Re: [PATCH v7 02/26] x86/mm: Relocate page fault error codes to traps.h

[Ricardo Neri]

On Sat, 2017-05-27 at 12:13 +0200, Borislav Petkov wrote:
> On Fri, May 26, 2017 at 08:40:26PM -0700, Ricardo Neri wrote:
> > This change was initially intended to only rename the error codes,
> > without functional changes. Would making change be considered a
> change
> > in functionality?
> 
> How?
> 
> The before-and-after asm should be the identical.

Yes but it reads differently. I just wanted to double check. I will make
this change, which keeps functionality but is written differently.

Thanks and BR,
Ricardo


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Re: [PATCH v7 02/26] x86/mm: Relocate page fault error codes to traps.h

[Borislav Petkov]

On Fri, May 26, 2017 at 08:40:26PM -0700, Ricardo Neri wrote:
> This change was initially intended to only rename the error codes,
> without functional changes. Would making change be considered a change
> in functionality?

How?

The before-and-after asm should be the identical.

-- 
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 
(AG Nürnberg)
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Re: [PATCH v7 02/26] x86/mm: Relocate page fault error codes to traps.h

[Ricardo Neri]

On Sun, 2017-05-21 at 16:23 +0200, Borislav Petkov wrote:
> On Fri, May 05, 2017 at 11:17:00AM -0700, Ricardo Neri wrote:
> > Up to this point, only fault.c used the definitions of the page fault error
> > codes. Thus, it made sense to keep them within such file. Other portions of
> > code might be interested in those definitions too. For instance, the User-
> > Mode Instruction Prevention emulation code will use such definitions to
> > emulate a page fault when it is unable to successfully copy the results
> > of the emulated instructions to user space.
> > 
> > While relocating the error code enumeration, the prefix X86_ is used to
> > make it consistent with the rest of the definitions in traps.h. Of course,
> > code using the enumeration had to be updated as well. No functional changes
> > were performed.
> > 
> > Cc: Thomas Gleixner 
> > Cc: Ingo Molnar 
> > Cc: "H. Peter Anvin" 
> > Cc: Andy Lutomirski 
> > Cc: "Kirill A. Shutemov" 
> > Cc: Josh Poimboeuf 
> > Cc: Dave Hansen 
> > Cc: Paul Gortmaker 
> > Cc: x...@kernel.org
> > Reviewed-by: Andy Lutomirski 
> > Signed-off-by: Ricardo Neri 
> > ---
> >  arch/x86/include/asm/traps.h | 18 +
> >  arch/x86/mm/fault.c  | 88 
> > +---
> >  2 files changed, 52 insertions(+), 54 deletions(-)
> 
> ...
> 
> > @@ -1382,7 +1362,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long 
> > error_code,
> >  * space check, thus avoiding the deadlock:
> >  */
> > if (unlikely(!down_read_trylock(>mmap_sem))) {
> > -   if ((error_code & PF_USER) == 0 &&
> > +   if ((error_code & X86_PF_USER) == 0 &&
> 
>   if (!(error_code & X86_PF_USER))

This change was initially intended to only rename the error codes,
without functional changes. Would making change be considered a change
in functionality? The behavior would be preserved, though.

Thanks and BR,
Ricardo


> 
> With that fixed:
> 
> Reviewed-by: Borislav Petkov 

Thank you for your review!

BR,
Ricardo
> 
> -- 
> Regards/Gruss,
> Boris.
> 
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 
> 21284 (AG Nürnberg)


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Re: [PATCH v7 02/26] x86/mm: Relocate page fault error codes to traps.h

[Borislav Petkov]

On Fri, May 05, 2017 at 11:17:00AM -0700, Ricardo Neri wrote:
> Up to this point, only fault.c used the definitions of the page fault error
> codes. Thus, it made sense to keep them within such file. Other portions of
> code might be interested in those definitions too. For instance, the User-
> Mode Instruction Prevention emulation code will use such definitions to
> emulate a page fault when it is unable to successfully copy the results
> of the emulated instructions to user space.
> 
> While relocating the error code enumeration, the prefix X86_ is used to
> make it consistent with the rest of the definitions in traps.h. Of course,
> code using the enumeration had to be updated as well. No functional changes
> were performed.
> 
> Cc: Thomas Gleixner 
> Cc: Ingo Molnar 
> Cc: "H. Peter Anvin" 
> Cc: Andy Lutomirski 
> Cc: "Kirill A. Shutemov" 
> Cc: Josh Poimboeuf 
> Cc: Dave Hansen 
> Cc: Paul Gortmaker 
> Cc: x...@kernel.org
> Reviewed-by: Andy Lutomirski 
> Signed-off-by: Ricardo Neri 
> ---
>  arch/x86/include/asm/traps.h | 18 +
>  arch/x86/mm/fault.c  | 88 
> +---
>  2 files changed, 52 insertions(+), 54 deletions(-)

...

