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x86/context-tracking: Remove exception_enter/exit() from do_page_fault() 

do_page_fault(), like other exceptions, is already covered by
user_enter() and user_exit() when the exception triggers in userspace.

As explained in:

  8c84014f3b ("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:

  9999c8c01f ("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>
This commit is contained in:
Frederic Weisbecker 2019-12-27 17:36:11 +01:00 committed by Ingo Molnar
parent c79f46a282
commit ee6352b2c4
1 changed files with 12 additions and 27 deletions
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39
arch/x86/mm/fault.c
View File

@ -1486,27 +1486,6 @@ void do_user_addr_fault(struct pt_regs *regs,
}
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);