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[PATCH 2/2] kcov: make kcov work properly with KASLR enabled

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  [PATCH 2/2] kcov: make kcov work properly with KASLR enabled Alexander Popov <alex.popov@linux.com> - 2016-12-11 02:00 +0100
    Re: [PATCH 2/2] kcov: make kcov work properly with KASLR enabled Dmitry Vyukov <dvyukov@google.com> - 2016-12-11 10:40 +0100
      Re: [PATCH 2/2] kcov: make kcov work properly with KASLR enabled Alexander Popov <alex.popov@linux.com> - 2016-12-11 22:40 +0100
        Re: [PATCH 2/2] kcov: make kcov work properly with KASLR enabled Dmitry Vyukov <dvyukov@google.com> - 2016-12-12 08:00 +0100

#1539937 — [PATCH 2/2] kcov: make kcov work properly with KASLR enabled

Subtract KASLR offset from the kernel addresses reported by kcov.
Tested on x86_64 and AArch64 (Hikey LeMaker).

Signed-off-by: Alexander Popov <alex.popov@linux.com>
---
 kernel/kcov.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/kcov.c b/kernel/kcov.c
index 3cbb0c8..f8f3f4c 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -14,6 +14,7 @@
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
 #include <linux/kcov.h>
+#include <asm/setup.h>
 
 /*
  * kcov descriptor (one per opened debugfs file).
@@ -68,6 +69,11 @@ void notrace __sanitizer_cov_trace_pc(void)
 	if (mode == KCOV_MODE_TRACE) {
 		unsigned long *area;
 		unsigned long pos;
+		unsigned long ip = _RET_IP_;
+
+#ifdef CONFIG_RANDOMIZE_BASE
+		ip -= kaslr_offset();
+#endif
 
 		/*
 		 * There is some code that runs in interrupts but for which
@@ -81,7 +87,7 @@ void notrace __sanitizer_cov_trace_pc(void)
 		/* The first word is number of subsequent PCs. */
 		pos = READ_ONCE(area[0]) + 1;
 		if (likely(pos < t->kcov_size)) {
-			area[pos] = _RET_IP_;
+			area[pos] = ip;
 			WRITE_ONCE(area[0], pos);
 		}
 	}
-- 
2.7.4

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#1539995

On Sun, Dec 11, 2016 at 1:50 AM, Alexander Popov <alex.popov@linux.com> wrote:
> Subtract KASLR offset from the kernel addresses reported by kcov.
> Tested on x86_64 and AArch64 (Hikey LeMaker).
>
> Signed-off-by: Alexander Popov <alex.popov@linux.com>
> ---
>  kernel/kcov.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kcov.c b/kernel/kcov.c
> index 3cbb0c8..f8f3f4c 100644
> --- a/kernel/kcov.c
> +++ b/kernel/kcov.c
> @@ -14,6 +14,7 @@
>  #include <linux/debugfs.h>
>  #include <linux/uaccess.h>
>  #include <linux/kcov.h>
> +#include <asm/setup.h>
>
>  /*
>   * kcov descriptor (one per opened debugfs file).
> @@ -68,6 +69,11 @@ void notrace __sanitizer_cov_trace_pc(void)
>         if (mode == KCOV_MODE_TRACE) {
>                 unsigned long *area;
>                 unsigned long pos;
> +               unsigned long ip = _RET_IP_;
> +
> +#ifdef CONFIG_RANDOMIZE_BASE
> +               ip -= kaslr_offset();
> +#endif
>
>                 /*
>                  * There is some code that runs in interrupts but for which
> @@ -81,7 +87,7 @@ void notrace __sanitizer_cov_trace_pc(void)
>                 /* The first word is number of subsequent PCs. */
>                 pos = READ_ONCE(area[0]) + 1;
>                 if (likely(pos < t->kcov_size)) {
> -                       area[pos] = _RET_IP_;
> +                       area[pos] = ip;
>                         WRITE_ONCE(area[0], pos);
>                 }
>         }
> --
> 2.7.4


Hi,

I think generally this is the right thing to do.

 There are 2 pending patches for kcov by +Quentin (hopefully in mm):
"kcov: add AFL-style tracing"
"kcov: size of arena is now given in bytes"
https://groups.google.com/forum/#!topic/syzkaller/gcqbIhKjGcY
https://groups.google.com/d/msg/syzkaller/gcqbIhKjGcY/KQFryjBKCAAJ

Your patch probably conflicts with them.
Should you base them on top of these patches, so that Andrew can merge
it without conflicts?

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#1540067

On 11.12.2016 12:32, Dmitry Vyukov wrote:
> On Sun, Dec 11, 2016 at 1:50 AM, Alexander Popov <alex.popov@linux.com> wrote:
>> Subtract KASLR offset from the kernel addresses reported by kcov.
>> Tested on x86_64 and AArch64 (Hikey LeMaker).
>>
>> Signed-off-by: Alexander Popov <alex.popov@linux.com>
>> ---
>>  kernel/kcov.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> I think generally this is the right thing to do.
> 
>  There are 2 pending patches for kcov by +Quentin (hopefully in mm):
> "kcov: add AFL-style tracing"
> "kcov: size of arena is now given in bytes"
> https://groups.google.com/forum/#!topic/syzkaller/gcqbIhKjGcY
> https://groups.google.com/d/msg/syzkaller/gcqbIhKjGcY/KQFryjBKCAAJ
> 
> Your patch probably conflicts with them.
> Should you base them on top of these patches, so that Andrew can merge
> it without conflicts?

Excuse me, I can't find these patches in:
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git
git://git.cmpxchg.org/linux-mmots.git

Could you point at the tree which I can rebase onto?
Should I cherry-pick Quentin's patches manually?

Best regards,
Alexander

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#1540147

On Sun, Dec 11, 2016 at 10:37 PM, Alexander Popov <alex.popov@linux.com> wrote:
> On 11.12.2016 12:32, Dmitry Vyukov wrote:
>> On Sun, Dec 11, 2016 at 1:50 AM, Alexander Popov <alex.popov@linux.com> wrote:
>>> Subtract KASLR offset from the kernel addresses reported by kcov.
>>> Tested on x86_64 and AArch64 (Hikey LeMaker).
>>>
>>> Signed-off-by: Alexander Popov <alex.popov@linux.com>
>>> ---
>>>  kernel/kcov.c | 8 +++++++-
>>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> I think generally this is the right thing to do.
>>
>>  There are 2 pending patches for kcov by +Quentin (hopefully in mm):
>> "kcov: add AFL-style tracing"
>> "kcov: size of arena is now given in bytes"
>> https://groups.google.com/forum/#!topic/syzkaller/gcqbIhKjGcY
>> https://groups.google.com/d/msg/syzkaller/gcqbIhKjGcY/KQFryjBKCAAJ
>>
>> Your patch probably conflicts with them.
>> Should you base them on top of these patches, so that Andrew can merge
>> it without conflicts?
>
> Excuse me, I can't find these patches in:
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git
> git://git.cmpxchg.org/linux-mmots.git
>
> Could you point at the tree which I can rebase onto?
> Should I cherry-pick Quentin's patches manually?


Quentin, do you know destiny of your patches? They does not seem to be
in mm tree.

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