> @@ -1382,7 +1362,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long 
> error_code,
>* space check, thus avoiding the deadlock:
>*/
>   if (unlikely(!down_read_trylock(>mmap_sem))) {
> - if ((error_code & PF_USER) == 0 &&
> + if ((error_code & X86_PF_USER) == 0 &&

if (!(error_code & X86_PF_USER))

With that fixed:

Reviewed-by: Borislav Petkov 

-- 
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 
(AG Nürnberg)
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[PATCH v7 02/26] x86/mm: Relocate page fault error codes to traps.h

[Ricardo Neri]

Up to this point, only fault.c used the definitions of the page fault error
codes. Thus, it made sense to keep them within such file. Other portions of
code might be interested in those definitions too. For instance, the User-
Mode Instruction Prevention emulation code will use such definitions to
emulate a page fault when it is unable to successfully copy the results
of the emulated instructions to user space.

While relocating the error code enumeration, the prefix X86_ is used to
make it consistent with the rest of the definitions in traps.h. Of course,
code using the enumeration had to be updated as well. No functional changes
were performed.

Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Andy Lutomirski 
Cc: "Kirill A. Shutemov" 
Cc: Josh Poimboeuf 
Cc: Dave Hansen 
Cc: Paul Gortmaker 
Cc: x...@kernel.org
Reviewed-by: Andy Lutomirski 
Signed-off-by: Ricardo Neri 
---
 arch/x86/include/asm/traps.h | 18 +
 arch/x86/mm/fault.c  | 88 +---
 2 files changed, 52 insertions(+), 54 deletions(-)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 01fd0a7..4a2e585 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -148,4 +148,22 @@ enum {
X86_TRAP_IRET = 32, /* 32, IRET Exception */
 };
 
+/*
+ * Page fault error code bits:
+ *
+ *   bit 0 ==   0: no page found   1: protection fault
+ *   bit 1 ==   0: read access 1: write access
+ *   bit 2 ==   0: kernel-mode access  1: user-mode access
+ *   bit 3 ==  1: use of reserved bit detected
+ *   bit 4 ==  1: fault was an instruction fetch
+ *   bit 5 ==  1: protection keys block access
+ */
+enum x86_pf_error_code {
+   X86_PF_PROT =   1 << 0,
+   X86_PF_WRITE=   1 << 1,
+   X86_PF_USER =   1 << 2,
+   X86_PF_RSVD =   1 << 3,
+   X86_PF_INSTR=   1 << 4,
+   X86_PF_PK   =   1 << 5,
+};
 #endif /* _ASM_X86_TRAPS_H */
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 8ad91a0..32f3070 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -29,26 +29,6 @@
 #include 
 
 /*
- * Page fault error code bits:
- *
- *   bit 0 ==   0: no page found   1: protection fault
- *   bit 1 ==   0: read access 1: write access
- *   bit 2 ==   0: kernel-mode access  1: user-mode access
- *   bit 3 ==  1: use of reserved bit detected
- *   bit 4 ==  1: fault was an instruction fetch
- *   bit 5 ==  1: protection keys block access
- */
-enum x86_pf_error_code {
-
-   PF_PROT =   1 << 0,
-   PF_WRITE=   1 << 1,
-   PF_USER =   1 << 2,
-   PF_RSVD =   1 << 3,
-   PF_INSTR=   1 << 4,
-   PF_PK   =   1 << 5,
-};
-
-/*
  * Returns 0 if mmiotrace is disabled, or if the fault is not
  * handled by mmiotrace:
  */
@@ -149,7 +129,7 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, 
unsigned long addr)
 * If it was a exec (instruction fetch) fault on NX page, then
 * do not ignore the fault:
 */
-   if (error_code & PF_INSTR)
+   if (error_code & X86_PF_INSTR)
return 0;
 
instr = (void *)convert_ip_to_linear(current, regs);
@@ -179,7 +159,7 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, 
unsigned long addr)
  * siginfo so userspace can discover which protection key was set
  * on the PTE.
  *
- * If we get here, we know that the hardware signaled a PF_PK
+ * If we get here, we know that the hardware signaled a X86_PF_PK
  * fault and that there was a VMA once we got in the fault
  * handler.  It does *not* guarantee that the VMA we find here
  * was the one that we faulted on.
@@ -205,7 +185,7 @@ static void fill_sig_info_pkey(int si_code, siginfo_t *info,
/*
 * force_sig_info_fault() is called from a number of
 * contexts, some of which have a VMA and some of which
-* do not.  The PF_PK handing happens after we have a
+* do not.  The X86_PF_PK handing happens after we have a
 * valid VMA, so we should never reach this without a
 * valid VMA.
 */
@@ -695,7 +675,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long 
error_code,
if (!oops_may_print())
return;
 
-   if (error_code & PF_INSTR) {
+   if (error_code & X86_PF_INSTR) {
unsigned int level;
pgd_t *pgd;