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WSL2-Linux-Kernel
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x86/traps: Restructure #DB handling 

Now that there are separate entry points, move the kernel/user_mode specifc
checks into the entry functions so the common handling code does not need
the extra mode checks. Make the code more readable while at it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135315.283276272@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-05-04 19:56:26 +02:00
Родитель 4c0dcd8350
Коммит 9347f41352
1 изменённых файлов: 35 добавлений и 34 удалений
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69
arch/x86/kernel/traps.c
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@ -775,39 +775,12 @@ static __always_inline void debug_exit(unsigned long dr7)
*
* May run on IST stack.
*/
static noinstr void handle_debug(struct pt_regs *regs, unsigned long dr6)
static void noinstr handle_debug(struct pt_regs *regs, unsigned long dr6,
bool user_icebp)
{
struct task_struct *tsk = current;
int user_icebp = 0;
int si_code;
/*
* The SDM says "The processor clears the BTF flag when it
* generates a debug exception." Clear TIF_BLOCKSTEP to keep
* TIF_BLOCKSTEP in sync with the hardware BTF flag.
*/
clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP);
if (unlikely(!user_mode(regs) && (dr6 & DR_STEP) &&
is_sysenter_singlestep(regs))) {
dr6 &= ~DR_STEP;
if (!dr6)
return;
/*
* else we might have gotten a single-step trap and hit a
* watchpoint at the same time, in which case we should fall
* through and handle the watchpoint.
*/
}
/*
* If dr6 has no reason to give us about the origin of this trap,
* then it's very likely the result of an icebp/int01 trap.
* User wants a sigtrap for that.
*/
if (!dr6 && user_mode(regs))
user_icebp = 1;
/* Store the virtualized DR6 value */
tsk->thread.debugreg6 = dr6;
@ -832,9 +805,7 @@ static noinstr void handle_debug(struct pt_regs *regs, unsigned long dr6)
if (v8086_mode(regs)) {
handle_vm86_trap((struct kernel_vm86_regs *) regs, 0,
X86_TRAP_DB);
cond_local_irq_disable(regs);
debug_stack_usage_dec();
return;
goto out;
}
if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
@ -848,9 +819,12 @@ static noinstr void handle_debug(struct pt_regs *regs, unsigned long dr6)
set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
regs->flags &= ~X86_EFLAGS_TF;
}
si_code = get_si_code(tsk->thread.debugreg6);
if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp)
send_sigtrap(regs, 0, si_code);
out:
cond_local_irq_disable(regs);
debug_stack_usage_dec();
}
@ -859,7 +833,27 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
unsigned long dr6)
{
nmi_enter();
handle_debug(regs, dr6);
/*
* The SDM says "The processor clears the BTF flag when it
* generates a debug exception." Clear TIF_BLOCKSTEP to keep
* TIF_BLOCKSTEP in sync with the hardware BTF flag.
*/
clear_thread_flag(TIF_BLOCKSTEP);
/*
* Catch SYSENTER with TF set and clear DR_STEP. If this hit a
* watchpoint at the same time then that will still be handled.
*/
if ((dr6 & DR_STEP) && is_sysenter_singlestep(regs))
dr6 &= ~DR_STEP;
/*
* If DR6 is zero, no point in trying to handle it. The kernel is
* not using INT1.
*/
if (dr6)
handle_debug(regs, dr6, false);
nmi_exit();
}
@ -867,7 +861,14 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
unsigned long dr6)
{
idtentry_enter(regs);
handle_debug(regs, dr6);
clear_thread_flag(TIF_BLOCKSTEP);
/*
* If dr6 has no reason to give us about the origin of this trap,
* then it's very likely the result of an icebp/int01 trap.
* User wants a sigtrap for that.
*/
handle_debug(regs, dr6, !dr6);
idtentry_exit(regs);
}