On 10/20/2012 1:16 PM, Al Viro wrote:

On Sat, Oct 20, 2012 at 04:34:01PM +0100, Al Viro wrote:

quoted

On Sat, Oct 20, 2012 at 09:06:57AM -0400, Chris Metcalf wrote:

quoted

First, the compat_sys_execve() declaration provided in
arch/tile/include/asm/compat.h isn't right, so I deleted that (you had only
deleted the PTREGS_SYSCALL trampoline declaration, _compat_sys_execve).

However, then arch/tile/kernel/compat.c failed to build, because
<linux/compat.h> is included before <asm/unistd.h>, and <asm/unistd.h>
provides __ARCH_WANT_SYS_EXECVE, and so we end up with no declaration at
all for compat_sys_execve.  For most platforms this is no big deal, but on
tile we use the __SYSCALL #define to provide the actual syscall table, and
for that to work we need a declaration in scope for each syscall at the
time we create the table.

The best solution seems likely to be to copy the other place in
<linux/compat.h> where we need to do something configurable (that is,
CONFIG_ARCH_WANT_OLD_COMPAT_IPC), and just convert __ARCH_WANT_SYS_EXECVE
to be a Kconfig option.

Frankly, I hope to get rid of the damn thing completely.  By now we have
at least some variant of execve conversions for just about everything;
I certainly hope that by the beginning of the next cycle we'll have it
defined on everything.  And put unconditional declarations in syscalls.h
and compat.h

Actually, we can make the declaration in linux/compat.h unconditional
right now.  The only obstacle is the situation on arm64; there the mainline
has C variant of that sucker (with struct pt_regs * in arguments) in
arch/arm64/kernel/sys_compat.c.  So we could ask Linus to pull
git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64 execve
and then do the following in one patch:
	introduce current_pt_regs() on tile (from your commit)
	get rid of pt_regs * argument in tile compat_sys_execve(), making it
use current_pt_regs(); kill its wrapper
	kill the declarations of compat_sys_execve()/_compat_sys_execve()
in tile asm/compat.h
	make declaration in linux/compat.h unconditional
Note that this does *not* depend on kernel_thread/kernel_execve patch -
kernel_execve() is never going to hit compat_sys_execve(), since it's
only called from kernel threads and those are not going to be 32bit.
After that we can do kernel_thread/kernel_execve commit and
sys_execve() conversion with nothing outside of arch/tile touched.

Another possible variant is for you to merge that branch from arm64 tree
(only 3 commits it it) and then do as described above.  I.e. on top of
that apply the thing below, followed by your kernel_thread()/kernel_execve()
patch (sans current_pt_regs() part), followed by obviously massaged parts
of generic sys_execve for tile patch I've sent.  FWIW, I've put the
whole series (based at the end of arm64 branch) in signal.git#arch-tile.
Comments?

I fetched the series from your arch-tile branch and built it, and it works
fine.  It looks good from my inspection:

Acked-by: Chris Metcalf <redacted>

As you had suggested in an earlier email, I went ahead and eliminated the
special pt_regs handling for sigaltstack, rt_sigreturn, and clone.  (Also a
tilepro-specific syscall that was also using PTREG_SYSCALL.)  I'll send it
separately and you can include it in your tree if you like.

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com