cvs commit: src/sys/alpha/linux linux_sysvec.csrc/sys/alpha/osf1 src/sys/compat/ia32imgact_svr4.c svr4_sysvec.c ...

[Maxim Sobolev]

John Baldwin wrote:
> On Monday 31 January 2005 06:10 pm, Maxim Sobolev wrote:
> 
>>John Baldwin wrote:
>>
>>>On Saturday 29 January 2005 06:12 pm, Maxim Sobolev wrote:
>>>
>>>>sobomax     2005-01-29 23:12:00 UTC
>>>>
>>>> FreeBSD src repository
>>>>
>>>> Modified files:
>>>>   sys/alpha/linux      linux_sysvec.c
>>>>   sys/alpha/osf1       imgact_osf1.c osf1_sysvec.c
>>>>   sys/amd64/linux32    linux32_sysvec.c
>>>>   sys/compat/ia32      ia32_sysvec.c
>>>>   sys/compat/pecoff    imgact_pecoff.c
>>>>   sys/compat/svr4      imgact_svr4.c svr4_sysvec.c
>>>>   sys/i386/ibcs2       ibcs2_sysvec.c imgact_coff.c
>>>>   sys/i386/linux       imgact_linux.c linux_sysvec.c
>>>>                        linux_machdep.c
>>>>   sys/kern             imgact_aout.c imgact_elf.c imgact_gzip.c
>>>>                        imgact_shell.c kern_exec.c kern_kse.c
>>>>   sys/modules          Makefile
>>>>   sys/sys              imgact.h syscallsubr.h
>>>> Log:
>>>> o Split out kernel part of execve(2) syscall into two parts: one that
>>>>   copies arguments into the kernel space and one that operates
>>>>   completely in the kernel space;
>>>>
>>>> o use kernel-only version of execve(2) to kill another stackgap in
>>>>   linuxlator/i386.
>>>>
>>>> Obtained from:  DragonFlyBSD (partially)
>>>> MFC after:      2 weeks
>>>
>>>Cool, this had been on my anti-stackgap todo list as well.
>>>
>>
>>:-)
>>
>>We have been tolerating this stackgap hack for too long.
>>
>>Right now linuxlator/i386 is almost stackgap-free. The only remaining
>>stackgap is in semctl(2) syscal, which in my opinion it is very
>>over/under engineered API, so that there is no a good clean way to do
>>the split. At the same time, it's not the one used oftenly, so that  I
>>can wait when I (or somebody else) is in the right mood to do the
>>remaining work.
>>
>>Other arches/emulation layers are awaiting for somebody (maintainers?)
>>to do the work, which will be very easy one, since most popular kernel
>>interfaces that work on userland structures/buffers have been split.
> 
> 
> That's not the only one.  All the filesystem system calls use the stackgap to 
> handle the /compat/linux namespace.  Fixing that will not be trivial, as it 
> will involve teaching namei() to retrieve filenames using a uio or some such 
> so that names can either be in user space or in kernel space.  Either that or 
> we add native support for prefixes like /compat/foo to namei() by sticking a 
> pointer to a prefix in struct sysent or some such.

Hmm, are you 100% sure? As long as I can see they all use LCONVPATH() 
macros, which in turn uses linux_emul_convpath() function from 
linux_util.c. The latter function is stackgap-free. The only 
commonly-used function "infected" with stackgap in linuxlator is 
linux_emul_find (and so that CHECKALT*() macroses that use it). My plan 
was to remove that function entirely, but apparently it is still used in 
non-i386 versions of linuxlator, so that it can be done yet.

-Maxim