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powerpc: Snapshot thread flags

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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, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.

Convert them all to the new flag accessor helpers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Link: https://lore.kernel.org/r/20211129130653.2037928-11-mark.rutland@arm.com
This commit is contained in:
Mark Rutland 2021-11-29 13:06:52 +00:00 committed by Thomas Gleixner
parent 08b0af5b2a
commit 985faa7868
2 changed files with 7 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
arch/powerpc/kernel/interrupt.c
View file

@ -181,7 +181,7 @@ 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);
@ -343,7 +343,7 @@ interrupt_exit_user_prepare_main(unsigned long ret, struct pt_regs *regs)
unsigned long ti_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();
if (ti_flags & _TIF_NEED_RESCHED) {
@ -359,7 +359,7 @@ interrupt_exit_user_prepare_main(unsigned long ret, struct pt_regs *regs)
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)) {
@ -437,7 +437,7 @@ 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)))) {
@ -532,8 +532,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
unsigned long flags;
unsigned long ret = 0;
unsigned long kuap;
bool stack_store = current_thread_info()->flags &
_TIF_EMULATE_STACK_STORE;
bool stack_store = read_thread_flags() & _TIF_EMULATE_STACK_STORE;
if (regs_is_unrecoverable(regs))
unrecoverable_exception(regs);
@ -554,7 +553,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
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();
}

3
arch/powerpc/kernel/ptrace/ptrace.c
View file

@ -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);