This commit introduce the `struct config_btf_arg_depth`. It append
`btf_argN` to `struct event_config` as an array of children to dig
in any structure.

For more details, any `btf_argN` can have a list of childrens as
follow.
For example, file->f_path is 152 bytes, so the array will look like
[{ offset: 152, is_pointer: 0 }, { offset: 0, is_pointer: 0 } ...].

The max value `MAX_BTF_ARG_DEPTH` as been set
arbitrary as the verifier need a fixed size.

Signed-off-by: Tristan d'Audibert <[email protected]>

The aim of this commit is to enable the loop on the current hook arguments
and move the buffer at config->btf_argN[i]->offset defined in
userspace. The new offset is then written in the original variable to
keep the same behaviour.
The result of this is the rewrite of the current argument buffer with the
required data.

Signed-off-by: Tristan d'Audibert <[email protected]>

This commit make a closer relationship between the defined
`GenericStringToType` arguments and the existing BTF types.

For instance:
`struct file` with btf is called `file` and also exists in
`GenericStringToType` with the same alias.
But `struct qstr d_name->name` has a returned type `unsigned char` wich
does not exist yet in `GenericStringToType`.
The same thing happened with `linux_binprm->filename` has the type is
`char`

Signed-off-by: Tristan d'Audibert <[email protected]>

The function recursively search in the structure for childrens matching
`pathToFound`. The variable `i` is used here as the depth in the
`pathToFound` array.

For instance, if the search is in the linux_binprm structure and the
path is as follow `file.f_path.dentry.d_name.name`, the following
actions will be done.
- Look for the variable name `file` inside `linux_binprm`.
- If the matches, it stores the offset from linux_binprm where the `file`
  variable can be found.
- Then it take the btf type `file` and search for parameter named
  `f_path`.

Signed-off-by: Tristan d'Audibert <[email protected]>

This commit add 2 parameters to give the ability to the user to search
for a specific variable following a "path" as follow:
```yml
...
    args:
      - index: 0
        type: "linux_binprm"
        extractParam: "file.f_path.dentry.d_name.name"
        overwriteType: "string"
...
```
The above config can be used to extract a specific parameter from the
structure at index 0.

Signed-off-by: Tristan d'Audibert <[email protected]>

The OverwriteType parameter should be deleted if `argSelectorType` can use
the `EventConfig` structure to search for the correct Type.

Signed-off-by: Tristan d'Audibert <[email protected]>

Search if every types defined by the user with ExtractParam exists as BTF
types and store their offsets in ConfigBtfArg.

This function do a basic split on `ExtractParam` to obtain the "path"
to the required data. Then, the array is gave to `btf.FindNextBTFType` to
find the offsets of each elements until we reach the required data.
The output is stored in EventConfig to keep the normal behaviour.

For example, if the arg 0 is `struct linux_binprm` and ExtractParam is
set to `file.f_path.dentry.d_name.name`, the output will give an array
of all the offsets from there parents as such
[{ offset: 96, is_pointer: 0 }, { offset: 152, is_pointer: 1 }, ...]
From input = "linux_binprm -> file.f_path.dentry.d_name.name"

Signed-off-by: Tristan d'Audibert <[email protected]>

This commit update `addLsm` function to use the parameters `ExtractParam`
and `OverwriteType` in order to look for the child members in BTF
structure.

Signed-off-by: Tristan d'Audibert <[email protected]>

…probes

Uprobe offsets can't be found in BTF file. Thus, if the user defines
these specific parameters, they are ignored and a warning is displayed

Signed-off-by: Tristan d'Audibert <[email protected]>

Add very similar code as in `genericlsm.go` file to handle those params.
In a future commit, a refactoring should be acheived to avoid code
redundant code with `genericlsm.go`

Signed-off-by: Tristan d'Audibert <[email protected]>