1 files changed, 51 insertions, 1 deletions

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 36fd42091fa7..9538f00827a9 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -41,6 +41,9 @@
 /* Adjust the return address of a call insn */
 #define UPROBE_FIX_CALL 0x2
 
+/* Instruction will modify TF, don't change it */
+#define UPROBE_FIX_SETF 0x4
+
 #define UPROBE_FIX_RIP_AX       0x8000
 #define UPROBE_FIX_RIP_CX       0x4000
 
@@ -239,6 +242,10 @@ static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)
         insn_get_opcode(insn);  /* should be a nop */
 
         switch (OPCODE1(insn)) {
+        case 0x9d:
+                /* popf */
+                auprobe->fixups |= UPROBE_FIX_SETF;
+                break;
         case 0xc3:              /* ret/lret */
         case 0xcb:
         case 0xc2:
@@ -646,7 +653,7 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
  * Skip these instructions as per the currently known x86 ISA.
  * 0x66* { 0x90 | 0x0f 0x1f | 0x0f 0x19 | 0x87 0xc0 }
  */
-bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
         int i;
 
@@ -673,3 +680,46 @@ bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
         }
         return false;
 }
+
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        bool ret = __skip_sstep(auprobe, regs);
+        if (ret && (regs->flags & X86_EFLAGS_TF))
+                send_sig(SIGTRAP, current, 0);
+        return ret;
+}
+
+void arch_uprobe_enable_step(struct arch_uprobe *auprobe)
+{
+        struct task_struct *task = current;
+        struct arch_uprobe_task *autask = &task->utask->autask;
+        struct pt_regs *regs = task_pt_regs(task);
+
+        autask->saved_tf = !!(regs->flags & X86_EFLAGS_TF);
+
+        regs->flags |= X86_EFLAGS_TF;
+        if (test_tsk_thread_flag(task, TIF_BLOCKSTEP))
+                set_task_blockstep(task, false);
+}
+
+void arch_uprobe_disable_step(struct arch_uprobe *auprobe)
+{
+        struct task_struct *task = current;
+        struct arch_uprobe_task *autask = &task->utask->autask;
+        bool trapped = (task->utask->state == UTASK_SSTEP_TRAPPED);
+        struct pt_regs *regs = task_pt_regs(task);
+        /*
+         * The state of TIF_BLOCKSTEP was not saved so we can get an extra
+         * SIGTRAP if we do not clear TF. We need to examine the opcode to
+         * make it right.
+         */
+        if (unlikely(trapped)) {
+                if (!autask->saved_tf)
+                        regs->flags &= ~X86_EFLAGS_TF;
+        } else {
+                if (autask->saved_tf)
+                        send_sig(SIGTRAP, task, 0);
+                else if (!(auprobe->fixups & UPROBE_FIX_SETF))
+                        regs->flags &= ~X86_EFLAGS_TF;
+        }
+}