NB: WTF is fpregs_get() playing at???
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Note: riscv_fpr_get() used to forget to zero-pad at the end.
Not worth -stable...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

NB: it used to do short store; fix is needed earlier in the series.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

NB: there's a direct call of fpregs_get() left in dump_fpu().
To be taken out once we convert ELF_FDPIC to use of regset.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

NB: compat NT_S390_LAST_BREAK might be better as compat_long_t
rather than long.  User-visible ABI, again...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Note: compat variant of REGSET_TM_CGPR is almost certainly wrong;
it claims to be 48*64bit, but just as compat REGSET_GPR it stores
44*32bit of (truncated) registers + 4 32bit zeros... followed by
48 more 32bit zeroes.  Might be too late to change - it's a userland
ABI, after all ;-/
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

	All instances of ->get() in arch/x86 switched; that might or might
not be worth splitting up.  Notes:

	* for xstateregs_get() the amount we want to store is determined at
the boot time; see init_xstate_size() and update_regset_xstate_info() for
details.  task->thread.fpu.state.xsave ends with a flexible array member and
the amount of data in it depends upon the FPU features supported/enabled.

	* fpregs_get() writes slightly less than full ->thread.fpu.state.fsave
(the last word is not copied); we pass the full size of state.fsave and let
membuf_write() trim to the amount declared by regset - __regset_get() will
make sure that the space in buffer is no more than that.

	* copy_xstate_to_user() and its helpers are gone now.

	* fpregs_soft_get() was getting user_regset_copyout() arguments
wrong.  Since "x86: x86 user_regset math_emu" back in 2008...  I really
doubt that it's worth splitting out for -stable, though - you need
a 486SX box for that to trigger...

[Kevin's braino fix for copy_xstate_to_kernel() essentially duplicated here]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

->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>

Turn copy_regset_to_user() into regset_get_alloc() + copy_to_user().
Now all ->get() calls have a kernel buffer as destination.

Note that we'd already eliminated the callers of copy_regset_to_user()
with non-zero offset; now that argument is simply unused.

Uninlined, while we are at it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Two new helpers: given a process and regset, dump into a buffer.
regset_get() takes a buffer and size, regset_get_alloc() takes size
and allocates a buffer.

Return value in both cases is the amount of data actually dumped in
case of success or -E...  on error.

In both cases the size is capped by regset->n * regset->size, so
->get() is called with offset 0 and size no more than what regset
expects.

binfmt_elf.c callers of ->get() are switched to using those; the other
caller (copy_regset_to_user()) will need some preparations to switch.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

[a couple of unused variables left behind by the previous version
spotted by kernel test robot <lkp@intel.com>]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

don't bother with copy_regset_from_user() (not to mention
set_fs())
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

same as for sparc32, and that's it - no more caller of ->get() with
non-zero pos.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

the life is much simpler if copy_regset_to_user() (and ->get())
gets called only with pos == 0; sparc32 PTRACE_GETREGS and
PTRACE_GETFPREGS are among the few things that use it to fetch
pieces of regset _not_ starting at the beginning.  It's actually
easier to define a separate regset that would provide what
we need, rather than trying to cobble that from the one
PTRACE_GETREGSET uses.

Extra ->get() instances do not amount to much code and once
we get the conversion of ->get() to new API (dependent upon the
lack of weird callers of ->get()) they'll shrink a lot, along
with the rest of ->get() instances...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

... for fetching the register window from target's stack, rather
than open-coding it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

similar to previous commit...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

We know this won't be called for child == current, so we don't need
to bother with callbacks, etc. - just do unw_init_from_blocked_task(),
unw_unwind_to_user() and do the payload of gpregs_[gs]et().  For
one register.  Which is to say, access_elf_reg().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

now access_elf_reg() does the right thing for everything other than
r0, we can simplify do_grepgs_[gs]et()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Now it's easy to make elf_access_gpreg() handle the rest of global
registers (r16..r31).  That gets rid of the hole in the registers
elf_access_reg() can handle, which will allow to simplify its callers
later in the series.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

The function takes the register number, finds the corresponding field
of pt_regs for registers that are saved there or does the unwind for the
registers that end up spilled on the kernel stack.  Then it reads from
or writes to the resulting location.

Unfortunately, finding the required pt_regs field is done by rather
horrible switch.  It's microoptimized in all the wrong places - it
even uses the knowledge that fields for r8..r11 follow each other
in pt_regs layout, while r12..r13 are not adjacent to those, etc.

All of that is to encode the mapping from register numbers to offsets +
the information that r4..r7 are not to be found in pt_regs.

It's deeply in nasal demon territory, at that - the games it plays
with pointer arithmetics on addresses of structure members are
undefined behaviour.

Valid C ends up with better code in this case: just initialize a constant
array with offsets of relevant pt_regs fields and we don't need that
switch anymore.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

dead since the removal of aout coredump support...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

... then copy_to_user() the results
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>