err)) { error_setg(errp, "Error saving FDT to file %s: %s", filename, err->message); } } Also, I think the error message "does not have a FDT" should say "an FDT".