Messages in this thread | | | Subject | Re: [patch part-II V2 12/13] x86/entry: Move irq flags tracing to prepare_exit_to_usermode() | From | Alexandre Chartre <> | Date | Tue, 10 Mar 2020 15:03:46 +0100 |
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On 3/8/20 11:24 PM, Thomas Gleixner wrote: > This is another step towards more C-code and less convoluted ASM. > > Note, that trace_hardirqs_on() is still incorrect vs. RCU idle when the > tracepoint is used by e.g. BPF. Will be addressed in the next step. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > > V2: New patch simplifying the conversion and addressing Alex' review > comment of redundant tracing. > --- > arch/x86/entry/common.c | 1 + > arch/x86/entry/entry_32.S | 12 ++++-------- > arch/x86/entry/entry_64.S | 4 ---- > arch/x86/entry/entry_64_compat.S | 14 +++++--------- > 4 files changed, 10 insertions(+), 21 deletions(-)
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
alex.
> --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -253,6 +253,7 @@ static noinline void __prepare_exit_to_u > > user_enter_irqoff(); > mds_user_clear_cpu_buffers(); > + trace_hardirqs_on(); > } > NOKPROBE_SYMBOL(prepare_exit_to_usermode); > > --- a/arch/x86/entry/entry_32.S > +++ b/arch/x86/entry/entry_32.S > @@ -811,8 +811,7 @@ SYM_CODE_START(ret_from_fork) > /* When we fork, we trace the syscall return in the child, too. */ > movl %esp, %eax > call syscall_return_slowpath > - STACKLEAK_ERASE > - jmp restore_all > + jmp .Lsyscall_32_done > > /* kernel thread */ > 1: movl %edi, %eax > @@ -855,7 +854,7 @@ SYM_CODE_START_LOCAL(ret_from_exception) > TRACE_IRQS_OFF > movl %esp, %eax > call prepare_exit_to_usermode > - jmp restore_all > + jmp restore_all_switch_stack > SYM_CODE_END(ret_from_exception) > > SYM_ENTRY(__begin_SYSENTER_singlestep_region, SYM_L_GLOBAL, SYM_A_NONE) > @@ -968,8 +967,7 @@ SYM_FUNC_START(entry_SYSENTER_32) > > STACKLEAK_ERASE > > -/* Opportunistic SYSEXIT */ > - TRACE_IRQS_ON /* User mode traces as IRQs on. */ > + /* Opportunistic SYSEXIT */ > > /* > * Setup entry stack - we keep the pointer in %eax and do the > @@ -1072,11 +1070,9 @@ SYM_FUNC_START(entry_INT80_32) > movl %esp, %eax > call do_int80_syscall_32 > .Lsyscall_32_done: > - > STACKLEAK_ERASE > > -restore_all: > - TRACE_IRQS_ON > +restore_all_switch_stack: > SWITCH_TO_ENTRY_STACK > CHECK_AND_APPLY_ESPFIX > > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -172,8 +172,6 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_h > movq %rsp, %rsi > call do_syscall_64 /* returns with IRQs disabled */ > > - TRACE_IRQS_ON /* return enables interrupts */ > - > /* > * Try to use SYSRET instead of IRET if we're returning to > * a completely clean 64-bit userspace context. If we're not, > @@ -340,7 +338,6 @@ SYM_CODE_START(ret_from_fork) > UNWIND_HINT_REGS > movq %rsp, %rdi > call syscall_return_slowpath /* returns with IRQs disabled */ > - TRACE_IRQS_ON /* user mode is traced as IRQS on */ > jmp swapgs_restore_regs_and_return_to_usermode > > 1: > @@ -617,7 +614,6 @@ SYM_CODE_START_LOCAL(common_interrupt) > .Lretint_user: > mov %rsp,%rdi > call prepare_exit_to_usermode > - TRACE_IRQS_ON > > SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL) > #ifdef CONFIG_DEBUG_ENTRY > --- a/arch/x86/entry/entry_64_compat.S > +++ b/arch/x86/entry/entry_64_compat.S > @@ -132,8 +132,8 @@ SYM_FUNC_START(entry_SYSENTER_compat) > movq %rsp, %rdi > call do_fast_syscall_32 > /* XEN PV guests always use IRET path */ > - ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ > - "jmp .Lsyscall_32_done", X86_FEATURE_XENPV > + ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \ > + "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV > jmp sysret32_from_system_call > > .Lsysenter_fix_flags: > @@ -244,8 +244,8 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_aft > movq %rsp, %rdi > call do_fast_syscall_32 > /* XEN PV guests always use IRET path */ > - ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ > - "jmp .Lsyscall_32_done", X86_FEATURE_XENPV > + ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \ > + "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV > > /* Opportunistic SYSRET */ > sysret32_from_system_call: > @@ -254,7 +254,7 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_aft > * stack. So let's erase the thread stack right now. > */ > STACKLEAK_ERASE > - TRACE_IRQS_ON /* User mode traces as IRQs on. */ > + > movq RBX(%rsp), %rbx /* pt_regs->rbx */ > movq RBP(%rsp), %rbp /* pt_regs->rbp */ > movq EFLAGS(%rsp), %r11 /* pt_regs->flags (in r11) */ > @@ -393,9 +393,5 @@ SYM_CODE_START(entry_INT80_compat) > > movq %rsp, %rdi > call do_int80_syscall_32 > -.Lsyscall_32_done: > - > - /* Go back to user mode. */ > - TRACE_IRQS_ON > jmp swapgs_restore_regs_and_return_to_usermode > SYM_CODE_END(entry_INT80_compat) >
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