Kernelnewbies Digest, Vol 32, Issue 20
Saket Sinha
saket.sinha89 at gmail.com
Mon Jul 15 08:46:55 EDT 2013
This program is compiling fine on the same compiler.
Output:
in main..
Hi
I think than Mandeep's code should also compile
#define push_root()\{
recursive_mutex_lock(&context->id_lock);\
context->uid = current_fsuid();\
context->gid = current_fsgid();\
do{\
struct cred *new2 = prepare_creds();\
commit_creds(new2);\
}while(0)
Regards,
Saket Sinha
On Mon, Jul 15, 2013 at 5:45 PM, Murali Annamneni <a.murali at hcl.com> wrote:
> Hi Saket Sinha
>
> Just try as below example -
>
> #include <stdio.h>
>
> #define pushme \
> do \
> { \
> printf("Hi...\n"); \
> } while(0);
>
> int main()
> {
> printf("in main\n");
> pushme
> return 0;
> }
>
>
>
> Thanks & Regards
> Murali Annamneni
>
>
> -----Original Message-----
> From: kernelnewbies-bounces at kernelnewbies.org [mailto:
> kernelnewbies-bounces at kernelnewbies.org] On Behalf Of
> kernelnewbies-request at kernelnewbies.org
> Sent: Monday, July 15, 2013 5:03 PM
> To: kernelnewbies at kernelnewbies.org
> Subject: Kernelnewbies Digest, Vol 32, Issue 20
>
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> Today's Topics:
>
> 1. Re: Inline Macro issue (Saket Sinha)
> 2. Re: Inline Macro issue (Mandeep Sandhu)
> 3. Re: Inline Macro issue (anish singh)
> 4. Re: Inline Macro issue (Saket Sinha)
> 5. Re: Inline Macro issue (Saket Sinha)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 15 Jul 2013 15:54:55 +0530
> From: Saket Sinha <saket.sinha89 at gmail.com>
> Subject: Re: Inline Macro issue
> To: Srinivas Ganji <srinivasganji.kernel at gmail.com>
> Cc: kernelnewbies at kernelnewbies.org
> Message-ID:
> <
> CAK25hWO3zbFu8MgXtPSpGq_0uj+qv07hGJjp018heGTDABN7nA at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear Srinivas,
>
> If you are suggesting something like
>
> #define push_root \ *{*
> new1 =prepare_creds(); \
> new1->uid = 0; \
> new1->gid = 0; \
> commit_creds(new1)
> *}*
> *
> *
> Sorry I am still getting a compiler error.
>
> Regards,
> Saket Sinha
> *
> *
>
>
> On Mon, Jul 15, 2013 at 2:25 PM, Srinivas Ganji <
> srinivasganji.kernel at gmail.com> wrote:
>
> > A small suggestion, use begin { and end } braces for declaring your
> macro.
> > May be I am wrong, but you can try this. Then, the declaration become
> > local to that block.
> >
> > Regards,
> > Srinivas
> >
> >
> > On Mon, Jul 15, 2013 at 1:03 AM, Saket Sinha <saket.sinha89 at gmail.com
> >wrote:
> >
> >> "current" in kernel is a global macro, that always point to the
> >> "struct task_struct * " of the currently executing task (for details
> >> on task_struct, ref Robert Love, pg 24-27).
> >>
> >> Now I have a macro called push root which has the following purpose-
> >> "to push root user and group to current context so to set current
> >> uid and gid to 0."
> >>
> >> Now in kernel 3.8.3, I would do something like
> >>
> >> struct cred *new1;
> >> new1 =prepare_creds();
> >> new1->uid = 0;
> >> new1->gid = 0;
> >> commit_creds(new1);
> >>
> >> So macro definition of push root, according to what I have proposed
> >> above, should be
> >> #define push_root \
> >> new1 =prepare_creds(); \
> >> new1->uid = 0; \
> >> new1->gid = 0; \
> >> commit_creds(new1)
> >>
> >> But I am getting errors like multiple declaration of new1 etc.
