Jan Kiszka wrote:
> As we may switch the Linux context as a result of calling
> __ipipe_dispatch_event and, thus, may leave it with a different root
> domain state independent of the return code, we have to call __fixup_if
> unconditionally. Moreover, we should also always check for pending VIRQs
> on return.
>
> Signed-off-by: Jan Kiszka <[email protected]>
>
> ---
> arch/x86/kernel/ipipe.c | 24 ++++++++++++++++--------
> 1 file changed, 16 insertions(+), 8 deletions(-)
>
> Index: b/arch/x86/kernel/ipipe.c
> ===================================================================
> --- a/arch/x86/kernel/ipipe.c
> +++ b/arch/x86/kernel/ipipe.c
> @@ -540,6 +540,7 @@ asmlinkage void __ipipe_unstall_iret_roo
> asmlinkage int __ipipe_syscall_root(struct pt_regs regs)
> {
> unsigned long flags;
> + int dont_pass;
>
> __fixup_if(®s);
>
> @@ -551,8 +552,9 @@ asmlinkage int __ipipe_syscall_root(stru
> tail work has to be performed (for handling signals etc). */
>
> if (__ipipe_syscall_watched_p(current, regs.orig_ax) &&
> - __ipipe_event_monitored_p(IPIPE_EVENT_SYSCALL) &&
> - __ipipe_dispatch_event(IPIPE_EVENT_SYSCALL,®s) > 0) {
> + __ipipe_event_monitored_p(IPIPE_EVENT_SYSCALL)) {
> + dont_pass = __ipipe_dispatch_event(IPIPE_EVENT_SYSCALL,®s);
> +
> /* We might enter here over a non-root domain and exit
> * over the root one as a result of the syscall
> * (i.e. by recycling the register set of the current
> @@ -568,9 +570,10 @@ asmlinkage int __ipipe_syscall_root(stru
> if ((ipipe_root_cpudom_var(irqpend_himask) &
> IPIPE_IRQMASK_VIRT) != 0)
> __ipipe_sync_pipeline(IPIPE_IRQMASK_VIRT);
> local_irq_restore_hw(flags);
> - return -1;
> - }
> - return 1;
> + if (dont_pass)
> + return -1;
> + } else if (dont_pass)
> + return 1;
> }
>
> return 0;
> @@ -610,6 +613,7 @@ asmlinkage int __ipipe_preempt_schedule_
> asmlinkage int __ipipe_syscall_root(struct pt_regs *regs)
> {
> unsigned long flags;
> + int pass;
>
> __fixup_if(regs);
>
This needs fixing; a thread relaxing to secondary mode to run a regular Linux
syscall would trigger the issue as well.
> @@ -621,8 +625,9 @@ asmlinkage int __ipipe_syscall_root(stru
> tail work has to be performed (for handling signals etc). */
>
> if (__ipipe_syscall_watched_p(current, regs->orig_ax) &&
> - __ipipe_event_monitored_p(IPIPE_EVENT_SYSCALL) &&
> - __ipipe_dispatch_event(IPIPE_EVENT_SYSCALL, regs) > 0) {
> + __ipipe_event_monitored_p(IPIPE_EVENT_SYSCALL)) {
> + pass = !__ipipe_dispatch_event(IPIPE_EVENT_SYSCALL, regs);
> +
> /* We might enter here over a non-root domain and exit
> * over the root one as a result of the syscall
> * (i.e. by recycling the register set of the current
> @@ -632,6 +637,9 @@ asmlinkage int __ipipe_syscall_root(stru
> * stall bit on exit. */
> __fixup_if(regs);
>
> + if (pass)
> + return 0;
> +
> if (ipipe_root_domain_p && !in_atomic()) {
We may remove the in_atomic() check. This is legacy code that does not serve any
purpose in recent kernels.
> /* Sync pending VIRQs before _TIF_NEED_RESCHED is
> tested. */
> local_irq_save_hw(flags);
> @@ -648,7 +656,7 @@ asmlinkage int __ipipe_syscall_root(stru
> return 1;
> }
>
> - return 0;
> + return 0;
> }
>
> #endif /* !CONFIG_X86_32 */
>
--
Philippe.
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