x86, traps: converge do_debug handlers

Make the x86_64-version and the i386-version of do_debug
more similar.

 - introduce preempt_conditional_sti/cli to i386. The preempt-count
	is now elevated during the trap handler, like on x86_64. It
	does not run on a separate stack, however.
 - replace an open-coded "send_sigtrap"
 - copy some comments

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 8 deletions

diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index be73323ca952..a851eca6d04c 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -380,7 +380,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
 {
         struct task_struct *tsk = current;
         unsigned long condition;
-        siginfo_t info;
+        int si_code;
 
         get_debugreg(condition, 6);
 
@@ -394,6 +394,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
                                                 SIGTRAP) == NOTIFY_STOP)
                 return;
 
+        /* It's safe to allow irq's after DR6 has been saved */
         preempt_conditional_sti(regs);
 
         /* Mask out spurious debug traps due to lazy DR7 setting */
@@ -402,6 +403,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
                         goto clear_dr7;
         }
 
+        /* Save debug status register where ptrace can see it */
         tsk->thread.debugreg6 = condition;
 
         /*
@@ -413,15 +415,14 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
                         goto clear_TF_reenable;
         }
 
+        si_code = get_si_code(condition);
         /* Ok, finally something we can handle */
-        tsk->thread.trap_no = 1;
-        tsk->thread.error_code = error_code;
-        info.si_signo = SIGTRAP;
-        info.si_errno = 0;
-        info.si_code = get_si_code(condition);
-        info.si_addr = user_mode(regs) ? (void __user *)regs->ip : NULL;
-        force_sig_info(SIGTRAP, &info, tsk);
+        send_sigtrap(tsk, regs, error_code, si_code);
 
+        /*
+         * Disable additional traps. They'll be re-enabled when
+         * the signal is delivered.
+         */
 clear_dr7:
         set_debugreg(0, 7);
         preempt_conditional_cli(regs);