> >>
> >> Even if I declare prepare_creds outside macro definition like
> >>
> >> new1 =prepare_creds();
> >> #define push_root \
> >> new1->uid = 0; \
> >> new1->gid = 0; \
> >> commit_creds(new1)
> >>
> >> I think I am facing the issue that the macros are inlined during
> >> compilation, so when the compiler wants to replace them, it raises
> issues.
> >>
> >> I could think of two ways to solve this issue-
> >>
> >> 1. define a new macro like #define prep_root() which defines the var
> >> once for all, and that I have to put it at the begin of each function
> >> needing push_root. This is not a very good method.
> >>
> >> 2. I should still try to go with inlined functions but how ?
> >>
> >> Can someone suggest anything
> >>
> >> Regards,
> >> Saket Sinha
> >>
> >> _______________________________________________
> >> Kernelnewbies mailing list
> >> Kernelnewbies at kernelnewbies.org
> >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >>
> >>
> >
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> ------------------------------
>
> Message: 2
> Date: Mon, 15 Jul 2013 16:24:18 +0530
> From: Mandeep Sandhu <mandeepsandhu.chd at gmail.com>
> Subject: Re: Inline Macro issue
> To: Saket Sinha <saket.sinha89 at gmail.com>
> Cc: Srinivas Ganji <srinivasganji.kernel at gmail.com>, kernelnewbies
> <kernelnewbies at kernelnewbies.org>
> Message-ID:
> <CAC+QLdQbBuNEW7EKZk4vUTNuu2LGSZ6gJhf4bde3gC+=
> D9FP8w at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> On Mon, Jul 15, 2013 at 3:54 PM, Saket Sinha <saket.sinha89 at gmail.com
> >wrote:
>
> > Dear Srinivas,
> >
> > If you are suggesting something like
> >
> > #define push_root \ *{*
> > new1 =prepare_creds(); \
> > new1->uid = 0; \
> > new1->gid = 0; \
> > commit_creds(new1)
> > *}*
> > *
> > *
> > Sorry I am still getting a compiler error.
> >
>
> What errors is the compiler giving?
>
> Last time you mentioned that it's saying new1 has multiple def's.
>
> Is it possible your macro has a declaration of new1 in it. So if you use
> the macro in the same scope, you'll get re-def errors.
>
> You can also try and look at the intermediate file for your source code,
> i.e after the pre-processing is done (*.i files).
>
> I don't remember the exact gcc option. Try --save-temps and look at the
> <source file name>.i file.
>
> HTH,
> -mandeep
>
>
>
> >
> > Regards,
> > Saket Sinha
> > *
> > *
> >
> >
> > On Mon, Jul 15, 2013 at 2:25 PM, Srinivas Ganji <
> > srinivasganji.kernel at gmail.com> wrote:
> >
> >> A small suggestion, use begin { and end } braces for declaring your
> >> macro. May be I am wrong, but you can try this. Then, the declaration
> >> become local to that block.
> >>
> >> Regards,
> >> Srinivas
> >>
> >>
> >> On Mon, Jul 15, 2013 at 1:03 AM, Saket Sinha <saket.sinha89 at gmail.com
> >wrote:
> >>
> >>> "current" in kernel is a global macro, that always point to the
> >>> "struct task_struct * " of the currently executing task (for details
> >>> on task_struct, ref Robert Love, pg 24-27).
> >>>
> >>> Now I have a macro called push root which has the following
> >>> purpose- "to push root user and group to current context so to set
> >>> current uid and gid to 0."
> >>>
> >>> Now in kernel 3.8.3, I would do something like
> >>>
> >>> struct cred *new1;
> >>> new1 =prepare_creds();
> >>> new1->uid = 0;
> >>> new1->gid = 0;
> >>> commit_creds(new1);
> >>>
> >>> So macro definition of push root, according to what I have proposed
> >>> above, should be
> >>> #define push_root \
> >>> new1 =prepare_creds(); \
> >>> new1->uid = 0; \
> >>> new1->gid = 0; \
> >>> commit_creds(new1)
> >>>
> >>> But I am getting errors like multiple declaration of new1 etc.
> >>>
> >>> Even if I declare prepare_creds outside macro definition like
> >>>
> >>> new1 =prepare_creds();
> >>> #define push_root \
> >>> new1->uid = 0; \
> >>> new1->gid = 0; \
> >>> commit_creds(new1)
> >>>
> >>> I think I am facing the issue that the macros are inlined during
> >>> compilation, so when the compiler wants to replace them, it raises
> issues.
