Re: [tip:x86/mm] x86/mm: Break out user address space handling

Eric W. Biederman
2018-10-15T05:44:22Z

tip-bot for Dave Hansen <tipbot@zytor.com> writes:

> Commit-ID: aa37c51b9421d66f7931c5fdcb9ce80c450974be
> Gitweb: https://git.kernel.org/tip/aa37c51b9421d66f7931c5fdcb9ce80c450974be
> Author: Dave Hansen <dave.hansen@linux.intel.com>
> AuthorDate: Fri, 28 Sep 2018 09:02:23 -0700
> Committer: Peter Zijlstra <peterz@infradead.org>
> CommitDate: Tue, 9 Oct 2018 16:51:15 +0200
>
> x86/mm: Break out user address space handling
>
> The last patch broke out kernel address space handing into its own
> helper. Now, do the same for user address space handling.
>
> Cc: x86@kernel.org
> Cc: Jann Horn <jannh@google.com>
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Andy Lutomirski <luto@kernel.org>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: http://lkml.kernel.org/r/20180928160223.9C4F6440@viggo.jf.intel.com
> ---
> arch/x86/mm/fault.c | 47 ++++++++++++++++++++++++++++-------------------
> 1 file changed, 28 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index c7e32f453852..0d1f5d39fc63 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -966,6 +966,7 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
> __bad_area(regs, error_code, address, vma, SEGV_ACCERR);
> }
>
> +/* Handle faults in the kernel portion of the address space */
^^^^^^
I believe you mean the __user__ portion of the address space.
Given that the call chain is:

do_user_addr_fault
handle_mm_fault
do_sigbus

> static void
> do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
> u32 *pkey, unsigned int fault)
> @@ -1254,14 +1255,11 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
> }
> NOKPROBE_SYMBOL(do_kern_addr_fault);
>
> -/*
> - * This routine handles page faults. It determines the address,
> - * and the problem, and then passes it off to one of the appropriate
> - * routines.
> - */
> -static noinline void
> -__do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
> - unsigned long address)
> +/* Handle faults in the user portion of the address space */
> +static inline
> +void do_user_addr_fault(struct pt_regs *regs,
> + unsigned long hw_error_code,
> + unsigned long address)
> {
> unsigned long sw_error_code;
> struct vm_area_struct *vma;
> @@ -1274,17 +1272,6 @@ __do_page_fault(struct pt_regs *regs, unsigned long hw_error_code,
> tsk = current;
> mm = tsk->mm;
>
> - prefetchw(&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);
> - return;
> - }
> -
> /* kprobes don't want to hook the spurious faults: */
> if (unlikely(kprobes_fault(regs)))
> return;
> @@ -1488,6 +1475,28 @@ good_area:
>
> check_v8086_mode(regs, address, tsk);
> }
> +NOKPROBE_SYMBOL(do_user_addr_fault);
> +
> +/*
> + * This routine handles page faults. It determines the address,
> + * and the problem, and then passes it off to one of the appropriate
> + * routines.
> + */
> +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 nokprobe_inline void

Eric