s390/test_unwind: add CALL_ON_STACK tests

Add CALL_ON_STACK helper testing. Tests make sure that we can unwind from
switched stack to original one up to task pt_regs (nodat -> task stack).

UWM_SWITCH_STACK could not be used together with UWM_THREAD because
get_stack_info explicitly restricts unwinding to task stack if
task != current.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/lib/test_unwind.c b/arch/s390/lib/test_unwind.c
index 2839f8cb691d5ec8ce371148e57406457120a09c..687a6922bedaa041b0961fc30650d764a2e549b4 100644 (file)
--- a/arch/s390/lib/test_unwind.c
+++ b/arch/s390/lib/test_unwind.c
@@ -43,7 +43,7 @@ static noinline int test_unwind(struct task_struct *task, struct pt_regs *regs,
        int ret = 0;
        char *bt;
 
-       bt = kmalloc(BT_BUF_SIZE, GFP_KERNEL);
+       bt = kmalloc(BT_BUF_SIZE, GFP_ATOMIC);
        if (!bt) {
                pr_err("failed to allocate backtrace buffer\n");
                return -ENOMEM;
@@ -98,11 +98,12 @@ struct 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_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. */
 
 static __always_inline unsigned long get_psw_addr(void)
 {
@@ -146,7 +147,16 @@ static noinline int unwindme_func3(struct unwindme *u)
 /* This function must appear in the backtrace. */
 static noinline int unwindme_func2(struct unwindme *u)
 {
-       return unwindme_func3(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. */
@@ -215,9 +225,11 @@ do {                                                                       \
        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);