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x86/debug: Move historical SYSENTER junk into exc_debug_kernel()
The historical SYSENTER junk is explicitly for from-kernel, so move it to the #DB-from-kernel handler. It is ordered after the notifier, which is important for KGDB which uses TF single-step and needs to consume the event before that point. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Daniel Thompson <daniel.thompson@linaro.org> Link: https://lore.kernel.org/r/20200902133201.031099736@infradead.org
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4182e94369
commit
4eb5acc391
1 changed files with 25 additions and 24 deletions
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@ -783,7 +783,7 @@ static __always_inline unsigned long debug_read_clear_dr6(void)
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*
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* May run on IST stack.
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*/
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static void handle_debug(struct pt_regs *regs, unsigned long dr6)
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static bool handle_debug(struct pt_regs *regs, unsigned long *dr6)
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{
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struct task_struct *tsk = current;
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bool icebp;
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@ -793,15 +793,13 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6)
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* then it's very likely the result of an icebp/int01 trap.
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* User wants a sigtrap for that.
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*/
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icebp = !dr6;
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icebp = !*dr6;
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/* Store the virtualized DR6 value */
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tsk->thread.debugreg6 = dr6;
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tsk->thread.debugreg6 = *dr6;
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if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0,
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SIGTRAP) == NOTIFY_STOP) {
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return;
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}
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if (notify_die(DIE_DEBUG, "debug", regs, (long)dr6, 0, SIGTRAP) == NOTIFY_STOP)
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return true;
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/* It's safe to allow irq's after DR6 has been saved */
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cond_local_irq_enable(regs);
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@ -815,25 +813,15 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6)
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/*
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* Reload dr6, the notifier might have changed it.
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*/
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dr6 = tsk->thread.debugreg6;
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*dr6 = tsk->thread.debugreg6;
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if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
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/*
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* Historical junk that used to handle SYSENTER single-stepping.
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* This should be unreachable now. If we survive for a while
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* without anyone hitting this warning, we'll turn this into
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* an oops.
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*/
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tsk->thread.debugreg6 &= ~DR_STEP;
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set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
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regs->flags &= ~X86_EFLAGS_TF;
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}
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if (dr6 & (DR_STEP | DR_TRAP_BITS) || icebp)
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send_sigtrap(regs, 0, get_si_code(dr6));
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if (*dr6 & (DR_STEP | DR_TRAP_BITS) || icebp)
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send_sigtrap(regs, 0, get_si_code(*dr6));
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out:
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cond_local_irq_disable(regs);
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return false;
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}
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static __always_inline void exc_debug_kernel(struct pt_regs *regs,
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@ -876,7 +864,20 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
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if (!dr6)
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goto out;
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handle_debug(regs, dr6);
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if (handle_debug(regs, &dr6))
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goto out;
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if (WARN_ON_ONCE(dr6 & DR_STEP)) {
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/*
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* Historical junk that used to handle SYSENTER single-stepping.
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* This should be unreachable now. If we survive for a while
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* without anyone hitting this warning, we'll turn this into
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* an oops.
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*/
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dr6 &= ~DR_STEP;
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set_thread_flag(TIF_SINGLESTEP);
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regs->flags &= ~X86_EFLAGS_TF;
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}
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out:
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instrumentation_end();
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@ -906,7 +907,7 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
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irqentry_enter_from_user_mode(regs);
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instrumentation_begin();
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handle_debug(regs, dr6);
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handle_debug(regs, &dr6);
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instrumentation_end();
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irqentry_exit_to_user_mode(regs);
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