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x86/entry: Implement user mode C entry points for #DB and #MCE
The MCE entry point uses the same mechanism as the IST entry point for now. For #DB split the inner workings and just keep the nmi_enter/exit() magic in the IST variant. Fixup the ASM code to emit the proper noist_##cfunc call. 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/20200505135315.177564104@linutronix.de
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f08e32ec3c
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3 changed files with 94 additions and 30 deletions
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@ -657,7 +657,7 @@ SYM_CODE_START(\asmsym)
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/* Switch to the regular task stack and use the noist entry point */
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.Lfrom_usermode_switch_stack_\@:
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idtentry_body vector \cfunc, has_error_code=0
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idtentry_body vector noist_\cfunc, has_error_code=0 sane=1
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_ASM_NOKPROBE(\asmsym)
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SYM_CODE_END(\asmsym)
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@ -1904,25 +1904,51 @@ static void unexpected_machine_check(struct pt_regs *regs)
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/* Call the installed machine check handler for this CPU setup. */
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void (*machine_check_vector)(struct pt_regs *) = unexpected_machine_check;
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DEFINE_IDTENTRY_MCE(exc_machine_check)
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static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
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{
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/*
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* Only required when from kernel mode. See
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* mce_check_crashing_cpu() for details.
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*/
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if (machine_check_vector == do_machine_check &&
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mce_check_crashing_cpu())
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return;
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if (user_mode(regs))
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idtentry_enter(regs);
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else
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nmi_enter();
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machine_check_vector(regs);
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if (user_mode(regs))
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idtentry_exit(regs);
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else
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nmi_exit();
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}
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static __always_inline void exc_machine_check_user(struct pt_regs *regs)
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{
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idtentry_enter(regs);
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machine_check_vector(regs);
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idtentry_exit(regs);
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}
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#ifdef CONFIG_X86_64
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/* MCE hit kernel mode */
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DEFINE_IDTENTRY_MCE(exc_machine_check)
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{
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exc_machine_check_kernel(regs);
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}
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/* The user mode variant. */
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DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
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{
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exc_machine_check_user(regs);
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}
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#else
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/* 32bit unified entry point */
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DEFINE_IDTENTRY_MCE(exc_machine_check)
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{
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if (user_mode(regs))
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exc_machine_check_user(regs);
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else
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exc_machine_check_kernel(regs);
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}
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#endif
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/*
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* Called for each booted CPU to set up machine checks.
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* Must be called with preempt off:
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@ -775,20 +775,12 @@ static __always_inline void debug_exit(unsigned long dr7)
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*
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* May run on IST stack.
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*/
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DEFINE_IDTENTRY_DEBUG(exc_debug)
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static noinstr void 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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unsigned long dr6, dr7;
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int user_icebp = 0;
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int si_code;
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debug_enter(&dr6, &dr7);
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if (user_mode(regs))
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idtentry_enter(regs);
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else
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nmi_enter();
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/*
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* The SDM says "The processor clears the BTF flag when it
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* generates a debug exception." Clear TIF_BLOCKSTEP to keep
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@ -800,7 +792,7 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
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is_sysenter_singlestep(regs))) {
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dr6 &= ~DR_STEP;
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if (!dr6)
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goto exit;
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return;
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/*
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* else we might have gotten a single-step trap and hit a
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* watchpoint at the same time, in which case we should fall
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@ -821,12 +813,12 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
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#ifdef CONFIG_KPROBES
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if (kprobe_debug_handler(regs))
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goto exit;
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return;
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#endif
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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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goto exit;
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return;
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/*
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* Let others (NMI) know that the debug stack is in use
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@ -842,7 +834,7 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
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X86_TRAP_DB);
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cond_local_irq_disable(regs);
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debug_stack_usage_dec();
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goto exit;
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return;
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}
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if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
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@ -861,15 +853,61 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
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send_sigtrap(regs, 0, si_code);
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cond_local_irq_disable(regs);
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debug_stack_usage_dec();
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}
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exit:
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if (user_mode(regs))
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idtentry_exit(regs);
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else
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static __always_inline void exc_debug_kernel(struct pt_regs *regs,
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unsigned long dr6)
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{
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nmi_enter();
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handle_debug(regs, dr6);
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nmi_exit();
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}
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static __always_inline void exc_debug_user(struct pt_regs *regs,
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unsigned long dr6)
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{
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idtentry_enter(regs);
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handle_debug(regs, dr6);
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idtentry_exit(regs);
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}
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#ifdef CONFIG_X86_64
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/* IST stack entry */
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DEFINE_IDTENTRY_DEBUG(exc_debug)
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{
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unsigned long dr6, dr7;
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debug_enter(&dr6, &dr7);
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exc_debug_kernel(regs, dr6);
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debug_exit(dr7);
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}
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/* User entry, runs on regular task stack */
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DEFINE_IDTENTRY_DEBUG_USER(exc_debug)
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{
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unsigned long dr6, dr7;
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debug_enter(&dr6, &dr7);
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exc_debug_user(regs, dr6);
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debug_exit(dr7);
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}
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#else
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/* 32 bit does not have separate entry points. */
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DEFINE_IDTENTRY_DEBUG(exc_debug)
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{
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unsigned long dr6, dr7;
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debug_enter(&dr6, &dr7);
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if (user_mode(regs))
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exc_debug_user(regs, dr6);
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else
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exc_debug_kernel(regs, dr6);
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debug_exit(dr7);
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}
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#endif
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/*
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* Note that we play around with the 'TS' bit in an attempt to get
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* the correct behaviour even in the presence of the asynchronous
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