diff options
| -rw-r--r-- | arch/s390/Kconfig | 14 | ||||
| -rw-r--r-- | arch/s390/lib/Makefile | 3 | ||||
| -rw-r--r-- | arch/s390/lib/test_unwind.c | 231 |
3 files changed, 248 insertions, 0 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index f0df9e48e651..2528eb9d01fb 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -1018,3 +1018,17 @@ config S390_GUEST the KVM hypervisor. endmenu + +menu "Selftests" + +config S390_UNWIND_SELFTEST + def_tristate n + prompt "Test unwind functions" + help + This option enables s390 specific stack unwinder testing kernel + module. This option is not useful for distributions or general + kernels, but only for kernel developers working on architecture code. + + Say N if you are unsure. + +endmenu diff --git a/arch/s390/lib/Makefile b/arch/s390/lib/Makefile index d7c218e8b559..28fd66d558ff 100644 --- a/arch/s390/lib/Makefile +++ b/arch/s390/lib/Makefile @@ -11,3 +11,6 @@ lib-$(CONFIG_UPROBES) += probes.o # Instrumenting memory accesses to __user data (in different address space) # produce false positives KASAN_SANITIZE_uaccess.o := n + +obj-$(CONFIG_S390_UNWIND_SELFTEST) += test_unwind.o +CFLAGS_test_unwind.o += -fno-optimize-sibling-calls diff --git a/arch/s390/lib/test_unwind.c b/arch/s390/lib/test_unwind.c new file mode 100644 index 000000000000..5636da941f1f --- /dev/null +++ b/arch/s390/lib/test_unwind.c @@ -0,0 +1,231 @@ +// 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/wait.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_KERNEL); + 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 (!addr || frame_count == max_frames) + break; + sprint_symbol(sym, addr); + if (bt_pos < BT_BUF_SIZE) { + bt_pos += snprintf(bt + bt_pos, BT_BUF_SIZE - bt_pos, "%s\n", sym); + 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 (!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; + struct completion task_ready; + wait_queue_head_t task_wq; + unsigned long sp; +}; + +/* 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. */ + +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; +} + +/* 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; + } 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) +{ + 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); +} + +/* 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 + 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_SP | UWM_REGS); + TEST(UWM_CALLER | UWM_SP); + TEST(UWM_CALLER | UWM_SP | UWM_REGS); + TEST(UWM_THREAD); + TEST(UWM_THREAD | UWM_SP); + TEST(UWM_THREAD | UWM_CALLER | UWM_SP); +#undef TEST + + return ret; +} + +static void test_unwind_exit(void) +{ +} + +module_init(test_unwind_init); +module_exit(test_unwind_exit); +MODULE_LICENSE("GPL"); |