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iii-iVasily Gorbik
iii-i
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Vasily Gorbik
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s390/unwind: add a test for the internal API
unwind_for_each_frame can take at least 8 different sets of parameters. Add a test to make sure they all are handled in a sane way. Reviewed-by: Heiko Carstens <[email protected]> Signed-off-by: Ilya Leoshkevich <[email protected]> Co-developed-by: Vasily Gorbik <[email protected]> Signed-off-by: Vasily Gorbik <[email protected]>
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‎arch/s390/Kconfig

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@@ -1018,3 +1018,17 @@ config S390_GUEST
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the KVM hypervisor.
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endmenu
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menu "Selftests"
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config S390_UNWIND_SELFTEST
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def_tristate n
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prompt "Test unwind functions"
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help
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This option enables s390 specific stack unwinder testing kernel
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module. This option is not useful for distributions or general
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kernels, but only for kernel developers working on architecture code.
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Say N if you are unsure.
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endmenu

‎arch/s390/lib/Makefile

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@@ -11,3 +11,6 @@ lib-$(CONFIG_UPROBES) += probes.o
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# Instrumenting memory accesses to __user data (in different address space)
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# produce false positives
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KASAN_SANITIZE_uaccess.o := n
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obj-$(CONFIG_S390_UNWIND_SELFTEST) += test_unwind.o
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CFLAGS_test_unwind.o += -fno-optimize-sibling-calls

