* Fwd: Need Help regarding Reading and Writting to a file from kernel function file [not found] <CAGaWEbomboZ=MCT4GaKj+5tUNDGc5ZknvhLTikCPSWpjY5E7hA@mail.gmail.com> @ 2019-09-24 7:10 ` Sahibzada Irfanullah 2019-09-24 7:35 ` Greg KH 2019-09-24 8:48 ` Valdis Klētnieks 0 siblings, 2 replies; 6+ messages in thread From: Sahibzada Irfanullah @ 2019-09-24 7:10 UTC (permalink / raw) To: kernelnewbies [-- Attachment #1.1: Type: text/plain, Size: 1164 bytes --] Dear Sir, Hope you are doing well. Actually, I have one problem metioned in the subject line. The problem is: I am trying to write/read page faulted physical addresses to a file in a kernel (v5.3-1) function, i.e., handle_ept_violation() which is present in vmx.c. I have followed this <https://stackoverflow.com/questions/1184274/read-write-files-within-a-linux-kernel-module>, it's working as a standalone kernel module when I load/unload this kernel module, but when I try to use this code in the handle_ept_violation() function, I can't able to open the file and get the error codes, i.e., -2, -3, or -13. It's compiled successfully but generate the error at runtime. I searched for error codes online but I didn't find any help. Can anyone please provide me with any good guidlines, or links where I can start and solve this problem in a fast way. Thank you very much -- Regards, *Mr. Irfan Ullah* PhD Candidate Data and Knowledge Engineering(DKE) Lab Department of Computer Science and Engineering Kyung Hee University, South Korea. +82-010-591-51651 <+82%2010-3877-8867> sahibzada.iu@gmail.com sahibzada_irfanullah -- Regards, *Mr. Irfanullah* [-- Attachment #1.2: Type: text/html, Size: 4584 bytes --] [-- Attachment #2: Type: text/plain, Size: 170 bytes --] _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Fwd: Need Help regarding Reading and Writting to a file from kernel function file 2019-09-24 7:10 ` Fwd: Need Help regarding Reading and Writting to a file from kernel function file Sahibzada Irfanullah @ 2019-09-24 7:35 ` Greg KH 2019-09-24 8:48 ` Valdis Klētnieks 1 sibling, 0 replies; 6+ messages in thread From: Greg KH @ 2019-09-24 7:35 UTC (permalink / raw) To: Sahibzada Irfanullah; +Cc: kernelnewbies On Tue, Sep 24, 2019 at 04:10:07PM +0900, Sahibzada Irfanullah wrote: > Dear Sir, > Hope you are doing well. Actually, I have one problem metioned in the > subject line. The problem is: I am trying to write/read page faulted > physical addresses to a file in a kernel (v5.3-1) function, i.e., > handle_ept_violation() which is present in vmx.c. I have followed this > <https://stackoverflow.com/questions/1184274/read-write-files-within-a-linux-kernel-module>, > it's working as a standalone kernel module when I load/unload this kernel > module, but when I try to use this code in the handle_ept_violation() > function, I can't able to open the file and get the error codes, i.e., -2, > -3, or -13. It's compiled successfully but generate the error at runtime. I > searched for error codes online but I didn't find any help. > Can anyone please provide me with any good guidlines, or links where I can > start and solve this problem in a fast way. Please do not try to read or write a file from within the kernel, that way almost always lies madness and major problems. Step back and try to describe the problem you are attempting to solve here first. Odds are it can be done in a much better way. Also, do you have a pointer to your code anywhere? thanks, greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Fwd: Need Help regarding Reading and Writting to a file from kernel function file 2019-09-24 7:10 ` Fwd: Need Help regarding Reading and Writting to a file from kernel function file Sahibzada Irfanullah 2019-09-24 7:35 ` Greg KH @ 2019-09-24 8:48 ` Valdis Klētnieks 2019-09-24 9:51 ` Saket Sinha 2019-09-24 10:02 ` Martin Christian 1 sibling, 2 replies; 6+ messages in thread From: Valdis Klētnieks @ 2019-09-24 8:48 UTC (permalink / raw) To: Sahibzada Irfanullah; +Cc: kernelnewbies [-- Attachment #1.1: Type: text/plain, Size: 1026 bytes --] On Tue, 24 Sep 2019 16:10:07 +0900, Sahibzada Irfanullah said: > subject line. The problem is: I am trying to write/read page faulted > physical addresses to a file in a kernel (v5.3-1) function, i.e., > handle_ept_violation() which is present in vmx.c. I have followed this > <https://stackoverflow.com/questions/1184274/read-write-files-within-a-linux-kernel-module>, Just because somebody on stackoverflow gave a guide doesn't mean it's a good idea. What problem are you trying to solve here? Are you trying to write the faulted pages themselves to a file? In that case, just creating the file, using something like 'dd if=/dev/zero of=/your/file/here bs=1M count=4096' and then using mkswap and swapon will probably work much better. If you're trying to produce a trace of