Re: [PATCH 2/2] userfaultfd.2: fix userfaultfd_demo output

[Alejandro Colomar <alx.manpages@gmail.com>]

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Hi Nadav,

On 3/7/22 19:48, Nadav Amit wrote:
> From: Nadav Amit <namit@vmware.com>
> 
> A bug in the kernel caused in recent version a different output (masked
> offset). Update the output of the demo program accordingly.

I'd like to have some more information about this in the commit message.
I don't really understand it.  When was the bug introduced?  When was it
fixed?  Was the example in the page created in a buggy version?

Thanks,
Alex

> 
> Signed-off-by: Nadav Amit <namit@vmware.com>
> ---
>  man2/userfaultfd.2 | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2
> index cee7c01d2..779ff8817 100644
> --- a/man2/userfaultfd.2
> +++ b/man2/userfaultfd.2
> @@ -648,7 +648,7 @@ Address returned by mmap() = 0x7fd30106c000
>  
>  fault_handler_thread():
>      poll() returns: nready = 1; POLLIN = 1; POLLERR = 0
> -    UFFD_EVENT_PAGEFAULT event: flags = 0; address = 7fd30106c00f
> +    UFFD_EVENT_PAGEFAULT event: flags = 0; address = 7fd30106c000
>          (uffdio_copy.copy returned 4096)
>  Read address 0x7fd30106c00f in main(): A
>  Read address 0x7fd30106c40f in main(): A
> @@ -657,7 +657,7 @@ Read address 0x7fd30106cc0f in main(): A
>  
>  fault_handler_thread():
>      poll() returns: nready = 1; POLLIN = 1; POLLERR = 0
> -    UFFD_EVENT_PAGEFAULT event: flags = 0; address = 7fd30106d00f
> +    UFFD_EVENT_PAGEFAULT event: flags = 0; address = 7fd30106d000
>          (uffdio_copy.copy returned 4096)
>  Read address 0x7fd30106d00f in main(): B
>  Read address 0x7fd30106d40f in main(): B
> @@ -666,7 +666,7 @@ Read address 0x7fd30106dc0f in main(): B
>  
>  fault_handler_thread():
>      poll() returns: nready = 1; POLLIN = 1; POLLERR = 0
> -    UFFD_EVENT_PAGEFAULT event: flags = 0; address = 7fd30106e00f
> +    UFFD_EVENT_PAGEFAULT event: flags = 0; address = 7fd30106e000
>          (uffdio_copy.copy returned 4096)
>  Read address 0x7fd30106e00f in main(): C
>  Read address 0x7fd30106e40f in main(): C

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