‎arch/s390/lib/test_unwind.c

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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Test module for unwind_for_each_frame
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*/
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#define pr_fmt(fmt) "test_unwind: " fmt
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#include <asm/unwind.h>
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#include <linux/completion.h>
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#include <linux/kallsyms.h>
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#include <linux/kthread.h>
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#include <linux/module.h>
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#include <linux/string.h>
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#include <linux/wait.h>
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#define BT_BUF_SIZE (PAGE_SIZE * 4)
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/*
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* To avoid printk line limit split backtrace by lines
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*/
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static void print_backtrace(char *bt)
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{
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char *p;
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while (true) {
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p = strsep(&bt, "\n");
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if (!p)
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break;
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pr_err("%s\n", p);
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}
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}
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/*
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* Calls unwind_for_each_frame(task, regs, sp) and verifies that the result
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* contains unwindme_func2 followed by unwindme_func1.
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*/
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static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs,
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unsigned long sp)
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{
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int frame_count, prev_is_func2, seen_func2_func1;
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const int max_frames = 128;
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struct unwind_state state;
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size_t bt_pos = 0;
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int ret = 0;
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char *bt;
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bt = kmalloc(BT_BUF_SIZE, GFP_KERNEL);
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if (!bt) {
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pr_err("failed to allocate backtrace buffer\n");
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return -ENOMEM;
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}
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/* Unwind. */
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frame_count = 0;
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prev_is_func2 = 0;
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seen_func2_func1 = 0;
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unwind_for_each_frame(&state, task, regs, sp) {
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unsigned long addr = unwind_get_return_address(&state);
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char sym[KSYM_SYMBOL_LEN];
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if (!addr || frame_count == max_frames)
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break;
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sprint_symbol(sym, addr);
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if (bt_pos < BT_BUF_SIZE) {
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bt_pos += snprintf(bt + bt_pos, BT_BUF_SIZE - bt_pos, "%s\n", sym);
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if (bt_pos >= BT_BUF_SIZE)
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pr_err("backtrace buffer is too small\n");
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}
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frame_count += 1;
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if (prev_is_func2 && str_has_prefix(sym, "unwindme_func1"))
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seen_func2_func1 = 1;
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prev_is_func2 = str_has_prefix(sym, "unwindme_func2");
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}
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/* Check the results. */
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if (!seen_func2_func1) {
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pr_err("unwindme_func2 and unwindme_func1 not found\n");
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ret = -EINVAL;
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}
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if (frame_count == max_frames) {
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pr_err("Maximum number of frames exceeded\n");
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ret = -EINVAL;
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}
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if (ret)
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print_backtrace(bt);
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kfree(bt);
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return ret;
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}
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/* State of the task being unwound. */
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struct unwindme {
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int flags;
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struct completion task_ready;
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wait_queue_head_t task_wq;
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unsigned long sp;
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};
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/* Values of unwindme.flags. */
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#define UWM_DEFAULT 0x0
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#define UWM_THREAD 0x1 /* Unwind a separate task. */
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#define UWM_REGS 0x2 /* Pass regs to test_unwind(). */
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#define UWM_SP 0x4 /* Pass sp to test_unwind(). */
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#define UWM_CALLER 0x8 /* Unwind starting from caller. */
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static __always_inline unsigned long get_psw_addr(void)
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{
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unsigned long psw_addr;
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asm volatile(
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"basr %[psw_addr],0\n"
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: [psw_addr] "=d" (psw_addr));
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return psw_addr;
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}
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/* This function may or may not appear in the backtrace. */
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static noinline int unwindme_func4(struct unwindme *u)
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{
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if (!(u->flags & UWM_CALLER))
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u->sp = current_frame_address();
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if (u->flags & UWM_THREAD) {
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complete(&u->task_ready);
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wait_event(u->task_wq, kthread_should_park());
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kthread_parkme();
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return 0;
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} else {
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struct pt_regs regs;
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memset(&regs, 0, sizeof(regs));
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regs.psw.addr = get_psw_addr();
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regs.gprs[15] = current_stack_pointer();
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return test_unwind(NULL,
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(u->flags & UWM_REGS) ? &regs : NULL,
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(u->flags & UWM_SP) ? u->sp : 0);
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}
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}
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/* This function may or may not appear in the backtrace. */
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static noinline int unwindme_func3(struct unwindme *u)
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{
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u->sp = current_frame_address();
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return unwindme_func4(u);
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}
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/* This function must appear in the backtrace. */
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static noinline int unwindme_func2(struct unwindme *u)
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{
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return unwindme_func3(u);
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}
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/* This function must follow unwindme_func2 in the backtrace. */
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static noinline int unwindme_func1(void *u)
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{
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return unwindme_func2((struct unwindme *)u);
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}
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/* Spawns a task and passes it to test_unwind(). */
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static int test_unwind_task(struct unwindme *u)
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{
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struct task_struct *task;
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int ret;
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/* Initialize thread-related fields. */
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init_completion(&u->task_ready);
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init_waitqueue_head(&u->task_wq);
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/*
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* Start the task and wait until it reaches unwindme_func4() and sleeps
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* in (task_ready, unwind_done] range.
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*/
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task = kthread_run(unwindme_func1, u, "%s", __func__);
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if (IS_ERR(task)) {
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pr_err("kthread_run() failed\n");
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return PTR_ERR(task);
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}
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/*
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* Make sure task reaches unwindme_func4 before parking it,
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* we might park it before kthread function has been executed otherwise
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*/
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wait_for_completion(&u->task_ready);
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kthread_park(task);
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/* Unwind. */
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ret = test_unwind(task, NULL, (u->flags & UWM_SP) ? u->sp : 0);
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kthread_stop(task);
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return ret;
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}
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static int test_unwind_flags(int flags)
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{
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struct unwindme u;
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u.flags = flags;
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if (u.flags & UWM_THREAD)
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return test_unwind_task(&u);
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else
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return unwindme_func1(&u);
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}
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static int test_unwind_init(void)
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{
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int ret = 0;
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#define TEST(flags) \
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do { \
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pr_info("[ RUN ] " #flags "\n"); \
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if (!test_unwind_flags((flags))) { \
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pr_info("[ OK ] " #flags "\n"); \
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} else { \
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pr_err("[ FAILED ] " #flags "\n"); \
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ret = -EINVAL; \
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} \
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} while (0)
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TEST(UWM_DEFAULT);
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TEST(UWM_SP);
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TEST(UWM_REGS);
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TEST(UWM_SP | UWM_REGS);
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TEST(UWM_CALLER | UWM_SP);
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TEST(UWM_CALLER | UWM_SP | UWM_REGS);
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TEST(UWM_THREAD);
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TEST(UWM_THREAD | UWM_SP);
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TEST(UWM_THREAD | UWM_CALLER | UWM_SP);
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#undef TEST
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return ret;
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}
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static void test_unwind_exit(void)
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{
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}
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module_init(test_unwind_init);
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module_exit(test_unwind_exit);
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MODULE_LICENSE("GPL");

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