Messages in this thread | | | Subject | Re: [patch V4 part 2 05/18] x86/entry: Move irq tracing on syscall entry to C-code | From | Alexandre Chartre <> | Date | Thu, 7 May 2020 15:55:40 +0200 |
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On 5/5/20 3:41 PM, Thomas Gleixner wrote: > Now that the C entry points are safe, move the irq flags tracing code into > the entry helper: > > - Invoke lockdep before calling into context tracking > > - Use the safe trace_hardirqs_on_prepare() trace function after context > tracking established state and RCU is watching. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > arch/x86/entry/common.c | 21 +++++++++++++++++++-- > arch/x86/entry/entry_32.S | 12 ------------ > arch/x86/entry/entry_64.S | 2 -- > arch/x86/entry/entry_64_compat.S | 18 ------------------ > 4 files changed, 19 insertions(+), 34 deletions(-) > > --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -40,19 +40,36 @@ > #include <trace/events/syscalls.h> > > #ifdef CONFIG_CONTEXT_TRACKING > -/* Called on entry from user mode with IRQs off. */ > +/** > + * enter_from_user_mode - Establish state when coming from user mode > + * > + * Syscall entry disables interrupts, but user mode is traced as interrupts > + * enabled. Also with NO_HZ_FULL RCU might be idle. > + * > + * 1) Tell lockdep that interrupts are disabled > + * 2) Invoke context tracking if enabled to reactivate RCU > + * 3) Trace interrupts off state > + */ > __visible noinstr void enter_from_user_mode(void) > { > enum ctx_state state = ct_state(); > > + lockdep_hardirqs_off(CALLER_ADDR0); > user_exit_irqoff(); > > instr_begin(); > CT_WARN_ON(state != CONTEXT_USER); > + trace_hardirqs_off_prepare(); > instr_end(); > } > #else > -static inline void enter_from_user_mode(void) {} > +static __always_inline void enter_from_user_mode(void) > +{ > + lockdep_hardirqs_off(CALLER_ADDR0); > + instr_begin(); > + trace_hardirqs_off_prepare(); > + instr_end(); > +} > #endif > > static noinstr void exit_to_user_mode(void) > --- a/arch/x86/entry/entry_32.S > +++ b/arch/x86/entry/entry_32.S > @@ -967,12 +967,6 @@ SYM_FUNC_START(entry_SYSENTER_32) > jnz .Lsysenter_fix_flags > .Lsysenter_flags_fixed: > > - /* > - * User mode is traced as though IRQs are on, and SYSENTER > - * turned them off. > - */ > - TRACE_IRQS_OFF > - > movl %esp, %eax > call do_fast_syscall_32 > /* XEN PV guests always use IRET path */ > @@ -1082,12 +1076,6 @@ SYM_FUNC_START(entry_INT80_32) > > SAVE_ALL pt_regs_ax=$-ENOSYS switch_stacks=1 /* save rest */ > > - /* > - * User mode is traced as though IRQs are on, and the interrupt gate > - * turned them off. > - */ > - TRACE_IRQS_OFF > - > movl %esp, %eax > call do_int80_syscall_32 > .Lsyscall_32_done: > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -167,8 +167,6 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_h > > PUSH_AND_CLEAR_REGS rax=$-ENOSYS > > - TRACE_IRQS_OFF > - > /* IRQs are off. */ > movq %rax, %rdi > movq %rsp, %rsi > --- a/arch/x86/entry/entry_64_compat.S > +++ b/arch/x86/entry/entry_64_compat.S > @@ -129,12 +129,6 @@ SYM_FUNC_START(entry_SYSENTER_compat) > jnz .Lsysenter_fix_flags > .Lsysenter_flags_fixed: > > - /* > - * User mode is traced as though IRQs are on, and SYSENTER > - * turned them off. > - */ > - TRACE_IRQS_OFF > - > movq %rsp, %rdi > call do_fast_syscall_32 > /* XEN PV guests always use IRET path */ > @@ -247,12 +241,6 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_aft > pushq $0 /* pt_regs->r15 = 0 */ > xorl %r15d, %r15d /* nospec r15 */ > > - /* > - * User mode is traced as though IRQs are on, and SYSENTER > - * turned them off. > - */ > - TRACE_IRQS_OFF > - > movq %rsp, %rdi > call do_fast_syscall_32 > /* XEN PV guests always use IRET path */ > @@ -403,12 +391,6 @@ SYM_CODE_START(entry_INT80_compat) > xorl %r15d, %r15d /* nospec r15 */ > cld > > - /* > - * User mode is traced as though IRQs are on, and the interrupt > - * gate turned them off. > - */ > - TRACE_IRQS_OFF > - > movq %rsp, %rdi > call do_int80_syscall_32 > .Lsyscall_32_done: >
enter_from_user_mode() is also called with the CALL_enter_from_user_mode macro, which is used in interrupt_entry() and identry. Don't you need to also remove the TRACE_IRQS_OFF there now?
alex.
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