uprobes/x86: Introduce uprobe_xol_ops and arch_uprobe->ops

Introduce arch_uprobe->ops pointing to the "struct uprobe_xol_ops",
move the current UPROBE_FIX_{RIP*,IP,CALL} code into the default
set of methods and change arch_uprobe_pre/post_xol() accordingly.

This way we can add the new uprobe_xol_ops's to handle the insns
which need the special processing (rip-relative jmp/call at least).

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

2 files changed, 74 insertions, 40 deletions

diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index 3087ea9c5f2e..9f8210bcbb49 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -33,12 +33,17 @@ typedef u8 uprobe_opcode_t;
 #define UPROBE_SWBP_INSN                0xcc
 #define UPROBE_SWBP_INSN_SIZE              1
 
+struct uprobe_xol_ops;
+
 struct arch_uprobe {
-        u16                             fixups;
         union {
                 u8                      insn[MAX_UINSN_BYTES];
                 u8                      ixol[MAX_UINSN_BYTES];
         };
+
+        u16                             fixups;
+        const struct uprobe_xol_ops     *ops;
+
 #ifdef CONFIG_X86_64
         unsigned long                   rip_rela_target_address;
 #endif
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 3bb4198aa588..13ad8a38c2d9 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -402,6 +402,64 @@ static int validate_insn_bits(struct arch_uprobe *auprobe, struct mm_struct *mm,
 }
 #endif /* CONFIG_X86_64 */
 
+struct uprobe_xol_ops {
+        bool    (*emulate)(struct arch_uprobe *, struct pt_regs *);
+        int     (*pre_xol)(struct arch_uprobe *, struct pt_regs *);
+        int     (*post_xol)(struct arch_uprobe *, struct pt_regs *);
+};
+
+static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        pre_xol_rip_insn(auprobe, regs, &current->utask->autask);
+        return 0;
+}
+
+/*
+ * Adjust the return address pushed by a call insn executed out of line.
+ */
+static int adjust_ret_addr(unsigned long sp, long correction)
+{
+        int rasize, ncopied;
+        long ra = 0;
+
+        if (is_ia32_task())
+                rasize = 4;
+        else
+                rasize = 8;
+
+        ncopied = copy_from_user(&ra, (void __user *)sp, rasize);
+        if (unlikely(ncopied))
+                return -EFAULT;
+
+        ra += correction;
+        ncopied = copy_to_user((void __user *)sp, &ra, rasize);
+        if (unlikely(ncopied))
+                return -EFAULT;
+
+        return 0;
+}
+
+static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        struct uprobe_task *utask = current->utask;
+        long correction = (long)(utask->vaddr - utask->xol_vaddr);
+        int ret = 0;
+
+        handle_riprel_post_xol(auprobe, regs, &correction);
+        if (auprobe->fixups & UPROBE_FIX_IP)
+                regs->ip += correction;
+
+        if (auprobe->fixups & UPROBE_FIX_CALL)
+                ret = adjust_ret_addr(regs->sp, correction);
+
+        return ret;
+}
+
+static struct uprobe_xol_ops default_xol_ops = {
+        .pre_xol  = default_pre_xol_op,
+        .post_xol = default_post_xol_op,
+};
+
 /**
  * arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
  * @mm: the probed address space.
@@ -464,6 +522,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
         if (fix_call)
                 auprobe->fixups |= UPROBE_FIX_CALL;
 
+        auprobe->ops = &default_xol_ops;
         return 0;
 }
 
@@ -485,33 +544,8 @@ int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
         if (test_tsk_thread_flag(current, TIF_BLOCKSTEP))
                 set_task_blockstep(current, false);
 
-        pre_xol_rip_insn(auprobe, regs, &utask->autask);
-        return 0;
-}
-
-/*
- * This function is called by arch_uprobe_post_xol() to adjust the return
- * address pushed by a call instruction executed out of line.
- */
-static int adjust_ret_addr(unsigned long sp, long correction)
-{
-        int rasize, ncopied;
-        long ra = 0;
-
-        if (is_ia32_task())
-                rasize = 4;
-        else
-                rasize = 8;
-
-        ncopied = copy_from_user(&ra, (void __user *)sp, rasize);
-        if (unlikely(ncopied))
-                return -EFAULT;
-
-        ra += correction;
-        ncopied = copy_to_user((void __user *)sp, &ra, rasize);
-        if (unlikely(ncopied))
-                return -EFAULT;
-
+        if (auprobe->ops->pre_xol)
+                return auprobe->ops->pre_xol(auprobe, regs);
         return 0;
 }
 
@@ -560,11 +594,8 @@ bool arch_uprobe_xol_was_trapped(struct task_struct *t)
 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
         struct uprobe_task *utask = current->utask;
-        long correction;
-        int result = 0;
 
         WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
-
         current->thread.trap_nr = utask->autask.saved_trap_nr;
         /*
          * arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
@@ -576,15 +607,9 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
         else if (!(auprobe->fixups & UPROBE_FIX_SETF))
                 regs->flags &= ~X86_EFLAGS_TF;
 
-        correction = (long)(utask->vaddr - utask->xol_vaddr);
-        handle_riprel_post_xol(auprobe, regs, &correction);
-        if (auprobe->fixups & UPROBE_FIX_IP)
-                regs->ip += correction;
-
-        if (auprobe->fixups & UPROBE_FIX_CALL)
-                result = adjust_ret_addr(regs->sp, correction);
-
-        return result;
+        if (auprobe->ops->post_xol)
+                return auprobe->ops->post_xol(auprobe, regs);
+        return 0;
 }
 
 /* callback routine for handling exceptions. */
@@ -642,6 +667,10 @@ static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
         int i;
 
+        if (auprobe->ops->emulate)
+                return auprobe->ops->emulate(auprobe, regs);
+
+        /* TODO: move this code into ->emulate() hook */
         for (i = 0; i < MAX_UINSN_BYTES; i++) {
                 if (auprobe->insn[i] == 0x66)
                         continue;