what pages are being faulted, you can probably do a better job by using 'perf' to produce trace events with a lot of added data for you, or use debugfs or netlink and a userspace program to read the data and write it to disk from userspace. [-- Attachment #1.2: Type: application/pgp-signature, Size: 832 bytes --] [-- Attachment #2: Type: text/plain, Size: 170 bytes --] _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Fwd: Need Help regarding Reading and Writting to a file from kernel function file 2019-09-24 8:48 ` Valdis Klētnieks @ 2019-09-24 9:51 ` Saket Sinha 2019-09-24 13:32 ` Greg KH 2019-09-24 10:02 ` Martin Christian 1 sibling, 1 reply; 6+ messages in thread From: Saket Sinha @ 2019-09-24 9:51 UTC (permalink / raw) To: Valdis Klētnieks; +Cc: Sahibzada Irfanullah, kernelnewbies Hi, I am sorry but I am really tempted to share - https://www.linuxjournal.com/article/8110 But as suggested, you should never try this. Regards, Saket Sinha On Tue, Sep 24, 2019 at 10:50 AM Valdis Klētnieks <valdis.kletnieks@vt.edu> wrote: > > On Tue, 24 Sep 2019 16:10:07 +0900, Sahibzada Irfanullah said: > > > subject line. The problem is: I am trying to write/read page faulted > > physical addresses to a file in a kernel (v5.3-1) function, i.e., > > handle_ept_violation() which is present in vmx.c. I have followed this > > <https://stackoverflow.com/questions/1184274/read-write-files-within-a-linux-kernel-module>, > > Just because somebody on stackoverflow gave a guide doesn't mean it's > a good idea. > > What problem are you trying to solve here? Are you trying to write the faulted > pages themselves to a file? In that case, just creating the file, using something like > 'dd if=/dev/zero of=/your/file/here bs=1M count=4096' and then using mkswap > and swapon will probably work much better. > > If you're trying to produce a trace of what pages are being faulted, you can > probably do a better job by using 'perf' to produce trace events with a lot of > added data for you, or use debugfs or netlink and a userspace program to read > the data and write it to disk from userspace. > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Fwd: Need Help regarding Reading and Writting to a file from kernel function file 2019-09-24 9:51 ` Saket Sinha @ 2019-09-24 13:32 ` Greg KH 0 siblings, 0 replies; 6+ messages in thread From: Greg KH @ 2019-09-24 13:32 UTC (permalink / raw) To: Saket Sinha; +Cc: Sahibzada Irfanullah, Valdis Klētnieks, kernelnewbies On Tue, Sep 24, 2019 at 11:51:57AM +0200, Saket Sinha wrote: > Hi, > > I am sorry but I am really tempted to share - > https://www.linuxjournal.com/article/8110 That's out of date, and the stack overflow link points to it. Maybe someday I'll update that article somewhere else, as it's actually much simpler to do this now than it was when I wrote that article. But it still doesn't make it something that anyone should do :) thanks, greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Fwd: Need Help regarding Reading and Writting to a file from kernel function file 2019-09-24 8:48 ` Valdis Klētnieks 2019-09-24 9:51 ` Saket Sinha @ 2019-09-24 10:02 ` Martin Christian 1 sibling, 0 replies; 6+ messages in thread From: Martin Christian @ 2019-09-24 10:02 UTC (permalink / raw) To: kernelnewbies [-- Attachment #1.1.1: Type: text/plain, Size: 822 bytes --] > Just because somebody on stackoverflow gave a guide doesn't mean it's > a good idea. I'll put that on my quotation list. ;-) Regards, Martin -- Dipl.-Inf. Martin Christian Senior Berater Entwicklung Hardware Division Verteidigung secunet Security Networks AG Tel.: +49 201 5454-3612, Fax +49 201 5454-1323 E-Mail: martin.christian@secunet.com Ammonstraße 74, 01067 Dresden www.secunet.com __________________________________________________________________________ secunet Security Networks AG Sitz: Kurfürstenstraße 58, 45138 Essen, Deutschland Amtsgericht Essen HRB 13615 Vorstand: Axel Deininger (Vors.), Torsten Henn, Dr. Kai Martius, Thomas Pleines Aufsichtsratsvorsitzender: Ralf Wintergerst __________________________________________________________________________ [-- Attachment #1.2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 833 bytes --] [-- Attachment #2: Type: text/plain, Size: 170 bytes --] _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ^ permalink raw reply [flat|nested] 6+ messages in thread
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[not found] <CAGaWEbomboZ=MCT4GaKj+5tUNDGc5ZknvhLTikCPSWpjY5E7hA@mail.gmail.com>
2019-09-24 7:10 ` Fwd: Need Help regarding Reading and Writting to a file from kernel function file Sahibzada Irfanullah
2019-09-24 7:35 ` Greg KH
2019-09-24 8:48 ` Valdis Klētnieks
2019-09-24 9:51 ` Saket Sinha
2019-09-24 13:32 ` Greg KH
2019-09-24 10:02 ` Martin Christian
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