qemu-e2k/plugins/loader.c

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/*
* QEMU Plugin Core Loader Code
*
* This is the code responsible for loading and unloading the plugins.
* Aside from the basic housekeeping tasks we also need to ensure any
* generated code is flushed when we remove a plugin so we cannot end
* up calling and unloaded helper function.
*
* Copyright (C) 2017, Emilio G. Cota <cota@braap.org>
* Copyright (C) 2019, Linaro
*
* License: GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "qemu/osdep.h"
#include "qemu/error-report.h"
#include "qemu/config-file.h"
#include "qapi/error.h"
#include "qemu/lockable.h"
#include "qemu/option.h"
#include "qemu/rcu_queue.h"
#include "qemu/qht.h"
#include "qemu/bitmap.h"
#include "qemu/xxhash.h"
#include "qemu/plugin.h"
#include "hw/core/cpu.h"
#include "exec/exec-all.h"
#ifndef CONFIG_USER_ONLY
#include "hw/boards.h"
#endif
cfi: Initial support for cfi-icall in QEMU LLVM/Clang, supports runtime checks for forward-edge Control-Flow Integrity (CFI). CFI on indirect function calls (cfi-icall) ensures that, in indirect function calls, the function called is of the right signature for the pointer type defined at compile time. For this check to work, the code must always respect the function signature when using function pointer, the function must be defined at compile time, and be compiled with link-time optimization. This rules out, for example, shared libraries that are dynamically loaded (given that functions are not known at compile time), and code that is dynamically generated at run-time. This patch: 1) Introduces the CONFIG_CFI flag to support cfi in QEMU 2) Introduces a decorator to allow the definition of "sensitive" functions, where a non-instrumented function may be called at runtime through a pointer. The decorator will take care of disabling cfi-icall checks on such functions, when cfi is enabled. 3) Marks functions currently in QEMU that exhibit such behavior, in particular: - The function in TCG that calls pre-compiled TBs - The function in TCI that interprets instructions - Functions in the plugin infrastructures that jump to callbacks - Functions in util that directly call a signal handler Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com> Acked-by: Alex Bennée <alex.bennee@linaro.org Message-Id: <20201204230615.2392-3-dbuono@linux.vnet.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-12-05 00:06:12 +01:00
#include "qemu/compiler.h"
#include "plugin.h"
/*
* For convenience we use a bitmap for plugin.mask, but really all we need is a
* u32, which is what we store in TranslationBlock.
*/
QEMU_BUILD_BUG_ON(QEMU_PLUGIN_EV_MAX > 32);
struct qemu_plugin_desc {
char *path;
char **argv;
QTAILQ_ENTRY(qemu_plugin_desc) entry;
int argc;
};
struct qemu_plugin_parse_arg {
QemuPluginList *head;
struct qemu_plugin_desc *curr;
};
QemuOptsList qemu_plugin_opts = {
.name = "plugin",
.implied_opt_name = "file",
.head = QTAILQ_HEAD_INITIALIZER(qemu_plugin_opts.head),
.desc = {
/* do our own parsing to support multiple plugins */
{ /* end of list */ }
},
};
typedef int (*qemu_plugin_install_func_t)(qemu_plugin_id_t, const qemu_info_t *, int, char **);
extern struct qemu_plugin_state plugin;
void qemu_plugin_add_dyn_cb_arr(GArray *arr)
{
uint32_t hash = qemu_xxhash2((uint64_t)(uintptr_t)arr);
bool inserted;
inserted = qht_insert(&plugin.dyn_cb_arr_ht, arr, hash, NULL);
g_assert(inserted);
}
static struct qemu_plugin_desc *plugin_find_desc(QemuPluginList *head,
const char *path)
{
struct qemu_plugin_desc *desc;
QTAILQ_FOREACH(desc, head, entry) {
if (strcmp(desc->path, path) == 0) {
return desc;
}
}
return NULL;
}
static int plugin_add(void *opaque, const char *name, const char *value,
Error **errp)
{
struct qemu_plugin_parse_arg *arg = opaque;
struct qemu_plugin_desc *p;
if (strcmp(name, "file") == 0) {
if (strcmp(value, "") == 0) {
error_setg(errp, "requires a non-empty argument");
return 1;
}
p = plugin_find_desc(arg->head, value);
if (p == NULL) {
p = g_new0(struct qemu_plugin_desc, 1);
p->path = g_strdup(value);
QTAILQ_INSERT_TAIL(arg->head, p, entry);
}
arg->curr = p;
} else if (strcmp(name, "arg") == 0) {
if (arg->curr == NULL) {
error_setg(errp, "missing earlier '-plugin file=' option");
return 1;
}
p = arg->curr;
p->argc++;
p->argv = g_realloc_n(p->argv, p->argc, sizeof(char *));
p->argv[p->argc - 1] = g_strdup(value);
} else {
error_setg(errp, "-plugin: unexpected parameter '%s'; ignored", name);
}
return 0;
}
void qemu_plugin_opt_parse(const char *optarg, QemuPluginList *head)
{
struct qemu_plugin_parse_arg arg;
QemuOpts *opts;
opts = qemu_opts_parse_noisily(qemu_find_opts("plugin"), optarg, true);
if (opts == NULL) {
exit(1);
}
arg.head = head;
arg.curr = NULL;
qemu_opt_foreach(opts, plugin_add, &arg, &error_fatal);
qemu_opts_del(opts);
}
/*
* From: https://en.wikipedia.org/wiki/Xorshift
* This is faster than rand_r(), and gives us a wider range (RAND_MAX is only
* guaranteed to be >= INT_MAX).
