Inline Macro issue

[Saket Sinha]

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
>>
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>>
>>
>
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