s390/uprobes: fix user space PER events

If uprobes are single stepped for example with gdb, the behavior should
now be correct. Before this patch, when gdb was single stepping a uprobe,
the result was a SIGILL.
When PER is active for any storage alteration and a uprobe is hit, a storage
alteration event is indicated. These over indications are filterd out by gdb,
if no change has happened within the observed area.

Signed-off-by: Jan Willeke <willeke@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/uprobes.c b/arch/s390/kernel/uprobes.c
index f6b3cd0..cc73280 100644 (file)
--- a/arch/s390/kernel/uprobes.c
+++ b/arch/s390/kernel/uprobes.c
@@ -48,6 +48,30 @@ bool arch_uprobe_xol_was_trapped(struct task_struct *tsk)
        return false;
 }
 
+static int check_per_event(unsigned short cause, unsigned long control,
+                          struct pt_regs *regs)
+{
+       if (!(regs->psw.mask & PSW_MASK_PER))
+               return 0;
+       /* user space single step */
+       if (control == 0)
+               return 1;
+       /* over indication for storage alteration */
+       if ((control & 0x20200000) && (cause & 0x2000))
+               return 1;
+       if (cause & 0x8000) {
+               /* all branches */
+               if ((control & 0x80800000) == 0x80000000)
+                       return 1;
+               /* branch into selected range */
+               if (((control & 0x80800000) == 0x80800000) &&
+                   regs->psw.addr >= current->thread.per_user.start &&
+                   regs->psw.addr <= current->thread.per_user.end)
+                       return 1;
+       }
+       return 0;
+}
+
 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
        int fixup = probe_get_fixup_type(auprobe->insn);
@@ -71,9 +95,13 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
                if (regs->psw.addr - utask->xol_vaddr == ilen)
                        regs->psw.addr = utask->vaddr + ilen;
        }
-       /* If per tracing was active generate trap */
-       if (regs->psw.mask & PSW_MASK_PER)
-               do_per_trap(regs);
+       if (check_per_event(current->thread.per_event.cause,
+                           current->thread.per_user.control, regs)) {
+               /* fix per address */
+               current->thread.per_event.address = utask->vaddr;
+               /* trigger per event */
+               set_pt_regs_flag(regs, PIF_PER_TRAP);
+       }
        return 0;
 }
 
@@ -106,6 +134,7 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
        clear_thread_flag(TIF_UPROBE_SINGLESTEP);
        regs->int_code = auprobe->saved_int_code;
        regs->psw.addr = current->utask->vaddr;
+       current->thread.per_event.address = current->utask->vaddr;
 }
 
 unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline,
@@ -146,17 +175,20 @@ static void adjust_psw_addr(psw_t *psw, unsigned long len)
        __rc;                                           \
 })
 
-#define emu_store_ril(ptr, input)                      \
+#define emu_store_ril(regs, ptr, input)                        \
 ({                                                     \
        unsigned int mask = sizeof(*(ptr)) - 1;         \
+       __typeof__(ptr) __ptr = (ptr);                  \
        int __rc = 0;                                   \
                                                        \
        if (!test_facility(34))                         \
                __rc = EMU_ILLEGAL_OP;                  \
-       else if ((u64 __force)ptr & mask)               \
+       else if ((u64 __force)__ptr & mask)             \
                __rc = EMU_SPECIFICATION;               \
-       else if (put_user(*(input), ptr))               \
+       else if (put_user(*(input), __ptr))             \
                __rc = EMU_ADDRESSING;                  \
+       if (__rc == 0)                                  \
+               sim_stor_event(regs, __ptr, mask + 1);  \
        __rc;                                           \
 })
 
@@ -197,6 +229,25 @@ union split_register {
        s16 s16[4];
 };
 
+/*
+ * If user per registers are setup to trace storage alterations and an
+ * emulated store took place on a fitting address a user trap is generated.
+ */
+static void sim_stor_event(struct pt_regs *regs, void *addr, int len)
+{
+       if (!(regs->psw.mask & PSW_MASK_PER))
+               return;
+       if (!(current->thread.per_user.control & PER_EVENT_STORE))
+               return;
+       if ((void *)current->thread.per_user.start > (addr + len))
+               return;
+       if ((void *)current->thread.per_user.end < addr)
+               return;
+       current->thread.per_event.address = regs->psw.addr;
+       current->thread.per_event.cause = PER_EVENT_STORE >> 16;
+       set_pt_regs_flag(regs, PIF_PER_TRAP);
+}
+
 /*
  * pc relative instructions are emulated, since parameters may not be
  * accessible from the xol area due to range limitations.
@@ -249,13 +300,13 @@ static void handle_insn_ril(struct arch_uprobe *auprobe, struct pt_regs *regs)
                        rc = emu_load_ril((u32 __user *)uptr, &rx->u64);
                        break;
                case 0x07: /* sthrl */
-                       rc = emu_store_ril((u16 __user *)uptr, &rx->u16[3]);
+                       rc = emu_store_ril(regs, (u16 __user *)uptr, &rx->u16[3]);
                        break;
                case 0x0b: /* stgrl */
-                       rc = emu_store_ril((u64 __user *)uptr, &rx->u64);
+                       rc = emu_store_ril(regs, (u64 __user *)uptr, &rx->u64);
                        break;
                case 0x0f: /* strl */
-                       rc = emu_store_ril((u32 __user *)uptr, &rx->u32[1]);
+                       rc = emu_store_ril(regs, (u32 __user *)uptr, &rx->u32[1]);
                        break;
                }
                break;