1 files changed, 17 insertions, 12 deletions

diff --git a/arch/x86_64/kernel/ptrace.c b/arch/x86_64/kernel/ptrace.c
index 2d50024c9f30..addc14af0c56 100644
--- a/arch/x86_64/kernel/ptrace.c
+++ b/arch/x86_64/kernel/ptrace.c
@@ -116,17 +116,17 @@ unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *r
         return addr;
 }
 
-static int is_at_popf(struct task_struct *child, struct pt_regs *regs)
+static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
 {
         int i, copied;
-        unsigned char opcode[16];
+        unsigned char opcode[15];
         unsigned long addr = convert_rip_to_linear(child, regs);
 
         copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
         for (i = 0; i < copied; i++) {
                 switch (opcode[i]) {
-                /* popf */
-                case 0x9d:
+                /* popf and iret */
+                case 0x9d: case 0xcf:
                         return 1;
 
                         /* CHECKME: 64 65 */
@@ -138,14 +138,17 @@ static int is_at_popf(struct task_struct *child, struct pt_regs *regs)
                 case 0x26: case 0x2e:
                 case 0x36: case 0x3e:
                 case 0x64: case 0x65:
-                case 0xf0: case 0xf2: case 0xf3:
+                case 0xf2: case 0xf3:
                         continue;
 
-                /* REX prefixes */
                 case 0x40 ... 0x4f:
+                        if (regs->cs != __USER_CS)
+                                /* 32-bit mode: register increment */
+                                return 0;
+                        /* 64-bit mode: REX prefix */
                         continue;
 
-                        /* CHECKME: f0, f2, f3 */
+                        /* CHECKME: f2, f3 */
 
                 /*
                  * pushf: NOTE! We should probably not let
@@ -186,10 +189,8 @@ static void set_singlestep(struct task_struct *child)
          * ..but if TF is changed by the instruction we will trace,
          * don't mark it as being "us" that set it, so that we
          * won't clear it by hand later.
-         *
-         * AK: this is not enough, LAHF and IRET can change TF in user space too.
          */
-        if (is_at_popf(child, regs))
+        if (is_setting_trap_flag(child, regs))
                 return;
 
         child->ptrace |= PT_DTRACE;
@@ -420,9 +421,13 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                                 if ((0x5554 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
                                         break;
                         if (i == 4) {
-                                child->thread.debugreg7 = data;
+                          child->thread.debugreg7 = data;
+                          if (data)
+                                set_tsk_thread_flag(child, TIF_DEBUG);
+                          else
+                                clear_tsk_thread_flag(child, TIF_DEBUG);
                           ret = 0;
-                  }
+                        }
                   break;
                 }
                 break;