x86/context-tracking: Remove exception_enter/exit() from do_page_fault() (ee6352b2) · Commits · 戴 / test

do_page_fault(), like other exceptions, is already covered by user_enter() and user_exit() when the exception triggers in userspace. As explained in: ("x86/entry: Remove exception_enter() from most trap handlers") exception_enter/exit() only remained to handle possible page fault from kernel mode while context tracking is in CONTEXT_USER mode, ie: on kernel entry before we manage to call user_exit(). The only known offender was do_fast_syscall_32() fetching EBP register from where vDSO stashed it. Meanwhile this got fixed in: ("x86/entry: Call enter_from_user_mode() with IRQs off") that moved enter_from_user_mode() before the call to get_user(). So we can safely remove it now. Signed-off-by:

Frederic Weisbecker <frederic@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Jim Mattson <jmattson@google.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Wanpeng Li <wanpengli@tencent.com> Link: https://lkml.kernel.org/r/20191227163612.10039-2-frederic@kernel.org Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/mm/fault.c

+12 −27

Original line number	Diff line number	Diff line
		@@ -1486,27 +1486,6 @@ good_area:
		}
		NOKPROBE_SYMBOL(do_user_addr_fault);

		/*
		* Explicitly marked noinline such that the function tracer sees this as the
		* page_fault entry point.
		*/
		static noinline void
		__do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
		unsigned long address)
		{
		prefetchw(&current->mm->mmap_sem);

		if (unlikely(kmmio_fault(regs, address)))
		return;

		/* Was the fault on kernel-controlled part of the address space? */
		if (unlikely(fault_in_kernel_space(address)))
		do_kern_addr_fault(regs, hw_error_code, address);
		else
		do_user_addr_fault(regs, hw_error_code, address);
		}
		NOKPROBE_SYMBOL(__do_page_fault);

		static __always_inline void
		trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
		@@ -1521,13 +1500,19 @@ trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
		}

		dotraplinkage void
		do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address)
		do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
		unsigned long address)
		{
		enum ctx_state prev_state;
		prefetchw(&current->mm->mmap_sem);
		trace_page_fault_entries(regs, hw_error_code, address);

		prev_state = exception_enter();
		trace_page_fault_entries(regs, error_code, address);
		__do_page_fault(regs, error_code, address);
		exception_exit(prev_state);
		if (unlikely(kmmio_fault(regs, address)))
		return;

		/* Was the fault on kernel-controlled part of the address space? */
		if (unlikely(fault_in_kernel_space(address)))
		do_kern_addr_fault(regs, hw_error_code, address);
		else
		do_user_addr_fault(regs, hw_error_code, address);
		}
		NOKPROBE_SYMBOL(do_page_fault);

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