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 52d056a5f89fc3f3e7c49c72467c4dc3a55c2414..e27a7d3b0364628b17eee8f3942719f121606cc7 100644 (file)
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -7,6 +7,8 @@
  * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
  */
 
+#define pr_fmt(fmt) "kprobes: " fmt
+
 #include <linux/moduleloader.h>
 #include <linux/kprobes.h>
 #include <linux/ptrace.h>
@@ -120,9 +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))
@@ -240,7 +288,7 @@ void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
        ri->fp = NULL;
 
        /* Replace the return addr with trampoline addr */
-       regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
+       regs->gprs[14] = (unsigned long) &__kretprobe_trampoline;
 }
 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 
@@ -259,7 +307,7 @@ static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
                 * is a BUG. The code path resides in the .kprobes.text
                 * section and is executed with interrupts disabled.
                 */
-               pr_err("Invalid kprobe detected.\n");
+               pr_err("Failed to recover from reentered kprobes.\n");
                dump_kprobe(p);
                BUG();
        }
@@ -332,8 +380,8 @@ NOKPROBE_SYMBOL(kprobe_handler);
  */
 static void __used kretprobe_trampoline_holder(void)
 {
-       asm volatile(".global kretprobe_trampoline\n"
-                    "kretprobe_trampoline: bcr 0,0\n");
+       asm volatile(".global __kretprobe_trampoline\n"
+                    "__kretprobe_trampoline: bcr 0,0\n");
 }
 
 /*
@@ -341,7 +389,7 @@ static void __used kretprobe_trampoline_holder(void)
  */
 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
-       regs->psw.addr = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
+       regs->psw.addr = __kretprobe_trampoline_handler(regs, NULL);
        /*
         * By returning a non-zero value, we are telling
         * kprobe_handler() that we don't want the post_handler
@@ -507,7 +555,7 @@ int kprobe_exceptions_notify(struct notifier_block *self,
 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
 
 static struct kprobe trampoline = {
-       .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+       .addr = (kprobe_opcode_t *) &__kretprobe_trampoline,
        .pre_handler = trampoline_probe_handler
 };
 
@@ -518,6 +566,6 @@ int __init arch_init_kprobes(void)
 
 int arch_trampoline_kprobe(struct kprobe *p)
 {
-       return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
+       return p->addr == (kprobe_opcode_t *) &__kretprobe_trampoline;
 }
 NOKPROBE_SYMBOL(arch_trampoline_kprobe);