> >>>
> >>> I could think of two ways to solve this issue-
> >>>
> >>> 1. define a new macro like #define prep_root() which defines the var
> >>> once for all, and that I have to put it at the begin of each
> >>> function needing push_root. This is not a very good method.
> >>>
> >>> 2. I should still try to go with inlined functions but how ?
> >>>
> >>> Can someone suggest anything
> >>>
> >>> Regards,
> >>> Saket Sinha
> >>>
> >>> _______________________________________________
> >>> Kernelnewbies mailing list
> >>> Kernelnewbies at kernelnewbies.org
> >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >>>
> >>>
> >>
> >
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies at kernelnewbies.org
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
> >
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> ------------------------------
>
> Message: 3
> Date: Mon, 15 Jul 2013 16:54:33 +0530
> From: anish singh <anish198519851985 at gmail.com>
> Subject: Re: Inline Macro issue
> To: Saket Sinha <saket.sinha89 at gmail.com>
> Cc: Srinivas Ganji <srinivasganji.kernel at gmail.com>, Mandeep Sandhu
> <mandeepsandhu.chd at gmail.com>, kernelnewbies
> <kernelnewbies at kernelnewbies.org>
> Message-ID:
> <
> CAK7N6vp2BCz_B5K2PNvdRJpt-xoqhfNSW9MmavohG1__p9CFiA at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> Do one simple thing.Write a test code
> which uses that macro and paste it
> here in ideone.com
>
> On Mon, Jul 15, 2013 at 4:50 PM, Saket Sinha <saket.sinha89 at gmail.com>
> wrote:
> > Mandip:
> > Error is expected error or declaration at the end of input
> > Anish:
> > that '\' should not be there first of all and even if I put it same
> > error
> >
>
>
>
> ------------------------------
>
> Message: 4
> Date: Mon, 15 Jul 2013 16:50:34 +0530
> From: Saket Sinha <saket.sinha89 at gmail.com>
> Subject: Re: Inline Macro issue
> To: Mandeep Sandhu <mandeepsandhu.chd at gmail.com>,
> anish198519851985 at gmail.com
> Cc: Srinivas Ganji <srinivasganji.kernel at gmail.com>, kernelnewbies
> <kernelnewbies at kernelnewbies.org>
> Message-ID:
> <
> CAK25hWMLndvytwZ0YVFMXhrd44Jb479HmiYLZ48Umozz1pz7vQ at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Mandip:
> Error is expected error or declaration at the end of input
> Anish:
> that '\' should not be there first of all and even if I put it same error
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> ------------------------------
>
> Message: 5
> Date: Mon, 15 Jul 2013 17:02:49 +0530
> From: Saket Sinha <saket.sinha89 at gmail.com>
> Subject: Re: Inline Macro issue
> To: anish singh <anish198519851985 at gmail.com>
> Cc: Srinivas Ganji <srinivasganji.kernel at gmail.com>, Mandeep Sandhu
> <mandeepsandhu.chd at gmail.com>, kernelnewbies
> <kernelnewbies at kernelnewbies.org>
> Message-ID:
> <
> CAK25hWMvjdABa-KS1Ru1bBWaETd7JHKOGXdqhyY8ROLksSKi3w at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear Anish,
>
> Actually its kernel module, so then I will have to write all the dummy
> equivalent of the structures and functions involved.
>
> I can do this....give my system on remote.
>
> Regards,
> Saket Sinha
>
>
>
> On Mon, Jul 15, 2013 at 4:54 PM, anish singh <anish198519851985 at gmail.com
> >wrote:
>
> > Do one simple thing.Write a test code
> > which uses that macro and paste it
> > here in ideone.com
> >
> > On Mon, Jul 15, 2013 at 4:50 PM, Saket Sinha <saket.sinha89 at gmail.com>
> > wrote:
> > > Mandip:
> > > Error is expected error or declaration at the end of input
> > > Anish:
> > > that '\' should not be there first of all and even if I put it same
> > > error
> > >
> >
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> End of Kernelnewbies Digest, Vol 32, Issue 20
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