test_unwind.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* Test module for unwind_for_each_frame
*/
#define pr_fmt(fmt) "test_unwind: " fmt
#include <asm/unwind.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/kprobes.h>
#include <linux/wait.h>
#include <asm/irq.h>
#include <asm/delay.h>
#define BT_BUF_SIZE (PAGE_SIZE * 4)
/*
* To avoid printk line limit split backtrace by lines
*/
static void print_backtrace(char *bt)
{
char *p;
while (true) {
p = strsep(&bt, "\n");
if (!p)
break;
pr_err("%s\n", p);
}
}
/*
* Calls unwind_for_each_frame(task, regs, sp) and verifies that the result
* contains unwindme_func2 followed by unwindme_func1.
*/
static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs,
unsigned long sp)
{
int frame_count, prev_is_func2, seen_func2_func1;
const int max_frames = 128;
struct unwind_state state;
size_t bt_pos = 0;
int ret = 0;
char *bt;
bt = kmalloc(BT_BUF_SIZE, GFP_ATOMIC);
if (!bt) {
pr_err("failed to allocate backtrace buffer\n");
return -ENOMEM;
}
/* Unwind. */
frame_count = 0;
prev_is_func2 = 0;
seen_func2_func1 = 0;
unwind_for_each_frame(&state, task, regs, sp) {
unsigned long addr = unwind_get_return_address(&state);
char sym[KSYM_SYMBOL_LEN];
if (frame_count++ == max_frames)
break;
if (state.reliable && !addr) {
pr_err("unwind state reliable but addr is 0\n");
return -EINVAL;
}
sprint_symbol(sym, addr);
if (bt_pos < BT_BUF_SIZE) {
bt_pos += snprintf(bt + bt_pos, BT_BUF_SIZE - bt_pos,
state.reliable ? " [%-7s%px] %pSR\n" :
"([%-7s%px] %pSR)\n",
stack_type_name(state.stack_info.type),
(void *)state.sp, (void *)state.ip);
if (bt_pos >= BT_BUF_SIZE)
pr_err("backtrace buffer is too small\n");
}
frame_count += 1;
if (prev_is_func2 && str_has_prefix(sym, "unwindme_func1"))
seen_func2_func1 = 1;
prev_is_func2 = str_has_prefix(sym, "unwindme_func2");
}
/* Check the results. */
if (unwind_error(&state)) {
pr_err("unwind error\n");
ret = -EINVAL;
}
if (!seen_func2_func1) {
pr_err("unwindme_func2 and unwindme_func1 not found\n");
ret = -EINVAL;
}
if (frame_count == max_frames) {
pr_err("Maximum number of frames exceeded\n");
ret = -EINVAL;
}
if (ret)
print_backtrace(bt);
kfree(bt);
return ret;
}
/* State of the task being unwound. */
struct unwindme {
int flags;
int ret;
struct task_struct *task;
struct completion task_ready;
wait_queue_head_t task_wq;
unsigned long sp;
};
static struct unwindme *unwindme;
/* Values of unwindme.flags. */
#define UWM_DEFAULT 0x0
#define UWM_THREAD 0x1 /* Unwind a separate task. */
#define UWM_REGS 0x2 /* Pass regs to test_unwind(). */
#define UWM_SP 0x4 /* Pass sp to test_unwind(). */
#define UWM_CALLER 0x8 /* Unwind starting from caller. */
#define UWM_SWITCH_STACK 0x10 /* Use CALL_ON_STACK. */
#define UWM_IRQ 0x20 /* Unwind from irq context. */
#define UWM_PGM 0x40 /* Unwind from program check handler. */
static __always_inline unsigned long get_psw_addr(void)
{
unsigned long psw_addr;
asm volatile(
"basr %[psw_addr],0\n"
: [psw_addr] "=d" (psw_addr));
return psw_addr;
}
#ifdef CONFIG_KPROBES
static int pgm_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
struct unwindme *u = unwindme;
u->ret = test_unwind(NULL, (u->flags & UWM_REGS) ? regs : NULL,
(u->flags & UWM_SP) ? u->sp : 0);
return 0;
}
#endif
/* This function may or may not appear in the backtrace. */
static noinline int unwindme_func4(struct unwindme *u)
{
if (!(u->flags & UWM_CALLER))
u->sp = current_frame_address();
if (u->flags & UWM_THREAD) {
complete(&u->task_ready);
wait_event(u->task_wq, kthread_should_park());
kthread_parkme();
return 0;
#ifdef CONFIG_KPROBES
} else if (u->flags & UWM_PGM) {
struct kprobe kp;
int ret;
unwindme = u;
memset(&kp, 0, sizeof(kp));
kp.symbol_name = "do_report_trap";
kp.pre_handler = pgm_pre_handler;
ret = register_kprobe(&kp);
if (ret < 0) {
pr_err("register_kprobe failed %d\n", ret);
