Merge tag 's390-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

[sfrench/cifs-2.6.git] / arch / s390 / kernel / kprobes.c

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index c505c0ee5f473e08e7d4481206ea64a5e5be3c33..e27a7d3b0364628b17eee8f3942719f121606cc7 100644 (file)
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -122,9 +122,55 @@ static void s390_free_insn_slot(struct kprobe *p)
 }
 NOKPROBE_SYMBOL(s390_free_insn_slot);
 
+/* Check if paddr is at an instruction boundary */
+static bool can_probe(unsigned long paddr)
+{
+       unsigned long addr, offset = 0;
+       kprobe_opcode_t insn;
+       struct kprobe *kp;
+
+       if (paddr & 0x01)
+               return false;
+
+       if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
+               return false;
+
+       /* Decode instructions */
+       addr = paddr - offset;
+       while (addr < paddr) {
+               if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
+                       return false;
+
+               if (insn >> 8 == 0) {
+                       if (insn != BREAKPOINT_INSTRUCTION) {
+                               /*
+                                * Note that QEMU inserts opcode 0x0000 to implement
+                                * software breakpoints for guests. Since the size of
+                                * the original instruction is unknown, stop following
+                                * instructions and prevent setting a kprobe.
+                                */
+                               return false;
+                       }
+                       /*
+                        * Check if the instruction has been modified by another
+                        * kprobe, in which case the original instruction is
+                        * decoded.
+                        */
+                       kp = get_kprobe((void *)addr);
+                       if (!kp) {
+                               /* not a kprobe */
+                               return false;
+                       }
+                       insn = kp->opcode;
+               }
+               addr += insn_length(insn >> 8);
+       }
+       return addr == paddr;
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
-       if ((unsigned long) p->addr & 0x01)
+       if (!can_probe((unsigned long)p->addr))
                return -EINVAL;
        /* Make sure the probe isn't going on a difficult instruction */
        if (probe_is_prohibited_opcode(p->addr))