Re: [tip:x86/mm] x86/mm: Break out user address space handling
* Eric W. Biederman wrote:
> tip-bot for Dave Hansen writes:
>
> > Commit-ID: aa37c51b9421d66f7931c5fdcb9ce80c450974be
> > Gitweb:
> > https://git.kernel.org/tip/aa37c51b9421d66f7931c5fdcb9ce80c450974be
> > Author: Dave Hansen
> > AuthorDate: Fri, 28 Sep 2018 09:02:23 -0700
> > Committer: Peter Zijlstra
> > 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: x...@kernel.org
> > Cc: Jann Horn
> > Cc: Sean Christopherson
> > Cc: Thomas Gleixner
> > Cc: Andy Lutomirski
> > Signed-off-by: Dave Hansen
> > Signed-off-by: Peter Zijlstra (Intel)
> > Link: http://lkml.kernel.org/r/20180928160223.9c4f6...@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
It's both:
/* Handle faults in the kernel portion of the address space */
static void
do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long
address,
u32 *pkey, unsigned int fault)
{
struct task_struct *tsk = current;
int code = BUS_ADRERR;
/* Kernel mode? Handle exceptions or die: */
if (!(error_code & X86_PF_USER)) {
no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
return;
}
/* User-space => ok to do another page fault: */
if (is_prefetch(regs, error_code, address))
return;
tsk->thread.cr2 = address;
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = X86_TRAP_PF;
Note the X86_PF_USER check: that's what determines whether the fault was
for user or system mappings.
I agree that the comment is misleading and should be clarified.
Thanks,
Ingo
Re: [tip:x86/mm] x86/mm: Break out user address space handling
tip-bot for Dave Hansen writes:
> Commit-ID: aa37c51b9421d66f7931c5fdcb9ce80c450974be
> Gitweb:
> https://git.kernel.org/tip/aa37c51b9421d66f7931c5fdcb9ce80c450974be
> Author: Dave Hansen
> AuthorDate: Fri, 28 Sep 2018 09:02:23 -0700
> Committer: Peter Zijlstra
> 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: x...@kernel.org
> Cc: Jann Horn
> Cc: Sean Christopherson
> Cc: Thomas Gleixner
> Cc: Andy Lutomirski
> Signed-off-by: Dave Hansen
> Signed-off-by: Peter Zijlstra (Intel)
> Link: http://lkml.kernel.org/r/20180928160223.9c4f6...@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(¤t->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
[tip:x86/mm] x86/mm: Break out user address space handling
Commit-ID: aa37c51b9421d66f7931c5fdcb9ce80c450974be
Gitweb: https://git.kernel.org/tip/aa37c51b9421d66f7931c5fdcb9ce80c450974be
Author: Dave Hansen
AuthorDate: Fri, 28 Sep 2018 09:02:23 -0700
Committer: Peter Zijlstra
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: x...@kernel.org
Cc: Jann Horn
Cc: Sean Christopherson
Cc: Thomas Gleixner
Cc: Andy Lutomirski
Signed-off-by: Dave Hansen
Signed-off-by: Peter Zijlstra (Intel)
Link: http://lkml.kernel.org/r/20180928160223.9c4f6...@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 */
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(¤t->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
