Messages in this thread Patch in this message | | | From | Mark Rutland <> | Subject | [RFC PATCH 09/10] powerpc: snapshot thread flags | Date | Wed, 9 Jun 2021 13:20:00 +0100 |
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Some thread flags can be set remotely, and so even when IRQs are disabled, the flags can change under our feet. Generally this is unlikely to cause a problem in practice, but it is somewhat unsound, and KCSAN will legitimately warn that there is a data race.
To avoid such issues, we should snapshot the flags prior to using them. Let's use the new helpers to do so on powerpc.
Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> --- arch/powerpc/kernel/interrupt.c | 16 ++++++++-------- arch/powerpc/kernel/ptrace/ptrace.c | 3 +-- 2 files changed, 9 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index e0938ba298f2..f6150a4b3d1b 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c @@ -92,7 +92,7 @@ notrace long system_call_exception(long r3, long r4, long r5, local_irq_enable(); - if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) { + if (unlikely(read_thread_flags() & _TIF_SYSCALL_DOTRACE)) { if (unlikely(trap_is_unsupported_scv(regs))) { /* Unsupported scv vector */ _exception(SIGILL, regs, ILL_ILLOPC, regs->nip); @@ -257,7 +257,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3, /* Check whether the syscall is issued inside a restartable sequence */ rseq_syscall(regs); - ti_flags = current_thread_info()->flags; + ti_flags = read_thread_flags(); if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && is_not_scv) { if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) { @@ -284,7 +284,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3, local_irq_disable(); again: - ti_flags = READ_ONCE(current_thread_info()->flags); + ti_flags = read_thread_flags(); while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) { local_irq_enable(); if (ti_flags & _TIF_NEED_RESCHED) { @@ -300,7 +300,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3, do_notify_resume(regs, ti_flags); } local_irq_disable(); - ti_flags = READ_ONCE(current_thread_info()->flags); + ti_flags = read_thread_flags(); } if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) { @@ -373,7 +373,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned local_irq_save(flags); again: - ti_flags = READ_ONCE(current_thread_info()->flags); + ti_flags = read_thread_flags(); while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) { local_irq_enable(); /* returning to user: may enable */ if (ti_flags & _TIF_NEED_RESCHED) { @@ -384,7 +384,7 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned do_notify_resume(regs, ti_flags); } local_irq_disable(); - ti_flags = READ_ONCE(current_thread_info()->flags); + ti_flags = read_thread_flags(); } if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && IS_ENABLED(CONFIG_PPC_FPU)) { @@ -450,7 +450,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign kuap = kuap_get_and_assert_locked(); - if (unlikely(current_thread_info()->flags & _TIF_EMULATE_STACK_STORE)) { + if (unlikely(read_thread_flags() & _TIF_EMULATE_STACK_STORE)) { clear_bits(_TIF_EMULATE_STACK_STORE, ¤t_thread_info()->flags); ret = 1; } @@ -463,7 +463,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsign again: if (IS_ENABLED(CONFIG_PREEMPT)) { /* Return to preemptible kernel context */ - if (unlikely(current_thread_info()->flags & _TIF_NEED_RESCHED)) { + if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) { if (preempt_count() == 0) preempt_schedule_irq(); } diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c index 0a0a33eb0d28..d174570a144e 100644 --- a/arch/powerpc/kernel/ptrace/ptrace.c +++ b/arch/powerpc/kernel/ptrace/ptrace.c @@ -260,8 +260,7 @@ long do_syscall_trace_enter(struct pt_regs *regs) { u32 flags; - flags = READ_ONCE(current_thread_info()->flags) & - (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE); + flags = read_thread_flags() & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE); if (flags) { int rc = tracehook_report_syscall_entry(regs); -- 2.11.0
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