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->regset_get() takes task+regset+buffer, returns the amount of free space
left in the buffer on success and -E... on error.
buffer is represented as struct membuf - a pair of (kernel) pointer
and amount of space left
Primitives for writing to such:
* membuf_write(buf, data, size)
* membuf_zero(buf, size)
* membuf_store(buf, value)
These are implemented as inlines (in case of membuf_store - a macro).
All writes are sequential; they become no-ops when there's no space
left. Return value of all primitives is the amount of space left
after the operation, so they can be used as return values of ->regset_get().
Example of use:
// stores pt_regs of task + 64 bytes worth of zeroes + 32bit PID of task
int foo_get(struct task_struct *task, const struct regset *regset,
struct membuf to)
{
membuf_write(&to, task_pt_regs(task), sizeof(struct pt_regs));
membuf_zero(&to, 64);
return membuf_store(&to, (u32)task_tgid_vnr(task));
}
regset_get()/regset_get_alloc() taught to use that thing if present.
By the end of the series all users of ->get() will be converted;
then ->get() and ->get_size() can go.
Note that unlike ->get() this thing always starts at offset 0 and,
since it only writes to kernel buffer, can't fail on copyout.
It can, of course, fail for other reasons, but those tend to
be less numerous.
The caller guarantees that the buffer size won't be bigger than
regset->n * regset->size. That simplifies life for quite a few
instances.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.