*/
static uint64_t xorshift64star(uint64_t x)
{
x ^= x >> 12; /* a */
x ^= x << 25; /* b */
x ^= x >> 27; /* c */
return x * UINT64_C(2685821657736338717);
}
cfi: Initial support for cfi-icall in QEMU LLVM/Clang, supports runtime checks for forward-edge Control-Flow Integrity (CFI). CFI on indirect function calls (cfi-icall) ensures that, in indirect function calls, the function called is of the right signature for the pointer type defined at compile time. For this check to work, the code must always respect the function signature when using function pointer, the function must be defined at compile time, and be compiled with link-time optimization. This rules out, for example, shared libraries that are dynamically loaded (given that functions are not known at compile time), and code that is dynamically generated at run-time. This patch: 1) Introduces the CONFIG_CFI flag to support cfi in QEMU 2) Introduces a decorator to allow the definition of "sensitive" functions, where a non-instrumented function may be called at runtime through a pointer. The decorator will take care of disabling cfi-icall checks on such functions, when cfi is enabled. 3) Marks functions currently in QEMU that exhibit such behavior, in particular: - The function in TCG that calls pre-compiled TBs - The function in TCI that interprets instructions - Functions in the plugin infrastructures that jump to callbacks - Functions in util that directly call a signal handler Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com> Acked-by: Alex Bennée <alex.bennee@linaro.org Message-Id: <20201204230615.2392-3-dbuono@linux.vnet.ibm.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-12-05 00:06:12 +01:00
/*
* Disable CFI checks.
* The install and version functions have been loaded from an external library
* so we do not have type information
*/
QEMU_DISABLE_CFI
static int plugin_load(struct qemu_plugin_desc *desc, const qemu_info_t *info, Error **errp)
{
qemu_plugin_install_func_t install;
struct qemu_plugin_ctx *ctx;
gpointer sym;
int rc;
ctx = qemu_memalign(qemu_dcache_linesize, sizeof(*ctx));
memset(ctx, 0, sizeof(*ctx));
ctx->desc = desc;
ctx->handle = g_module_open(desc->path, G_MODULE_BIND_LOCAL);
if (ctx->handle == NULL) {
error_setg(errp, "Could not load plugin %s: %s", desc->path, g_module_error());
goto err_dlopen;
}
if (!g_module_symbol(ctx->handle, "qemu_plugin_install", &sym)) {
error_setg(errp, "Could not load plugin %s: %s", desc->path, g_module_error());
goto err_symbol;
}
install = (qemu_plugin_install_func_t) sym;
/* symbol was found; it could be NULL though */
if (install == NULL) {
error_setg(errp, "Could not load plugin %s: qemu_plugin_install is NULL",
desc->path);
goto err_symbol;
}
if (!g_module_symbol(ctx->handle, "qemu_plugin_version", &sym)) {
error_setg(errp, "Could not load plugin %s: plugin does not declare API version %s",
desc->path, g_module_error());
goto err_symbol;
} else {
int version = *(int *)sym;
if (version < QEMU_PLUGIN_MIN_VERSION) {
error_setg(errp, "Could not load plugin %s: plugin requires API version %d, but "
"this QEMU supports only a minimum version of %d",
desc->path, version, QEMU_PLUGIN_MIN_VERSION);
goto err_symbol;
} else if (version > QEMU_PLUGIN_VERSION) {
error_setg(errp, "Could not load plugin %s: plugin requires API version %d, but "
"this QEMU supports only up to version %d",
desc->path, version, QEMU_PLUGIN_VERSION);
goto err_symbol;
}
}
qemu_rec_mutex_lock(&plugin.lock);
/* find an unused random id with &ctx as the seed */
ctx->id = (uint64_t)(uintptr_t)ctx;
for (;;) {
void *existing;
ctx->id = xorshift64star(ctx->id);
existing = g_hash_table_lookup(plugin.id_ht, &ctx->id);
if (likely(existing == NULL)) {
bool success;
success = g_hash_table_insert(plugin.id_ht, &ctx->id, &ctx->id);
g_assert(success);
break;
}
}
QTAILQ_INSERT_TAIL(&plugin.ctxs, ctx, entry);
ctx->installing = true;
rc = install(ctx->id, info, desc->argc, desc->argv);
ctx->installing = false;
if (rc) {
error_setg(errp, "Could not load plugin %s: qemu_plugin_install returned error code %d",
desc->path, rc);
/*
* we cannot rely on the plugin doing its own cleanup, so
* call a full uninstall if the plugin did not yet call it.
