diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2020-09-02 15:25:56 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-09-04 15:12:53 +0200 |
| commit | 4eb5acc39187a7ba578fbb44f7bb1965057309ae (patch) | |
| tree | b05b08c752d75121ce36ae7f6ec6dfddf17064a8 /arch/x86/kernel/traps.c | |
| parent | 4182e9436916a48f16207f0619562f1d3843a0c8 (diff) | |
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
Diffstat (limited to 'arch/x86/kernel/traps.c')
| -rw-r--r-- | arch/x86/kernel/traps.c | 49 |
1 files changed, 25 insertions, 24 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 24e09f825a93..2605686ad31e 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -783,7 +783,7 @@ static __always_inline unsigned long debug_read_clear_dr6(void) * * May run on IST stack. */ -static void handle_debug(struct pt_regs *regs, unsigned long dr6) +static bool handle_debug(struct pt_regs *regs, unsigned long *dr6) { struct task_struct *tsk = current; bool icebp; @@ -793,15 +793,13 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6) * then it's very likely the result of an icebp/int01 trap. * User wants a sigtrap for that. */ - icebp = !dr6; + icebp = !*dr6; /* Store the virtualized DR6 value */ - tsk->thread.debugreg6 = dr6; + tsk->thread.debugreg6 = *dr6; - if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0, - SIGTRAP) == NOTIFY_STOP) { - return; - } + if (notify_die(DIE_DEBUG, "debug", regs, (long)dr6, 0, SIGTRAP) == NOTIFY_STOP) + return true; /* It's safe to allow irq's after DR6 has been saved */ cond_local_irq_enable(regs); @@ -815,25 +813,15 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6) /* * Reload dr6, the notifier might have changed it. */ - dr6 = tsk->thread.debugreg6; + *dr6 = tsk->thread.debugreg6; - if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) { - /* - * Historical junk that used to handle SYSENTER single-stepping. - * This should be unreachable now. If we survive for a while - * without anyone hitting this warning, we'll turn this into - * an oops. - */ - tsk->thread.debugreg6 &= ~DR_STEP; - set_tsk_thread_flag(tsk, TIF_SINGLESTEP); - regs->flags &= ~X86_EFLAGS_TF; - } - - if (dr6 & (DR_STEP | DR_TRAP_BITS) || icebp) - send_sigtrap(regs, 0, get_si_code(dr6)); + if (*dr6 & (DR_STEP | DR_TRAP_BITS) || icebp) + send_sigtrap(regs, 0, get_si_code(*dr6)); out: cond_local_irq_disable(regs); + + return false; } static __always_inline void exc_debug_kernel(struct pt_regs *regs, @@ -876,7 +864,20 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs, if (!dr6) goto out; - handle_debug(regs, dr6); + if (handle_debug(regs, &dr6)) + goto out; + + if (WARN_ON_ONCE(dr6 & DR_STEP)) { + /* + * Historical junk that used to handle SYSENTER single-stepping. + * This should be unreachable now. If we survive for a while + * without anyone hitting this warning, we'll turn this into + * an oops. + */ + dr6 &= ~DR_STEP; + set_thread_flag(TIF_SINGLESTEP); + regs->flags &= ~X86_EFLAGS_TF; + } out: instrumentation_end(); @@ -906,7 +907,7 @@ static __always_inline void exc_debug_user(struct pt_regs *regs, irqentry_enter_from_user_mode(regs); instrumentation_begin(); - handle_debug(regs, dr6); + handle_debug(regs, &dr6); instrumentation_end(); irqentry_exit_to_user_mode(regs); |