From f0a97af83f6287357dcc100c859ec0066f164f32 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 20 Aug 2015 22:03:21 -0700 Subject: [PATCH] x86/traps: Weaken context tracking entry assertions We were asserting that we were all the way in CONTEXT_KERNEL when exception handlers were called. While having this be true is, I think, a nice goal (or maybe a variant in which we assert that we're in CONTEXT_KERNEL or some new IRQ context), we're not quite there. In particular, if an IRQ interrupts the SYSCALL prologue and the IRQ handler in turn causes an exception, the exception entry will be called in RCU IRQ mode but with CONTEXT_USER. This is okay (nothing goes wrong), but until we fix up the SYSCALL prologue, we need to avoid warning. Signed-off-by: Andy Lutomirski Acked-by: Frederic Weisbecker Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Sasha Levin Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/c81faf3916346c0e04346c441392974f49cd7184.1440133286.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/traps.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 86a82eafb96f..45e8d9891fa3 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -112,7 +112,7 @@ static inline void preempt_conditional_cli(struct pt_regs *regs) void ist_enter(struct pt_regs *regs) { if (user_mode(regs)) { - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); } else { /* * We might have interrupted pretty much anything. In @@ -282,7 +282,7 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str, { siginfo_t info; - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) != NOTIFY_STOP) { @@ -364,7 +364,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) const struct bndcsr *bndcsr; siginfo_t *info; - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); if (notify_die(DIE_TRAP, "bounds", regs, error_code, X86_TRAP_BR, SIGSEGV) == NOTIFY_STOP) return; @@ -442,7 +442,7 @@ do_general_protection(struct pt_regs *regs, long error_code) { struct task_struct *tsk; - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); conditional_sti(regs); if (v8086_mode(regs)) { @@ -496,7 +496,7 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) return; ist_enter(regs); - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP, SIGTRAP) == NOTIFY_STOP) @@ -729,14 +729,14 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr) dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code) { - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); math_error(regs, error_code, X86_TRAP_MF); } dotraplinkage void do_simd_coprocessor_error(struct pt_regs *regs, long error_code) { - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); math_error(regs, error_code, X86_TRAP_XF); } @@ -749,7 +749,7 @@ do_spurious_interrupt_bug(struct pt_regs *regs, long error_code) dotraplinkage void do_device_not_available(struct pt_regs *regs, long error_code) { - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); BUG_ON(use_eager_fpu()); #ifdef CONFIG_MATH_EMULATION @@ -775,7 +775,7 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code) { siginfo_t info; - CT_WARN_ON(ct_state() != CONTEXT_KERNEL); + rcu_lockdep_assert(rcu_is_watching(), "entry code didn't wake RCU"); local_irq_enable(); info.si_signo = SIGILL; -- 2.20.1