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
---
arch/x86/kernel/traps_32.c | 30 +++++++++++++++++++++---------
arch/x86/kernel/traps_64.c | 17 +++++++++--------
include/asm-x86/ptrace.h | 4 ----
3 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kernel/traps_32.c b/arch/x86/kernel/traps_32.c
index 6ecc1b7..da97cd2 100644
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -89,6 +89,20 @@ static inline void conditional_sti(struct pt_regs *regs)
local_irq_enable();
}

+static inline void preempt_conditional_sti(struct pt_regs *regs)
+{
+ inc_preempt_count();
+ if (regs->flags & X86_EFLAGS_IF)
+ local_irq_enable();
+}
+
+static inline void preempt_conditional_cli(struct pt_regs *regs)
+{
+ if (regs->flags & X86_EFLAGS_IF)
+ local_irq_disable();
+ dec_preempt_count();
+}
+
static inline void
die_if_kernel(const char *str, struct pt_regs *regs, long err)
{
@@ -499,7 +513,7 @@ dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
{
struct task_struct *tsk = current;
- unsigned int condition;
+ unsigned long condition;
int si_code;

get_debugreg(condition, 6);
@@ -517,9 +531,9 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
SIGTRAP) == NOTIFY_STOP)
return;
+
/* It's safe to allow irq's after DR6 has been saved */
- if (regs->flags & X86_EFLAGS_IF)
- local_irq_enable();
+ preempt_conditional_sti(regs);

/* Mask out spurious debug traps due to lazy DR7 setting */
if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) {
@@ -538,16 +552,11 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
* kernel space (but re-enable TF when returning to user mode).
*/
if (condition & DR_STEP) {
- /*
- * We already checked v86 mode above, so we can
- * check for kernel mode by just checking the CPL
- * of CS.
- */
if (!user_mode(regs))
goto clear_TF_reenable;
}

- si_code = get_si_code((unsigned long)condition);
+ si_code = get_si_code(condition);
/* Ok, finally something we can handle */
send_sigtrap(tsk, regs, error_code, si_code);

@@ -557,15 +566,18 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
*/
clear_dr7:
set_debugreg(0, 7);
+ preempt_conditional_cli(regs);
return;

debug_vm86:
handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1);
+ preempt_conditional_cli(regs);
return;

clear_TF_reenable:
set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
regs->flags &= ~X86_EFLAGS_TF;
+ preempt_conditional_cli(regs);
return;
}

diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index d4e02c1..80dbbc7 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -381,7 +381,7 @@ 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);

@@ -399,6 +399,7 @@ 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 */
@@ -407,6 +408,7 @@ 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;

/*
@@ -418,15 +420,14 @@ 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);
diff --git a/include/asm-x86/ptrace.h b/include/asm-x86/ptrace.h
index ac578f1..a202552 100644
--- a/include/asm-x86/ptrace.h
+++ b/include/asm-x86/ptrace.h
@@ -174,12 +174,8 @@ extern unsigned long profile_pc(struct pt_regs *regs);

extern unsigned long
convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs);
-
-#ifdef CONFIG_X86_32
extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
int error_code, int si_code);
-#endif
-
void signal_fault(struct pt_regs *regs, void __user *frame, char *where);

extern long syscall_trace_enter(struct pt_regs *);
--
1.5.4.3

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