return -EINVAL;
}
/*
* trigger specification exception
*/
asm volatile(
" mvcl %%r1,%%r1\n"
"0: nopr %%r7\n"
EX_TABLE(0b, 0b)
:);
unregister_kprobe(&kp);
unwindme = NULL;
return u->ret;
#endif
} else {
struct pt_regs regs;
memset(®s, 0, sizeof(regs));
regs.psw.addr = get_psw_addr();
regs.gprs[15] = current_stack_pointer();
return test_unwind(NULL,
(u->flags & UWM_REGS) ? ®s : NULL,
(u->flags & UWM_SP) ? u->sp : 0);
}
}
/* This function may or may not appear in the backtrace. */
static noinline int unwindme_func3(struct unwindme *u)
{
u->sp = current_frame_address();
return unwindme_func4(u);
}
/* This function must appear in the backtrace. */
static noinline int unwindme_func2(struct unwindme *u)
{
int rc;
if (u->flags & UWM_SWITCH_STACK) {
preempt_disable();
rc = CALL_ON_STACK(unwindme_func3, S390_lowcore.nodat_stack, 1, u);
preempt_enable();
return rc;
} else {
return unwindme_func3(u);
}
}
/* This function must follow unwindme_func2 in the backtrace. */
static noinline int unwindme_func1(void *u)
{
return unwindme_func2((struct unwindme *)u);
}
static void unwindme_irq_handler(struct ext_code ext_code,
unsigned int param32,
unsigned long param64)
{
struct unwindme *u = READ_ONCE(unwindme);
if (u && u->task == current) {
unwindme = NULL;
u->task = NULL;
u->ret = unwindme_func1(u);
}
}
static int test_unwind_irq(struct unwindme *u)
{
preempt_disable();
if (register_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler)) {
pr_info("Couldn't register external interrupt handler");
return -1;
}
u->task = current;
unwindme = u;
udelay(1);
unregister_external_irq(EXT_IRQ_CLK_COMP, unwindme_irq_handler);
preempt_enable();
return u->ret;
}
/* Spawns a task and passes it to test_unwind(). */
static int test_unwind_task(struct unwindme *u)
{
struct task_struct *task;
int ret;
/* Initialize thread-related fields. */
init_completion(&u->task_ready);
init_waitqueue_head(&u->task_wq);
/*
* Start the task and wait until it reaches unwindme_func4() and sleeps
* in (task_ready, unwind_done] range.
*/
task = kthread_run(unwindme_func1, u, "%s", __func__);
if (IS_ERR(task)) {
pr_err("kthread_run() failed\n");
return PTR_ERR(task);
}
/*
* Make sure task reaches unwindme_func4 before parking it,
* we might park it before kthread function has been executed otherwise
*/
wait_for_completion(&u->task_ready);
kthread_park(task);
/* Unwind. */
ret = test_unwind(task, NULL, (u->flags & UWM_SP) ? u->sp : 0);
kthread_stop(task);
return ret;
}
static int test_unwind_flags(int flags)
{
struct unwindme u;
u.flags = flags;
if (u.flags & UWM_THREAD)
return test_unwind_task(&u);
else if (u.flags & UWM_IRQ)
return test_unwind_irq(&u);
else
return unwindme_func1(&u);
}
static int test_unwind_init(void)
{
int ret = 0;
#define TEST(flags) \
do { \
pr_info("[ RUN ] " #flags "\n"); \
if (!test_unwind_flags((flags))) { \
pr_info("[ OK ] " #flags "\n"); \
} else { \
pr_err("[ FAILED ] " #flags "\n"); \
ret = -EINVAL; \
} \
} while (0)
TEST(UWM_DEFAULT);
TEST(UWM_SP);
TEST(UWM_REGS);
TEST(UWM_SWITCH_STACK);
TEST(UWM_SP | UWM_REGS);
TEST(UWM_CALLER | UWM_SP);
TEST(UWM_CALLER | UWM_SP | UWM_REGS);
TEST(UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
TEST(UWM_THREAD);
TEST(UWM_THREAD | UWM_SP);
TEST(UWM_THREAD | UWM_CALLER | UWM_SP);
TEST(UWM_IRQ);
TEST(UWM_IRQ | UWM_SWITCH_STACK);
TEST(UWM_IRQ | UWM_SP);
TEST(UWM_IRQ | UWM_REGS);
TEST(UWM_IRQ | UWM_SP | UWM_REGS);
TEST(UWM_IRQ | UWM_CALLER | UWM_SP);
TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS);
TEST(UWM_IRQ | UWM_CALLER | UWM_SP | UWM_REGS | UWM_SWITCH_STACK);
#ifdef CONFIG_KPROBES
TEST(UWM_PGM);
TEST(UWM_PGM | UWM_SP);
TEST(UWM_PGM | UWM_REGS);
TEST(UWM_PGM | UWM_SP | UWM_REGS);
#endif
#undef TEST
return ret;
}
static void test_unwind_exit(void)
{
}
module_init(test_unwind_init);
module_exit(test_unwind_exit);
MODULE_LICENSE("GPL");