*/
if (!ctx->uninstalling) {
plugin_reset_uninstall(ctx->id, NULL, false);
}
}
qemu_rec_mutex_unlock(&plugin.lock);
return rc;
err_symbol:
g_module_close(ctx->handle);
err_dlopen:
qemu_vfree(ctx);
return 1;
}
/* call after having removed @desc from the list */
static void plugin_desc_free(struct qemu_plugin_desc *desc)
{
int i;
for (i = 0; i < desc->argc; i++) {
g_free(desc->argv[i]);
}
g_free(desc->argv);
g_free(desc->path);
g_free(desc);
}
/**
* qemu_plugin_load_list - load a list of plugins
* @head: head of the list of descriptors of the plugins to be loaded
*
* Returns 0 if all plugins in the list are installed, !0 otherwise.
*
* Note: the descriptor of each successfully installed plugin is removed
* from the list given by @head.
*/
int qemu_plugin_load_list(QemuPluginList *head, Error **errp)
{
struct qemu_plugin_desc *desc, *next;
g_autofree qemu_info_t *info = g_new0(qemu_info_t, 1);
info->target_name = TARGET_NAME;
info->version.min = QEMU_PLUGIN_MIN_VERSION;
info->version.cur = QEMU_PLUGIN_VERSION;
#ifndef CONFIG_USER_ONLY
MachineState *ms = MACHINE(qdev_get_machine());
info->system_emulation = true;
info->system.smp_vcpus = ms->smp.cpus;
info->system.max_vcpus = ms->smp.max_cpus;
#else
info->system_emulation = false;
#endif
QTAILQ_FOREACH_SAFE(desc, head, entry, next) {
int err;
err = plugin_load(desc, info, errp);
if (err) {
return err;
}
QTAILQ_REMOVE(head, desc, entry);
}
return 0;
}
struct qemu_plugin_reset_data {
struct qemu_plugin_ctx *ctx;
qemu_plugin_simple_cb_t cb;
bool reset;
};
static void plugin_reset_destroy__locked(struct qemu_plugin_reset_data *data)
{
struct qemu_plugin_ctx *ctx = data->ctx;
enum qemu_plugin_event ev;
bool success;
/*
* After updating the subscription lists there is no need to wait for an RCU
* grace period to elapse, because right now we either are in a "safe async"
* work environment (i.e. all vCPUs are asleep), or no vCPUs have yet been
* created.
*/
for (ev = 0; ev < QEMU_PLUGIN_EV_MAX; ev++) {
plugin_unregister_cb__locked(ctx, ev);
}
if (data->reset) {
g_assert(ctx->resetting);
if (data->cb) {
data->cb(ctx->id);
}
ctx->resetting = false;
g_free(data);
return;
}
g_assert(ctx->uninstalling);
/* we cannot dlclose if we are going to return to plugin code */
if (ctx->installing) {
error_report("Calling qemu_plugin_uninstall from the install function "
"is a bug. Instead, return !0 from the install function.");
abort();
}
success = g_hash_table_remove(plugin.id_ht, &ctx->id);
g_assert(success);
QTAILQ_REMOVE(&plugin.ctxs, ctx, entry);
if (data->cb) {
data->cb(ctx->id);
}
if (!g_module_close(ctx->handle)) {
warn_report("%s: %s", __func__, g_module_error());
}
plugin_desc_free(ctx->desc);
qemu_vfree(ctx);
g_free(data);
}
static void plugin_reset_destroy(struct qemu_plugin_reset_data *data)
{
qemu_rec_mutex_lock(&plugin.lock);
plugin_reset_destroy__locked(data);
qemu_rec_mutex_lock(&plugin.lock);
}
static void plugin_flush_destroy(CPUState *cpu, run_on_cpu_data arg)
{
struct qemu_plugin_reset_data *data = arg.host_ptr;
g_assert(cpu_in_exclusive_context(cpu));
tb_flush(cpu);
plugin_reset_destroy(data);
}
void plugin_reset_uninstall(qemu_plugin_id_t id,
qemu_plugin_simple_cb_t cb,
bool reset)
{
struct qemu_plugin_reset_data *data;
struct qemu_plugin_ctx *ctx;
WITH_QEMU_LOCK_GUARD(&plugin.lock) {
ctx = plugin_id_to_ctx_locked(id);
if (ctx->uninstalling || (reset && ctx->resetting)) {
return;
}
ctx->resetting = reset;
ctx->uninstalling = !reset;
}
data = g_new(struct qemu_plugin_reset_data, 1);
data->ctx = ctx;
data->cb = cb;
data->reset = reset;
/*
* Only flush the code cache if the vCPUs have been created. If so,
* current_cpu must be non-NULL.
*/
if (current_cpu) {
async_safe_run_on_cpu(current_cpu, plugin_flush_destroy,
RUN_ON_CPU_HOST_PTR(data));
} else {
/*
* If current_cpu isn't set, then we don't have yet any vCPU threads
* and we therefore can remove the callbacks synchronously.
*/
plugin_reset_destroy(data);
}
}